ALBERT

Description: 〈h3〉Abstract〈/h3〉 〈p〉The scarcity of rainfall data is one of the main problems affecting the use of hydrological models. Several model satellite-based rainfall estimates (SREs) have been developed to provide an alternative to poorly or ungauged basins. The aim of this work was to evaluate the suitability of SREs for hydrological modeling using a semi-distributed model in the transboundary basin of Medjerda, shared by Tunisia and Algeria. Two satellite-based rainfall products (PERSIANN-CDR and CHIRPSv2) were first compared to rain gauge observations based on sub-basin and point-to-pixel analysis. The selected SREs products were then used as inputs to simulate discharge at a daily time-step over the 1996–2016 period. The simulated streamflows were compared to data measured at four runoff gauging stations and at the outlet of two dams. It was first shown that both SRE products perform weakly at daily scale but that the CHIRPSv2 product performs better at monthly scale. Second, comparison at sub-basin scale led to a better correlation with rain gauge observations than point-to-pixel analysis. Third, direct sampling can be reliably used to fill gaps in discharge time series by using auxiliary stations highly correlated with the target station. Finally, the CHIPRSv2 daily satellite rainfall product is more efficient and more suitable than the PERSIANN-CDR product for hydrological modeling. Thus, CHIRPSv2 can be used as an alternative or as a complementary source of information to simulate hydrological models in arid and semi-arid regions and can successfully solve the issue of missing rainfall data in transboundary catchments.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper presents an evaluation of the Weather Research and Forecasting (WRF) model in simulating wet and dry West African monsoon (WAM) rainfall seasons. Three model experiments with varying selected microphysics (MP), cumulus convection (CU), and planetary boundary layer (PBL) schemes based on previous study were performed. Each of the model combinations is used to run four WAM seasons that consist of two wet (2008 and 2010) and two dry years (2001 and 2011). To investigate the behavior of WAM in the context of wet and dry years, the four seasons were used to compute composites of wet and dry WAM seasons in terms of rainfall amount. The analyses majorly focus on the rainfall composites relative to rainfall from Global Precipitation Climatology Project (GPCP) and Tropical Rainfall Measurement Mission (TRMM) as well as temperature, moisture, and atmospheric circulation fields with respect to NCEP reanalyses. This study documents significant sensitivity in simulation of the West African monsoon to the choices of the MP, CU, and PBL schemes. The simulation with the combination of WRF single moment 5 (WSM5) MP, Yonsei University (YSU) PBL, and new Simplified Arakawa-Schubert CU (WSM5-YSU-nSAS) shows good spatial distribution pattern of rainfall and the dynamics associated with the monsoon. Quantitatively, the combination shows less agreement in distinguishing the selected WAM seasons compared with the Goddard MP, Mellor-Yamada-Janjic PBL, and Betts-Miller-Janjić CU (GD-MYJ-BMJ) and the WSM5, Mellor-Yamada-Nakanishi-Niino 2.5 level and new Tiedtke CU (WSM5-MYNN-nTDK). Also, the dynamical structures of the wet and dry WAM circulation composites are reasonably reproduced in GD-MYJ-BMJ and WSM5-YSU-nSAS. The GD-MYJ-BMJ was able to distinguish between wet and dry years and thus underscores its potential to reproduce climate change signals in future work.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The freeze/thaw process and the surface energy budget of the seasonally frozen ground in the source region of the Yellow River were investigated by using observed soil temperature and moisture and the energy flux from May 12, 2014, to May 11, 2015. Compared with the Maduo site, the starting date of the freezing process was later and the freezing depth was shallower at Maqu site. The maximum frozen depth was about 320 cm at Maduo site and 90 cm at Maqu site. The soil temperature of Maqu site was higher than of Maduo site due to lower latitude and altitude. The soil was the driest under the depth of 40 cm and 80 cm at Maduo and Maqu sites, respectively. The diurnal amplitudes of soil temperature of Maduo site were larger than of Maqu site at four freeze/thaw stages; the amplitudes were the largest in the completely thawed stage (9.19 °C and 4.35 °C) and minimal in the freezing stage (1.23 °C and 0.47 °C). The diurnal amplitudes of soil moisture of Maqu site were greater than of Maduo site at all stages. The net radiation Rn’s seasonal change was hardly influenced by the freeze/thaw process. The mean ground heat flux (G〈sub〉0〈/sub〉) was negative during the freezing and completely frozen stage and positive during the thawing and completely thawed stage. During the completely thawed and frozen stages, the latent heat flux (LE) and sensible heat flux (H) predominated in the surface energy distribution, respectively. Overall, the variations of fluxes were affected by both the monsoon and freeze/thaw process of the soil layer in seasonally frozen region. The freeze/thaw process had a significant effect on the diurnal change of G〈sub〉0〈/sub〉 during the freezing stage. The annual energy closure status of Maduo and Maqu sites was 0.77 and 0.58, respectively. The energy closure status was the highest during the completely thawed stage at Maduo site and during the thawing stage at Maqu site and lowest during the freezing stage among the four stages, due to the snow cover’s impact. Overall, the freeze/thaw process and the high albedo caused by snow cover had effects on the energy closure status.〈/p〉

Description: 〈p〉The presentation of Fig. 4 was incorrect.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study evaluates the monthly, seasonal, and annual characteristics of near-surface air temperature as a function of both elevation and geographical coordinates over Pakistan, using a climatic data set from 53 observation stations ranging between 5 and 2317 m asl and stepwise multiple regression. Forcing processes for temperature gradient (TG) variation were determined by analyzing its relationship with moisture flux (〈em〉qv〈/em〉) and gradients of rainfall and saturation vapor pressure (〈em〉e〈/em〉〈sub〉s〈/sub〉). The bi-model pattern of TG〈sub〉E〈/sub〉 (temperature gradient with topographic elevation), which earlier studies (TAAC 113(3):671-682, TAAC 132:1129-1141) from the southern slopes of the Himalayas have observed, is also consistent in this study region. However, the forcing strengths, mechanisms, and processes for the monthly variations in TGs magnitude and their diurnal range are somewhat different. The annual cycle of TG〈sub〉E〈/sub〉 in this study is inversely (positively) associated with the rainfall (〈em〉e〈/em〉〈sub〉s〈/sub〉) gradient. Monsoon and orographic controls for TG〈sub〉E〈/sub〉 are stronger in summer, especially in the day, while the influences of inversions and mountainous topoclimate are higher during the non-monsoon period, in particular in winter and at night. Mountain barrier effects are higher in summer, which considerably hamper the relationship between temperature and geographical coordinates and rainfall and elevations. Steeper values of mean TG〈sub〉E〈/sub〉s in the non-monsoon period are the result of strong dry convectional cooling at higher elevations due to high thermal forcing effects at lower elevations. Sensible heating reduction due to westerly-driven precipitation and cloud cover in daytime in the northern mountainous region (or higher latitudes) further strengthens the TG〈sub〉E〈/sub〉 value in this period. This effect is weaker in the surrounding regions; therefore, the TG〈sub〉E〈/sub〉 magnitude in this study is expected to be higher, especially in the pre-monsoon season. Gradients are more shallow in winter (excluding latitude), but values are greater than those in summer, due to distinct variations in moisture and cloud amount, i.e., lower in winter and higher in summer, particularly at lower elevations. Observed distinct differences in TG diurnal range between elevation (high) and latitude (low) in this study are due to a wide variation in temperature, topography, and elevations within the same latitudinal belts. In this study, the lowest gradient values for elevation are observed in August and the highest in May, 1 month later than observed in adjacent mountain regions due to the late arrival of monsoon moisture in summer and intense thermal forcing effects following the wet early pre-monsoon months. Distinct variability of gradient magnitudes between the northern mountainous region and the southern flat terrain is due to differences in topoclimates, moisture amounts, elevations, and geographical coordinates.〈/p〉

Description: 〈p〉The original version of this article unfortunately contained a mistake.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Land surface temperature (LST) plays a key role in the surface energy budget computation and land surface process studies. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the Aqua and Terra satellites provide comprehensive global LST estimates at a fine spatial resolution. The MODIS products were recently upgraded to Collection 6, and shown to be more accurate than its predecessor Collection 5 products. In this study, LST and its variability have been examined across India from Collection 6 of the Aqua MODIS data at 0.05° spatial resolution for the period of 2003 to 2017. All-India mean LST characteristics show distinctive features as compared to the well-documented mean characteristics of near-surface air temperature. All land cover types except permanent snow and ice, and cold desert areas exhibit bimodal peaks in seasonal variations of daytime LST. The daytime LST over the coldest and high-altitude regions of northern India shows anomalous positive linear relationship with NDVI at a monthly scale. However, monthly domain-mean daytime LST of cropland regions is largely negatively correlated with NDVI as compared to other land cover types. Results reveal that about 17% of the Indian landmass received its hottest LST during 2010 followed by 2016. Linear trend analysis for the 15-year period of mean annual LST shows a decrease in diurnal temperature range over most parts of the country due to rather rapid increase in nighttime LST than daytime LST, similar as changes in near-surface air temperature across the country.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study presents the first comprehensive evaluation of the performance of the monthly TRMM rainfall product (3B43-v7) in capturing the rainfall patterns, on the geographic area of the central Mediterranean during the period 1998–2017. Monthly rainfall data from a network of ground-based stations were used to compute a series of spatiotemporal evaluation statistics for the satellite measurement accuracy. These statistics showed a satisfactory accuracy of the examined satellite products in capturing seasonal and annual rainfall patterns, having rather high correlation coefficients (0.75 to 0.96). Nevertheless, a slight 〈em〉overestimation〈/em〉 of the rainfall values (with a mean value lower than 15 mm) implied by the TRMM was found at seasonal basis with the exception of 〈em〉winter〈/em〉 when a small 〈em〉underestimation〈/em〉 (with a mean value amounting to 8 mm) was detected. The 〈em〉overestimation〈/em〉 tendency was mainly detected over the northern and the western parts of the studied domain, where the effect of the earth surface altitude seems to be important. An 〈em〉underestimation〈/em〉 tendency prevails over the marine regions and seems to be associated with the rain rate (in the sense that heavy rainfall episodes are underestimated more). The overall biases of the TRMM rainfall product in respect to the control ground-based station sample found to be within ± 0.2 of the local rainfall standard deviation and nonstatistically significant almost in half of the cases in all seasons except winter. The possible causes of the detected diversity of the seasonal error statistics behavior were further explored and discussed.〈/p〉

Description: 〈p〉Figures 3 and 4 were the same.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A suite of Regional Climate Model (RegCM) experiments are performed over south Asia to examine the skill of RegCM to simulate the seasonal and sub-seasonal mean features of Indian summer monsoon (ISM). Because of coupled nature of ISM, three model experiments with RegCM are conducted to examine the skill of coupled and uncoupled configurations of RegCM by forcing it with observed SST (Exp1), coupling it to a simple slab ocean model (SOM) with constant mixed layer depth (MLD; Exp2) and with climatology of MLD (Exp3). The coupled experiments show an overall improvement in several aspects of ISM variability at seasonal and intraseasonal time-scales, despite bias in simulated SSTs. Between coupled experiments; Exp3 reduces biases in SST distribution over the region to the north of Arabian Peninsula, eastern Arabian Sea (AS), and broadly over north Indian Ocean (NIO). Noteworthy is the improved precipitation over central India (CI), head Bay of Bengal (BoB), as well as the representation of easterly wind shear in coupled experiments. At intraseasonal time scales, Exp3 produces spectral peaks above red noise at 25–50-day and 15–20-day periods closely representing the northward propagating intraseasonal mode and quasi-biweekly oscillating mode as in observed precipitation. The improved representation of spatial distribution of intraseasonal activity over NIO as well as the SST and precipitation relationships over head BoB and eastern AS is attributed to better representation of air-sea interaction in Exp3. In brief, the coupling improves the model skill for the true representation of mean ISM variability during boreal summer, and the thorough evaluation of model for longer periods is required to employ it as a downscaling tool for regional climate change studies.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Spatiotemporal changes of temperature and precipitation extremes from 1956 to 2015 were analyzed at 200 representative weather stations evenly distributed in the temperate continental zone (TCZ), temperate monsoon zone (TMZ), mountain plateau zone (MPZ), and (sub) tropical monsoon zone (SMZ) of China, using 16 extreme temperature and 11 extreme precipitation indexes. The results showed that warm days (TX90p) and warm nights (TN90p) increased significantly, while cool days (TX10p) and cool nights (TN10p) decreased significantly in the whole China. Overall increasing trends were found for maximum and minimum daily maximum temperature (TXx and TXn) and maximum and minimum daily minimum temperature (TNx and TNn). Warm indexes, including summer days (SU25), tropical nights (TR20), warm spell duration indicator (WSDI), and growing season length (GSL), showed increasing trends, whereas cold indexes such as frost days (FD0), ice days (ID0), cold spell duration indicator (CSDI), and diurnal temperature range (DTR) showed decreasing trends. These extreme temperature indexes exhibited high correlations with mean air temperature. MPZ exhibited the most remarkable change magnitudes among the four zones, while the smallest changes occurred in SMZ. An accelerating warming trend was particularly observed since 1986. Nationally, only daily rainfall intensity (SDII) showed significantly increasing trends, while the increasing trends of other precipitation indexes were not significant. Apart from consecutive wet days (CWD), changes of precipitation extremes presented increasing trends. PRCPTOT and R10mm exhibited the highest correlation coefficient across contrasting climatic zones. Regionally averaged precipitation totals were decreasing in TMZ during 1956–1985, but increasing trends were identified after 1985. The upward tendency of precipitation totals in MPZ and the west part of TCZ may alleviate the pressure of water shortage in arid and semi-arid regions of China, but the upward trend in SMZ, especially in the coastal areas of southeastern China, may aggravate the risk of flood-induced disasters in these regions.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The existing study was taken to represent the current information in order to develop a mass-balanced ecosystem model within the resettled maritime boundary area of the Bay of Bengal (BoB), Bangladesh from July 2016 to June 2017 through ECOPATH approach covering over 90 000 km〈sup〉2〈/sup〉. A total of 19 functional groups were considered representing all trophic levels in the foodweb where estimated trophic interactions between the groups were varied from 1 (primary producers and detritus) to 3.45 (sharks). The ecotrophic efficiency (EE) of most of the consumers was greater than 0.80; symbolizing a largely exploited ecosystem and high energy transfer from lower to higher trophic levels. Moreover, the gross efficiency (0.001 8) and transfer efficiency (11.12%) of the whole system symbolizes the “Developing Systems” with somewhat maturity currently. Ecosystem’s overhead (64.6) and ascendancy (35.4) also designate the ecosystem’s stability. Thus, this study determines that the resettled maritime area of BoB reserves significant backup strength to face stress situations having capacity to rapid restoration to the original states.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The response of glutathione S-transferase (GST) in 〈em〉Zostera marina〈/em〉 to temperature variation was analyzed at molecular level by cloning the microsomal GST gene and texting the microsomal GST expression regularity under different temperature. Specific speaking, express 〈em〉Zm〈/em〉GST in 〈em〉Escherichia coli〈/em〉, then purify the recombinant protein and make the thermal stability analysis. Therefore, the experiments were carried out to provide a theoretical basis for the further elaboration to the population degradation mechanisms of 〈em〉Z. marina〈/em〉. In conclusion, the thermostability and the response of 〈em〉Zm〈/em〉GST gene to temperature changes can determine its temperature tolerance range, and affect its resilience in turn.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Hydrothermal precipitates associated with active vents in the eastern Manus Basin, an actively opening back-arc basin in the Bismarck Sea, Papua New Guinea, are among the most Cu-rich on the modern seafloor. The volcanic rocks associated with this mineralization may be insufficiently enriched in Cu to account for the Cu content of the sulfides by simple leaching. The PACMANUS hydrothermal field lies in the eastern portion of the eastern Manus Basin. Mass balance modeling of the PACMANUS hydrothermal system indicates that simple leaching of a stationary reaction zone (0.144 km〈sup〉3〈/sup〉) by hydrothermal fluids cannot yield the Cu found in associated sulfide deposits because unacceptably high leaching, transportation and precipitation efficiencies are required to derive the Cu in sulfides by leaching processes. With 100% leaching, transport and precipitating efficiency, 0.166 km〈sup〉3〈/sup〉 of volcanic rocks would need to be leached to account for the Cu budget of hydrothermal sulfide deposits. The key requirement for forming metal-rich magmatic fluids is a large amount of metals available to enter the exsolved vapor phase. Magmas generated in the eastern Manus Basin inherently have high 〈em〉f〈/em〉O〈sub〉2〈/sub〉 because of metasomatism of the mantle source by oxidized materials from the subducted slab, leading to copper enrichment in the magma chamber. Moreover, the presence of Cu in gas-rich melt inclusi on bubbles in Pual Ridge andesite is evidence that degassing and partitioning of Cu into the magmatic volatile phase has occurred in the eastern Manus Basin. Numerical mass balance modeling indicates that approximately 0.236 Mt Cu was potentially transferred to the hydrothermal system per cubic kilometer magma. Magmatic degassing seems to play a more significant role than leaching.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The objective of this work is to investigate the interaction between the climate indices precipitation concentration degree (PCD), precipitation concentration period (PCP), and oceanic patterns associated with drought disasters in the Northeast of Brazil (NEB). The average values of drought disasters were situated at the semi-arid zone, while the hotspots between 95 and 99% of significance were more centralized, particularly in the states of Ceará, Rio Grande do Norte, Paraíba, and Pernambuco, where significant areas were located. The PCD patterns showed that precipitation was concentrated in the north of this region and the wettest quarter happened from February to April, in accordance with PCP patterns. The analysis of variance (ANOVA) A showed evidence of the variability of PDC and PCP in relation to the well-known variability modes of the oceans. However, only two areas of NEB presented statistical significance.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Based on daily mean temperature data from 32 meteorological stations in the Qinling Mountains (QMs) of China, we analyzed the characteristics and differences of the spatiotemporal changes in the climatic growing season (CGS) in the QMs from 1964 to 2015. Our results are as follows. First, over the past 52 years, the temperature of the QMs significantly increased at a mean rate of 0.22 °C/decade (〈em〉P〈/em〉 〈 0.01) in over 98.04% of the area. Significant north–south spatial differences were observed in temperature changes; also, significant differences in the temperature changing trends were observed before and after the abrupt change in temperature. Second, the spatial distributions of the mean growing season start (GSS), end (GSE), and length (GSL) in the QMs varied based on regional differences in latitude and topography. Notably, the GSS, GSE, and GSL were gradually delayed, advanced, and shortened, respectively, as latitude and elevation increased. After the abrupt change in temperature, whether it is in the NSQM (northern slopes of the QMs) or the SSQM (southern slopes of the QMs), the GSS, GSE, and GSL expanded into high-elevation areas. Third, over the past 52 years, the GSS in the QMs exhibited a significant advancing trend of 2.7 days/decade, the GSE was delayed at a rate of 0.66 days/decade, and the GSL displayed a significant extension of 3.36 days/decade. Before the abrupt change in temperature, the GSS, GSE, and GSL exhibited non-significant changing trends; however, the trends in the GSS, GSE, and GSL were more significant after the abrupt change than before. Fourth, the GSS, GSE, and GSL trends in the QMs were significantly different in the NSQM and SSQM regions. After the abrupt change, the GSS, GSE, and GSL trends along the NSQM were more significant than those along the SSQM.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The morphology of seven specimens of 〈em〉Chrysaora chinensis〈/em〉 (Scyphomedusae, Semaestomae) obtained from four sites off the coast of Peninsular Malaysia was examined. Morphological characteristics of 〈em〉C. chinensis〈/em〉 that encompasses structures such as the bell, tentacles, oral arms, stomach, manubrium, radial canals and gonads were described in detail. A total of 107 specimens that represented 〈em〉C. chinensis〈/em〉 populations of four coastal areas of Peninsular Malaysia (East-Central, East-North, West-Central, and West-North) were also analysed for shape variation using geometric morphometric analysis. Procrustes superimposition, Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) were applied to the images of gastrovascular pouches of 〈em〉C. chinensis〈/em〉 to extract the shape information. Independent contrasts were used for comparisons between shapes. There were no significant differences in shape variation between all the specimens based on the PCA results. However, CVA results showed shape variations between specimens taken from the four areas of Peninsular Malaysia, especially with higher magnitudes of Mahalanobis distances between the east and west coast areas, including between East-Central and East-North, but lower magnitudes were detected between the West-Central and West-North.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Various population structures or spatial heterogeneities in population distribution have been an important source of model misspecification and have had an impact on estimation performance in fisheries stock assessment. In this study, we simulated the Indian Ocean albacore spatial heterogeneity in age-structure using Stock Synthesis according to the stage-dependent migration rate and region-dependent fishing mortality rate and generated the stock assessment data. Based on these data, we investigated the performances of different spatial configurations, selectivity curves and selections of CPUE (catch per unit effort) indices of the assessment models which were used to account for spatial heterogeneity. The results showed: (1) although the spatially explicit configurations, which exactly matched the operating model, provided unbiased and accurate estimates of relative spawning biomass, relative fishing mortality rate and maximum sustainable yield in all simulation scenarios, their performance may be very poor if there were mismatches between them and the operating model due to gaps in knowledge and data; (2) for spatially explicit assessment configuration, the correct boundary was required, but for non-spatially explicit assessment configuration, it seemed more important for analysts to partition the area to properly reflect the transition in field data and to effectively account for the impacts of ignoring the spatial structure by using the additional spatially referenced parameters; (3) although the areas-as-fleets methods and flexible time-varying selectivity curves could be used as better alternative approaches to account for spatial structure, these configurations could not completely eliminate the impacts of model misspecification and the quality of estimates of different quantities from the same assessment model may be inconsistent or the performance of the same assessment configuration may fluctuate significantly between simulation scenarios; (4) although the worst estimates could generally be avoided by using multiple CPUE indices, there were no best solutions to select or regenerate the CPUE indices to account for the impacts of the ignored spatial structure to obviously improve the quality of stock assessment. Compared with the results of assessment model configurations which are used to account for the spatial structure by different modelers, the performances of the configurations are always casespecific except for spatially explicit configurations which exactly match the operating model. In this sense, our study will not only provide some insights into the current Indian Ocean albacore stock assessment but also enrich existing knowledge regarding the performance of assessment configurations to account for spatial structure.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉With the decline of fish stocks, the proportions of economically important invertebrates like crustaceans and cephalopods have increased in the Bohai Sea. The community structure and trophic level of economically important invertebrates were analyzed using the bottom trawl survey data collected by the Yellow Sea Fisheries Research Institute in the Bohai Sea in May and August of 1958–1959, 1982, 1992–1993, 2004, 2009 and 2015. A total of 37 species of economically important invertebrates, belonging to 5 orders, 24 families, were captured. The biomass densities of economically important invertebrates in the Bohai Sea displayed an overall downward trend from 1982 to 2015. 〈em〉Oratosquilla oratoria〈/em〉 and 〈em〉Loligo〈/em〉 spp. were the most dominant species in the past 30 years, the biomass proportion of 〈em〉O. oratoria〈/em〉 increased gradually in both May and August from 1982 to 2015. Moreover, biodiversity indices of economically important invertebrates in the Bohai Sea appeared to decline from 1982 to 2004 and then increased in 2015. Similarly, the mean trophic level of economically important invertebrates declined from 1982 to 2004 and increased slightly in 2015. Overall, although the proportions of invertebrates have increased, the biomass densities in the Bohai Sea have displayed an overall downward trend from 1982 to 2015. The increases in the biodiversity and trophic level of economically important invertebrates after the 2000s, possibly benefit from stock enhancement projects implemented by governments at different levels and national fishery management measures such as the “double-control” of the total number and engine power of fishing vessels and summer moratorium of fishing.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study examines the effects of Stokes drift on pollutant transport within the surf zone on a plane beach both numerically and experimentally. Firstly, the numerical model is described. The wave-induced current is modeled using the concept of the radiation stress. The wave propagation model is based on the wave energy conservation equation. And the advective diffusion model including the Stokes drift is used to describe the pollutant transport in the surf zone. Model validation was achieved in this case versus an analytical solution for an instantaneous point source in a uniform horizontal flow. This study also describes a laboratory experiment on dye release in the surf zone over a plane beach. We examined the final inclination angle required by a continuously released pollutant plume to reach the shoreline under both cases, and transport velocities in the alongshore and cross-shore directions were estimated by linearly fitting the location of a dye-patch front at different time. Results show that this dye patch moved shoreward with an approximate speed of 0.05 m/s (0.017 m/s) between 10 s and 40 s and 0.001 m/s (0.011 m/s) after 40 s for Case 1 (2). This model was then used to simulate pollutant transport in the surf zone on a plane beach as reproduced in the current experiment. Comparisons between our dye transport experiment and numerical results were then also conducted; the data showed that the numerical results including Stokes drift agreed more closely with experimental results than those without it. The data showed that the pollutant was generally transported obviously shoreward in addition to its expected drift along the shore. We also suggest that Stokes drift plays an important role in pollutant movement in the surf zone, especially shoreward.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉There are well-established chemical and turbidity anomalies in the plumes occurring vicinity of hydrothermal vents, which are used to indicate their existence and locations. We here develop a small, accurate multi-channel chemical sensor to detect such anomalies which can be used in deep-sea at depths of more than 4 000 m. The design allowed five all-solid-state electrodes to be mounted on it and each (apart from one reference electrode) could be changed according to chemicals to be measured. Two experiments were conducted using the chemical sensors. The first was a shallow-sea trial which included sample measurements and 〈em〉in situ〈/em〉 monitoring. pH, Eh, CO〈span〉 〈sub〉3〈/sub〉 〈sup〉2−〈/sup〉 〈/span〉 and SO〈span〉 〈sub〉4〈/sub〉 〈sup〉2−〈/sup〉 〈/span〉 electrodes were utilized to demonstrate that the chemical sensor was accurate and stable outside the laboratory. In the second experiment, the chemical sensor was integrated with pH, Eh, CO〈span〉 〈sub〉3〈/sub〉 〈sup〉2−〈/sup〉 〈/span〉 and H〈sub〉2〈/sub〉S electrodes, and was used in 29 scans of the seabed along the Southwest Indian Ridge (SWIR) to detect hydrothermal vents, from which 27 sets of valid data were obtained. Hydrothermal vents were identified by analyzing the chemical anomalies, the primary judging criteria were decreasing voltages of Eh and H〈sub〉2〈/sub〉S, matched by increasing voltages of pH and CO〈span〉 〈sub〉3〈/sub〉 〈sup〉2−〈/sup〉 〈/span〉. We proposed that simultaneous detection of changes in these parameters will indicate a hydrothermal vent. Amongst the 27 valid sets of data, five potential hydrothermal vents were targeted using the proposed method. We suggest that our sensors could be widely employed by marine scientists.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Bohai Sea is extremely susceptible to storm surges induced by extratropical storms and tropical cyclones in nearly every season. In order to relieve the impacts of storm surge disasters on structures and human lives in coastal regions, it is very important to understand the occurring of the severe storm surges. The previous research is mostly restricted to a single type of storm surge caused by extratropical storm or tropical cyclone. In present paper, a coupled atmosphere-ocean model is developed to study the storm surges induced by two types of extreme weather conditions. Two special cases happened in the Bohai Sea are simulated successively. The wind intensity and minimum sea-level pressure derived from the Weather Research and Forecasting (WRF) model agree well with the observed data. The computed time series of water level obtained from the Regional Ocean Modeling System (ROMS) also are in good agreement with the tide gauge observations. The structures of the wind fields and average currents for two types of storm surges are analyzed and compared. The results of coupled model are compared with those from the uncoupled model. The case studies indicate that the wind field and structure of the ocean surface current have great differences between extratropical storm surge and typhoon storm surge. The magnitude of storm surge in the Bohai Sea is shown mainly determined by the ocean surface driving force, but greatly affected by the coastal geometry and bathymetry.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Arctic sea ice cover has declined at an unprecedented pace since the late 20th century. As a result, the feedback of sea ice anomalies for atmospheric circulation has been increasingly evidenced. While climatic models almost consistently reproduced a decreasing trend of sea ice cover, the reported results show a large distribution. To evaluate the performance of models for simulating Arctic sea ice cover and its potential role in climate change, this study constructed a reasonable metric by synthesizing both linear trends and anomalies of sea ice. This study particularly focused on the Barents Sea and the Kara Sea, where sea ice anomalies have the highest potential to affect the atmosphere. The investigated models can be grouped into three categories according to their normalized skill scores. The strong contrast among the multi-model ensemble means of different groups demonstrates the robustness and rationality of this method. Potential factors that account for the different performances of climate models are further explored. The results show that model performance depends more on the ozone datasets that are prescribed by the model rather than on the chemical representation of ozone.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Better forecast of tropical cyclone (TC) can help to reduce risk and enhance management. The TC forecast depends on the scientific understanding of oceanic processes, air-sea interaction and finally, the atmospheric process. The TC Viyaru is taken as an example, which is formed at the end of 11 May 2013 and sustains up to 17 May 2013 during pre-monsoon season. Argo data are used to investigate ocean response processes by comparing pre- and post-conditions of the TC. Eight oceanic parameters including the sea surface temperature (SST), the sea surface salinity (SSS), and the barrier layer thickness (BLT), the 26°C isotherm depth in the ocean (〈em〉D〈/em〉〈sub〉26〈/sub〉), the isothermal layer depth (ILD), the mixed layer depth (MLD), the tropical cyclone heat potential (TCHP) and the effective oceanic layer for cyclogenesis (EOLC) are chosen to evaluate the pre- and post-conditions of the TC along the track of Viyaru. The values of the SST, 〈em〉D〈/em〉〈sub〉26〈/sub〉, BLT, TCHP and EOLC in the pre-cyclonic condition are higher than the post-cyclonic condition, while the SSS, ILD and MLD in the post-cyclonic condition are higher than the pre-cyclonic condition of the ocean due to strong cyclonic winds and subsurface upwelling. It is interesting that the strong intensity of the TC reduces less SST and vice versa. The satisfied real time Argo data is not available in the northern Bay of Bengal especially in the coastal region. A weather research and forecasting model is employed to hindcast the track of Viyaru, and the satellite data from the National Center Environmental Prediction are used to assess the hindcast.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉There were two severe coral bleaching events at Ko Khang Khao, the inner Gulf of Thailand, occurred during the prolonged period of the elevated sea surface temperature (SST) in 2010 and low salinity as well as turbidity due to heavy flooding in 2011. The bleaching index (〈em〉BI〈/em〉) and mortality index (〈em〉MI〈/em〉) are calculated to compare the susceptibilities of coral species in the two bleaching events. The BI and MI vary significantly among the study sites and bleaching events. The most susceptible corals during both bleaching events are 〈em〉Acropora millepora〈/em〉, 〈em〉Pocillopora damicornis〈/em〉 and 〈em〉Pavona decussate〈/em〉, while the most resistant species were 〈em〉Galaxea fascicularis, Fungia fungites, Pavona frondifera, Oulastrea crispate〈/em〉, and 〈em〉Symphyllia recta〈/em〉. The corals 〈em〉Favia favus, Goniopora columna, Platygyra pini, Symphyllia agaricia〈/em〉 were relatively more tolerant to high SST but they are relatively more susceptible to low salinity. Coral bleaching is a phenomenon that the dissociation stress of the symbiotic relationship between zooxanthellae and their cnidarian host results in the reduction in photosynthetic pigment concentration. Among stressors, both prolonged exposure of high SST and low salinity, above and below their thresholds, respectively. The long-term resilience of coral communities at Ko Khang Khao and other coral communities close to the mouth of large rivers may depend on the frequency and duration of the exposure on the elevated SST due to atmospheric heating and low salinity due to river flooding.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Monsoon rainfall exhibits the prominent diurnal variability. It is essential to capture the diurnal behaviour of the rainfall on the spatiotemporal scale by mesoscale models for its accurate prediction. The present study appraises the diurnal variability of simulated rainfall by Weather Research and Forecasting (WRF) model over the South Asian region during Indian summer monsoon seasons of the years 2008–2012. For examining the amplitude, phase, and variance of the simulated diurnal cycle of rainfall, harmonic analysis of model outputs are carried out and compared it with that of TRMM rainfall estimates to quantify errors. The model is overall successful in simulating the pattern of diurnal variation of rainfall, but underestimates its amplitude compared to the observed one especially over the western Himalayas, northeast India, central India, and the north Bay of Bengal (BoB). However, the amplitudes of the diurnal variation match well over south BoB. The simulated phases of the diurnal cycle either leads (over central India and NW India by 3 h) or lags (over the sub-Himalayan region by 12 h) than the observed phase angle. The simulated time of maximum rainfall matches over south Peninsula, while over the west coast, neither observation nor forecast shows pronounced diurnal cycle. The north BoB shows morning maxima in rainfall in both observation and forecast; however, over south BoB, the time of maximum simulated rainfall leads by 3 h. Even though the model is overall successful in representing the diurnal variation of rainfall, it requires improvement for proper representation of phase and sub-diurnal variation appropriately.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The bulk transfer method is commonly used to calculate the surface sensible heat (SSH) flux in climatology and in the numerical model, but in the calculation, the value of the bulk transfer coefficient for heat (〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉) is generally regarded as a fixed value (e.g., 0.004 in the Tibetan Plateau), without considering its seasonal variations and regional differences. In this study, a new method for upscaling data from the local to regional scale is proposed and tested to estimate 〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉 over the east-central Tibetan Plateau (TP) using the latest version Global Inventory Modeling and Mapping Studies (GIMMS), Normalized Difference Vegetation Index (NDVI) dataset, and micrometeorological observations collected at four field sites. Results suggest that the proposed method is capable of reflecting the variations in 〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉 at the regional scale in a climatic context. It is a relatively reliable way of estimating the value of 〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉 using satellite remote sensing data and field observations. Then, the monthly values of 〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉 and the SSH flux at 70 China Meteorological Administration (CMA) stations on the east-central TP during the period 1982–2012 are estimated. Results show that the value of 〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉 ranges from 0.0025–0.0050, with obvious seasonal variations and spatial differences. Because the surface vegetation coverage in the southeastern part of the TP is better than that in the north-central part, the values of 〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉 are higher than that in the north-central part of the TP throughout the year. The SSH flux also shows obvious seasonal variations and spatial differences, which is strongest in spring, followed by summer and autumn, and smallest in winter. Furthermore, the seasonal mean SSH has undergone a significant interdecadal transition in the early 2000s, from the previous weakening trend to the strengthening trend. Based on the results of this study, the values of 〈em〉C〈/em〉〈sub〉〈em〉h〈/em〉〈/sub〉 obtained from a limited number of local field observations on the plateau can be applied to more CMA stations at the regional scale. Such a method can improve the calculation accuracy of the SSH flux over the TP and aid studies of plateau meteorology and climatology.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Bohai Sea is a shallow semi-enclosed inner sea with an average depth of 18 m and is located at the west of the northern Yellow Sea. The climatological circulation pattern in summer of the Bohai Sea is studied by using a wave-tide-circulation coupled model. The simulated temperature and the circulation agree with the observation well. The result shows that the circulation pattern of the Bohai Sea is jointly influenced by the tidal residual current, wind and baroclinic current. There exists an obvious density current along the temperature front from the west part of the Liaodong Bay to the offshore area of the Huanghe Estuary. In the Liaodong Bay there exists a clockwise gyre in the area north to the 40°N. While in the area south to the 40°N the circulation shows a two-gyre structure, the flow from the offshore area of the Huanghe Estuary to the Liaodong Bay splits into two branches in the area between 39°N and 40°N. The west branch turns into north-west and forms an anti-clockwise gyre with the south-westward density current off the west of the Liaodong Bay. The east branch turns to the east and forms a clockwise gyre with the flow along the east coast of the Liaodong Bay. The forming mechanism of the circulation is also discussed in this paper.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Satellite remote sensing of inland water body requires a high spatial resolution and a multiband narrow spectral resolution, which makes the fusion between panchromatic (PAN) and multi-spectral (MS) images particularly important. Taking the Daquekou section of the Qiantang River as an observation target, four conventional fusion methods widely accepted in satellite image processing, including pan sharpening (PS), principal component analysis (PCA), Gram-Schmidt (GS), and wavelet fusion (WF), are utilized to fuse MS and PAN images of GF-1. The results of subjective and objective evaluation methods application indicate that GS performs the best, followed by the PCA, the WF and the PS in the order of descending. The existence of a large area of the water body is a dominant factor impacting the fusion performance. Meanwhile, the ability of retaining spatial and spectral informations is an important factor affecting the fusion performance of different fusion methods. The fundamental difference of reflectivity information acquisition between water and land is the reason for the failure of conventional fusion methods for land observation such as the PS to be used in the presence of the large water body. It is suggested that the adoption of the conventional fusion methods in the observing water body as the main target should be taken with caution. The performances of the fusion methods need re-assessment when the large-scale water body is present in the remote sensing image or when the research aims for the water body observation.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉One of the problems experienced in marine geophysical exploration is that the layered features in the migration imaging profile are blurred and the seismic energy reflected is weaker in the middle or lower parts. In this study we model the seismic wavefield records in the undulating seafloor when there is both a slight change and significant change in seafloor topography to analyze its influence on the seismic reflection data and migration imaging profiles. We compare and analyze the wave field records collected at the same point on the original and modified velocity models, and the cross-bonding resulting migration imaging profiles. The results show that whether the seismic reflection data collection is performed along the direction of the survey line or against the direction of the survey line, slight changes in the seafloor topography have little effect on the wave field records and the migration profile, while significant changes in the seafloor topography have great effect on both the wave field records and migration profile.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The undrained shear strength of shallow strata is a critical parameter for safety design in deep-water operations. 〈em〉In situ〈/em〉 piezocone penetration tests (CPTU) and laboratory experiments are performed at Site W18-19 in the Shenhu area, northern South China Sea, where China’s first marine hydrate exploitation operation is due to be located. The validation of the undrained shear strength prediction model based on CPTU parameters. Different laboratory tests, including pocket penetrometer, torvane, miniature vane and unconsolidated undrained triaxial tests, are employed to solve empirical cone coefficients by statistical and mathematical methods. Finally, an optimized model is proposed to describe the longitudinal distribution of undrained shear strength in calcareous clay strata in the Shenhu area. Research results reveal that average empirical cone coefficients based on total cone resistance, effective resistance, and excess-pore pressure are 13.8, 4.2 and 14.4, respectively. The undrained shear strength prediction model shows a good fit with the laboratory results only within specific intervals based on their compaction degree and gas-bearing conditions. The optimized prediction model in piecewise function format can be used to describe the longitudinal distribution of the undrained shear strength for calcareous clay within all depth intervals from the mud-line to the upper boundary of hydrate-bearing sediments (HBS). The optimized prediction result indicates that the effective cone resistance model is suitable for very soft to firm calcareous clays, the excess-pore pressure model can depict the undrained shear strength for firm to very stiff but gas-free clays, while the total cone resistance model is advantageous for evaluating the undrained shear strength for very stiff and gassy clays. The optimized model in piecewise function format can considerably improve the adaptability of empirical models for calcareous clay in the Shenhu area. These results are significant for safety evaluations of proposed hydrate exploitation projects.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An integrated analysis of internal solitary wave (ISW) observations obtained from two moorings over the continental slope in the northern South China Sea (SCS) leads to an assessment of the vertical heat transport of the ISWs. The clusters of ISW packets are phase-locked to the fortnightly cycle of the semidiurnal tide. The ISWs appear during large semidiurnal tides, and there is a period of 5–6 d when no ISWs are observed. The effect of the ISWs on the continental slope heat budget is observed. The ISWs can modify a local temperature field in which the temperature in the upper layer can be changed by O (100) °C after the ISWs passed the mooring. Both ISWinduced diffusion and ISW-induced advection contribute to the temperature variation. The estimates imply an average vertical heat flux of 0.01 to 0.1 MW/m〈sup〉2〈/sup〉 in the ISWs in the upper 500 m of the water column. The vertical heat transport ranges from 0.56 to 2.83 GJ/m〈sup〉2〈/sup〉 with a mean value of 1.63 GJ/m〈sup〉2〈/sup〉. The observations suggest that the vertical heat transport is proportional to the maximum vertical displacement.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study investigates the potential impacts of climate change on wind power over West Africa under various global warming levels. For the study, we analysed eleven multi-model multi-ensemble simulation datasets from the Coordinated Regional Climate Downscaling Experiment (CORDEX) project. The model simulations for the present-day climate were compared with available station observation data and two examples of reanalysis data (ERA-INTERIM and ERA-20C). The results show that model ensemble mean gives a realistic simulation of wind speed and wind power density (WPD) over West Africa, although it overestimates them. In agreement with the reanalysis, the models indicate that the strongest winds and largest WPD are in the Sahel zone, especially around Dakar. However, while the regional climate models (RCMs) show thirteen cities are viable for potential wind power generation in the historical climate, the reanalysis indicates only four Sahelian cities are suitable for it. The RCMs project an increase in monsoon wind speed and WPD over West African cities and the magnitude of the increase grows with the global warming levels. Nevertheless, the increase is not sufficient to make the cities in the Guinean and Savannah zones viable for wind power generation in the warmer climate. The results of the study may guide policymakers on harnessing wind power potential to meet the electricity demands of West Africa in the future.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Land surface air temperature (SAT) change is one of the core issues in monitoring and assessing regional climate change. In this study, the characteristics of SAT change over DPR Korea for the period 1918–2015 were investigated using a high-quality historical dataset. Results show that the region-averaged annual mean SAT increased 0.21 °C/decade for the period 1918–2015 on the basis of data from four stations and 0.19 °C/decade for the period 1941–2015 as estimated based on data from nine stations. Before the 1970s, Pyongyang station in the central region experienced the largest warming trend. Linear trends of seasonal mean SAT during 1941–1970 were negative for all seasons in eastern coast and for summer and autumn in western coast and northern inland areas. Since 1971, however, the annual and seasonal mean SAT trends have shifted to positive values in all regions, with winter experiencing the most rapid warming. During the period of global warming slowdown since 1998 or 2000, no significant seasonal warming trend of wintertime was detectable, and this caused the smallest winter warming for the last 45 years. Other seasons also witnessed a generally weakened warming during 1971–2015 compared to that of 1971–2000. The results of the study will help in understanding regional climate change and in assessing the impacts of climate change on economic and natural ecosystems in the country.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study attempts to make comparison between different parametric regressive models for the bivariate binary data with a machine learning technique. The data on sequential occurrence of rainfall in consecutive days is considered. The outcomes are classified as rainfall in both days, rainfall in one of the consecutive days, and no rainfall in both days. The occurrence of rainfall in consecutive days is analyzed by using statistical models with covariate dependence and classification tree for the period from 1980 to 2014. We have used relative humidity, minimum temperature, maximum temperature, sea level pressure, sunshine hour, and cloud cover in the model as covariates. The binary outcome variable is defined as the occurrence or non-occurrence of rainfall. Five regions of Bangladesh are considered in this study and one station from each region is selected on the basis of two criteria: (i) contains fewer missing values and (ii) representative of the regional characteristics geographically. Several measures are used to compare the models based on Markov chain and classification tree. It is found that for yearly data, both the Markov model and classification tree performed satisfactorily. However, the seasonal data show variation of rainfall. In some seasons, both models perform equally good such as monsoon, pre-monsoon, and post-monsoon, but in the winter season, the Markov model works poorly whereas classification tree fails to work. Additionally, we also observe that the Markov model performed consistently for each season and performs better compared with the classification tree. It has been demonstrated that the covariate-dependent Markov models can be used as classifiers alternative to the classification tree. It is revealed that the predictive ability of the covariate-dependent Markov model based on Markovian assumption performs either better or equally good compared with the classification tree. The joint models also consistently showed better predictive performance compared with regressive model for whole year data as well as for several seasonal data.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The rapid development of cities has led to the urban sprawl to the suburbs. Studies have shown that urban sprawl leads to the increasing intensity of heat island effect. This paper, based on the DMSP/OLS nighttime light data and the MODIS land surface temperature data during the years 2000, 2005, and 2013, discussed the spatial and temporal characteristics of urban sprawl, urban heat island intensity in China, and their relationship, respectively. The results show that (1) the national urban expansion index showed an upward trend. The urban area was 104,000 km〈sup〉2〈/sup〉 in 2000, 169,000 km〈sup〉2〈/sup〉 in 2005, and 312,000 km〈sup〉2〈/sup〉 in 2013.The average annual growth rate was 10.2% in 2000–2005, 8% in 2000–2013, and 8.8% in 2000–2013. (2) The national heat island index also showed an upward trend; total heat island intensity was 716.73 °C in 2000, 812.84 °C in 2005, and 995.46 °C in 2013. The annual average growth rate was 2.55% in 2000–2005, 2.57% in 2005–2013, and 2.56% in 2000–2013. (3) There is a positive correlation between urban spatial expansion and heat island intensity in China. The urban and suburban range of China can be objectively extracted from the DMSP/OLS nighttime light data every year and superimposed with the MODIS land surface temperature data of the same period, which ensures the correctness of the urban heat island intensity based on the actual changes of suburban areas and main urban areas in each city, and overcomes the calculation error of the traditional method, which neglects that some suburbs have become urban areas and are still regarded as suburbs. These results provide spatiotemporal changes characterization of urban area in China during recent decades, which are helpful in decision-making of land management and planning for sustainable development.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Storm is a convective cell much smaller than a mesoscale convective system (MCS) but typically larger than a cumulonimbus cloud and heavy precipitation and lightning are often associated with it. Storms contribute major fraction of the convective precipitation in MCSs. Storm characteristics and precipitation estimates around New Delhi (28.6°N, 77.2°E; an Indian land location) during June–September period of the year 2013 are reported here using data of C-band polarimetric Doppler weather radar. Storms, defined based on radar reflectivity thresholds (30 dBZ for simple storms and 40 dBZ for intense storms), are tracked and their properties are extracted. Our results show that about 80% of storms exist for 1 h or less. The areas of 90% of simple storms are less than 100 km〈sup〉2〈/sup〉 and the largest area averaged over storm lifespan does not exceed 400 km〈sup〉2〈/sup〉. The majority of storms (〉 80%) move with speeds less than 30 km h〈sup〉−1〈/sup〉. About 60–65% of simple/intense storms have echo top heights between 6 and 10 km, while only few of them exceed 17 km. The values of average thickness of simple and intense storms lie between ~ 2–10 and ~ 1–7 km, respectively. It is not the vertical extent of a storm but its area-time integral that correlates better with the total precipitation amount. Around the New Delhi area, daily accumulated precipitation derived from relations incorporating polarimetric variables is in good agreement with the rain gauge measurements while that obtained from relations based on radar reflectivity factor (Z〈sub〉〈em〉h〈/em〉〈/sub〉) alone highly underestimates precipitation. This suggests that polarimetric capability is needed in Doppler weather radars to get the realistic precipitation estimates. The mean precipitation water content derived from Z〈sub〉〈em〉h〈/em〉〈/sub〉 (~ 0.96 g m〈sup〉−3〈/sup〉) is about 30–40% less compared to that derived from polarimetric relations. Our findings on storm properties have implications for cloud parameterizations and in short-term weather forecasting.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The evolution of mean annual minimum (TMIN) and maximum temperature (TMAX) on the Swiss Plateau shows distinct differences over the last 150 years. TMIN increased relatively steadily by about 3 °C. TMAX increased by only 1.5 °C with substantial decadal variability and hardly any increase until about 1940. However, in the most recent decades, TMAX trends are somewhat larger than TMIN trends. While most aspects of the TMIN evolution can be well explained by the global forcing and the modifying effects of the large-scale atmospheric flow alone, local sunshine duration (SD) information is crucial to explain major features of the TMAX series and the differences between TMIN and TMAX since about 1950. SD shows no clear trend until 1950, a decline from 1950 to 1980 and an increase since 1980 resembling the global dimming and brightening signal. TMAX is strongly influenced by SD and the TMAX evolution can be well reconstructed with local TMIN and SD. Strong TMAX declines are found from 1950 to the 1970s. TMIN shows no trend in this period. Between 1980 and about 2005, both TMIN and TMAX show strong increases caused by the greenhouse gas forcing, decreasing aerosols and probably also decreasing cloud cover. Since about 2005, the increases are weaker. The brightening has weakened and the warming effect of the continuously growing greenhouse gas forcing has additionally been reduced by cooling effects caused by large-scale atmospheric flow anomalies. The reasons for the considerable differences in the TMIN and TMAX evolution prior to 1950 remain unknown and further investigations are needed to shed more light on this disparity.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In the present study, the temperature data of 125 stations (1941 to 2012) over parts of India have been analysed to evaluate trends and homogeneity using various statistical tests. The annual average, maximum, and minimum temperature data showed a positive trend of 0.44 °C/100 years, 0.51 °C/100 years, and 0.19 °C/100 years, respectively. All the seasonal temperature variables exhibited a positive trend with exception of the minimum temperature of the monsoon season which showed the negative trend at the rate of 0.05 °C/100 years. The maximum temperature of monsoon season depicted a maximum increase at the rate of 0.80 °C/100 years. The results indicated that the process of urbanisation impacted over the change in temperatures. The homogeneity analysis showed the break years at 1972, 1974, and 1977 for annual average, maximum, and minimum temperatures, respectively, for entire India. The seasonal analysis exhibited that the minimum temperatures of both winter and monsoon seasons and the maximum temperature of the post-monsoon season were homogeneous in nature. The rate of change in magnitude for all annual and seasonal temperature variables showed a considerable increase after the break years.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Recent advances in variable-resolution (VR) global models provide the tools necessary to investigate local and global impacts of land cover by embedding a high-resolution grid over areas of interest in a seamless and computationally efficient manner. We used two eddy covariance tower clusters in the Eastern USA to evaluate surface energy fluxes (latent heat, λ〈em〉E〈/em〉; sensible heat, 〈em〉H〈/em〉; net radiation, 〈em〉R〈/em〉〈sub〉n〈/sub〉; and ground heat, 〈em〉G〈/em〉) and surface properties (aerodynamic resistance to heat transfer, 〈em〉r〈/em〉〈sub〉aero〈/sub〉; Bowen ratio, 〈em〉β〈/em〉; and albedo, 〈em〉α〈/em〉) by uncoupled point simulations of the land-only Community Land Model (PTCLM4.5) and two coupled land–atmosphere Community Earth System Model (CESM1.3) simulations. The CESM simulations included a 1° uniform grid global simulation and global 1° simulation with a 0.25° refined VR grid over the Eastern USA. Tower clusters included the following plant functional types—broadleaf deciduous temperate (hardwood) forest, C3 non-Arctic grass (grass), a cropland, and needleleaf evergreen temperate (pine) forest. During the growing season, diurnal cycles of λ〈em〉E〈/em〉 and 〈em〉H〈/em〉 for grass and the cropland were simulated well by PTCLM4.5 and VR-CESM1.3; however, λ〈em〉E〈/em〉 (〈em〉H〈/em〉) was biased low (high) at the hardwood and pine forested sites, contributing to biases in 〈em〉β.〈/em〉 Growing season 〈em〉R〈/em〉〈sub〉n〈/sub〉 was generally well simulated by CLM4.5 and VR-CESM1.3; however, modeled elevated albedo (indicative of snow cover) persisted longer in winter and spring leading to large biases in 〈em〉R〈/em〉〈sub〉n〈/sub〉 and 〈em〉α〈/em〉. The introduction of a VR grid does not adversely impact surface energy fluxes compared to 1° uniform grids and highlights the usefulness of this approach for future efforts to predict land–atmosphere fluxes across heterogeneous landscapes.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉When long time series are analyzed, two nearby periods may show significantly different trends, which is known as trend turning. Trend turning is common in climate time series and crucial when climate change is investigated. However, the available detection methods for climate trend turnings are relatively few, especially for the methods which have the ability of detecting multiple trend turnings. In this article, we propose a new methodology named as the running slope difference (RSD) 〈em〉t〈/em〉 test to detect multiple trend turnings. This method employs a 〈em〉t〈/em〉-distributed statistic of slope difference to test the sub-series trend difference of the time series, thereby identifying the turning points. We compare the RSD 〈em〉t〈/em〉 test method with some other existing trend turning detection methods in an idealized time series case and several climate time series cases. The results indicate that the RSD 〈em〉t〈/em〉 test method is an effective tool for detecting climate trend turnings.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Sea ice drift is mainly controlled by ocean currents, local wind, and internal ice stress. Information on sea ice motion, especially 〈em〉in situ〈/em〉 synchronous observation of an ice velocity, a current velocity, and a wind speed, is of great significance to identify ice drift characteristics. A sea ice substitute, the so-called “modelled ice”, which is made by polypropylene material with a density similar to Bohai Sea ice, is used to complete a free drift experiment in the open sea. The trajectories of isolated modelled ice, currents and wind in the Bohai Sea during non-frozen and frozen periods are obtained. The results show that the currents play a major role while the wind plays a minor role in the free drift of isolated modelled ice when the wind is mild in the Bohai Sea. The modelled ice drift is significantly affected by the ocean current and wind based on the ice–current–wind relationship established by a multiple linear regression. The modelled ice velocity calculated by the multiple linear regression is close to that of the 〈em〉in situ〈/em〉 observation, the magnitude of the error between the calculated and observed ice velocities is less than 12.05%, and the velocity direction error is less than 6.21°. Thus, the ice velocity can be estimated based on the observed current velocity and wind speed when the 〈em〉in situ〈/em〉 observed ice velocity is missing. And the modelled ice of same thickness with a smaller density is more sensitive to the current velocity and the wind speed changes. In addition, the modelled ice drift characteristics are shown to be close to those of the real sea ice, which indicates that the modelled ice can be used as a good substitute of real ice for 〈em〉in situ〈/em〉 observation of the free ice drift in the open sea, which helps solve time availability, safety and logistics problems related to 〈em〉in situ〈/em〉 observation on real ice.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉On the basis of Argo profile data of the temperature and salinity from January 2001 to July 2014, the spatial distributions of an upper ocean heat content (OHC) and ocean salt content (OSC) of the western Pacific warm pool (WPWP) region and their seasonal and interannual variations are studied by a cyclostationary empirical orthogonal function (CSEOF) decomposition, a maximum entropy spectral analysis, and a correlation analysis. Probable reasons for variations are discussed. The results show the following. (1) The OHC variations in the subsurface layer of the WPWP are much greater than those in the surface layer. On the contrary, the OSC variations are mainly in the surface layer, while the subsurface layer varies little. (2) Compared with the OSC, the OHC of the WPWP region is more affected by El Niño-Southern Oscillation (ENSO) events. The CSEOF analysis shows that the OHC pattern in mode 1 has strong interannual oscillation, with eastern and western parts opposite in phase. The distribution of the OSC has a positive-negative-positive tripole pattern. Time series analysis shows that the OHC has three phase adjustments with the occurrence of ENSO events after 2007, while the OSC only had one such adjustment during the same period. Further analysis indicates that the OHC variations are mainly caused by ENSO events, local winds, and zonal currents, whereas the OSC variations are caused by much more complex reasons. Two of these, the zonal current and a freshwater flux, have a positive feedback on the OSC change in the WPWP region.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Miocene epoch marks the most crucial period during the Cenozoic cooling trend, characterized by the Middle Miocene Climatic Optimum (MMCO) and a series of short–lived cooling events (Miocene isotope events). To understand the paleoenvironmental evolution along the shallow water shelf in the South China Sea during the Miocene, the benthic foraminiferal assemblage and total organic carbon content (TOC) were analyzed at Hole LF 14 located in the Lufeng Sag, northern South China Sea. Three benthic foraminiferal assemblages (e.g., the 〈em〉Uvigerina〈/em〉 spp. assemblage, the Cibicides spp. assemblage, and the 〈em〉Cibicidoides〈/em〉 spp. assemblage), corresponding to different watermass conditions, were recognized based on Q–mode factor analysis. Early studies suggested that Hole LF14 was deposited under semienclosed bay, middle to outer shelf or even upper bathyal environment during ~18.7–4.53 Ma. The dominant 〈em〉Uvigerina〈/em〉 spp. assemblage was characterized by low diversity and shallow infaunal to infaunal species, indicating a warm, low–oxygenation and eutrophic conditions since the Early Miocene to MMCO (~18.7–14.24 Ma). An abrupt sea level drop and significant faunal changes were recorded during 14.24–13.41 Ma, suggesting development of the East Antarctic Ice Sheets, which resulted in a drop of sea level and change in benthic foraminiferal assemblages along the shallow water shelf. Beyond the 〈em〉Uvigerina〈/em〉 spp. assemblage, the 〈em〉Cibicides〈/em〉 spp. assemblage became important during the middle–late Middle Miocene (14.24–11.54 Ma). This assemblage was dominated by epifaunal species with relative high diversity, suggesting high–energy, high–oxygenation and oligotrophic conditions with episodic supply of organic food. The dominant 〈em〉Cibicidoides〈/em〉 spp. assemblage with high diversity, indicates a mesotrophic conditions with relative high–oxygen content during the Late Miocene to Pliocene (11.54–4.53 Ma). The appearance and continuous occurrence of 〈em〉Ammonia〈/em〉 spp. and 〈em〉Pseudorotalia〈/em〉 spp. since 10.02 Ma, may reflect the influence of the Kuroshio Current.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Phytoplankton physiologies are dynamic and have sensitive responses to the ambient environment. In this paper, we examine photosynthetic physiologies of phytoplankton communities with Phyto-PAM in the eastern equatorial Indian Ocean during the spring inter-monsoon. Environmental parameters were measured to investigate the coupling between phytoplankton photosynthetic physiologies and their habitats. During the cruise, the water column was highly stratified. The mixed layer extended to about 75 m and was characterized by high temperature (〉28°C) and low nutrient level. The 〈em〉F〈/em〉〈sub〉v〈/sub〉/〈em〉F〈/em〉〈sub〉m〈/sub〉 values and chlorophyll 〈em〉a〈/em〉 (Chl 〈em〉a〈/em〉) concentrations were lower at the surface, as consequences of nutrient depletion and photo-inhibition. Subsurface Chl 〈em〉a〈/em〉 maximum (SCM) occurred between 75 and 100 m, and had the highest 〈em〉F〈/em〉〈sub〉v〈/sub〉/〈em〉F〈/em〉〈sub〉m〈/sub〉 values. The formation of SCM was a balance between nutrient availability and light limitation. The SCM may contribute significantly to pelagic food web and primary production in the water column. Phytoplankton in different layers encountered different light, trophic and hydrographic dynamics and evolved distinct photosynthetic characteristics. Despite of co-limitation of nutrient limitation and photo-inhibition, phytoplankton in the surface layer showed their acclimation to high irradiance, had lower light utilization efficiencies (α: 0.061±0.032) and could exploit a wide range of light irradiance. Whereas, phytoplankton in the SCM layers presented the highest light utilization efficiencies (α: 0.146±0.48), which guaranteed higher photosynthetic capacities under low light level. These results provide insights into phytoplankton photo-adaption strategies in this less explored region.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Researchers have calibrated satellite signals successfully using novel artificial intelligence (AI) methods to estimate discharge at ungauged river sites accurately. However, common AI methods including neural networks have a recognized defect in time series forecasting known as input imitation error. The present study addresses this significant source of error by combining evolutionary polynomial regression (EPR) with the Nondominated Sorting Genetic Algorithm (NSGA-II) for multiobjective optimization. This new method of forecasting signal time series is called the evolutionary polynomial regression-time series predictor (EPR-T). EPR-T can simultaneously minimize the model prediction error based on traditional performance indices as well as a new index, peak similarity (PS), to prevent the model from imitating its input variables when forecasting. The prediction accuracy of the new EPR-T and traditional AI methods is compared for six case studies, namely the Connecticut, Missouri, Pee Dee, Red, White, and Willamette rivers. The results demonstrate the considerably superior accuracy of EPR-T over the regular EPR method.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Understanding the changing characteristics and related mechanisms behind precipitation extremes is crucial for developing adaptive measures of water resource management as well as flood risk management. Based on daily precipitation measurement taken at 57 meteorological stations from 1960 to 2016, the variability of precipitation extremes over the Yangtze River Delta (YRD) is analyzed utilizing a Mann-Kendall trend test as well as a Hurst exponent analysis. Moreover, the climatic teleconnection that occurs from large-scale atmospheric circulation and such precipitation extremes is also investigated with the help of a wavelet coherence analysis. Results indicate that most extreme precipitation indices predominantly exhibit significant positive trends, indicating a wetting trend in the YRD over the past 61 years. Meanwhile, the contribution of precipitation of very wet days to annual total wet-day precipitation increased significantly. Furthermore, the increasing trend of precipitation extremes in the YRD is found to be attributable to the frequency and intensity, rather than to the duration of extreme precipitation events. The patterns of variation in these precipitation extremes reveal dramatic spatial heterogeneity, with extreme events concentrated primarily along the coastal plains. Overall, the YRD will likely face more severe flood risks in the foreseeable future. This is especially the case for the southern and central-western regions of the YRD. In contrast, the northern region of the YRD is forecast to become drier over time. The increasing trends in precipitation extremes for the YRD observed in this study are found to be linked closely with the positive anomalies of the El Niño-Southern Oscillation as well as the negative anomalies of the East Asian summer monsoon.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉One of the solutions for resolving the problem of energy production deficit in Central Africa is to promote renewable energy sources. The knowledge of the solar variability represents a determining factor for design, dimensioning, performance assessment, and energetic management of renewable energy conversion systems. In this work, we analyze the behaviour of solar radiation from diurnal to seasonal time scales for the region of Douala, the largest industrial city of Cameroon. Observed data of temperature, sunshine duration and precipitation, and satellite estimates of solar radiation (from Soda Solar Project) and cloudiness (acquired from Meteosat Second Generation) were used. The results show that the solar radiation annual cycle at Douala can be decomposed into four seasons: the main dry season in December–January–February (DJF) which corresponds to the most illuminated season, the main rainy season in June–July–August–September (JJAS) which is the least illuminated, and two intermediate periods, March–April–May (MAM) and October–November (ON) which correspond to semi-illuminated periods. Using a hierarchical clustering analysis (HCA), we found that Douala usually experiences five main types of solar radiation diurnal cycles depicting very bright to obscure days. A characterization of sky conditions during these five diurnal cycles shows a predominance of low and high opaque clouds during obscure days.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The relationship between blocking events and mean precipitation frequency (MPF) was investigated in this work for Turkey during 1977–2016. The overall MPF for the examined stations during blocked days (nonblocked days) fluctuated between 0.15 and 0.43 (0.12 and 0.38). The ratio of MPF during the blocked days to nonblocked days ranges between 12 and 38%. During the winter season, the country has higher MPF values during blocked days. The greatest ratio of MPF values during blocked days to nonblocked days is observed in summer due to smaller values of MPF occurring during this season overall. Higher MPF occurs when the event center was located between 0〈sup〉o〈/sup〉 and 30〈sup〉o〈/sup〉 E (mean 0.27, range 0.17–0.51). There is no relationship between blocking duration and MPF for all seasons. There is a positive relationship between blocking intensity and MPF during summer (CC = 0.35, significant at the 95% level) and fall (CC = 0.43, significant at the 95% level). The relationship between blocking longitudinal extent and MPF is significant at the 95% confidence level during the summer and fall seasons with correlation coefficients of 0.29 and 0.25, respectively. A composite of the 10 blocking events associated with the largest MPF demonstrated that there is moist advection via westerly flow into Turkey in all seasons. During winter, a greater proportion of these events is observed during the La Niña phase of El Niño Southern Oscillation, but during El Niño in spring and summer. For the blocking case study (31 October to 5 November 2009) associated with the largest MPF, the mean value across the country was 0.73. The mean total precipitation during this period was 63.4 mm.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor- and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water (salinity 25, 17, 13 and 7.5), the effective Photosystem II quantum yield (Δ〈em〉F〈/em〉/〈em〉F〈/em〉〈sub〉m〈/sub〉′) decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching (NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water (salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased Δ〈em〉F〈/em〉/〈em〉F〈/em〉〈sub〉m〈/sub〉′ accompanied with increased NPQ, and followed by the recovery-induced increase in Δ〈em〉F〈/em〉/〈em〉F〈/em〉〈sub〉m〈/sub〉′ and decrease in NPQ. A similar response pattern as Δ〈em〉F〈/em〉/〈em〉F〈/em〉〈sub〉m〈/sub〉′ to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon (〈sup〉14〈/sup〉C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this paper, trends of minimum and maximum temperatures in Iran were studied using time series of daily minimum and maximum temperatures of 45 meteorological stations from 1976 to 2005 (as the baseline period). Mann-Kendall test, for maximum and minimum temperature, was obtained 1.85 and 3.56, respectively, which was positive and significant. The slope of the trend line for maximum and minimum temperature was obtained 0.23 and 0.39 °C decade〈sup〉−1〈/sup〉, respectively. In this study, the trend of extreme temperature indicators was also evaluated. According to the obtained results, in annual terms, TX10, FDO, TN10, and IDO indices have had a negative trend at most stations, but TX90, TR20, TNx, TNx, TXn, TN90, SDI, and SU25 indices showed a positive trend. In the seasonal scale, the indices of cold days (TX10) and cold nights (TN10) showed significant negative trends in most seasons. Warm days (TX90) and warm nights (TN90) showed significant positive trends at most stations. The results of future simulations using several general circulation models in different time periods showed that the highest increase in maximum and minimum temperature related to the RCP8.5 scenario in periods of 2071 to 2099. The results also showed that northwest of Iran would have the highest temperature rise. The results also showed that the probability density function of the minimum and maximum temperatures will shift to warmer temperatures. This could be an indication of climate change in the future decades in Iran.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper analyses a recently created continuous 305-year (1711–2016) monthly rainfall series for the island of Ireland. The findings are as follows. The excess skewness in the monthly series may be eradicated by using a Box-Cox transformation with parameter equal to 0.6: a value very similar to that found for the U.K. and its regions. There is no evidence of either an overall stochastic trend or of evolving monthly seasonal patterns, but positive linear trends are found for January, March, and December and a negative linear trend is found for July. Analysis of the seasonal and annual series (which require no transformation) confirms the implication from the monthly data that winters have become progressively wetter and summers progressively drier, with the positive linear trend for winter being twice the size of the negative summer trend. Since there is no trend in either spring or autumn rainfall, annual rainfall shows a positive linear trend. Given that the rainfall series exists for over three centuries, breaks and structural shifts in the model were investigated. Five breaks were identified, three of which occurred in the early portion of the series during the eighteenth century. However, trends were found to be much more stable from the middle of the nineteenth century. For the seasonal series, only a single break, at 1790 for the winter series, was found: it was only after this break that winters became wetter; before then, winter rainfall had a negative trend. In terms of predictability, predictions from the model were found to be more volatile during the second half of the eighteenth century and again from 1976 onwards.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Soil moisture (SM) feedback on climate variables especially temperature is an important aspect in land-atmosphere coupling. Based on the Global Land Data Assimilation System (GLDAS) V2.0 SM data and the gridded observational temperature data, we statistically analyze the thermal feedback of SM over North China (NC). The results show that SM exerts a decreasing trend under the background of evident warming over NC, inducing a decadal enhancement of SM feedbacks on the local temperature and extreme hot events. The SM feedback contributes 6% of the total air temperature variation during 1961–2012, while it reaches 36% after the regional warming during 1994–2012. Such SM affecting temperature is mainly reflected in its feedback on daily maximum temperature, which is also intensified during the warm period. The decadal intensification is also found in the feedback of SM on hot extremes. Further analyses show that the abnormal changes of the latent and sensible heat fluxes caused by the SM anomaly are the main reasons that affect the thermal conditions. Besides, the rising Bowen ratio indicates that upward thermal transfer on the land surface is enhanced in recent years, which suggests that the atmosphere is more sensible to the abnormal heating on the ground. This consequently translates into the decadal intensification of the local thermal feedback of SM in summer over NC.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Investigation of precipitation characteristics on daily, monthly, and annual time scales can contribute to gaining important information related to temporal and spatial distribution of precipitation or even flow rate challenges (e.g., hydrological droughts). The low levels of long-term precipitation and high variability in different time scales are considered the main inherent characteristics of climate in Iran. Due to the direct effects of precipitation on water resources, especially on the river flow rate, it is necessary to assess the efficient indices to visualize the variations in the components of water resources. One of the main indices is the precipitation concentration index (PCI) which is known as a strong indicator of the precipitation distribution generally used on annual and seasonal scales. In this study, drought analysis in the Lake Urmia Basin (LUB) located in northwest of Iran was performed with the daily river flow rate and monthly precipitation values within the period of 1984–2013. The results of changes in precipitation indicated that the irregularity of precipitation distribution had grown in spring months. Also, due to the diminishing precipitation trend on the annual time scale, PCI index also increased. It is concluded that LUB detected a significant descending trend on the annual, spring, and winter time scales in the last 30 years. The PCI values were proved high irregularity in summer with PCI amount of 20.1 and most regularity in winter with PCI amount of 10.4. This paper also aims to assess the effects of PCI on the river flow rate along with the flow shortness volume values using hydrometric and rain gauge stations within LUB. The results obtained from the changes in river flow rate and flow shortness volume revealed that the river flow rate has mostly a falling trend. Finally, it was observed that the time when the river flow rate data changed happened after beginning of changes in the precipitation data. A decrease in inflow from 900 million cubic meters up to 14 billion cubic meters with high flow shortness volume may happen in worst conditions. These results highlighted the importance of applying water resources management in LUB.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Cluster extreme event (CEE), which is characterized by large affected area and long duration of extreme weather, has been arousing the worldwide serious concerns due to its severe impact on society. The winter cluster extreme events of low temperature (LT_CEEs) in the northern hemisphere from 1979 to 2013 are identified with a simplified objective method based on ERA-Interim and JRA-25 daily minimum surface air temperature. The probability density function (PDF) distributions of most indices in the winter LT_CEEs derived from the two datasets are well consistent with each other, especially in the occurrence frequency, duration, and affected area. As expected, the downward trend of all indices in recent 35 years under global warming is congruously revealed from both reanalysis. Nevertheless, the various indices of the winter LT_CEEs after 1998 are generally stable accompanied with slight upward trend, which might be closely related to the speed slowdown of global warming but require further investigation. Similar analysis was carried out with the simulated results of BCC_CSM1.1 model under four scenarios of RCP2.6, RCP4.5, RCP6.0, and RCP8.5. The occurrence frequency of the winter LT_CEEs under RCP2.6 remains stable after 2050, but significantly decreases under RCP4.5 and RCP6.0, and disappears under RCP8.5 scenario. Overall, the descent rate of the winter LT_CEEs accelerates with the emission rise.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Protease-producing bacteria and their extracellular proteases are key players in degrading organic nitrogen to drive marine nitrogen cycling and yet knowledge on both of them is still very limited. This study screened protease-producing bacteria from the South China Sea sediments and analyzed the diversity of their extracellular proteases at the family level through N-terminal amino acid sequencing. Results of the 16S rRNA gene sequence analysis showed that all screened protease-producing bacteria belonged to the class Gammaproteobacteria and most of them were affiliated with different genera within the orders Alteromonadales and Vibrionales. The Nterminal amino acid sequence analysis for fourteen extracellular proteases from fourteen screened bacterial strains revealed that all these proteases belonged to the M4 family of metalloproteases or the S8 family of serine proteases. This study presents new details on taxa of marine sedimentary protease-producing bacteria and types of their extracellular proteases, which will help to comprehensively understand the process and mechanism of the microbial enzymatic degradation of marine sedimentary organic nitrogen.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Subei Shoal is a special coastal area with complex physical oceanographic properties in the Yellow Sea. In the present study, the distribution of phytoplankton and its correlation with environmental factors were studied during spring and summer of 2012 in the Subei Shoal of the Yellow Sea. Phytoplankton species composition and abundance data were accomplished by Utermöhl method. Diatoms represented the greatest cellular abundance during the study period. In spring, the phytoplankton cell abundance ranged from 1.59×10〈sup〉3〈/sup〉 to 269.78×10〈sup〉3〈/sup〉 cell/L with an average of 41.80×10〈sup〉3〈/sup〉 cell/L, and 〈em〉Skeletonema〈/em〉 sp. and 〈em〉Paralia sulcata〈/em〉 was the most dominant species. In summer, the average phytoplankton cell abundance was 72.59×10〈sup〉3〈/sup〉 cell/L with the range of 1.78×10〈sup〉3〈/sup〉 to 574.96×10〈sup〉3〈/sup〉 cell/L, and the main dominant species was 〈em〉Pseudo-nitzschia pungens, Skeletonema〈/em〉 sp., 〈em〉Dactyliosolen fragilissima〈/em〉 and 〈em〉Chaetoceros curvisetus〈/em〉. The results of a redundancy analysis (RDA) showed that turbidity, temperature, salinity, pH, dissolved oxygen (DO), the ratio of dissolved inorganic nitrogen to silicate and SiO〈sub〉4〈/sub〉-Si (DIN/SiO〈sub〉4〈/sub〉-Si) were the most important environmental factors controlling phytoplankton assemblages in spring or summer in the Subei Shoal of the Yellow Sea.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Surface sensible heat flux (〈em〉SH〈/em〉) and latent heat flux (〈em〉LH〈/em〉) are important variables linking the energy and hydrological cycles over the Tibetan Plateau (TP). Through comparison with eddy covariance observations of turbulent fluxes at two sites from 2013 to 2015 and at eight sites in August 2014 over the TP, five reanalysis flux products were evaluated for monthly mean biases and daily variations after bilinear interpolation. The results showed the JRA-55 and ERA-Interim reanalyses had optimal performances regarding 〈em〉SH〈/em〉, while NCEP2 had reasonable performance regarding 〈em〉LH〈/em〉. The 〈em〉SH〈/em〉 in the reanalysis data generally reached maximum negative biases in winter and minimum positive biases in summer, whereas the seasonal bias of 〈em〉LH〈/em〉 was found opposite to that of 〈em〉SH〈/em〉. The diurnal variation of reanalysis fluxes was found consistent with observed data at most sites, and the diurnal 〈em〉SH〈/em〉 and 〈em〉LH〈/em〉 maxima were all overestimated except 〈em〉SH〈/em〉 in the JRA-55 at Nagri. The 〈em〉SH〈/em〉 bias and the bias of the surface wind speed in NCEP2 were highly significantly correlated, suggesting the bias in the surface wind dominates the 〈em〉SH〈/em〉 bias over the TP in NCEP2. Large spreads of averaged biases and standard deviation errors were found among the five reanalysis bulk variables. In particular, the maximum-minimum ranges of the biases of surface wind speed and ground-air–specific humidity contrast were 〉 5 m s〈sup〉−1〈/sup〉 and 〉 15 g kg〈sup〉−1〈/sup〉, respectively.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Autumn rain of West China (ARWC), a typical climate phenomenon characterized by continuous rainfall, is prone to flooding and secondary disasters. The ARWC in 2017, the greatest one since the last 30 years, resulted in an economic loss of 1.9 billion dollars and serious social impacts. It is thus urgent to understand the cause for this anomaly. In this article, the atmospheric circulations affecting the 2017’s ARWC are identified. They are (1) a dipole pattern with the blocking over Europe and the trough over Lake Balkhash, which favors the southward outbreak of cold airs into West China, (2) increased water vapor transportation toward West China from the Pacific and Indian Oceans, and (3) a strengthening and northward displacement of the East Asian jet stream. The cold sea surface temperature anomaly (SSTA) in the equatorial central Pacific provides a superimposed effect. Further analysis reveals a synergic role in the interannual variability of the ARWC from the anomalies of the atmospheric circulation over Lake Balkhash and the SST in the equatorial central Pacific. The combination of anomalous trough over Lake Balkhash with cold SSTA in the equatorial central Pacific is most favorable for the increase of ARWC, while that of anomalous ridge with warm SSTA generally results in a decrease of ARWC. The combination of anomalous ridge with cold SSTA or that of anomalous trough with warm SSTA has no specific indication for ARWC anomalies.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The statistical characteristics of precipitation play an extremely important role in the risk assessment of drought and flood disasters and water resource management. In this paper, the precipitation concentration degree (PCD), precipitation concentration period (PCP) and precipitation concentration index (PCI) were used to analyse the spatiotemporal variation in precipitation concentration characteristics in China from 1960 to 2015. In addition, the cross-wavelet transform was used to analyse the possible dependencies and spatial characteristics between these three precipitation concentration indices (PCD, PCP and PCI) and monsoon indices (East Asian summer monsoon index, EASMI; South Asian summer monsoon index, SASMI; and South China Sea summer monsoon index, SCSSMI) of nine river basins in China. The results show that the spatial distribution of precipitation concentration indices in China has obvious north-south and east-west variability. China’s precipitation concentration indices are generally declining, with weak volatility. Among these indices, the PCD (〈em〉P〈/em〉 〈 0.05) and PCI (〈em〉P〈/em〉 〈 0.01) have decreased significantly at rates of − 0.005/10 year and − 0.006/10 year, respectively, while there has been no obvious decrease in the PCP. Compared with the PCD before 1978, the PCD in the rainy season after 1978 has decreased. In most areas, the rainy season is concentrated in July every year; however, the rainy season has been delayed in the middle and lower reaches of the Yangtze River and has advanced mainly in the other basins. The PCI has declined since 1978, indicating a decreasing contribution of heavy precipitation to the total annual precipitation, but this change in the PCI has occurred mainly at high-value stations (PCI 〉 0.7), and the PCI at low-value stations has increased. Most of China’s precipitation concentration indices and monsoon indices, as well as the NWRB, have small-scale (2–4 years) or medium-scale (12–15 years) oscillation periods. The oscillation periods between the precipitation concentration indices and monsoon indices in the Yangtze and Pearl River basins are more significant than those in other basins. The results of this study can help to understand the differences among the precipitation concentration characteristics in different basins in China and the intrinsic relationship between these characteristics and the summer monsoon and provide a reference for further research.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Water requirement is sensitive to the impacts of climate change, especially in Bangladesh because of limited freshwater availability in the dry season, despite the fact that the country’s agriculture sector requires large quantities of water for the crop production. Hence, gaining a better understanding of changes in water requirements in Bangladesh during dry periods is important in the management of agricultural water resources. This study assesses the recent impacts of climate change on the design water requirement (DWR) of the Boro rice–growing season in Bangladesh using a frequency analysis over a 5-year period. The reference evapotranspiration (ET〈sub〉ref〈/sub〉), crop evapotranspiration (ET〈sub〉p〈/sub〉), effective rainfall (ERF), and gross irrigation water requirements (GIWR) of Boro rice were estimated based on daily weather data for the period of 1984–2013 using the CROPWAT8.0 model. The results showed the significant decreasing trends of ET〈sub〉ref〈/sub〉 in most of these Boro rice growth stages in all districts. The GIWR of Boro rice and its trends demonstrated significant spatial heterogeneity in the last three decades due to significant changes in the ERF and ET〈sub〉p〈/sub〉. The DWR of Boro rice–growing season also supported the results of the GIWR, and the Weibull probability distribution function (PDF) is found to be an optimal PDF among eight PDFs for the estimation of DWR. Overall, the results indicate that a recent climate change does not only contribute to high water demands for the crop but also result in decrease water requirements due to variations in wind speed, sunshine hours, and relative humidity.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study assesses the high-resolution, 0.11° (12 km), Canadian Regional Climate Model Version 5 (CRCM5), interactively coupled to the one-dimensional Freshwater Lake model (FLake), to predict wintertime precipitation along the Canadian snowbelts of Lake Superior and Lake Huron. CRCM5–FLake was compared against various datasets to evaluate the 20-year (1995–2014) SWE and wintertime precipitation, seven lake-induced precipitation events and lake effect snowfall (LES) predictor variables during the months of December and January. The findings of SWE along both snowbelts in December and January show MBD ≤− 10 mm and ≤− 30 mm, respectively. Similarly, precipitation results along both snowbelts in December and January show MBD ≤− 5 mm and ≤− 10 mm, respectively. The negative biases in simulated SWE and precipitation, predominantly along the snowbelts, suggest that the model may un-realistically represent lake effect processes. Comparison of lake-induced precipitation events also indicates that the model mostly under-predicts the daily accumulated precipitation associated with each event but tends to accurately capture the timing and the general location of the squalls along the snowbelts, though not for highly localised snow bands. Furthermore, lake-wide results of LES predictor variables indicate that the model over-estimates lake surface temperature (LST) for both lakes during December and January and under-estimates ice cover concentrations for both lakes in December. The resultant biases could be attributed to limitations within the coupled RCM because the quality of reproducing lake-induced precipitation in this region is highly dependent on the performance of FLake.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study discusses the role of natural factors and related teleconnections for Indian summer monsoon (ISM) with a special emphasis on later two decades of the last century. The combined influence of the sun and volcanos on ISM is examined using observational data as well as CMIP5 model outputs. Possible mechanisms relating to a disruption of the usual ENSO-ISM teleconnection for those decades are explored. Observation suggested that the regional Hadley circulation, via the NAO in the northern hemisphere and Indian Ocean Dipole in the southern hemisphere, may have a role in the change in ISM behaviour. Such features though captured well in the observation are shown missing in models. Additionally, it indicates that differences among models mainly originate in a regional level, which could be due to inconsistency in representing regional teleconnection features. Interestingly, all models perform reasonably well in terms of global thermodynamic scaling arguments. The overall study underpins important areas, where natural factors influence regional climate, but models miss out and suggest discrepancies among each other. Such knowledge has major implications in regional as well as global scale. The modelling community will also greatly benefit by an improved representation of ENSO and ISM in models.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In the context of global warming, the future spatiotemporal distribution of aerosols in China is a common concern of the government and the scientific community. In this study, the regional climate model RegCM4 is used to simulate the spatiotemporal distribution of anthropogenic aerosols including sulfate, black carbon, and organic carbon in China around 2030 under the RCP4.5 and RCP8.5 scenarios and estimate the contributions of climate difference, emission difference, and extra-regional transport difference to the change of anthropogenic aerosol concentration in the study area. The results show that the annual average concentrations of anthropogenic aerosols around 2030 decreased significantly with respect to those around 2010, and the decrease amplitude of black carbon surface concentration is the smallest, especially in the RCP8.5 scenario. The annual averages for sulfate, black carbon, and organic carbon surface concentrations in the central and eastern parts of China will be 8.5, 1.7, and 3.7 μg m〈sup〉−3〈/sup〉, respectively, under the RCP4.5 scenario, whereas 10.0, 2.2, and 4.4 μg m〈sup〉−3〈/sup〉, respectively, under the RCP8.5 scenario. The surface concentration of sulfate is higher in summer and spring, while lower in winter and autumn. The surface concentrations of black carbon and organic carbon are higher in winter and lower in other seasons. The results of sensitivity experiments demonstrate that the future difference in local emissions between RCP8.5 and RCP4.5 scenarios has the greatest impact on the anthropogenic aerosol concentrations throughout China, while the effects of future climate difference and extra-regional transport difference are much smaller around 2030. For the aerosol column burdens, the effect of future local emission difference between the two scenarios is still dominant, and the effect of extra-regional transport difference becomes very significant during spring and winter for organic carbon and black carbon. The results of this paper suggest that the impacts of future climate difference and extra-regional transport difference between RCP8.5 and RCP4.5 scenarios on anthropogenic aerosols are non-negligible in certain regions and seasons besides the impact of future local emission difference in China around 2030.〈/p〉

Description: 〈p〉Equations 1–4 have been typed wrongly during the steps of corrections and some figures and tables are placed way too far from the citations.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉It is undeniable that winter weather is the most dangerous for all road users. Temperate climate creates winter weather conditions that are definitely challenging for road maintenance specialists: one year can be excessively snowy and relatively warm (high daily accident risk and maintenance costs), while the other would be cold and dry (lack of preparedness, lower maintenance, but higher standby costs). Therefore, with ongoing climate change, it is uncertain what weather can be expected in the future, especially with current predictions claiming climate change will bring higher variability and more frequent weather extremes. In order to estimate future impacts of climate change to road conditions (and traffic safety) during temperate winter, an analysis of climate model predictions was performed, using Lithuania as an example of such climate conditions. The focus of this analysis is on meteorological variables that are unfavourable for roads: number of days when air temperature fluctuates around 0 °C, number of days with snow and number of days with adverse driving conditions. Several time periods were chosen: reference (1986–2005), near-term (2016–2035) and long-term (2081–2100). The projections were made using Coupled Model Intercomparison Project Phase 5 (CMIP5) outputs of 4 Representative Concentration Pathways (RCP2.6, RCP4.5, RCP6.0 and RCP8.5). The data outputs of 3 global circulation models (GFDL-CM3, NorESM1-M and HadGEM2-ES) were statistically downscaled for meteorological stations in different regions of Lithuania in order to create distribution maps of climatic variables in the twenty-first century. Results showed that winter driving conditions should improve, and maintenance levels should decrease by the end of the twenty-first century. Nevertheless, a possibility remains that road maintenance and traffic safety might become less effective due to lack of awareness and preparedness, resulting in sudden and unexpected worsening of driving conditions on a day to day basis.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A prevailing, controversial hypothesis is that fishing pressure has played a greater role than climatic and environmental drivers, in changing fish species succession and biomass fluctuation in the South China Sea (SCS). Based on otter trawl survey data from 1959 to 2010 in the outer Beibu Gulf (OBG), northern SCS, large seasonal and interannual variation is reported for fish species composition, the proportional abundances of dominant taxa, and fish biomass. Generalized additive models are developed to quantify relationships between fish biomass and the external factors of fishing pressure and climate change. Fishing pressure proved to be the main driver of sharp declines in demersal fish stocks, with high-value species being replaced by low-value ones over time. Abrupt decreases in fish biomass during the years of 1993 and 1998 correspond to El Niño events, with climate change possibly the main driver of proportional representation of pelagic species in fisheries trawl catch. The need to differentiate impacts of fishing and environmental drivers on fish species with different life history strategies is stressed to better understand fish community dynamics.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉We quantified the 〈em〉δ〈/em〉〈sup〉13〈/sup〉C and 〈em〉δ〈/em〉〈sup〉15〈/sup〉N values in the lower beaks of Humboldt squid, 〈em〉Dosidicus gigas〈/em〉, collected from international waters off Costa Rica, Ecuador, Peru and Chile by Chinese squid jigging vessels during 2009, 2010 and 2013. There was a significant difference in the isotopic values among regions with the lowest value off Ecuador and the highest off Chile, which were interpreted as a function of trophic effects as well as baseline values. However, constant trophic level of 〈em〉D. gigas〈/em〉 across its geographic range showed that spatial variation in the baseline of primary production is the main driver responsible for the observed geographic isotope variability. Inter-regional difference and intra-regional convergence of isotope values indicated squid off Costa Rica, Ecuador and Chile belong to different geographically segregated populations, which were previously proved by integrated population identifying method. In contrast, the higher variations in 〈em〉δ〈/em〉〈sup〉13〈/sup〉C and 〈em〉δ〈/em〉〈sup〉15〈/sup〉N values in a given size group suggest the squid off Peru move and forage in different places. Moreover, potential population exchange could be responsible for the overlap of the isotope values between the squid off Peru and off Chile. On the whole, the spatial difference in isotopic values of Humboldt squid beaks improves our understanding of potential geographic population connectivity and movement.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An enhanced ARTSIST Sea Ice (ASI) algorithm is presented based on a data fusion method of calculating total sea ice concentration from high-frequency microwave data. Algorithms that use low-frequency data to calculate total sea ice concentration are less affected by atmosphere, but their spatial resolutions tend to be lower. In contrast, algorithms using high-frequency data have higher spatial resolution but are significantly influenced by atmosphere. Although errors can be eliminated using weather filters, the concentration of mixed pixels cannot be modified. Here, an enhanced ASI algorithm uses the 19 GHz polarization difference to modify the 91 GHz polarization difference, which is substituted into the ASI algorithm to calculate total sea ice concentration. Arctic total sea ice concentration results are obtained based on Special Sensor Microwave Imager Sounder (SSMIS) data on January 3, from 2008 to 2017. Total sea ice area and average concentration using the enhanced ASI algorithm are compared to traditional ASI and NASA Team results. In the Marginal Ice Zone, there is a considerable difference between the enhanced and traditional ASI algorithm results, with the former much closer to the NASA Team results. The proposed algorithm effectively modifies the concentration of the mixed pixels in the marginal zone.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The migration route of oceanic squid provides critical information for us to understand their spatial and temporal variations. Mark-recapture and electronic tags tend to be problematic during processing. Cephalopod hard structures such as the beak, containing abundant ecological information with stable morphology and statolith-like sequences of growth increments, may provide information for studying spatio-temporal distribution. In this study, we developed a method, which is based on elemental concentration of beaks at different ontogenetic stages and sampling locations, to reconstruct the squid migration route. We applied this method to 〈em〉Ommastrephes bartramii〈/em〉 in the North Pacific Ocean. Nine trace elements were detected in the rostrum sagittal sections (RSS) of the beak using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). For those elements, significant differences were found between the different ontogenetic stages for phosphorus (P), copper (Cu) and zinc (Zn). Sodium (Na), P and Zn were chosen as indicators of sea surface temperature (SST) and a regression model was estimated. The high probability of occurrence in a particular area represented the possible optimal squid location based on a Bayesian model. A reconstructed migration route in this study, combining all the locations at different ontogenetic stages, was consistent with that hypothesized in previous studies. This study demonstrates that the beak can provide useful information for identifying the migration routes of oceanic squid.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉〈em〉Euphausia superba〈/em〉 is a key species in the Southern Ocean that serves as a link between primary production and higher trophic levels. To investigate the feeding strategies of 〈em〉E. superba〈/em〉 from the eastern South Shetland Islands, fatty acid biomarkers, stable isotope signatures, and an incubation experiment were conducted. The results of the incubation experiment proved that adult 〈em〉E. superba〈/em〉 mainly fed on 2–20 μm particles, demonstrating the importance of nanoplankton in their diet. Moreover, significant positive relationships between 〈em〉δ〈/em〉〈sup〉15〈/sup〉N and body size demonstrated that size-related dietary shifts were present in 〈em〉E. superba〈/em〉. Evidence from principal component analysis and the C16:1ω7/C18:4ω3 ratio showed that juveniles preferentially fed on dinoflagellates and adults were more likely to feed on diatoms. Fatty acid profiles in adult 〈em〉E. superba〈/em〉 roughly mirrored the different trophic conditions and feeding strategies between stations. Adult 〈em〉E. superba〈/em〉 at Stas D2-07, D5-07, DA-01 and DA-02 exhibited elevated levels of C16:1ω7, C18:4ω3, C18:1ω9 and C18:1ω9/C18:1ω7, indicating higher levels of feeding on both phytoplankton and higher trophic diets. In contrast, adult 〈em〉E. superba〈/em〉 at Stas D1-03 and D1-04 were characterized by high levels of polyunsaturated fatty acids/saturated fatty acids ratios and low levels of C16:1ω7, C18:1ω7, C18:4ω3, C18:1ω9 and total fatty acids. We inferred that adult krill at Stas D1-03 and D1-04 still suffered from difficult dietary conditions after overwintering. The different dietary conditions between stations suggest a highly plastic feeding strategy of 〈em〉E. superba〈/em〉 in the eastern South Shetland Islands.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Pacific saury is an important high-seas fishery resource in the Northwest Pacific Ocean for the Chinese Mainland. Reliable and accurate catch per unit effort (CPUE) plays a significant rule in Pacific saury stock assessment. Many statistical models have been used in the previous CPUE standardization research. Here, we compare the performance of Generalized Linear Models (GLMs) and Generalized Additive Models (GAMs) using CPUE data collected from Chinese saury fishery in the Northwest Pacific Ocean from 2003 to 2017 (excluding data from Chinese Taipei), and evaluate the influence of spatial, temporal, environmental variables and vessel length on CPUE. Optimal GLM/GAM models were selected using the Bayesian information criterion (BIC). Explained deviance and 5-fold bootstrap cross-validation results were used to compare the performance of the two model types. Fitted GLMs accounted for 21.57% of the total model-explained deviance, while GAMs accounted for 38.95%. Predictive performance metrics and 5-fold cross-validation results showed that the best GAM performed better than the best GLM. Therefore, we recommend GAM as the preferred model for standardizing CPUE of Pacific saury in the Northwest Pacific Ocean.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉It is important to find a reliable method to estimate maximum sustainable yield (MSY) or total allowable catch (TAC) for fishery management, especially when the data availability is limited which is a case in China. A recently developed method (CMSY) is a data-poor method, which requires only catch data, resilience and exploitation history at the first and final years of the catch data. CMSY was used in this study to estimate the biological reference points for Largehead hairtail (〈em〉Trichiurus lepturus〈/em〉, Temminck and Schlegel) in the Yellow Sea and Bohai Sea, based on the fishery data from 〈em〉China Fishery Statistical Year Books〈/em〉 during 1986 to 2012. Additionally, Bayesian state-space Schaefer surplus production model (BSM) and the classical surplus production models (Schaefer and Fox) performed by software CEDA and ASPIC, were also projected in this study to compare with the performance of CMSY. The estimated MSYs from all models are about 19.7×10〈sup〉4〈/sup〉–27.0×10〈sup〉4〈/sup〉 t, while CMSY and BSM yielded more reasonable population parameter estimates (the intrinsic population growth rate and the carrying capacity). The biological reference points of 〈em〉B〈/em〉/〈em〉B〈/em〉〈sub〉MSY〈/sub〉 smaller than 1.0, while 〈em〉F〈/em〉/〈em〉F〈/em〉〈sub〉MSY〈/sub〉 higher than 1.0 revealed an over-exploitation of the fishery, indicating that more conservative management strategies are required for Largehead hairtail fishery.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Based on a comparison of synchronized temperature and salinity data collected in the eastern Qiongzhou Strait and at coastal marine stations, this study finds that, in summer, the variation in salinity near the Weizhou Island in Guangxi is similar to that in the eastern and central portions of the Qiongzhou Strait. Additionally, the Beihai Station in Guangxi exhibits a small salinity variation, whereas the Longmen and Bailongwei Stations, both of which are located far from the Qiongzhou Strait, mainly exhibit continental hydrological characteristics in summer. Moreover, a comparison of the multi-year ocean current data from the Qiongzhou Strait and ocean current observations from the Weizhou Island Station and recently installed current-measuring stations shows that the residual current in the Qiongzhou Strait flows westward in winter and summer. The numerical simulation results also indicate that water from the eastern Qiongzhou Strait enters the Beibu Gulf. The characteristics of the temperature and salinity distributions and analyses of the residual currents further confirm that the western Guangdong coastal current is the main source of the westward transport of water in the Qiongzhou Strait. The primary driver of the formation of the western Guangdong coastal current is the westward flow of freshwater from the Zhujiang (Pearl) River. This water enters the Beibu Gulf via the Qiongzhou Strait and enhances the formation of the cyclonic circulation in the northern Beibu Gulf. In summer, the strong influence of the southwesterly wind leads to the formation of a strong northward coastal current along the western coast of the Beibu Gulf. This process promotes the transport of low-salinity diluted water toward the open ocean and the formation of larger-scale cyclonic circulation around Weizhou Island in the eastern Beibu Gulf. The results of this study regarding the effects of the water inflow from the eastern Qiongzhou Strait to the Beibu Gulf on the Guangxi coastal circulation directly challenge conventional conclusions concerning the transport direction of water through the Qiongzhou Strait in winter and summer.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Yangjiang-Yitongdong Fault (YJF) is an important NW-trending regional fault, which divides the Zhujiang (Pearl) River Mouth Basin (ZRMB) into western and eastern segments. In Cenozoic, the northern continental margin of the South China Sea (SCS) underwent continental rifting, breakup, seafloor spreading and thermal subsidence processes, and the Cenozoic activities of YJF is one part of this series of complex processes. Two long NW-trending multichannel seismic profiles located on both sides of the YJF extending from the continental shelf to Continent-Ocean Boundary (COB) were used to study the tectonic and sedimentary characteristics of western ZRMB. Using the 2D-Move software and back-stripping method, we constructed the balance cross-section model and calculated the fault activity rate. Through the comprehensive consideration of tectonic position, tectonic evolution history, featured structure, and stress analysis, we deduced the activity history of the YJF in Cenozoic. The results showed that the YJF can be divided into two segments by the central uplift belt. From 65 Ma to 32 Ma, the YJF was in sinistral motion as a whole, inherited the preexisting sinistral motion of Mesozoic YJF, in which, the southern part of YJF was mainly in extension activity, controlling the formation and evolution of Yunkai Low Uplift, coupled with slight sinistral motion. From 32 Ma to 23.8 Ma, the sinistral motion in northern part of YJF continued, while the sinistral motion in southern part began to stop or shifted to a slightly dextral motion. After 23.8 Ma, the dextral motion in southern part of YJF continued, while the sinistral motion in northern part of YJF gradually stopped, or shifted to the slightly dextral motion. The shift of the YJF strike-slip direction may be related to the magmatic underplating in continent-ocean transition, southeastern ZRMB. According to the analysis of tectonic activity intensity and rift sedimentary structure, the activities of YJF in Cenozoic played a regulating role in the rift extension process of ZRMB.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Paralytic shellfish toxins (PSTs) are notorious neurotoxins that threaten public health and food safety worldwide. Although PST monitoring programs have recently been established throughout China, the profiles and variation of PSTs in important commercial clams (e.g., 〈em〉Mactra veneriformis, Ruditapes philippinarum〈/em〉, and 〈em〉Meretrix meretrix〈/em〉) along the Jiangsu Province coastline remain largely unexplored. In this study, a validated hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) method was used to examine PST profiles and levels in 540 clam samples from natural production areas along Jiangsu Province coastline during 2014–2016. Although the PST levels (≤6.38 μg saxitotoxin equivalents (eq)/kg) were consistently below European Union regulatory limits (≤800 μg saxitotoxin eq/kg) during this time period, saxitotoxin, decarbamoylsaxitotoxin, and gonyautoxins 1 and 4 were detected, and nearly 40% of the samples were saxitotoxin-positive. The PST levels also varied significantly by seasons, with peak values observed in May during 2014–2016. This is the first systematic report of PSTs in clams from Jiangsu Province, and additional research and protective measures are needed to ensure the safety of clams harvested in this area.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Understanding the effects of inbreeding is critical for the long-term viability of shellfish breeding and for understanding inbreeding depression (ID) of the offspring of selfed individuals and full-sib crosses. The bay scallop (〈em〉Argopecten irradians〈/em〉) is a simultaneous hermaphroditic marine bivalve with distinct male and female gonads and is a species with external fertilization. It is a canonical model invertebrate for analysis of the genetics of ID and evolution of outcrossing mating system. ID in bivalves is well documented with regard to the phenotype and molecular markers aspects, but little is known on how inbreeding affects genome-wide gene expression. Here, we compare the gene expression profiles of adductor muscle of 〈em〉A. irradians〈/em〉 lines inbred to 〈em〉F〈/em〉=0.5 with those of its counterpart outbred lines which are originated from the same paternal individual. Inbred and outbred individuals have some differences in growth traits. The shell length and the total weight of inbred scallops are lower than the counterpart of outbred lines. We found that 1 175 genes were up-regulated while 1 390 were downregulated in inbred lines. Regarding components, differentially expressed genes (DEGs) were concentrated on sarcomeres, contractile filaments, and cell membranes. Among others, whereas regarding their function, the Gene Ontology (GO) was concentrated on transferase, phosphotransferase, peptidase, and others. The DEGs-enriched metabolic pathways mainly belonged to the oxidative phosphorylation pathway and apoptosis pathway. We used another two families to verify our bioinformatic results. The selfed and the outbred family originated from different ancestors, but the selfed family showed obvious ID. By using real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), we verified that DEGs with inbreeding are involved in the oxidative phosphorylation and cell apoptosis pathways, suggesting that inbreeding may affect energy metabolism and homeostasis.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study explored the molecular diversity and biogeography of benthic ciliates in Chinese marginal seas, the Bohai Sea (BHS), North Yellow Sea (NYS) and South Yellow Sea (SYS). From a previous 18S rRNA gene pyrosequencing dataset of the benthic microeukaryotes, we retrieved the sequences affiliated with phylum Ciliophora and analyzed alpha and beta diversities of ciliate communities. We found that BHS had the highest ciliate operational taxonomic unit (OTU) richness than NYS and SYS, whereas the richness was not significantly different between summer and winter. Among all the measured environmental variables, water depth showed consistently the strongest correlations with alpha diversities. Overall, the class Spirotrichea (mostly Choreotrichia and unassigned lineages within the class) dominated the communities in terms of both relative proportion of sequences (77.0%) and OTU richness (66.5%). OTU-level ciliate community structure was significant different among the three basins, but not between the seasons. Structurally, significant differences in relative proportion among the basins were detected for the class Litostomatea, but not for other classes. Partial Mantel tests demonstrated that water depth difference was more important than geographic and environment distances in shaping the community structure of benthic ciliates in the studied area. About 60% OTUs were not assigned at a class or order level and at least 45% OTUs shared a sequence similarity no more than 97% with the described species, indicating a great potential for ciliate species discovery in the offshore sediments. Compared with previous morphology-based surveys, the spatial pattern of ciliate diversity (decreasing from NYS to SYS) is also identified in the present study. Nevertheless, structurally, the dominant class appeared to be Spirotrichea in the sequencing dataset, which differs from previous morphology-based results (dominance of classes Prostomatea and Karyorelictea in biomass). The potential causes for the discrepancies between molecular and morphological findings are also discussed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The carbonate-free fraction of 20 surface sediments collected from the ultraslow-spreading Southwest Indian Ridge (SWIR) was studied by grain size analysis and mineralogical analysis with X-ray powder diffraction (XRD), stereo microscopy and scanning electron microscopy (SEM). The characteristics of the carbonate-free fraction of the sediments were obtained, and related influential factors were discussed. The results show that the mean grain size of this fraction is in 1.96Φ–8.19Φ, with poorly sorting and unimodal, bimodal or irregular bimodal distribution patterns. Four grain size end members of the fraction are derived with the End Member Model method. The finest end member EM1 shows a significant contribution of terrigenous materials of the aeolian input and sediment carried by the bottom current. End member EM2 with medium size mainly reflects sediment of a siliceous bioclast origin. EM3 and EM4 are interpreted as representing the coarser volcanic materials related to bedrock weathering or volcanic activities. Multi-provenance is the dominant factor controlling the grain size pattern of the carbonate-free fraction of the sediments in that area. In addition, sediment transport processes such as the bottom current and wind are the minor factors that influence the grain size distribution of the carbonate-free fraction sediments.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In recent years, the spectacular massive green tide of 〈em〉Ulva prolifera〈/em〉 has become a recurrent phenomenon appearing every summer in the coastal waters off Qingdao (Yellow Sea, China), attracting the attention of scientists and local government. Based on multidisciplinary data collected during summer and winter, this study focuses on the hydrological characteristics and regional biogeochemical processes in coastal waters off Qingdao. The results show that the boundary of the Yellow Sea Cold Water Mass (YSCWM) can reach the Qingdao coastal region in summer and is locally raised to the upper layers to form coastal upwelling beyond tidal mixing and favorable wind. The regional summer upwelling off the Qingdao coast effectively enriches the nutrient concentrations in the upper water column and thus promotes growth of phytoplankton but reduces the dissolved oxygen (DO) concentration and pH value in the bottom. The regional summer upwelling off Qingdao coast may facilitate the growth and regional blooming of the 〈em〉U. prolifera〈/em〉 that migrate to this region with the southerly wind. Additionally, the effects of the front on the aggregation of 〈em〉U. prolifera〈/em〉 may be significant. In winter, the Yellow Sea Warm Current (YSWC) extends and spreads along the offshore region off the Subei Shoal towards the Qingdao coastal sea. This tongue-shaped warm water meets the cold coastal water off Qingdao, which leads to the formation of a physical front. As a consequence, remarkable fronts of nutrient and chlorophyll 〈em〉a〈/em〉 (Chl 〈em〉a〈/em〉) also form between the shoreward warm water and the cold coastal water. This study increases the understanding of the interactions between the regional physical, chemical, and biological processes off the Qingdao coast.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The climatic characteristics of 260 East Asian tropical monsoon depressions (EAMDs) are investigated using the ERA-Interim reanalysis dataset and a tracking dataset of global monsoon low-pressure systems. Most EAMDs form over the South China Sea (SCS) and the western tropical Pacific Ocean in July–October and have an average lifetime of 10 days. The vertical structures of EAMDs are usually upright or tilt slightly westward with height. The warm-over-cold thermal structure is a distinctive characteristic of EAMDs and two potential vorticity (PV) centers are related to the warm core in the upper level and the specific humidity center in the lower level, respectively. We divided the EAMDs into four groups: eastward-moving, westward-moving, turning, and northwestward-moving EAMDs. Most of the eastward-moving EAMDs form over the SCS in May and June, whereas the westward-moving EAMDs form over both the SCS and the western Pacific Ocean in July–October. The turning and northwestward-moving EAMDs are mainly generated over the western Pacific Ocean and have longer lifetimes. The structures of the eastward-moving and turning EAMDs show common characteristics in each stage. Their vertical structures change from upright in the developing and peak stages to northeast tilting with height in the attenuating stage, especially for the specific humidity. By contrast, the structures of westward- and northwestward-moving EAMDs show little change during their lifetime. They are symmetrical relative to the vertical axis of the EAMDs over their whole lifetime and only vary in strength.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉For any given time series, how to optimize its forecast strategies and what prediction model is adopted are of great importance. In order to reach this goal, insight from analyzing predictability of series with known structure information is necessary. Time series generated by theoretical models with four kinds of known predictive structures, i.e., short-term correlation, long-term correlation, and multifractal and chaotic patterns, are applied to demonstrate that there is a well-defined relation between series’ intrinsic predictability and prediction accuracy of any specific prediction model. And results show that both intrinsic predictability and prediction accuracy are enhanced by these well-defined structures. There are different regimes in the relation between intrinsic predictability and prediction accuracy for series with different known deterministic or stochastic predictive structures. These regimes in the relation between intrinsic predictability and prediction accuracy can guide us to preselect a suitable prediction model and forecast strategies for any underlying series by only analyzing the permutation entropy of a given series. Results from three pieces of climate series further confirm that insights from theoretical series with known structure information indeed work well.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The evolution of the natural and pristine Mediterranean coastline Port aux Princes-Sidi Daoued (Gulf of Tunis, NE-Tunisia) is studied during the period of 1887–2010 on the basis of an ancient minute of bathymetry (1887) and aerial photographs treated by numerical photogrammetric methods. Morphological changes of the coastline shows a general retreat despite the absence of the various anthropogenic actions. Adding to the drift currents and the currents of high energy that are generated by the N-W dominant waves along steeply sub-marine funds, the erosion is mainly due to the sea level rise which increased since the beginning of the 2000s. The Port aux Princes-Sidi Daoued coastline works as a single littoral cell limited by Jbel Korbous to the SW and the fishing harbor of Sidi Daoued to the N-E.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Cloud-free moderate-resolution imaging spectroradiometer (MODIS) images of the Zhujiang (Pearl) River Estuary (ZRE) taken between 2002 and 2012 are retrieved and used to study the spatial and temporal patterns of suspended sediment concentrations (SSCs) across the estuary under runoff, wind, and tropical storm conditions. Five typical dispersal patterns of suspended sediments in the estuary are defined: Case I shows generally low SSCs under low dynamics; Case II shows a river-dominant dispersal pattern of suspended sediments from the outlets, particularly from Modaomen, Jiaomen, Hengmen, and others; Case III shows wind-dominant dispersal of high SSCs derived from the west shoal and southwesterly transport under a strong NE wind; Case IV is the combination of relatively large runoff and wind; and Case V is caused by a strong tropical storm with high river discharge and wind, which is characterized by the high SSCs across the entire estuary that are transported eastward by winddriven and buoyancy currents outside the estuary. Runoff is a dominant factor that controls seasonal and annual SSC variations in the ZRE, with the area of high SSCs being largest in the summer and smallest in the spring. The correlation coefficients between the monthly averaged river-suspended sediment discharge and the area of the high SSCs are approximately 0.6. The wind power over the west shoal increases with a wind speed, which induces more sediment resuspension and shows a close relationship between the wind speed and high SSC area.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, we investigate spatial differences in thermal comfort conditions using the net effective temperature (〈em〉NET〈/em〉) considering the synthetic effects of air temperature, relative humidity, and wind speed. Using a daily-scale dataset of maximum air temperature (〈em〉T〈/em〉〈sub〉max〈/sub〉), relative humidity, and wind speed from 518 stations during 1960–2016 across China, we analyze the influence of different climate conditions on 〈em〉NET〈/em〉 or 〈em〉T〈/em〉〈sub〉max〈/sub〉 at three different levels of hot conditions (35 °C 〈 〈em〉T〈/em〉〈sub〉max〈/sub〉 〈em〉〈〈/em〉 37 °C, 〈em〉NET〈/em〉〈sub〉〈em〉T〈/em〉max35〈/sub〉 for 〈em〉HT〈/em〉〈sub〉35〈/sub〉 cases; 37 °C 〈 〈em〉T〈/em〉〈sub〉max〈/sub〉 〈em〉〈〈/em〉 40 °C, 〈em〉NET〈/em〉〈sub〉〈em〉T〈/em〉max37〈/sub〉 for 〈em〉HT〈/em〉〈sub〉37〈/sub〉 cases; 〈em〉NET =〈/em〉 27 °C, 〈em〉NET〈/em〉〈sub〉27〈/sub〉 cases). In 〈em〉HT〈/em〉〈sub〉35〈/sub〉 (〈em〉HT〈/em〉〈sub〉37〈/sub〉) cases, 〈em〉NET〈/em〉〈sub〉〈em〉T〈/em〉max35〈/sub〉 (〈em〉NET〈/em〉〈sub〉〈em〉T〈/em〉max37〈/sub〉) can reach up to 32 °C (34 °C) in southern China and also can be less than 29 °C (31 °C) in western Northwest China. In 〈em〉NET〈/em〉〈sub〉27〈/sub〉 cases as the threshold for the thermal sensation of very hot, 〈em〉T〈/em〉〈sub〉max〈/sub〉 should be over 33 °C in western Northwest China and was less than 30.5 °C in southern China, by contrast. With global warming, there is an increasing trend in the number of extreme hot days in most part of China, but a decreasing trend is detected in the part of Jianghuai region, partly due to the decreasing trend in 〈em〉T〈/em〉〈sub〉max〈/sub〉〈em〉.〈/em〉〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Iran is a part of the arid and semi-arid regions of the world and many of its areas suffer from repeated droughts. Due to the fact that recent droughts have put a lot of pressure on water supply systems, drought management have a particular importance. For this purpose, monitoring and forecasting systems can be considered as appropriate tools. In this research, monitoring and prediction of drought in the Urmia synoptic station in short-, medium-, and long-term timescales were investigated using the SPEI (standardized precipitation and evapotranspiration drought index) and gene expression programming model. For this purpose, the SPEI was calculated for timescales 1, 3, 6, 12, 24, and 48 months with using monthly rainfall and temperature data from 1951 to 2009, and its performance was compared with standard precipitation index (SPI). The results showed that the correlation coefficient of SPEI and SPI in the 3-, 12-, and 48-month timescales were 0.84, 0.845, and 0.776, respectively. The monitoring results showed two long periods of drought-related years 1959–1967 and 1998–2009 during the statistical period. After drought monitoring based on SPEI time series, drought was predicted using gene expression programming models with delays of 1 to 5 months. According to the results, the prediction accuracy was increased by increasing the scale of SPEI so that the correlation coefficient in the test stage in the one-month scale (SPEI1) increased from 0.215 to 0.984 in 48-month scale (SPEI48) and the overall accuracy of the model increased from 60.1 in SPEI1 to 92.3% in SPEI48.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Since the extra-tropical eddies carry a huge amount of moisture, heat, and momentum from their source regions to remote places, the long-term changes in their properties can lead to substantial changes in the Earth’s major climatic zones with huge socio-economic consequences. We present the long-term variability and trends in the spatial properties of the Rossby wave packets (RWPs) in the Northern Hemisphere in all seasons for the period of 1980–2013 using NCEP reanalysis for the three major storm track regions: Eurasian, North Pacific, and North Atlantic. A region of high-amplitude meandering flow in the upper troposphere that in the mid-latitudes travel in coherent wave train structures or wave packets is often referred to as a RWP. We found that the activity volume of the RWPs is largest during winter in all storm track basins. Our results suggest that the highest variability of the activity volume is in the North Atlantic region, while the minimum variability of this quantity is found during summer in the Eurasian basin. The largest relative frequency of significant wave packets is found in winter in the North Atlantic basin; however, the largest variability of this quantity is found in the North Pacific region during spring. The largest variability of the long-term daily maximum of WPA is found in the Eurasian region in winter and the minimum variability of this quantity is found in summer in the North Pacific region. The long-term northernmost point of the Rossby wave packets (which is an indicator of the meridional extent of the RWPs) shows that during autumn in the North Atlantic basin, the Rossby wave packets meander more than other seasons and regions. The minimum value of this quantity is found in the summer season in the Eurasian region. The largest variability of the northernmost edge of the RWPs is found in the autumn season in the Eurasian basin, while the minimum variability of this quantity is found in the autumn season in the North Atlantic region. We employ the non-parametric Mann-Kendall test to identify the statistically significant trends in the spatial properties of the Rossby wave packets. No significant trend is found for any diagnostic tools in any region and any season. This suggests that the global mean temperature rise or other climatic changes (over the 34-year period of this study) do not have a detectable impact on the Rossby wave packets.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Examining the physical mechanisms through which large-scale climate indicators, e.g., El Niño–Southern Oscillation and Indian Ocean Dipole, affect hydroclimatic variables in the tropics and extratropics is a forefront scientific challenge. We examined climatic teleconnections between large-scale climate indices and temperature variability over South Korea. To do this, we calculated not only leading patterns of observed monthly mean and extreme temperature through an empirical orthogonal teleconnection (EOT) decomposition technique but also statistical correlations on a monthly basis using cross-correlation and lag regression analyses for the leading modes and global atmospheric circulation dataset. As a result, the spatial pattern of the leading EOT modes for mean (extreme high) temperature represents an eastern (southern) coastal mode for boreal summer and a northern (middle) inland mode in boreal winter, while extreme low EOTs exhibit a northern inland mode in summer and a western coastal mode in winter. The temporal evolution of the leading EOT modes exhibits a mostly increasing trend and an interdecadal oscillation. The leading EOT modes of mean temperature explain more variance than those of extreme temperature during warm and cold seasons. The findings from this study illustrate that tropical ENSO forcing has a coherent association with August and December temperature patterns, while the Indian Ocean Dipole is identified as a driver for temperature variability during fall season. The monsoon circulation over the western North Pacific also exhibits a significant negative correlation with the December temperature EOTs. The leading EOTs for October temperature exhibit the positive correlation with the tropical cyclone variability, while the leading EOTs for mean and extreme high temperature exhibit significant negative correlations with the snow depth over northeastern Eurasia in November. The leading patterns of the August and December mean temperature time series are predictable at up to 5-month lead time from the tropical Pacific sea surface temperatures (SSTs), while a predictable response from Indian Ocean SSTs was detected at up to 4-month lead time.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The characteristics of eolian sand activity are greatly influenced by the wind regime, and wind regimes have been changing around the world in response to climate change. This has also been true in the desert area of northwestern China since 1965, and these changes have changed the region’s landforms, sandstorm frequency, and desertification. In this study, we analyzed the temporal and spatial variation of the region’s near-surface wind field since 1965. We found an average annual wind speed during this period of 1.7 m s〈sup〉−1〈/sup〉, with a decreasing trend from 1965 to 2000 and an increasing trend from 2000 to 2015. The maximum rate of decrease occurred in the spring and in the eastern Taklimakan Desert. The variation of the average wind speed depended on the frequency of winds strong enough to entrain sand (with a wind speed 〉 6 m s〈sup〉−1〈/sup〉). We also found that variations of the drift potential were primarily controlled by three prevailing wind groups (winds from the northwest, north, and northeast), but showed complex changes between seasons and regions. The wind direction in the Taklimakan Desert is characterized by two characteristics of branch and steering, the branch line is swinging in the direction of the east and the west (81.5° E~84° E). The changes in wind speed were mainly caused by a decreased frequency of strong winds, precipitation, and urban development. However, the variation of wind speed had less impact on the desert environment than the variation of wind direction.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The paper focuses on investigation of ‘twin’ subtropical oceanic highs of the Northern Hemisphere, i.e. the Azores High (AH) and the Hawaiian High (HH) in January and July based on gridded 2.5° × 2.5° data of Reanalysis Project of the National Center for Atmospheric Research for the period 1948–2018. The aim is to answer three questions: (1) Are there any connections between AH and HH (both within and between the systems)? (2) What is the long-term variability and trends of the basic characteristics of AH and HH? (3) Do the AH and HH move, and if so, in what directions? The most important results are as follows: (1) the long-term trend of sea level air pressure in the AH centre in January is positive, statistically significant with the increase of 0.63 hPa/10 years, (2) pressure in both centres significantly relates with the latitude of each system; variables characterising the HH in January explain 11% of variation of the variables of the AH in July, (3) the NE-SW/SW-NE index proves the shifting of the AH in January from the south-west to the north-east from the 1990s of the twentieth century and again to the south-west in the twenty-first century, (4) the HH in January and July moved generally from the north-east to the south-west until the end of the twentieth century and shifted again to north-east during the twenty-first century, (5) the AH in July was characterised by complicated displacement system with the prevalence of the shifting from the north-east to the south-west with the exception for the period 1980–1990. In winter, the AH moves towards the land area of Europe in the second half of the twentieth century, while the HH moves towards the open Pacific. The statistically significant increase of pressure in the centre of the AH in January is closely related to the shifting of the system to the north-east. The positive pressure trend in the centre of the AH in January combined with the zero trend in July is the cause of diminishing difference between summer and winter air pressure value of the high. Due to increased sea surface temperature of the Atlantic, the AH does not lose its strength in winter as it used to a few decades ago.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with 〈em〉in situ〈/em〉 observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler (ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind (R2 value ~96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high- and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth, an effect of “torque” or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A multi-index analysis including grain size, major and trace elements is performed on the surface sediments from the northeastern Beibu Gulf to trace the sources of the sediments and to understand the controlling factors for elements distribution. The mean grain size exhibits a wide variation ranging from 0.09Φ to 8.05Φ with an average value of 5.33Φ. The average contents of major elements descend in an order of 〈em〉c〈/em〉(SiO〈sub〉2〈/sub〉)〉〈em〉c〈/em〉(Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉)〉〈em〉c〈/em〉(Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉)〉〈em〉c〈/em〉(CaO)〉〈em〉c〈/em〉(MgO)〉〈em〉c〈/em〉(K〈sub〉2〈/sub〉O)〉〈em〉c〈/em〉(Na〈sub〉2〈/sub〉O)〉〈em〉c〈/em〉(TiO〈sub〉2〈/sub〉)〉〈em〉c〈/em〉(P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉)〉〈em〉c〈/em〉(MnO), while those of trace elements exhibit a descending order of 〈em〉c〈/em〉(Sr)〉〈em〉c〈/em〉(Rb)〉〈em〉c〈/em〉(V)〉〈em〉c〈/em〉(Zn)〉c(Cr)〉〈em〉c〈/em〉(Pb)〉〈em〉c〈/em〉(Ni)〉〈em〉c〈/em〉(Cu)〉〈em〉c〈/em〉(As). On the basis of elementary distribution characteristics and statistical analyses, the study area is divided into the four zones: Zone I is located in the northeastern coastal area of the gulf, which receives large amount of fluvial materials from local rivers in Guangxi and Guangdong, China, and the Qiongzhou Strait; Zone II is located in the center of the study area, where surface sediments exhibits a multiple source; Zone III is located in the Qiongzhou Strait, where surface sediments are dominated by materials from the Zhujiang River and Hainan; Zone IV is located in the southwest of the study area, where surface sediments are mainly originated from the Red River and Hainan. The statistical analyses of sediment geochemical characteristics reveal that the grain size, which is mainly influenced by hydrodynamics and mineral composition of terrigenous materials, is the leading factor controlling the elementary distribution. Meanwhile, impacts from anthropogenic activities and marine biogenic process will also be taken into consideration.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, the long-range relationships between North Atlantic Oscillation (NAO) and precipitation data obtained from Climate Prediction Centre (CPC) Merged Analysis of Precipitation (CMAP) from 1979 to 2016 are investigated using Detrended Fluctuation Moving Average Cross-Correlation Analysis (DMCA). In the atmosphere, teleconnections through strong convective processes sporadically affect various climatic regimes in Europe, Mediterranean basin, North Africa, Middle East, and Caucasus. The NAO is one of the teleconnection processes and results in heavy rainfall in the Mediterranean basin during its negative phase while it gives rise to rain in Europe during its positive phase. The DMCA technique shows that the NAO fluctuation series exhibit different long-range cross-correlation coefficients, ρDMCA(〈em〉s〈/em〉) with “s” being the moving average time window length, between the precipitation values and NAO. Large ρDMCA(〈em〉s〈/em〉) coefficients with time window(s) larger than 12 months were obtained particularly over the Mediterranean basin, near the North Pole including northern Europe. Furthermore, the ρDMCA(〈em〉s〈/em〉) coefficients were grouped into clusters using K-mean method to distinguish the similar patterns. The 1st cluster refers to the negative phase of the NAO indicating warm-rainy conditions and dry spells, which is especially evident in the Mediterranean basin. The 2nd cluster represents the long-range cross-correlation with respect to the positive phase of NAO and precipitation values, particularly for the Western and Northern Europe. Conversely, the 3rd cluster is evaluated as power law of long-range cross-correlations between the precipitation and NAO with respect to the different time scale processes.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The reconstruction of sea surface temperature (SST) is a key issue in research on paleoceanography. The recently related studies are mainly concentrated on the Quaternary. The skeletons of a typical species of benthonic foraminifer (〈em〉Amphistegina radiata〈/em〉) in the top 0–375.30 m interval of Well “Xike-1” reef core, Shidao Island, the Xisha Islands, are uniformly selected. The ratios of magnesium to calcium concentrations and other indicators are analyzed by an electron microprobe analysis (EMPA) with the purpose of estimating the paleo-SSTs since the Pliocene and further investigating the periodic change law of paleoclimate in the South China Sea (SCS). Meanwhile, the geologic significance of paleoclimatic events in the SCS is discussed with global perspectives. The results indicate that the paleo-SSTs reconstructed by the ratios of magnesium to calcium concentrations in the SCS show a general periodic trend of “high–low–high–low” in values changes since the Pliocene. By comparison, the fluctuations of reconstructed paleo-SSTs are much stronger in the Quaternary. Moreover, the variations of the ratios of magnesium to calcium concentrations in the 〈em〉A. radiata〈/em〉 skeletons have recorded a series of major paleoclimatic events since the Pliocene, of which the Quaternary glaciation events and the Arctic ice cap forming events during the late Pliocene are more significant. Thus, using the changes of the ratios of magnesium to calcium concentrations in the 〈em〉A. radiata〈/em〉 skeletons from Well “Xike-1” reef core to reflect the relative changes of paleo-SSTs is a relatively feasible and reliable way in the SCS, which is also proved by the correlation of drilling cores characteristics in this area.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Natural gas hydrate (NGH) is one of the important clean energy at present and even in the future. The study of its sedimentary environment and minerogenetic condition has long been a hot issue that has received much concern from geologists all over the world. China has successfully obtained the samples of NGH in Shenhu and Dongsha sea areas in 2007, 2013 and 2015, respectively. From this, the continental slope north of the South China Sea becomes an important test site for the study of NGH sedimentary genesis and minerogenetic condition. NGH has been found in Shenhu, Dongsha and Qiongdongnan areas within the continental slope north of South China Sea, at different depths of water, with different sedimentary characteristics, gas genesis, and minerogenetic conditions. Using a seismic sedimentology theory, combining seismic facies results of each facies, sedimentary facies and evolution of each area are documented in turn establishing a sedimentary model by considering palaeogeomorphology, sea level change and tectonic movement. The channel system and MTD (Mass Transport Deposition) system among these three areas were compared focusing on the developing position, appearance and controlling factors. Relative location among three areas is firstly defined that Dongsha area in a nearprovenance steep upper slope, Shenhu area in a normal gentle slope and Qiongdongnan area in an awayprovenance flat plain. Besides, their channel systems are classified into erosional, erosional-aggradational and aggradational channel, and MTD systems into headwall domain, translational domain and toe domain.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉〈em〉Qianlong-II〈/em〉 is a fully autonomous underwater vehicle designed for the investigation of submarine resources, particularly polymetallic sulfides. It was used to successfully explore hydrothermal fields on the Southwest Indian Ridge. Here, we summarized the exploration of hydrothermal systems using 〈em〉Qianlong-II〈/em〉, including detailed descriptions of its implementation along with the systems used for data management and fast mapping. We also introduced a method to remove platform magnetic interference using magnetic data while 〈em〉Qianlong-II〈/em〉 is spinning. Based on hydrothermal anomalies collected by 〈em〉Qianlong-II〈/em〉, we developed a rapid method for locating hydrothermal vents. Taking one dive as an example, we systemically demonstrated the process for analyzing hydrothermal survey data to locate hydrothermal vents.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Many hydrometeorological studies have evaluated the impact of climate variability on hydrologic extremes. Recent studies have shown that the varying state of climatic cycles has intensified the regional hydrologic cycle within a wide range of geographical regions in the state of Texas. These climatic cycles define numerous sea surface temperature and pressure anomalies which lead to heavy precipitation in a region. The objective of this paper is to quantify the impact of five major Atlantic and Pacific Ocean related climatic cycles, including (i) Atlantic Multidecadal Oscillation (AMO), (ii) North Atlantic Oscillation (NAO), (iii) Pacific Decadal Oscillation (PDO), (iv) Pacific North American Pattern (PNA), and (v) Southern Oscillation Index (SOI), on maximum daily precipitation within a year in various climate regions of Texas, using a weighted correlation approach incorporating Leave-One-Out Test (LOOT). The uncertainty in the estimated correlation coefficient is factored in by determining the sample correlation coefficient at the 95% confidence interval. The influence of these global scale climatic cycles on the regional hydrologic cycle is found to be governed by the integrated hydrometeorological properties of weather stations, including (i) station elevation, (ii) average temperature, and (iii) average total precipitation, in the months of extremes. Results of this study will help regional water boards prepare for extreme hydrometeorological events in a changing climate.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉〈em〉Pulleniatina obliquiloculata〈/em〉 shells from 16 core-top samples from the tropical Indo-Pacific Oceans are analyzed for the ratios of boron and cadmium to calcium (B/Ca and Cd/Ca). The B/Ca ratios show a very weak positive relationship with [B(OH)〈sub〉4〈/sub〉〈sup〉-〈/sup〉] and the dissolved carbonate species at the apparent calcification depth of 〈em〉P. obliquiloculata〈/em〉. The boron partition coefficients (KD) between 〈em〉P. obliquiloculata〈/em〉 B/Ca and seawater [B(OH)〈sub〉4〈/sub〉〈sup〉-〈/sup〉]/[HCO〈sub〉3〈/sub〉〈sup〉-〈/sup〉] distribute around 1.1×10-3–1.3×10〈sup〉-3〈/sup〉 with a mean value of (1.19±0.12)×10-3, and are significantly related to the nutrient concentration, especially phosphate. The lack of any clear correlation between the 〈em〉P. obliquiloculata〈/em〉 B/Ca and seawater carbonate chemical parameters suggests that the physiochemical controls on boron incorporation are masked by the complexity of natural seawater condition. But the significant dependence of KD on nutrient may likely be explained by a nutrient related growth-rate effect. Cd/Ca of 〈em〉P. obliquiloculata〈/em〉 shows significant correlation with seawater phosphate concentration, and its partition coefficients (DCd) are significantly related to temperature. A first-principle methodology of 〈em〉P. obliquiloculata〈/em〉 B/Ca is applied, with the aid of Cd/Ca as a phosphate proxy and a constraint on 〈em〉K〈/em〉〈sub〉D〈/sub〉, to estimating sea water carbonate chemistry (e.g., pH). The results are fairly promising and allow us to propose the possibility to apply the combination of B/Ca and Cd/Ca proxies (and also Mg/Ca and δ〈sup〉18〈/sup〉O for estimating temperature and salinity) for the paleoreconstruction of seawater carbonate chemistry.〈/p〉