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  • Articles  (6,008)
  • American Meteorological Society  (3,380)
  • De Gruyter  (1,660)
  • Blackwell Publishing Ltd
  • Springer Nature
  • Springer Science + Business Media
  • 2020-2023
  • 2020-2022  (4,217)
  • 1960-1964  (1,791)
  • Geosciences  (6,008)
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  • Articles  (6,008)
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  • 1
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    An automated common algorithm for planetary boundary layer retrievals using aerosol lidars in support of the U.S. EPA Photochemical Assessment Monitoring Stations Program (2020)
    American Meteorological Society
    Details
    Publication Date: 2020-08-26
    Description: A unique automated planetary boundary layer (PBL) retrieval algorithm is proposed as a common cross-platform method for use with commercially available ceilometers for implementation under the redesigned U.S. Environmental Protection Agency Photochemical Assessment Monitoring Stations program. This algorithm addresses instrument signal quality and screens for precipitation and cloud layers before the implementation of the retrieval methodology using the Haar wavelet covariance transform method. Layer attribution for the PBL height is supported with the use of continuation and time-tracking parameters, and uncertainties are calculated for individual PBL height retrievals. Commercial ceilometer retrievals are tested against radiosonde PBL height and cloud-base height during morning and late afternoon transition times, critical to air quality model prediction and when retrieval algorithms struggle to identify PBL heights. A total of 58 radiosonde profiles were used and retrievals for nocturnal stable layers, residual layers and mixing layers were assessed. Overall good agreement was found for all comparisons with one system showing limitations for the cases of nighttime surface stable layers and daytime mixing layer. It is recommended that nighttime shallow stable layer retrievals be performed with a recommended minimum height or with additional verification. Retrievals of residual layer heights and mixing layer comparisons revealed overall good correlations to radiosonde heights (correlation coefficients, r2, ranging from 0.89 – 0.96 and bias ranging from ~ -131 to +63 m, and r2 from 0.88 – 0.97 and bias from -119 to +101 m, respectively).
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 2
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    A modification of predictive three-component model for turbulent flows of complex slurries in pipelines based on experimental results (2020)
    De Gruyter
    Details
    Publication Date: 2020-09-01
    Description: The paper describes a mathematical and physical modelling of flow of complex slurries in pipelines, i.e. a flow of slurries composed of solids covering a very broad range of particle sizes that overlaps more than one flow patterns – non-Newtonian, pseudohomogeneous, heterogeneous and fully-stratified. A typical examples are residual products (“tailings”) from mining industry with normal average particle sizes of 20 to 100 μm or more. Experimental results of flows of complex slurries composing of non-Newtonian carrier fluid and three fractions of glass particles in 50 mm pipe are presented. Depending on the particle size, particles show different flow patterns and therefore considerable differences in pressure drops. Fine particles tend behave as a homogeneous matter, while coarser particles exhibit heterogeneous behaviour and even coarser particles form a sliding bed. A mathematical 3-component predictive model for turbulent flow of complex slurries is presented based on well-established semi-empirical formulae developed originally for flows with Newtonian carrier. The predicted values of pressure drops show very reasonable agreement with experimental results and indicate suitability of the model for engineering practice.
    Electronic ISSN: 0042-790X
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Natural Sciences in General
    Published by De Gruyter
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  • 3
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    Lithobiont-dependent ionic composition in runoff water (2020)
    De Gruyter
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    Publication Date: 2020-09-01
    Description: Rock dwelling organisms (lithobionts) such as cyanobacteria (prokaryotes) and chlorolichens (eukaryotes) abound in the Negev Desert, where they cover almost all calcareous bedrocks and rock particles (cobbles, boulders). In a small limestone watershed in the Negev Highlands, cyanobacteria inhabit the south-facing (SF) bedrocks, epilithic lichens (accompanied by endolithic lichens) inhabit the north-facing (NF) bedrocks, while endolithic lichens cover most of the cobbles and boulders in both aspects. In order to study their contribution to runoff water, a pair of runoff plots was established on habitats with cyanobacteria, endolithic lichens, and epilithic lichens. Rain and runoff were collected during the hydrological year 2006/07, and the chemical composition (Ca, Mg, Na, K, Cl, SO4, HCO3, Si) of the rain and runoff water was analyzed. Several patterns were observed: (a) as indicated by Si, more dust accumulated on the bedrocks; (b) all substrates exhibited high amounts of Ca, and HCO3; (c) while SF-bedrocks showed enrichment in K, both bedrocks (and especially the NF bedrocks), as well as the NF boulders showed an enrichment in Mg. While the enrichment in Ca and HCO3 can be explained by the contribution of the limestone parent material, the enrichment in K and Mg can be explained by the contribution of the living lithobionts, with K being mainly contributed by the cyanobacteria and Mg mainly by the epilithic lichens. Ion enrichment may therefore be aspect-dependent, reflecting the lithobiont distribution within the drainage basin, partially explaining the enrichment in K and Mg previously recorded in runoff water from the Negev.
    Electronic ISSN: 0042-790X
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Natural Sciences in General
    Published by De Gruyter
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  • 4
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    Effect of sand burial on the subcritical water repellency of a dominant moss crust in a revegetated area of the Tengger Desert, Northern China (2020)
    De Gruyter
    Details
    Publication Date: 2020-09-01
    Description: Sand burial is a ubiquitous disturbance that influences the ecological and hydrological properties of moss crusts in many sandy desert areas. There is little available information regarding the effect of sand burial on the water repellency (WR) of moss crusts in desert areas. Therefore, this study evaluated the effects of sand burial (sand depths of 0 (control), 0.5, 1, 2, 4 and 10 mm) followed by three simulated precipitation regimes (through applying 4 and 6 mm, 2 and 3 mm, and 1 and 1.5 mm of distilled water at 8-day intervals in spring and autumn, respectively) on the WR of a widespread moss crust dominated by Bryum argenteum Hedw. in a revegetated area of the Tengger Desert, China. The results showed moss crust WR remained subcritical during the whole experiment, and that it considerably decreased immediately after sand burial, even though the values of WR were significantly higher in autumn than those in spring under the same treatment (p 〈 0.05). Furthermore, the depth threshold (TD) values for sand burials that reduced WR to zero were 1 and 2 mm in spring and autumn, respectively. After a recovery period of nearly one-season (72 days), the WR of the moss crust significantly increased (p 〈 0.05). In addition, sand burial had two separate effects on moss crust WR. Specifically, shallower sand burial (burial depth less than 0.5 mm) increased moss crust WR, whereas deeper sand burial (burial depth exceeds 0.5 mm) decreased it. The TD values also significantly increased to 2 and 4 mm in spring and autumn, respectively. These findings about the effects of sand burial on moss crust WR provide additional information that can be used to better understand the influence of sand burial on moss crust colonization and maintenance in arid sand-burial-stressed ecosystems, and to help explain why there are some contrasting viewpoints on biocrust WR.
    Electronic ISSN: 0042-790X
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Natural Sciences in General
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  • 5
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    Changes in direct CO2 and N2O emissions from a loam Haplic Luvisol under conventional moldboard and reduced tillage during growing season and post-harvest period of red clover (2020)
    De Gruyter
    Details
    Publication Date: 2020-09-01
    Description: The objectives of the study were to: (1) assess the strength of associations of direct CO2 and N2O emissions with the seasonal variations in the relevant soil properties under both tillage systems; 2) evaluate how CT and RT affect magnitudes of seasonal CO2 and N2O fluxes from soil. Field studies were carried out on plots for conventional tillage (up to 0.22–0.25 m) and reduced tillage (up to 0.10–0.12 m) during the growing season and post-harvest period of red clover. The results showed that daily CO2 emissions significantly correlated only with soil temperature during the growing season under conventional and reduced tillage. Soil temperature demonstrated its highest influence on daily N2O emissions only at the beginning of the growing season in both tillage systems. There were no significant inter-system differences in daily CO2 and N2O emissions from soil during the entire period of observations. Over the duration of post-harvest period, water-filled pore space was a better predictor of daily CO2 emissions from soils under CT and RT. The conventional and reduced tillage did not cause significant differences in cumulative N2O and CO2 fluxes from soil.
    Electronic ISSN: 0042-790X
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Natural Sciences in General
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  • 6
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    Strata behavior and control strategy of backfilling collaborate with caving fully-mechanized mining (2020)
    De Gruyter
    Details
    Publication Date: 2020-08-24
    Description: This article analyzes the technical difficulties in full-section backfill mining and briefly introduces the technical principle and advantages of backfilling combined with caving fully mechanized mining (BCCFM). To reveal the strata behavior law of the BCCFM workface, this work establishes a three-dimensional numerical model and designs a simulation method by dynamically updating the modulus parameter of the filling body. By the analysis of numerical simulation, the following conclusions about strata behavior of the BCCFM workface were drawn. (1) The strata behavior of the BCCFM workface shows significant nonsymmetrical characteristics, and the pressure in the caving section is higher than that in the backfilling section. φ has the greatest influence on the backfilling section and the least influence on the caving section. C has a significant influence on the range of abutment pressure in the backfilling section. (2) There exits the transition area with strong mine pressure of the BCCFM workface. φ and C have significant effect on the degree of pressure concentration but little effect on the influence range of strong mine pressure in the transition area. (3) Under different conditions, the influence range of strong mine pressure is all less than 6 m. This article puts forward a control strategy of mine pressure in the transition area, which is appropriately improving the strength of the transition hydraulic support within the influence range (6 m) in the transition area according to the pressure concentration coefficient. The field measurement value of Ji15-31010 workface was consistent with numerical simulation, which verifies the reliability of control strategy of the BCCFM workface.
    Electronic ISSN: 2391-5447
    Topics: Geosciences
    Published by De Gruyter
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  • 7
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    Multi-temporal survey of diaphragm wall with terrestrial laser scanning method (2020)
    De Gruyter
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    Publication Date: 2020-08-24
    Description: The development of measurement technologies allows for acquiring various data. The Terrestrial Laser Scanning (TLS) technology is frequently combined with classic geodetic measurements – tacheometry or levelling. This article presents a process of the diaphragm wall monitoring during excavation supported with a top-down method. The construction technology applied required proper planning and performance of measurements in difficult construction site conditions in the city centre. TLS allowed for limiting works at daytime and performing monitoring during the night break in works at the construction site as well as limiting the impact of the subsoil process vibrations on the values of displacements and deformations determined. The authors present a comparison of the results of displacement and deformation measurements with a terrestrial laser scanning and tacheometric measurement method. The possibilities of using the data acquired, among others, for the indication of filtration areas, spatial surface deformation analyses and assessment of the wall execution compliance with the design are presented. The analyses carried out show that the TLS may be used in the investment process from the very beginning, being a component of the Building Information Modelling (BIM).
    Electronic ISSN: 2391-5447
    Topics: Geosciences
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  • 8
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    Dynamic Origin of the Interannual Variability of West China Autumn Rainfall (2020)
    American Meteorological Society
    Details
    Publication Date: 2020-10-07
    Description: The dynamic origin of the interannual variability of West China autumn rainfall (WCAR), a special weather/climate phenomenon over western-central China in September and October, was investigated via observational diagnosis and numerical simulations. Here we found that the interannual variability of WCAR is closely related to the local horizontal trough, which is passively induced by two lower-level anticyclonic (high pressure) anomalies over East Asia. The anticyclonic anomaly over the south is a Gill-type response to the central and eastern Pacific diabatic cooling, while that over the north is part of the mid- to high-latitude barotropic Rossby wave train, which could be induced by either the thermal forcing of the central and eastern Pacific Ocean sea surface temperature (SST) cooling or that of the subtropical northern Atlantic Ocean SST warming. The quasi-barotropic high pressure anomaly over East Asia acts as an “invisible mountain” that steers the low-level anomalous southwesterly into a southeasterly and hinders the water vapor going farther to the north, leading to enhanced WCAR. However, the real mountain ranges in the region (the Qinglin and Ba Mountains) have no essential impact on the formation and interannual variability of WCAR.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 9
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    Drier North American monsoon in contrast to Asian-African monsoon under global warming (2020)
    American Meteorological Society
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    Publication Date: 2020-08-27
    Description: Summer monsoon rainfall supplies over 55% of annual precipitation to global monsoon regions. As shown by more than 70% of models, including 30 models from CMIP5 and 30 models from CMIP6 under high-emission scenarios, North American (NAM) monsoon rainfall decreases in a warmer climate, in sharp contrast to the robust increase in Asian-African monsoon rainfall. A hierarchy of model experiments are analyzed to understand the mechanism for the reduced NAM monsoon rainfall in this study. Modeling evidence shows that the reduction of NAM monsoon rainfall is related to both direct radiative forcing of increased CO2 concentration and SST warming, manifested as fast and slow responses to abrupt CO2 quadrupling in CGCMs. A cyclone anomaly forms over the Eurasian-African continent due to enhanced land-sea thermal contrast under increased CO2 concentration, and this leads to a subsidence anomaly on its western flank, suppressing the NAM monsoon rainfall. The SST warming acts to further reduce the rainfall over the NAM monsoon region, and the El Niño-like SST warming pattern with enhanced SST warming over the equatorial Pacific plays a key role in suppressing NAM rainfall, whereas relative cooling over the subtropical North Atlantic has no contribution. A positive feedback between monsoon precipitation and atmospheric circulation helps to amplify the responses of monsoon rainfall.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 10
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    Soil Moisture–Evapotranspiration Overcoupling and L-Band Brightness Temperature Assimilation: Sources and Forecast Implications (2020)
    American Meteorological Society
    Details
    Publication Date: 2020-10-01
    Description: The assimilation of L-band surface brightness temperature (Tb) into the land surface model (LSM) component of a numerical weather prediction (NWP) system is generally expected to improve the quality of summertime 2-m air temperature (T2m) forecasts during water-limited surface conditions. However, recent retrospective results from the European Centre for Medium-Range Weather Forecasts (ECMWF) suggest that the assimilation of L-band Tb from the European Space Agency’s (ESA) Soil Moisture Ocean Salinity (SMOS) mission may, under certain circumstances, degrade the accuracy of growing-season 24-h T2m forecasts within the central United States. To diagnose the source of this degradation, we evaluate ECMWF soil moisture (SM) and evapotranspiration (ET) forecasts using both in situ and remote sensing resources. Results demonstrate that the assimilation of SMOS Tb broadly improves the ECMWF SM analysis in the central United States while simultaneously degrading the quality of 24-h ET forecasts. Based on a recently derived map of true global SM–ET coupling and a synthetic fraternal twin data assimilation experiment, we argue that the spatial and temporal characteristics of ECMWF SM analyses and ET forecast errors are consistent with the hypothesis that the ECMWF LSM overcouples SM and ET and, as a result, is unable to effectively convert an improved SM analysis into enhanced ET and T2m forecasts. We demonstrate that this overcoupling is likely linked to the systematic underestimation of root-zone soil water storage capacity by LSMs within the U.S. Corn Belt region.
    Print ISSN: 1525-755X
    Electronic ISSN: 1525-7541
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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