ALBERT

Beschreibung: A new 21.3m firn core was drilled in 2015 at a coastal Antarctic high-accumulation site in Adélie Land (66.78◦ S; 139.56◦ E, 602 m a.s.l.), named Terre Adélie 192A (TA192A). The mean isotopic values (−19.3 ‰ ± 3.1 ‰ for δ18O and 5.4 ‰±2.2 ‰ for deuterium excess) are consistent with other coastal Antarctic values. No significant isotope–temperature relationship can be evidenced at any timescale. This rules out a simple interpretation in terms of local temperature. An observed asymmetry in the δ18O seasonal cycle may be explained by the precipitation of air masses coming from the eastern and western sectors in autumn and winter, recorded in the d-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea ice extent (135–145◦ E) over the period 1998–2014. However, process studies focusing on resulting isotopic compositions and particularly the deuterium excess–δ18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.

Beschreibung: The timing and intensity of snowmelt processes on sea ice are key drivers determining the seasonal sea-ice energy and mass budgets. In the Arctic, satellite passive microwave and radar observations have revealed a trend towards an earlier snowmelt onset during the last decades, which is an important aspect of Arctic amplification and sea ice decline. Around Antarctica, snowmelt on perennial ice is weak and very different than in the Arctic, with most snow surviving the summer. Here we compile time series of snowmelt-onset dates on seasonal and perennial Antarctic sea ice from 1992 to 2014/15 using active microwave observations from European Remote Sensing Satellite (ERS-1/2), Quick Scatterometer (QSCAT) and Advanced Scatterometer (ASCAT) radar scatterometers. We define two snowmelt transition stages: A weak backscatter rise indicating the initial warming and destructive metamorphism of the snowpack (pre-melt), followed by a rapid backscatter rise indicating the onset of thaw-freeze cycles (snowmelt). Results show large interannual variability with an average pre-melt onset date of 29 November and melt onset of 10 December, respectively, on perennial ice, without any significant trends over the study period, consistent with the small trends of Antarctic sea ice extent. There was a latitudinal gradient from early snowmelt onsets in mid-November in the northern Weddell Sea to late (end-December) or even absent snowmelt conditions in the southern Weddell Sea. We show that QSCAT Ku-band (13.4 GHz signal frequency) derived pre-melt and snowmelt onset dates are earlier by 20 and 18 days, respectively, than ERS and ASCAT C-band (5.6 GHz) derived dates. This offset has been considered when constructing the time series. Snowmelt onset dates from passive microwave observations (37 GHz) are later by 14 and 6 days than those from the scatterometers, respectively. Based on these characteristic differences between melt onset dates observed by different microwave wavelengths, we developed a conceptual model which illustrates how the seasonal evolution of snow temperature profiles may affect different microwave bands with different penetration depths. These suggest that future multi-frequency active/passive microwave satellite missions could be used to resolve melt processes throughout the vertical snow column of thick snow on perennial Antarctic sea ice.

Beschreibung: Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data–model comparisons. Here, we illustrate this using 456 globally distributed speleothem δ18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model’s ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.

Beschreibung: We present here the first results, for the preindustrial and mid-Holocene climatological periods, of the newly developed isotope-enhanced version of the fully coupled Earth system model MPI-ESM, called hereafter MPI-ESM-wiso. The water stable isotopes H16O, H18O and HDO have been implemented into all components of the coupled model setup. The mid-Holocene provides the opportunity to evaluate the model response to changes in the seasonal and latitudinal distribution of insolation induced by different orbital forcing conditions. The results of our equilibrium simulations allow us to evaluate the performance of the isotopic model in simulating the spatial and temporal variations of water isotopes in the different compartments of the hydrological system for warm climates. For the preindustrial climate, MPI-ESM-wiso reproduces very well the observed spatial distribution of the isotopic content in precipitation linked to the spatial variations in temperature and precipitation rate. We also find a good model–data agreement with the observed distribution of isotopic composition in surface seawater but a bias with the presence of surface seawater that is too 18O-depleted in the Arctic Ocean. All these results are improved compared to the previous model version ECHAM5/MPIOM. The spatial relationships of water isotopic composition with temperature, precipitation rate and salinity are consistent with observational data. For the preindustrial climate, the interannual relationships of water isotopes with temperature and salinity are globally lower than the spatial ones, consistent with previous studies. Simulated results under mid-Holocene conditions are in fair agreement with the isotopic measurements from ice cores and continental speleothems. MPI-ESM-wiso simulates a decrease in the isotopic composition of precipitation from North Africa to the Tibetan Plateau via India due to the enhanced monsoons during the mid-Holocene. Over Greenland, our simulation indicates a higher isotopic composition of precipitation linked to higher summer temperature and a reduction in sea ice, shown by positive isotope–temperature gradient. For the Antarctic continent, the model simulates lower isotopic values over the East Antarctic plateau, linked to the lower temperatures during the mid-Holocene period, while similar or higher isotopic values are modeled over the rest of the continent. While variations of isotopic contents in precipitation over West Antarctica between mid-Holocene and preindustrial periods are partly controlled by changes in temperature, the transport of relatively 18O-rich water vapor near the coast to the western ice core sites could play a role in the final isotopic composition. So, more caution has to be taken about the reconstruction of past temperature variations during warm periods over this area. The coupling of such a model with an ice sheet model or the use of a zoomed grid centered on this region could help to better describe the role of the water vapor transport and sea ice around West Antarctica. The reconstruction of past salinity through isotopic content in sea surface waters can be complicated for regions with strong ocean dynamics, variations in sea ice regimes or significant changes in freshwater budget, giving an extremely variable relationship between the isotopic content and salinity of ocean surface waters over small spatial scales. These complicating factors demonstrate the complexity of interpreting water isotopes as past climate signals of warm periods like the mid-Holocene. A systematic isotope model intercomparison study for further insights on the model dependency of these results would be beneficial.

Beschreibung: Permafrost temperatures are increasing in Alaska due to climate change and in some cases permafrost is thawing and degrading. In areas where degradation has already occurred the effects can be dramatic, resulting in changing ecosystems, carbon release, and damage to infrastructure. However, in many areas we lack baseline data, such as subsurface temperatures, needed to assess future changes and potential risk areas. Besides climate, the physical properties of the vegetation cover and subsurface material have a major influence on the thermal state of permafrost. These properties are often directly related to the type of ecosystem overlaying permafrost. In this paper we demonstrate that classifying the landscape into general ecotypes is an effective way to scale up permafrost thermal data collected from field monitoring sites. Additionally, we find that within some ecotypes the absence of a moss layer is indicative of the absence of near-surface permafrost. As a proof of concept, we used the ground temperature data collected from the field sites to recode an ecotype land cover map into a map of mean annual ground temperature ranges at 1 m depth based on analysis and clustering of observed thermal regimes. The map should be useful for decision making with respect to land use and understanding how the landscape might change under future climate scenarios.

Beschreibung: Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales. In particular, vegetation and organic layer characteristics may act to protect permafrost in regions with a mean annual air temperature (MAAT) above 0°C. In this study, we document the presence of residual permafrost plateaus in the western Kenai Peninsula lowlands of south-central Alaska, a region with a MAAT of 1.5+/-1 °C (1981–2010). Continuous ground temperature measurements between 16 September 2012 and 15 September 2015, using calibrated thermistor strings, documented the presence of warm permafrost (-0.04 to -0.08 °C). Field measurements (probing) on several plateau features during the fall of 2015 showed that the depth to the permafrost table averaged 1.48m but at some locations was as shallow as 0.53 m. Late winter surveys (augering, coring, and GPR) in 2016 showed that the average seasonally frozen ground thickness was 0.45 m, overlying a talik above the permafrost table. Measured permafrost thickness ranged from 0.33 to 〉6.90 m. Manual interpretation of historic aerial photography acquired in 1950 indicates that residual permafrost plateaus covered 920 ha as mapped across portions of four wetland complexes encompassing 4810 ha. However, between 1950 and ca. 2010, permafrost plateau extent decreased by 60.0 %, with lateral feature degradation accounting for 85.0% of the reduction in area. Permafrost loss on the Kenai Peninsula is likely associated with a warming climate, wildfires that remove the protective forest and organic layer cover, groundwater flow at depth, and lateral heat transfer from wetland surface waters in the summer. Better understanding the resilience and vulnerability of ecosystem-protected permafrost is critical for mapping and predicting future permafrost extent and degradation across all permafrost regions that are currently warming. Further work should focus on reconstructing permafrost history in south-central Alaska as well as additional contemporary observations of these ecosystem-protected permafrost sites south of the regions with relatively stable permafrost.

Beschreibung: Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales. In particular, vegetation and organic layer characteristics may act to protect permafrost in regions with a mean annual air temperature (MAAT) above 0 °C. In this study, we document the presence of residual permafrost plateaus on the western Kenai Peninsula lowlands of southcentral Alaska, a region with a MAAT of 1.5 ± 1 °C (1981 to 2010). Continuous ground temperature measurements between 16 September 2012 and 15 September 2015, using calibrated thermistor strings, documented the presence of warm permafrost (−0.04 to −0.08 °C). Field measurements (probing) on several plateau features during the fall of 2015 showed that the depth to the permafrost table averaged 1.48 m but was as shallow as 0.53 m. Late winter surveys (drilling, coring, and GPR) in 2016 showed that the average seasonally frozen ground thickness was 0.45 m, overlying a talik above the permafrost table. Measured permafrost thickness ranged from 0.33 to 〉 6.90 m. Manual interpretation of historic aerial photography acquired in 1950 indicates that residual permafrost plateaus covered 920 ha as mapped across portions of four wetland complexes encompassing 4810 ha. However, between 1950 and ca. 2010, permafrost plateau extent decreased by 60 %, with lateral feature degradation accounting for 85 % of the reduction in area. Permafrost loss on the Kenai Peninsula is likely associated with a warming climate, wildfires that remove the protective forest and organic layer cover, groundwater flow at depth, and lateral heat transfer from wetland surface waters in the summer. Better understanding the resilience and vulnerability of ecosystem-protected permafrost is critical for mapping and predicting future permafrost extent and degradation across all permafrost regions that are currently warming. Further work should focus on reconstructing permafrost history in southcentral Alaska as well as additional contemporary observations of these ecosystem-protected permafrost sites lying south of the regions with relatively stable permafrost.

Beschreibung: In this study, we present results obtained from modelling the mid-Pliocene warm period using the Community Earth System Models (COSMOS, version: COSMOS-landveg r2413, 2009) with the two different sets of boundary conditions prescribed for the two phases of the Pliocene Model Intercomparison Project (PlioMIP). Boundary conditions, model forcing, and modelling methodology of the two phases of PlioMIP, tagged PlioMIP1 and PlioMIP2,differ considerably in palaeogeography, in particular with regards to the state of ocean gateways, ice-masks, vegetation and topography. Further differences between model setups as suggested for PlioMIP1 and PlioMIP2 consider updates to the concentration of atmospheric carbon dioxide (CO2), that is specified as 405 and 400 parts per million by volume (ppmv) for PlioMIP1 and PlioMIP2, respectively, as well as minor differences in the concentrations of methane (CH4) and nitrous oxide (N2O) due to changes in the protocol of the Paleoclimate Model Intercomparison Project (PMIP) from phase 3 to phase 4. With this manuscript, we bridge the gap between our contributions to PlioMIP1 (Stepanek and Lohmann, 2012) and PlioMIP2 (Stepanek et al., 2019). We highlight some of the effects that differences in the chosen Mid-Pliocene model setup (PlioMIP2 vs. PlioMIP1) have on the climate state as derived with the COSMOS, as this information will be valuable in the framework of the model-model and model-data-comparison within PlioMIP2. We evaluate the model sensitivity to improved mid-Pliocene boundary conditions using PlioMIP’s core mid-Pliocene experiments for PlioMIP1 and PlioMIP2, and present further simulations where we test model sensitivity to variations in palaeogeography, orbit and concentration of CO2. Firstly,we highlight major changes in boundary conditions from PlioMIP1 to PlioMIP2 and also the limitations recorded from the initial effort. The results derived from of our simulations show that COSMOS simulates a mid-Pliocene climate state that is 0.08 K colder in PlioMIP2, if compared to PlioMIP1. On one hand, high-latitude warming,which is supported by proxy evidence of the mid-Pliocene, is underestimated in simulations of both PlioMIP1 andPlioMIP2. On the other hand, spatial variations in surface air temperature (SAT), sea surface temperature (SST) as well as the distribution of sea ice suggest improvement of simulated SAT and SST in PlioMIP2 if employing the updated palaeogeography. The PlioMIP2 Mid-Pliocene simulation produces warmer SSTs in the Arctic and North Atlantic Ocean than derived from the respective PlioMIP1 climate state. The difference in prescribed CO2accountsfor 1.1 K of warming in the Arctic, leading to an ice-free summer in the PlioMIP1 simulation, and a quasi-ice-free summer in PlioMIP2. Furthermore, employing different orbital forcings in simulating the Mid-Pliocene lead to pronounced annual and seasonal variations, which is not accounted for by marine and terrestrial reconstruction of the time-slice.

Beschreibung: The Antarctic temperature changes over the past millennia remain more uncertain than in many other continental regions. This has several origins: (1) the number of high-resolution ice cores is small, in particular on the East Antarctic plateau and in some coastal areas in East Antarctica; (2) the short and spatially sparse instrumental records limit the calibration period for reconstructions and the assessment of the methodologies; (3) the link between isotope records from ice cores and local climate is usually complex and dependent on the spatial scales and timescales investigated. Here, we use climate model results, pseudo-proxy experiments and data assimilation experiments to assess the potential for reconstructing the Antarctic temperature over the last 2 millennia based on a new database of stable oxygen isotopes in ice cores compiled in the frame- work of Antarctica2k (Stenni et al., 2017). The well-known covariance between δ18O and temperature is reproduced in the two isotope-enabled models used (ECHAM5/MPI-OM and ECHAM5-wiso), but is generally weak over the different Antarctic regions, limiting the skill of the reconstructions. Furthermore, the strength of the link displays large variations over the past millennium, further affecting the potential skill of temperature reconstructions based on statistical methods which rely on the assumption that the last decades are a good estimate for longer temperature reconstructions. Using a data assimilation technique allows, in theory, for changes in the δ18O–temperature link through time and space to be taken into account. Pseudoproxy experiments confirm the benefits of using data assimilation methods instead of statistical methods that provide reconstructions with unrealistic variances in some Antarctic subregions. They also confirm that the relatively weak link between both variables leads to a limited potential for reconstructing temperature based on δ18O. However, the reconstruction skill is higher and more uniform among reconstruction methods when the reconstruction target is the Antarctic as a whole rather than smaller Antarctic subregions. This consistency between the methods at the large scale is also observed when reconstructing temperature based on the real δ18O regional composites of Stenni et al. (2017). In this case, temperature reconstructions based on data assimilation confirm the long-term cooling over Antarctica during the last millennium, and the later onset of anthropogenic warming compared with the simulations without data assimilation, which is especially visible in West Antarctica. Data assimilation also allows for models and direct observations to be reconciled by reproducing the east–west contrast in the recent temperature trends. This recent warming pattern is likely mostly driven by internal variability given the large spread of individual Paleoclimate Modelling Intercomparison Project (PMIP)/Coupled Model Intercomparison Project (CMIP) model realizations in simulating it. As in the pseudoproxy framework, the reconstruction methods perform differently at the subregional scale, especially in terms of the variance of the time series produced. While the potential benefits of using a data assimilation method instead of a statistical method have been highlighted in a pseudoproxy framework, the instrumental series are too short to confirm this in a realistic setup.

Beschreibung: Ice-wedge polygons are common features of lowland tundra in the continuous permafrost zone and prone to rapid degradation through melting of ground ice. There are many interrelated processes involved in ice-wedge thermokarst and it is a major challenge to quantify their influence on the stability of the permafrost underlying the landscape. In this study we used a numerical modelling approach to investigate the degradation of ice wedges with a focus on the influence of hydrological conditions. Our study area was Samoylov Island in the Lena River delta of northern Siberia, for which we had in situ measurements to evaluate the model. The tailored version of the CryoGrid 3 land surface model was capable of simulating the changing microtopography of polygonal tundra and also regarded lateral fluxes of heat, water, and snow. We demonstrated that the approach is capable of simulating ice-wedge degradation and the associated transition from a low-centred to a high-centred polygonal microtopography. The model simulations showed ice-wedge degradation under recent climatic conditions of the study area, irrespective of hydrological conditions. However, we found that wetter conditions lead to an earlier onset of degradation and cause more rapid ground subsidence. We set our findings in correspondence to observed types of ice-wedge polygons in the study area and hypothesized on remaining discrepancies between modelled and observed ice-wedge thermokarst activity. Our quantitative approach provides a valuable complement to previous, more qualitative and conceptual, descriptions of the possible pathways of ice-wedge polygon evolution. We concluded that our study is a blueprint for investigating thermokarst landforms and marks a step forward in understanding the complex interrelationships between various processes shaping ice-rich permafrost landscapes.

Beschreibung: Warming of the Arctic led to an increase in permafrost temperatures by about 0.3 �C during the last decade. Permafrost warming is associated with increasing sediment water content, permeability, and diffusivity and could in the long term alter microbial community composition and abundance even before permafrost thaws. We studied the long-term effect (up to 2500 years) of submarine permafrost warming on microbial communities along an onshore–offshore transect on the Siberian Arctic Shelf displaying a natural temperature gradient of more than 10 �C. We analysed the in situ development of bacterial abundance and community composition through total cell counts (TCCs), quantitative PCR of bacterial gene abundance, and amplicon sequencing and correlated the microbial community data with temperature, pore water chemistry, and sediment physicochemical parameters. On timescales of centuries, permafrost warming coincided with an overall decreasing microbial abundance, whereas millennia after warming microbial abundance was similar to cold onshore permafrost. In addition, the dissolved organic carbon content of all cores was lowest in submarine permafrost after millennial-scale warming. Based on correlation analysis, TCC, unlike bacterial gene abundance, showed a significant rank-based negative correlation with increasing temperature, while bacterial gene copy numbers showed a strong negative correlation with salinity. Bacterial community composition correlated only weakly with temperature but strongly with the pore water stable isotopes �18O and �D, as well as with depth. The bacterial community showed substantial spatial variation and an overall dominance of Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, and Proteobacteria, which are amongst the microbial taxa that were also found to be active in other frozen permafrost environments. We suggest that, millennia after permafrost warming by over 10 �C, microbial community composition and abundance show some indications for proliferation but mainly reflect the sedimentation history and paleoenvironment and not a direct effect through warming.

Beschreibung: The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface to bottom ocean biogeochemical data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of water samples. This update of GLODAPv2, v2.2019, adds data from 116 cruises to the previous version, extending its coverage in time from 2013 to 2017, while also adding some data from prior years. GLODAPv2.2019 includes measurements from more than 1.1 million water samples from the global oceans collected on 840 cruises. The data for the 12 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and CCl4) have undergone extensive quality control, especially systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but updated to WOCE exchange format and (ii) as a merged data product with adjustments applied to minimize bias. These adjustments were derived by comparing the data from the 116 new cruises with the data from the 724 quality-controlled cruises of the GLODAPv2 data product. They correct for errors related to measurement, calibration, and data handling practices, taking into account any known or likely time trends or variations. The compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 µmol kg−1 in dissolved inorganic carbon, 4 µmol kg−1 in total alkalinity, 0.01–0.02 in pH, and 5 % in the halogenated transient tracers. The compilation also includes data for several other variables, such as isotopic tracers. These were not subjected to bias comparison or adjustments. The original data, their documentation and DOI codes are available in the Ocean Carbon Data System of NOAA NCEI (https://www.nodc.noaa.gov/ocads/oceans/GLODAPv2_2019/, last access: 17 September 2019). This site also provides access to the merged data product, which is provided as a single global file and as four regional ones – the Arctic, Atlantic, Indian, and Pacific oceans – under https://doi.org/10.25921/xnme-wr20 (Olsen et al., 2019). The product files also include significant ancillary and approximated data. These were obtained by interpolation of, or calculation from, measured data. This paper documents the GLODAPv2.2019 methods and provides a broad overview of the secondary quality control procedures and results.

Beschreibung: We present a Lagrangian convective transport scheme developed for global chemistry and transport models, which considers the variable residence time that an air parcel spends in convection. This is particularly important for accurately simulating the tropospheric chemistry of short-lived species, e.g., for determining the time available for heterogeneous chemical processes on the surface of cloud droplets. In current Lagrangian convective transport schemes air parcels are stochastically redistributed within a fixed time step according to estimated probabilities for convective entrainment as well as the altitude of detrainment. We introduce a new scheme that extends this approach by modeling the variable time that an air parcel spends in convection by estimating vertical updraft velocities. Vertical updraft velocities are obtained by combining convective mass fluxes from meteorological analysis data with a parameterization of convective area fraction profiles. We implement two different parameterizations: a parameterization using an observed constant convective area fraction profile and a parameterization that uses randomly drawn profiles to allow for variability. Our scheme is driven by convective mass fluxes and detrainment rates that originate from an external convective parameterization, which can be obtained from meteorological analysis data or from general circulation models. We study the effect of allowing for a variable time that an air parcel spends in convection by performing simulations in which our scheme is implemented into the trajectory module of the ATLAS chemistry and transport model and is driven by the ECMWF ERA-Interim reanalysis data. In particular, we show that the redistribution of air parcels in our scheme conserves the vertical mass distribution and that the scheme is able to reproduce the convective mass fluxes and detrainment rates of ERA-Interim. We further show that the estimated vertical updraft velocities of our scheme are able to reproduce wind profiler measurements performed in Darwin, Australia, for velocities larger than 0.6 m s−1. SO2 is used as an example to show that there is a significant effect on species mixing ratios when modeling the time spent in convective updrafts compared to a redistribution of air parcels in a fixed time step. Furthermore, we perform long-time global trajectory simulations of radon-222 and compare with aircraft measurements of radon activity.

Beschreibung: Holocene permafrost from ice wedge polygons in the vicinity of large seabird breeding colonies in the Thule District, NW Greenland, was drilled to explore the relation between permafrost aggradation and seabird presence. The latter is reliant on the presence of the North Water Polynya (NOW) in the northern Baffin Bay. The onset of peat accumulation associated with the arrival of little auks (Alle alle) in a breeding colony at Annikitisoq, north of Cape York, is radiocarbon-dated to 4400 cal BP. A thick-billed murre (Uria lomvia) colony on Appat (Saunders Island) in the mouth of the Wolstenholme Fjord started 5650 cal BP. Both species provide marine-derived nutrients (MDNs) that fertilize vegetation and promote peat growth. The geochemical signature of organic matter left by the birds is traceable in the frozen Holocene peat. The peat accumulation rates at both sites are highest after the onset, decrease over time, and were about 2-times faster at the little auk site than at the thick-billed murre site. High accumulation rates induce shorter periods of organic matter (OM) decomposition before it enters the perennially frozen state. This is seen in comparably high C=N ratios and less depleted 13C, pointing to a lower degree of OM decomposition at the little auk site, while the opposite pattern can be discerned at the thick-billed murre site. Peat accumulation rates correspond to 15N trends, where decreasing accumulation led to increasing depletion in 15N as seen in the little-auk-related data. In contrast, the more decomposed OM of the thick-billed murre site shows almost stable 15N. Late Holocene wedge ice fed by cold season precipitation was studied at the little auk site and provides the first stable-water isotopic record from Greenland with mean 18O of 8:00:8, mean D of 36:25:7, mean d excess of 7:70:7, and a 18O-D slope of 7.27, which is close to those of the modern Thule meteoric water line. The syngenetic ice wedge polygon development is mirrored in testacean records of the little auk site and delineates polygon low-center, dry-out, and polygon-high-center stages. The syngenetic permafrost formation directly depending on peat growth (controlled by bird activity) falls within the period of neoglacial cooling and the establishment of the NOW, thus indirectly following the Holocene climate trends.

Beschreibung: Coastal erosion and flooding transform terrestrial landscapes into marine environments. In the Arctic, these processes inundate terrestrial permafrost with seawater and create submarine permafrost. Permafrost begins to warm under marine conditions, which can destabilize the sea floor and may release greenhouse gases. We report on the transition of terrestrial to submarine permafrost at a site where the timing of inundation can be inferred from the rate of coastline retreat. On Muostakh Island in the central Laptev Sea, East Siberia, changes in annual coastline position have been measured for decades and vary highly spatially. We hypothesize that these rates are inversely related to the inclination of the upper surface of submarine ice-bonded permafrost (IBP) based on the consequent duration of inundation with increasing distance from the shoreline. We compared rapidly eroding and stable coastal sections of Muostakh Island and find permafrost-table inclinations, determined using direct current resistivity, of 1 and 5 %, respectively. Determinations of submarine IBP depth from a drilling transect in the early 1980s were compared to resistivity profiles from 2011. Based on borehole observations, the thickness of unfrozen sediment overlying the IBP increased from 0 to 14m below sea level with increasing distance from the shoreline. The geoelectrical profiles showed thickening of the unfrozen sediment overlying ice-bonded permafrost over the 28 years since drilling took place. We use geoelectrical estimates of IBP depth to estimate permafrost degradation rates since inundation. Degradation rates decreased from over 0.4ma-1 following inundation to around 0.1ma-1 at the latest after 60 to 110 years and remained constant at this level as the duration of inundation increased to 250 years. We suggest that long-term rates are lower than these values, as the depth to the IBP increases and thermal and porewater solute concentration gradients over depth decrease. For the study region, recent increases in coastal erosion rate and changes in benthic temperature and salinity regimes are expected to affect the depth to submarine permafrost, leading to coastal regions with shallower IBP.

Beschreibung: TR17-08, a marine sedimentary core (14.6 m), was collected during 2017 from the Edisto Inlet (Ross Sea, Antarctica), a small fjord near Cape Hallett. The core is characterized by expanded laminated sedimentary sequences making it suitable for studying submillennial processes during the Early Holocene. By studying different well-known foraminifera species (Globocassidulina biora, G. subglobosa, Trifarina angulosa, Nonionella iridea, Epistominella exigua, Stainforthia feylingi, Miliammina arenacea, Paratrochammina bartrami and Portatrochammina antarctica), we were able to identify five different foraminiferal assemblages over the last ∼ 2000 years BP. Comparison with diatom assemblages and other geochemical proxies retrieved from nearby sediment cores in the Edisto Inlet (BAY05-20 and HLF17-1) made it possible to distinguish three different phases characterized by different environmental settings: (1) a seasonal phase (from 2012 to 1486 years BP) characterized by the dominance of calcareous species, indicating a seasonal opening of the inlet by more frequent events of melting of the sea-ice cover during the austral summer and, in general, a higher-productivity, more open and energetic environment; (2) a transitional phase (from 1486 to 696 years BP) during which the fjord experienced less extensive sea-ice melting, enhanced oxygen-poor conditions and carbonate dissolution conditions, indicated by the shifts from calcareous-dominated association to agglutinated-dominated association probably due to a freshwater input from the retreat of three local glaciers at the start of this period; and (3) a cooler phase (from 696 years BP to present) during which the sedimentation rate decreased and few to no foraminiferal specimens were present, indicating ephemeral openings or a more prolonged cover of the sea ice during the austral summer, affecting the nutrient supply and the sedimentation regime.

Beschreibung: Published

Beschreibung: 95–115

Beschreibung: OSA2: Evoluzione climatica: effetti e loro mitigazione

Beschreibung: JCR Journal

Beschreibung: Sources and Transformations of Anthropogenic Nitrogen along an Urban River-Estuarine Continuum Michael J. Pennino, Sujay S. Kaushal, Sudhir Murthy, Joel Blomquist, Jeff Cornwell, and Lora Harris Biogeosciences Discuss., doi:10.5194/bg-2016-264,2016 Manuscript under review for BG (discussion: open, 0 comments) The results of this manuscript report the analysis of the fate and transport of wastewater and anthropogenic nitrogen along the Potomac River Estuary, from Washington D.C. to the Chesapeake Bay. In conjunction with a mass balance approach, nitrate isotopes were used to estimate fluxes and trace the sources and transformations N along the estuary. This study shows that estuaries have a large capacity to transform N inputs, but with large seasonal variability due to hydrological extremes.

Beschreibung: Boreal fire records in Northern Hemisphere ice cores: A review Michel Legrand, Joseph McConnell, Hubertus Fischer, Eric W. Wolff, Susanne Preunkert, Nathan Chellman, Daiana Leuenberger, Olivia Maselli, Michael Sigl, Simon Schüpbach, and Mike Flannigan Clim. Past Discuss., doi:10.5194/cp-2016-70,2016 Manuscript under review for CP (discussion: open, 0 comments) Here we review previous attempts made to reconstruct past forest fire using chemical signals recorded in Greenland ice. We showed that the Greenland ice records of ammonium, found to be a good fire proxy, consistently indicate changing fire activity in Canada in response to past climatic conditions that occurred since the last 15 000 years including the little ice age and the last large climatic transition.

Beschreibung: Tectonothermal evolution in the core of an arcuate fold and thrust belt: the south-eastern sector of the Cantabrian Zone (Variscan belt, north-western Spain) María Luz Valín, Susana García-López, Covadonga Brime, Fernando Bastida, and Jesús Aller Solid Earth, 7, 1003-1022, doi:10.5194/se-7-1003-2016, 2016 The tectonothermal evolution of an area located in the core of the Ibero-Armorican Arc (Variscan belt) has been determined by using the conodont colour alteration index (CAI), Kübler index of illite (KI), the Árkai index of chlorite (AI) and the analysis of clay minerals and rock cleavage. The area is part of the Cantabrian Zone (CZ), which represents the foreland fold and thrust belt of the orogen. It has been thrust by several large units of the CZ, what resulted in the generation of a large number of synorogenic Carboniferous sediments. CAI, KI and AI values show an irregular distribution of metamorphic grade, independent of stratigraphic position. Two tectonothermal events have been distinguished in the area. The first one, poorly defined, is mainly located in the northern part. It gave rise to very-low-grade metamorphism in some areas and it was associated with a deformation event that resulted in the emplacement of the last large thrust unit and development of upright folds and associated cleavage ( S 1 ). The second tectonothermal event gave rise to low-grade metamorphism and cleavage ( S 2 ) crosscutting earlier upright folds in the central, western and southern parts of the study area. The event continued with the intrusion of small igneous rock bodies, which gave rise to contact metamorphism and hydrothermal alteration. This event was linked to an extensional episode due to a gravitational instability at the end of the Variscan deformation. This tectonothermal evolution occurred during the Gzhelian–Sakmarian. Subsequently, several hydrothermal episodes took place and local crenulation cleavage developed during the Alpine deformation.

Beschreibung: Microstructures and deformation mechanisms in Opalinus Clay: insights from scaly clay from the Main Fault in the Mont Terri Rock Laboratory (CH) Ben Laurich, Janos L. Urai, and Christophe Nussbaum Solid Earth Discuss., doi:10.5194/se-2016-94,2016 Manuscript under review for SE (discussion: open, 0 comments) Scaly clay is a well-known rock fabric that can develop in tectonic systems and that can alter the physical rock properties of a formation. However, internal microstructure and evolution of this fabric remains poorly understood. We examined the scaly microstructure of progressively faulted Opalinus Clay using optical as well as scanning electron microscopy. We present an evolutionary model for scaly clay that is of interest in the evaluation of Opalinus Clay to host radioactive waste.

Beschreibung: Microstructures and deformation mechanisms in Opalinus Clay: insights from scaly clay from the Main Fault in the Mont Terri Rock Laboratory (CH) Ben Laurich, Janos L. Urai, and Christophe Nussbaum Solid Earth Discuss., doi:10.5194/se-2016-94,2016 Manuscript under review for SE (discussion: open, 0 comments) Scaly clay is a well-known rock fabric that can develop in tectonic systems and that can alter the physical rock properties of a formation. However, internal microstructure and evolution of this fabric remains poorly understood. We examined the scaly microstructure of progressively faulted Opalinus Clay using optical as well as scanning electron microscopy. We present an evolutionary model for scaly clay that is of interest in the evaluation of Opalinus Clay to host radioactive waste.

Beschreibung: Fixation kinetics of chelated and non-chelated zinc in semi-arid alkaline soils: application to zinc management Theophilus K. Udeigwe, Madeleine Eichmann, and Matthew C. Menkiti Solid Earth, 7, 1023-1031, doi:10.5194/se-7-1023-2016, 2016 Micronutrient fixation leads to the reduction of plant-available portions. This study examined the fixation kinetics of chelated and non-chelated zinc (Zn) in semi-arid soils. About 30 % more Zn was fixed in the non-chelated system in the first 14 days. Slope of change of Zn to Cu (i.e., Cu–Zn) was higher than other micronutrients. Zn fixation kinetics were better described by a power-function model. Tools developed from this study will be used to advance micronutrient management.

Beschreibung: Improved MODIS Dark Target Aerosol Optical Depth algorithm over land: Angular effect Correction Yerong Wu, Martin de Graaf, and Massimo Menenti Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-185,2016 Manuscript under review for AMT (discussion: open, 0 comments) In this paper, we developed a new algorithm to improve the retrieval of Aerosol Optical Depth (AOD) over land with satellite measurement, by refining the shape of the spectral surface reflectance to improve the estimated background reflectance in the channel used for AOD retrieval. The results show that the angular effects of the retrievals are largely reduced, including fewer occurrences of negative retrievals. This implies that the users can get more accurate data without angular bias.

Beschreibung: Investigation of processes controlling summertime gaseous elemental mercury oxidation at midlatitudinal marine, coastal, and inland sites Zhuyun Ye, Huiting Mao, Che-Jen Lin, and Su Youn Kim Atmos. Chem. Phys., 16, 8461-8478, doi:10.5194/acp-16-8461-2016, 2016 In this study, a state-of-the-art chemical mechanism was incorporated into a box model to investigate the atmospheric Hg cycling in different environments. As a result, for each of the three environments, GOM diurnal cycles of over half the selected cases were reasonably represented by the box model. A realistic model can be a powerful tool, providing important information on atmospheric Hg cycling and implications for policy makers.

Beschreibung: Effects of polar stratospheric clouds in the Nimbus 7 LIMS Version 6 data set Ellis Remsberg and V. Lynn Harvey Atmos. Meas. Tech., 9, 2927-2946, doi:10.5194/amt-9-2927-2016, 2016 Emissions from polar stratospheric cloud (PSC) particles affect the retrieved ozone and water vapor from the Limb Infrared Monitor of the Stratosphere (LIMS) satellite experiment. Threshold criteria are applied to the retrieved ozone for the detection and screening of those effects. The PSC effects correlate very well with regions of coldest temperatures (

Beschreibung: The 1816 ‘year without a summer’ in an atmospheric reanalysis Philip Brohan, Gilbert P. Compo, Stefan Brönnimann, Robert J. Allan, Renate Auchmann, Yuri Brugnara, Prashant D. Sardeshmukh, and Jeffrey S. Whitaker Clim. Past Discuss., doi:10.5194/cp-2016-78,2016 Manuscript under review for CP (discussion: open, 0 comments) We have used modern weather forecasting tools to reconstruct the dreadful European weather of 200 years ago – 1816 was the ‘year without a summer’; harvests failed, and people starved. We can show that 1816’s extreme climate was caused by the eruption of the Tambora volcano the previous year. This means we have some chance of predicting such extreme summers if they occur in future, though this is still a challenge to today’s forecast models.

Beschreibung: Palynological evidence for late Miocene stepwise aridification on the northeastern Tibetan Plateau Jia Liu, Ji Jun Li, Chun Hui Song, Hao Yu, Ting Jiang Peng, Zheng Chuang Hui, and Xi Yan Ye Clim. Past, 12, 1473-1484, doi:10.5194/cp-12-1473-2016, 2016 The late Cenozoic basins in the northeastern Tibetan Plateau document both the tectonic uplift process and its associated environmental changes. Here, we investigated a late Miocene sporopollen record from the Tianshui Basin in the northeastern Tibetan Plateau. The results show that a persistent aridification trend parallels the global cooling of the late Miocene, and the stepwise vegetation succession is consistent with the major uplift events of the Tibetan Plateau.

Beschreibung: Gone or just out of sight? The apparent disappearance of aromatic litter components in soils Thimo Klotzbücher, Karsten Kalbitz, Chiara Cerli, Peter J. Hernes, and Klaus Kaiser SOIL, 2, 325-335, doi:10.5194/soil-2-325-2016, 2016 Uncertainties concerning stabilization of organic compounds in soil limit our basic understanding on soil organic matter (SOM) formation and our ability to model and manage effects of global change on SOM stocks. One controversially debated aspect is the contribution of aromatic litter components, such as lignin and tannins, to stable SOM forms. Here, we summarize and discuss the inconsistencies and propose research options to clear them.

Beschreibung: Structure of Suasselkä Postglacial Fault in northern Finland obtained by analysis of local events and ambient seismic noise Nikita Afonin, Elena Kozlovskaya, Ilmo Kukkonen, and DAFNE/FINLAND Working Group Solid Earth Discuss., doi:10.5194/se-2016-90,2016 Manuscript under review for SE (discussion: open, 0 comments) Understanding inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä post-glacial fault (SPGF) that was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised the area of about 20 to 100 km and consisted of 8 short-period and 4 broad-band 3-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September, 2011–May, 2013. Recordings of the array have being analyzed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä Gold Mine. As a result, we found several dozens of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green’s functions between pairs of stations in the frequency band of 0.1–1 Hz and to calculate correspondent surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curves inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low velocity region as a non-healed mechanically weak fault damage zone (FDZ) that remained after the last major earthquake that occurred after the last glaciation.

Beschreibung: Structure of Suasselkä Postglacial Fault in northern Finland obtained by analysis of local events and ambient seismic noise Nikita Afonin, Elena Kozlovskaya, Ilmo Kukkonen, and DAFNE/FINLAND Working Group Solid Earth Discuss., doi:10.5194/se-2016-90,2016 Manuscript under review for SE (discussion: open, 0 comments) Understanding inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä post-glacial fault (SPGF) that was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised the area of about 20 to 100 km and consisted of 8 short-period and 4 broad-band 3-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September, 2011–May, 2013. Recordings of the array have being analyzed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä Gold Mine. As a result, we found several dozens of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green’s functions between pairs of stations in the frequency band of 0.1–1 Hz and to calculate correspondent surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curves inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low velocity region as a non-healed mechanically weak fault damage zone (FDZ) that remained after the last major earthquake that occurred after the last glaciation.

Beschreibung: Comparison of box counting and correlation dimension methods in well logging data analysis associate with the texture of volcanic rocks D. Mou and Z. W. Wang Nonlin. Processes Geophys. Discuss., doi:10.5194/npg-2014-85,2016 Manuscript under review for NPG (discussion: open, 0 comments) We have developed a fractal analysis method to estimate the dimension of well logging curves in Liaohe oil field, China. The box counting and correlation dimension are methods that can be applied to predict the texture of volcanic rocks with calculation the fractal dimension of well logging curves. The well logging curves are composed of gamma ray (GR), compensated neutron logs (CNL), acoustic (AC), density (DEN), Resistivity lateral log deep ( R LLD ), every curve contains a total of 6000 logging data. The dimension of well logging curves are calculated using box counting and correlation algorithms respectively. It is shown that two types of dimension of CNL, DEN and AC have the same average value. The box counting dimension of volcanic lava is lower than the pyroclastic rock obviously. The majority of correlation dimension of volcanic lava is lower than the pyroclastic rock, but a small amount of correlation dimension of volcanic lava is equal to the pyroclastic rock. It is demonstrated that the box counting dimension is more suitable for predicting the texture of volcanic rocks. Applications to logging data, A well show the relationship between the fractal dimension and the texture of volcanic rock in certain depth.

Beschreibung: First year of the new Arctic AWIPEV-COSYNA cabled Underwater Observatory in Kongsfjorden, Spitsbergen Philipp Fischer, Max Schwanitz, Reiner Loth, Uwe Posner, Markus Brand, and Friedhelm Schröder Ocean Sci. Discuss., doi:10.5194/os-2016-52,2016 Manuscript under review for OS (discussion: open, 0 comments) We observed oceanographic and community data from October 2013 to November 2014 in the shallow waters of Kongsfjorden on the west coast of Svalbard (Norway) using remote controlled hydrographic and optic sensors. Daily vertical profiles of temperature, salinity and turbidity were sampled together with stereo images of the macrobiotic community, including fish. A distinct seasonal cycle in total species abundances was found with surprisingly high animal counts during the polar winter.

Beschreibung: Landfast ice thickness in the Canadian Arctic Archipelago from observations and models Stephen E. L. Howell, Frédéric Laliberté, Ron Kwok, Chris Derksen, and Joshua King The Cryosphere, 10, 1463-1475, doi:10.5194/tc-10-1463-2016, 2016 The Canadian Ice Service record of observed landfast ice and snow thickness represents one of the longest in the Arctic that spans over 5 decades. We analyze this record to report on long-term trends and variability of ice and snow thickness within the Canadian Arctic Archipelago (CAA). Results indicate a thinning of ice at several sites in the CAA. State-of-the-art climate models still have difficultly capturing observed ice thickness values in the CAA and should be used with caution.

Beschreibung: Coastal dynamics and submarine permafrost in shallow water of the central Laptev Sea, East Siberia Pier Paul Overduin, Sebastian Wetterich, Frank Günther, Mikhail N. Grigoriev, Guido Grosse, Lutz Schirrmeister, Hans-Wolfgang Hubberten, and Aleksandr Makarov The Cryosphere, 10, 1449-1462, doi:10.5194/tc-10-1449-2016, 2016 How fast does permafrost warm up and thaw after it is covered by the sea? Ice-rich permafrost in the Laptev Sea, Siberia, is rapidly eroded by warm air and waves. We used a floating electrical technique to measure the depth of permafrost thaw below the sea, and compared it to 60 years of coastline retreat and permafrost depths from drilling 30 years ago. Thaw is rapid right after flooding of the land and slows over time. The depth of permafrost is related to how fast the coast retreats.

Beschreibung: Age of the Mt. Ortles ice cores, the Tyrolean Iceman and glaciation of the highest summit of South Tyrol since the Northern Hemisphere Climatic Optimum Paolo Gabrielli, Carlo Barbante, Giuliano Bertagna, Michele Bertó, Daniel Binder, Alberto Carton, Luca Carturan, Federico Cazorzi, Giulio Cozzi, Giancarlo Dalla Fontana, Mary Davis, Fabrizio De Blasi, Roberto Dinale, Gianfranco Dragà, Giuliano Dreossi, Daniela Festi, Massimo Frezzotti, Jacopo Gabrieli, Stephan Galos, Patrick Ginot, Petra Heidenwolf, Theo M. Jenk, Natalie Kehrwald, Donald Kenny, Olivier Magand, Volkmar Mair, Vladimir Mikhalenko, Ping Nan Lin, Klaus Oeggl, Gianni Piffer, Mirko Rinaldi, Ulrich Schotterer, Margit Schwikowski, Roberto Seppi, Andrea Spolaor, Barbara Stenni, Davdi Tonidandel, CChiara Uglietti, Victor Zagorodnov, Thomas Zanoner, and Piero Zennaro The Cryosphere Discuss., doi:10.5194/tc-2016-159,2016 Manuscript under review for TC (discussion: open, 0 comments) New ice cores were extracted from Alto dell'Ortles, the highest glacier of South Tyrol in the Italian Alps, to check whether prehistoric ice, that is coeval to the famous 5200 years old Tyrolean Iceman, is still preserved in this region. Dating of the ice cores confirms the hypothesis and indicates that the drilling site was glaciated since the end of the Northern Hemisphere Climatic Optimum (7000 BP). We also infer that an unprecedented acceleration of the glacier flow has just recently begun.

Beschreibung: Combined diurnal variations of discharge and hydrochemistry of the Isunnguata Sermia outlet of the Greenland Ice Sheet give in sight on sub glacial conditions Joseph Graly, Joel Harrington, and Neil Humphrey The Cryosphere Discuss., doi:10.5194/tc-2016-137,2016 Manuscript under review for TC (discussion: open, 0 comments) At a major outlet of the Greenland Ice Sheet in West Greenland, we find that the chemical solutes is the emerging subglacial waters are out of phase with water discharge and can spike in concentration during waning flow. This suggests that the subglacial waters are spreading out across a large area of the glacial bed throughout the day, stimulating chemical weathering beyond the major water distribution channels.

Beschreibung: Why did the storm ex-Gaston (2010) fail to redevelop during the PREDICT experiment? Thomas M. Freismuth, Blake Rutherford, Mark A. Boothe, and Michael T. Montgomery Atmos. Chem. Phys., 16, 8511-8519, doi:10.5194/acp-16-8511-2016, 2016 Numerical model analyses are used to investigate the role of dry, environmental air in the failed redevelopment of a tropical cyclone (ex-Gaston, 2010). As early as 12:00 UTC 2 September 2010, a dry layer at and above 600 hPa results in a decrease in the vertical mass flux and vertical, relative vorticity. The intrusion of dry air led to a reduction in vorticity and a compromised pouch at these middle levels. This study supports work looking at the role of dry air in moist convection.

Beschreibung: A comparative analysis of UV nadir-backscatter and infrared limb-emission ozone data assimilation Rossana Dragani Atmos. Chem. Phys., 16, 8539-8557, doi:10.5194/acp-16-8539-2016, 2016 We present an assessment of ultraviolet nadir-backscatter and infrared limb-emission ozone data assimilation. Understanding the differences in the impact produced by the assimilation of limb and nadir ozone data is relevant to many applications, including climate reanalysis and air quality. The results show the potential and limitations of each dataset and support the need for a more balanced long-term availability of both types of sensors than currently envisaged.

Beschreibung: Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau Mathieu Casado, Amaelle Landais, Valérie Masson-Delmotte, Christophe Genthon, Erik Kerstel, Samir Kassi, Laurent Arnaud, Ghislain Picard, Frederic Prie, Olivier Cattani, Hans-Christian Steen-Larsen, Etienne Vignon, and Peter Cermak Atmos. Chem. Phys., 16, 8521-8538, doi:10.5194/acp-16-8521-2016, 2016 Climatic conditions in Concordia are very cold (−55 °C in average) and very dry, imposing difficult conditions to measure the water vapour isotopic composition. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces (down to 20 ppmv). Here we present the results results of a first campaign of measurement of isotopic composition of water vapour in Concordia, the site where the 800 000 years long ice core was drilled.

Beschreibung: Surface Renewal as a Significant Mechanism for Dust Emission Jie Zhang, Zhenjiao Teng, Ning Huang, Lei Guo, and Yaping Shao Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-421,2016 Manuscript under review for ACP (discussion: open, 0 comments) In spite of the tremendous efforts, many questions remain unanswered regarding dust emission mechanisms. A series of wind-tunnel experiments are carried out on dust emissions from different soil surfaces to better understand relevant mechanisms. Here are some interesting results that demonstrate the importance of surface renewal mechanism which was normally neglected in previous researches and is strongly recommended to be considered in future dust models.

Beschreibung: Variations in O 3 , CO, and CH 4 over the Bay of Bengal during the summer monsoon season: Ship-borne measurements and model simulations Imran A. Girach, Narendra Ojha, Prabha R. Nair, Andrea Pozzer, Yogesh K. Tiwari, K. Ravi Kumar, and Jos Lelieveld Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-595,2016 Manuscript under review for ACP (discussion: open, 0 comments) This study presents first ship-borne measurements of trace gases over the Bay of Bengal during summer monsoon. The observed variations in trace gases are shown to be due to dynamics/transport and en-route photochemistry. Analysis of meteorological and chemical fields shows that significantly lower ozone during rainfall is associated with the downdrafts. A regional model reproduces the observed variations and revealed the rapid transport of ozone across the Bay of Bengal during an event.

Beschreibung: Chemical Characteristics of Marine Fine Aerosols over Sea and at Offshore Islands during Three Cruise Sampling Campaigns in the Taiwan Strait– Sea Salts and Anthropogenic Particles Tsung-Chang Li, Chung-Shin Yuan, Chung-Hsuang Hung, Hsun-Yu Lin, Hu-Ching Huang, and Chon-Lin Lee Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-384,2016 Manuscript under review for ACP (discussion: open, 0 comments) This manuscript is significant because it is important to establish data on the background physicochemical characteristics of atmospheric fine particles, as well as their spatial distributions and seasonal variations given various meteorological conditions, and the results of this study will be very much valuable for clarifying the transportation PM 2.5 over sea and at the offshore islands at the Taiwan Strait, which can further fill the the important blank for the global atmospheric research.

Beschreibung: Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau Mathieu Casado, Amaelle Landais, Valérie Masson-Delmotte, Christophe Genthon, Erik Kerstel, Samir Kassi, Laurent Arnaud, Ghislain Picard, Frederic Prie, Olivier Cattani, Hans-Christian Steen-Larsen, Etienne Vignon, and Peter Cermak Atmos. Chem. Phys., 16, 8521-8538, doi:10.5194/acp-16-8521-2016, 2016 Climatic conditions in Concordia are very cold (−55 °C in average) and very dry, imposing difficult conditions to measure the water vapour isotopic composition. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces (down to 20 ppmv). Here we present the results results of a first campaign of measurement of isotopic composition of water vapour in Concordia, the site where the 800 000 years long ice core was drilled.

Beschreibung: On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East Dimitris Akritidis, Andrea Pozzer, Prodromos Zanis, Evangelos Tyrlis, Bojan Škerlak, Michael Sprenger, and Jos Lelieveld Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-547,2016 Manuscript under review for ACP (discussion: open, 0 comments) We investigate the contribution of tropopause folds in the summertime tropospheric ozone pool over the eastern Mediterranean and the Middle East. For this purpose we use the EMAC atmospheric chemistry climate model and a fold identification algorithm. A clear increase of ozone is found in the middle troposphere due to fold activity. The interannual variability of near surface ozone over the eastern Mediterranean is related to that of both tropopause folds and ozone in the free troposphere.

Beschreibung: A Polarimetric Scattering Database for Non-spherical Ice Particles at MicrowaveWavelengths Yinghui Lu, Zhiyuan Jiang, Kultegin Aydin, Johannes Verlinde, Eugene E. Clothiaux, and Giovanni Botta Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-228,2016 Manuscript under review for AMT (discussion: open, 0 comments) The database contains the complete(polarimatric) scattering information for different types of ice particles at different incident and scattered radiation directions at 4 microwave wavelengths. These results are useful for understanding the dependence of ice-particle scattering properties on ice-particle orientation with respect to the incident and scattered radiation. It is also useful in ice property retrievals, radar forward simulation.

Beschreibung: Variations in O 3 , CO, and CH 4 over the Bay of Bengal during the summer monsoon season: Ship-borne measurements and model simulations Imran A. Girach, Narendra Ojha, Prabha R. Nair, Andrea Pozzer, Yogesh K. Tiwari, K. Ravi Kumar, and Jos Lelieveld Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-595,2016 Manuscript under review for ACP (discussion: open, 0 comments) This study presents first ship-borne measurements of trace gases over the Bay of Bengal during summer monsoon. The observed variations in trace gases are shown to be due to dynamics/transport and en-route photochemistry. Analysis of meteorological and chemical fields shows that significantly lower ozone during rainfall is associated with the downdrafts. A regional model reproduces the observed variations and revealed the rapid transport of ozone across the Bay of Bengal during an event.

Beschreibung: A comparative analysis of UV nadir-backscatter and infrared limb-emission ozone data assimilation Rossana Dragani Atmos. Chem. Phys., 16, 8539-8557, doi:10.5194/acp-16-8539-2016, 2016 We present an assessment of ultraviolet nadir-backscatter and infrared limb-emission ozone data assimilation. Understanding the differences in the impact produced by the assimilation of limb and nadir ozone data is relevant to many applications, including climate reanalysis and air quality. The results show the potential and limitations of each dataset and support the need for a more balanced long-term availability of both types of sensors than currently envisaged.

Beschreibung: Why did the storm ex-Gaston (2010) fail to redevelop during the PREDICT experiment? Thomas M. Freismuth, Blake Rutherford, Mark A. Boothe, and Michael T. Montgomery Atmos. Chem. Phys., 16, 8511-8519, doi:10.5194/acp-16-8511-2016, 2016 Numerical model analyses are used to investigate the role of dry, environmental air in the failed redevelopment of a tropical cyclone (ex-Gaston, 2010). As early as 12:00 UTC 2 September 2010, a dry layer at and above 600 hPa results in a decrease in the vertical mass flux and vertical, relative vorticity. The intrusion of dry air led to a reduction in vorticity and a compromised pouch at these middle levels. This study supports work looking at the role of dry air in moist convection.

Beschreibung: Thermal infrared laser heterodyne spectro-radiometry for solar occultation atmospheric CO 2 measurements Alex Hoffmann, Neil A. Macleod, Marko Huebner, and Damien Weidmann Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-142,2016 Manuscript under review for AMT (discussion: open, 0 comments) This paper focuses on the demonstration and assessment of thermal infrared laser heterodyne spectro-radiometry for the remote sensing of carbon dioxide (CO 2 ). A research instrument has been developed and operated from the ground using direct sunlight to measure CO 2 to a high precision. This technology would enable the development of high-performance miniature ground-based sounders to complement existing measurement networks and contribute to the improvement of global carbon emission assessment.

Beschreibung: A Polarimetric Scattering Database for Non-spherical Ice Particles at MicrowaveWavelengths Yinghui Lu, Zhiyuan Jiang, Kultegin Aydin, Johannes Verlinde, Eugene E. Clothiaux, and Giovanni Botta Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-228,2016 Manuscript under review for AMT (discussion: open, 0 comments) The database contains the complete(polarimatric) scattering information for different types of ice particles at different incident and scattered radiation directions at 4 microwave wavelengths. These results are useful for understanding the dependence of ice-particle scattering properties on ice-particle orientation with respect to the incident and scattered radiation. It is also useful in ice property retrievals, radar forward simulation.

Beschreibung: Chemical Characteristics of Marine Fine Aerosols over Sea and at Offshore Islands during Three Cruise Sampling Campaigns in the Taiwan Strait– Sea Salts and Anthropogenic Particles Tsung-Chang Li, Chung-Shin Yuan, Chung-Hsuang Hung, Hsun-Yu Lin, Hu-Ching Huang, and Chon-Lin Lee Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-384,2016 Manuscript under review for ACP (discussion: open, 0 comments) This manuscript is significant because it is important to establish data on the background physicochemical characteristics of atmospheric fine particles, as well as their spatial distributions and seasonal variations given various meteorological conditions, and the results of this study will be very much valuable for clarifying the transportation PM 2.5 over sea and at the offshore islands at the Taiwan Strait, which can further fill the the important blank for the global atmospheric research.

Beschreibung: Evaluation of Machine Learning Algorithms for Classification of Primary Biological Aerosol using a new UV-LIF spectrometer Simon Ruske, David O. Topping, Virginia E. Foot, Paul H. Kaye, Warren R. Stanley, Ian Crawford, Andrew P. Morse, and Martin W. Gallagher Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-214,2016 Manuscript under review for AMT (discussion: open, 0 comments) Particles such as Bacteria, Pollen and Fungal spores have important implications within the environment and public health sectors. Here we evaluate the performance of various different methods for distinguishing between these different types of particles using a new instrument. We demonstrate that there may be better alternatives to the currently used methods which can be further investigated in future research.

Beschreibung: Identification of the cloud base height over the central Himalayan region: Intercomparison of Ceilometer and Doppler Lidar K. K. Shukla, K. Niranjan Kumar, D. V. Phanikumar, R. K. Newsom, V. R. Kotamarthi, T. B. M. J. Ouarda, and M. V. Ratnam Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-162,2016 Manuscript under review for AMT (discussion: open, 0 comments) Estimation of Cloud base height was carried out by using various ground based instruments (Doppler Lidar and Ceilometer) and satellite datasets (MODIS) over central Himalayan region for the first time. The present study demonstrates the potential of Doppler Lidar in precise estimation of cloud base height and updraft velocities. More such deployments will be invaluable inputs for regional weather prediction models over complex Himalayan terrains.

Beschreibung: On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East Dimitris Akritidis, Andrea Pozzer, Prodromos Zanis, Evangelos Tyrlis, Bojan Škerlak, Michael Sprenger, and Jos Lelieveld Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-547,2016 Manuscript under review for ACP (discussion: open, 0 comments) We investigate the contribution of tropopause folds in the summertime tropospheric ozone pool over the eastern Mediterranean and the Middle East. For this purpose we use the EMAC atmospheric chemistry climate model and a fold identification algorithm. A clear increase of ozone is found in the middle troposphere due to fold activity. The interannual variability of near surface ozone over the eastern Mediterranean is related to that of both tropopause folds and ozone in the free troposphere.

Beschreibung: Increased nitrate and decreased δ 15 N–NO 3 − in the Greenland Arctic after 1940 attributed to North American oil burning Nathan J. Chellman, Meredith G. Hastings, and Joseph R. McConnell The Cryosphere Discuss., doi:10.5194/tc-2016-163,2016 Manuscript under review for TC (discussion: open, 0 comments) This manuscript analyzes the changing sources of nitrate deposition to Greenland since 1760 CE using a dataset consisting of sub-seasonally resolved nitrogen isotopes of nitrate and source tracers. Correlations amongst ion concentration, source tracers, and the δ 15 N–NO 3 − provide evidence of the impact of biomass burning and fossil fuel combustion emissions of nitrogen oxides and suggest that oil combustion is the likely driver of increased nitrate concentration in Greenland ice since 1940 CE.

Beschreibung: Inversion of geothermal heat flux in a thermomechanically coupled nonlinear Stokes ice sheet model Hongyu Zhu, Noemi Petra, Georg Stadler, Tobin Isaac, Thomas J. R. Hughes, and Omar Ghattas The Cryosphere, 10, 1477-1494, doi:10.5194/tc-10-1477-2016, 2016 We study how well the basal geothermal heat flux can be inferred from surface velocity observations using a thermomechanically coupled nonlinear Stokes ice sheet model. The prospects and limitations of this inversion is studied in two and three dimensional model problems. We also argue that a one-way coupled approach for the adjoint equations motivated by staggered solvers for forward multiphysics problems can lead to an incorrect gradient and premature termination of the optimization iteration.

Beschreibung: Increased nitrate and decreased δ 15 N–NO 3 − in the Greenland Arctic after 1940 attributed to North American oil burning Nathan J. Chellman, Meredith G. Hastings, and Joseph R. McConnell The Cryosphere Discuss., doi:10.5194/tc-2016-163,2016 Manuscript under review for TC (discussion: open, 0 comments) This manuscript analyzes the changing sources of nitrate deposition to Greenland since 1760 CE using a dataset consisting of sub-seasonally resolved nitrogen isotopes of nitrate and source tracers. Correlations amongst ion concentration, source tracers, and the δ 15 N–NO 3 − provide evidence of the impact of biomass burning and fossil fuel combustion emissions of nitrogen oxides and suggest that oil combustion is the likely driver of increased nitrate concentration in Greenland ice since 1940 CE.

Beschreibung: Improving the inter-hemispheric gradient of total column atmospheric CO 2 and CH 4 in simulations with the ECMWF semi-Lagrangian atmospheric global model Anna Agusti-Panareda, Michail Diamantakis, Victor Bayona, Friedrich Klappenbach, and Andre Butz Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-143,2016 Manuscript under review for GMD (discussion: open, 0 comments) This paper demonstrates how important mass fixers can be in the simulation of long-lived greenhouse gases using transport models based on the highly efficient semi-lagrangian advection scheme. Mass fixers can have a large impact on the representation of the inter-hemispheric gradient of CO 2 and CH 4 , a crucial feature of their distribution. This work is relevant for models simulating atmospheric composition that use semi-lagrangian advection schemes both for climate and air quality applications.

Beschreibung: sUAS and their application in observing geomorphological processes Jozef Gallik and Lenka Bolešová Solid Earth, 7, 1033-1042, doi:10.5194/se-7-1033-2016, 2016 Technology is moving ahead very fast, and so researchers have new possibilities for their research. We tried to demonstrate benefits of using remote-sensing technology (Phantom 1 drone) such as its accuracy in the terrain, easy access to hardly accessible areas, and the possibility to collect data even during unfavourable weather conditions. The high mountainous environment provided us great conditions for testing the drone as a device for very easy and accurate mapping of natural phenomena.

Beschreibung: Response of seasonal soil freeze depth to climate change across China Xiaoqing Peng, Oliver W. Frauenfeld, Tingjun Zhang, Kang Wang, Bin Cao, Xinyue Zhong, Hang Su, and Cuicui Mu The Cryosphere Discuss., doi:10.5194/tc-2016-129,2016 Manuscript under review for TC (discussion: open, 0 comments) Previous researches paid more attention on the permafrost, e.g. active layer thickness, soil temperature, permafrost area extent, and associated with permafrost degradation leading other changes. However, seasonally frozen ground, vast area extent, did not focus by so much attention. Here, we combined more than 800 observation station data and gridded data to investigate soil freeze depth across China. The results indicate that soil freeze depth increase with climate warming.

Beschreibung: Slight glacier reduction over the northwestern Tibetan Plateau despite significant recent warming Yetang Wang, Shugui Hou, Wenling An, Hongxi Pang, and Yaping Liu The Cryosphere Discuss., doi:10.5194/tc-2016-165,2016 Manuscript under review for TC (discussion: open, 0 comments) This study further confirms "Pamir–Karakoram–Western-Kunlun-Mountain (northwestern Tibetan Plateau) Glacier Anomaly". Slight glacier reduction over the northwestern Tibetan Plateau may result from more accumulation from increased precipitation in winter which to great extent protects it from mass reductions under climate warming during 1961–2000. Warming slowdown since 2000 happening at this region may further mitigate glacier mass reduction.

Beschreibung: Response of seasonal soil freeze depth to climate change across China Xiaoqing Peng, Oliver W. Frauenfeld, Tingjun Zhang, Kang Wang, Bin Cao, Xinyue Zhong, Hang Su, and Cuicui Mu The Cryosphere Discuss., doi:10.5194/tc-2016-129,2016 Manuscript under review for TC (discussion: open, 0 comments) Previous researches paid more attention on the permafrost, e.g. active layer thickness, soil temperature, permafrost area extent, and associated with permafrost degradation leading other changes. However, seasonally frozen ground, vast area extent, did not focus by so much attention. Here, we combined more than 800 observation station data and gridded data to investigate soil freeze depth across China. The results indicate that soil freeze depth increase with climate warming.

Beschreibung: Effect of tropical cyclones on the stratosphere–troposphere exchange observed using satellite observations over the north Indian Ocean M. Venkat Ratnam, S. Ravindra Babu, S. S. Das, G. Basha, B. V. Krishnamurthy, and B. Venkateswararao Atmos. Chem. Phys., 16, 8581-8591, doi:10.5194/acp-16-8581-2016, 2016 The impact of cyclones that occurred over the north Indian Ocean during 2007–2013 on the STE process is quantified using satellite observations. It is shown that cyclones have a significant impact on the tropopause structure, ozone and water vapour budget, and consequentially STE in the UTLS region. The cross-tropopause mass flux from the stratosphere to the troposphere for cyclonic storms is found to be 0.05 ± 0.29 × 10 −3  kg m −2 , and for very severe cyclonic storms it is 0.5 ± 1.07 × 10 −3  kg m −2 .

Beschreibung: Variation of CCN activity during new particle formation events in the North China Plain Nan Ma, Chunsheng Zhao, Jiangchuan Tao, Zhijun Wu, Simonas Kecorius, Zhibin Wang, Johannes Größ, Hongjian Liu, Yuxuan Bian, Ye Kuang, Monique Teich, Gerald Spindler, Konrad Müller, Dominik van Pinxteren, Hartmut Herrmann, Min Hu, and Alfred Wiedensohler Atmos. Chem. Phys., 16, 8593-8607, doi:10.5194/acp-16-8593-2016, 2016 New particle formation (NPF) is one of main sources of cloud condensation nuclei (CCN) in the atmosphere. Based on in situ measurements, we found that CCN activity of newly formed particles largely differs in different NPF events. It is therefore difficult to find a simple parameterization of CCN activity for NPF events. Using a fixed size-resolved activation ratio curve or critical diameter is very likely to result in large biases up to 50 % in the calculated N CCN during NPF events.

Beschreibung: Real time retrieval of volcanic cloud particles and SO 2 by satellite using an improved simplified approach Sergio Pugnaghi, Lorenzo Guerrieri, Stefano Corradini, and Luca Merucci Atmos. Meas. Tech., 9, 3053-3062, doi:10.5194/amt-9-3053-2016, 2016 Volcanic plume removal (VPR) is a procedure developed to retrieve the ash optical depth, effective radius and mass, and sulfur dioxide mass contained in a volcanic cloud from the thermal radiance at 8.7, 11, and 12 µm. It is based on an estimation of a virtual image representing what the sensor would have seen in a multispectral thermal image if the volcanic cloud were not present. Ash and sulfur dioxide were retrieved by the first version of the VPR using a very simple atmospheric model that ignored the layer above the volcanic cloud. This new version takes into account the layer of atmosphere above the cloud as well as thermal radiance scattering along the line of sight of the sensor. In addition to improved results, the new version also offers an easier and faster preliminary preparation and includes other types of volcanic particles (andesite, obsidian, pumice, ice crystals, and water droplets). As in the previous version, a set of parameters regarding the volcanic area, particle types, and sensor is required to run the procedure. However, in the new version, only the mean plume temperature is required as input data. In this work, a set of parameters to compute the volcanic cloud transmittance in the three quoted bands, for all the aforementioned particles, for both Mt. Etna (Italy) and Eyjafjallajökull (Iceland) volcanoes, and for the Terra and Aqua MODIS instruments is presented. Three types of tests are carried out to verify the results of the improved VPR. The first uses all the radiative transfer simulations performed to estimate the above mentioned parameters. The second one makes use of two synthetic images, one for Mt. Etna and one for Eyjafjallajökull volcanoes. The third one compares VPR and Look-Up Table (LUT) retrievals analyzing the true image of Eyjafjallajökull volcano acquired by MODIS aboard the Aqua satellite on 11 May 2010 at 14:05 GMT.

Beschreibung: Temperature-dependence of aerosol optical depth over the southeastern US Tero Mielonen, Anca Hienola, Thomas Kühn, Joonas Merikanto, Antti Lipponen, Tommi Bergman, Hannele Korhonen, Pekka Kolmonen, Larisa Sogacheva, Darren Ghent, Antti Arola, Gerrit de Leeuw, and Harri Kokkola Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-625,2016 Manuscript under review for ACP (discussion: open, 0 comments) We studied the temperature dependence of AOD and its radiative effects over the southeastern US. We used spaceborne observations of AOD, LST and tropospheric NO 2 with simulations of ECHAM-HAMMOZ. The level of AOD in this region is governed by anthropogenic emissions but the temperature dependency is most likely caused by BVOC emissions. According to the observations and simulations, the regional clear-sky DRE for biogenic aerosols is −0.43 ± 0.88 W/m 2 /K and −0.86 ± 0.06 W/m 2 /K, respectively.

Beschreibung: Stratospheric Air Sub-sampler (SAS) and its application to analysis of Δ 17 O(CO 2 ) from small air samples collected with an AirCore Dorota Janina Mrozek, Carina van der Veen, Magdalena E. G. Hofmann, Huilin Chen, Rigel Kivi, Pauli Heikkinen, and Thomas Röckmann Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-124,2016 Manuscript under review for AMT (discussion: open, 0 comments) Stratospheric Air Sub-sampler (SAS) is a device to collect and to store the stratospheric profile of air collected with an AirCore (Karion et al, 2010) in numerous sub-samples. The sub-samples (each of 25 mL at ambient temperature and pressure) can be later introduced to the continuous flow systems to measure for example the isotopic composition of CO 2 . The performance of the coupled system is demonstrated for a set of air samples from an AirCore flight in November 2014 near Sodankylä, Finland.

Beschreibung: Real time retrieval of volcanic cloud particles and SO 2 by satellite using an improved simplified approach Sergio Pugnaghi, Lorenzo Guerrieri, Stefano Corradini, and Luca Merucci Atmos. Meas. Tech., 9, 3053-3062, doi:10.5194/amt-9-3053-2016, 2016 Volcanic plume removal (VPR) is a procedure developed to retrieve the ash optical depth, effective radius and mass, and sulfur dioxide mass contained in a volcanic cloud from the thermal radiance at 8.7, 11, and 12 µm. It is based on an estimation of a virtual image representing what the sensor would have seen in a multispectral thermal image if the volcanic cloud were not present. Ash and sulfur dioxide were retrieved by the first version of the VPR using a very simple atmospheric model that ignored the layer above the volcanic cloud. This new version takes into account the layer of atmosphere above the cloud as well as thermal radiance scattering along the line of sight of the sensor. In addition to improved results, the new version also offers an easier and faster preliminary preparation and includes other types of volcanic particles (andesite, obsidian, pumice, ice crystals, and water droplets). As in the previous version, a set of parameters regarding the volcanic area, particle types, and sensor is required to run the procedure. However, in the new version, only the mean plume temperature is required as input data. In this work, a set of parameters to compute the volcanic cloud transmittance in the three quoted bands, for all the aforementioned particles, for both Mt. Etna (Italy) and Eyjafjallajökull (Iceland) volcanoes, and for the Terra and Aqua MODIS instruments is presented. Three types of tests are carried out to verify the results of the improved VPR. The first uses all the radiative transfer simulations performed to estimate the above mentioned parameters. The second one makes use of two synthetic images, one for Mt. Etna and one for Eyjafjallajökull volcanoes. The third one compares VPR and Look-Up Table (LUT) retrievals analyzing the true image of Eyjafjallajökull volcano acquired by MODIS aboard the Aqua satellite on 11 May 2010 at 14:05 GMT.

Beschreibung: Evaluation of IWV from the numerical weather prediction WRF model with PPP GNSS processing for Bulgaria Tzvetan Simeonov, Dmitry Sidorov, Felix Norman Teferle, Georgi Milev, and Guergana Guerova Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-152,2016 Manuscript under review for AMT (discussion: open, 0 comments) Global Navigation Satellite Systems (GNSS) meteorology is an established operational service providing hourly updated GNSS tropospheric products to the National Meteorologic Services (NMS) in Europe. In the last decade through the ground-based GNSS network densification and new processing strategies like Precise Point Positioning (PPP) it has become possible to obtain sub-hourly tropospheric products for monitoring severe weather events. In this work one year (January–December 2013) of sub-hourly GNSS tropospheric products (Zenith Total Delay) are computed using the PPP strategy for seven stations in Bulgaria. In order to take advantage of the sub-hourly GNSS data to derive Integrated Water Vapour (IWV) surface pressure and temperature with similar temporal resolution is required. As the surface observations are on 3 hourly basis the first step is to compare the surface pressure and temperature from numerical weather prediction model Weather Forecasting and Research (WRF) with observations at three synoptic stations in Bulgaria. The mean difference between the two data-sets for 1) surface pressure is less than 0.5 hPa and the correlation is over 0.989, 2) temperature the largest mean difference is 1.1 °C and the correlation coefficient is over 0.957 and 3) IWV mean difference is in range 0.1–1.1 mm. The evaluation of WRF on annual bases shows IWV underestimation between 0.5 and 1.5 mm at five stations and overestimation at Varna and Rozhen. Varna and Rozhen have also much smaller correlation 0.9 and 0.76. The study of the monthly IWV variation shows that at those locations the GNSS IWV has unexpected drop in April and March respectively. The reason for this drop is likely problems with station raw data. At the remaining 5 stations a very good agreement between GNSS and WRF is observed with high correlation during the cold part of 2013 i.e. March, October and December (0.95) and low correlation during the warm part of 2013 i.e. April to August (below 0.9). The diurnal cycle of the WRF model shows a dry bias in the range of 0.5-1.5 mm. Between 00 and 01 UTC the GNSS IWV tends to be underestimate IWV which is likely due to the processing window used. The precipitation efficiency from GNSS and WRF show very good agreement on monthly bases with a maximum in May-June and minimum in August–September. The annual precipitation efficiency in 2013 at Lovech and Burgas is about 6 %.

Beschreibung: Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra Inge Juszak, Werner Eugster, Monique M. P. D. Heijmans, and Gabriela Schaepman-Strub Biogeosciences, 13, 4049-4064, doi:10.1594/PANGAEA.860561, 2016 Changes in Arctic vegetation composition and structure feed back to climate and permafrost. Using field observations at a Siberian tundra site, we find that dwarf shrubs absorb more solar radiation than wet sedges and thus amplify surface warming, especially during snow melt. On the other hand, permafrost thaw was enhanced below sedges as a consequence of high soil moisture. Standing dead sedge leaves affected the radiation budget strongly and deserve more scientific attention.

Beschreibung: Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt Maria-Angela Bassetti, Serge Berné, Marie-Alexandrine Sicre, Bernard Dennielou, Yoann Alonso, Roselyne Buscail, Bassem Jalali, Bertil Hebert, and Christophe Menniti Clim. Past, 12, 1539-1553, doi:10.5194/cp-12-1539-2016, 2016 This work represents the first attempt to decipher the linkages between rapid climate changes and continental Holocene paleohydrology in the NW Mediterranean shallow marine setting. Between 11 and 4 ka cal BP, terrigenous input increased and reached a maximum at 7 ka cal BP, probably as a result of a humid phase. From ca. 4 ka cal BP to the present, enhanced variability in the land-derived material is possibly due to large-scale atmospheric circulation and rainfall patterns in western Europe.

Beschreibung: Effects of Multiple Doppler Radar data assimilation on the numerical simulation of a Flash Flood Event during the HyMeX campaign Ida Maiello, Sabrina Gentile, Rossella Ferretti, Luca Baldini, Nicoletta Roberto, Errico Picciotti, Pier Paolo Alberoni, and Frank S. Marzano Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-320,2016 Manuscript under review for HESS (discussion: open, 0 comments) An analysis to evaluate the impact of assimilating multiple radar data with a three dimensional variational (3D-Var) system on a heavy precipitation event is presented. The main goal is to establish a general methodology to quantitatively assess the performance of flash-flood numerical weather prediction at mesoscale. In this respect, during the first Special Observation Period (SOP1) of HyMeX (Hydrological cycle in the Mediterranean Experiment) campaign several Intensive Observing Periods (IOPs) were launched and nine occurred in Italy. Among them IOP4 is chosen for this study because of its low predictability. This event hit central Italy on 14 September 2012 producing heavy precipitation and causing several damages. Data taken from three C-band radars running operationally during the event are assimilated to improve high resolution initial conditions. In order to evaluate the impact of the assimilation procedure at different horizontal resolution and to assess the impact of assimilating multiple radars data, several experiments using Weather Research and Forecasting (WRF) model are performed. Finally, the statistical indexes as accuracy, equitable threat score, false alarm ratio and frequency bias are used to objectively compare the experiments, using rain gauges data as benchmark.

Beschreibung: Model-based study of the role of rainfall and land use–land cover in the changes in the occurrence and intensity of Niger red floods in Niamey between 1953 and 2012 Claire Casse, Marielle Gosset, Théo Vischel, Guillaume Quantin, and Bachir Alkali Tanimoun Hydrol. Earth Syst. Sci., 20, 2841-2859, doi:10.5194/hess-20-2841-2016, 2016 Since 1950, the Niger River basin has overcome drastic changes. In Niamey city, the highest river levels and the longest flooded period ever recorded occurred in 2003, 2010, 2012 and 2013, with heavy casualties and property damage. The reasons for these changes, and the relative role of climate versus Land Use Land Cover changes are still debated and are investigated in this paper using observations and modelling. We conclude on the successive role of cover and then rainfall variability.

Beschreibung: Upscaling instantaneous to daily evapotranspiration using modelled daily shortwave radiation for remote sensing applications: an Artificial Neural Network approach Loise Wandera, Kaninska Mallick, Gerard Kiely, Olivier Roupsard, Matthias Peichl, and Vicenzo Magliulo Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-344,2016 Manuscript under review for HESS (discussion: open, 0 comments) Upscaling instantaneous to daily evapotranspiration (ET i to ET d ) is one of the central challenge in regional vegetation water use mapping using polar orbiting satellites. Here we developed a robust ET i upscaling for global studies using the ratio between daily and instantaneous global radiation (R Sd /R Si ). Using data from 126 FLUXNET tower sites this study demonstrated R Sd /R si ratio to be the most robust factor explaining ET d /ET i variability across variable sky conditions and multiple biomes.

Beschreibung: 4-D imaging of sub-second dynamics in pore-scale processes using real-time synchrotron X-ray tomography Katherine J. Dobson, Sophia B. Coban, Samuel A. McDonald, Joanna N. Walsh, Robert C. Atwood, and Philip J. Withers Solid Earth, 7, 1059-1073, doi:10.5194/se-7-1059-2016, 2016 State-of-the-art synchrotron x-ray imaging was used to observe micron scale transport processes in real time. The 20 Hz 3-D image acquisition rates give experimental data free from motion artefacts, and suitable for detailed quantitative analysis of the dynamic fluid distribution, flow pathways and processes. The method marks a major breakthrough in our ability to capture both sub-second and lower frequency non-equilibrium process in many geological or engineering systems.

Beschreibung: Alpine tectonic wedging and crustal delamination in the Cantabrian Mountains (NW Spain) Jorge Gallastegui, Javier A. Pulgar, and Josep Gallart Solid Earth, 7, 1043-1057, doi:10.5194/se-7-1043-2016, 2016 We present the interpretation of deep seismic reflection profile ESCIN-2 across the boundary between the Cantabrian Mountains and the Cenozoic Duero Basin (NW Spain). 2-D seismic modelling allowed us to construct a N-S geological cross section which is compatible with the rest of the geophysical data. This profile shows the importance of the N-S Alpine deformation. A wedge of Cantabrian margin crust indented southwards into the delaminated Iberian crust, forcing its northward subduction.

Beschreibung: Studying local earthquakes in the area Baltic-Bothnia Megashear using the data of the POLENET/LAPNET temporary array Olga Usoltseva and Elena Kozlovskaya Solid Earth, 7, 1095-1108, doi:10.5194/se-7-1095-2016, 2016 We address the problem of seismicity in the intraplate area of northern Fennoscandia using the information on local events recorded by the POLENET/LAPNET seismic array. We relocate the seismic events, calculate a 3-D tomographic P wave velocity model of the uppermost crust and investigate a focal mechanism of the event. Our results demonstrate that the Baltic-Bothnia Megashear is an important large-scale, reactivated tectonic structure that has to be taken into account when estimating seismic hazard.

Beschreibung: Studying local earthquakes in the area Baltic-Bothnia Megashear using the data of the POLENET/LAPNET temporary array Olga Usoltseva and Elena Kozlovskaya Solid Earth, 7, 1095-1108, doi:10.5194/se-7-1095-2016, 2016 We address the problem of seismicity in the intraplate area of northern Fennoscandia using the information on local events recorded by the POLENET/LAPNET seismic array. We relocate the seismic events, calculate a 3-D tomographic P wave velocity model of the uppermost crust and investigate a focal mechanism of the event. Our results demonstrate that the Baltic-Bothnia Megashear is an important large-scale, reactivated tectonic structure that has to be taken into account when estimating seismic hazard.

Beschreibung: Combined deep sampling and mass-based approaches to assess soil carbon and nitrogen losses due to land-use changes in karst area of southwestern China Yecui Hu, Zhangliu Du, Qibing Wang, and Guichun Li Solid Earth, 7, 1075-1084, doi:10.5194/se-7-1075-2016, 2016 We quantified the SOC and TN losses induced by land-use changes in a typical karst region of southwestern China. Converting from natural forest to croplands greatly led to SOC and TN losses (as higher as 37.8 %), but the magnitude depended on sampling depth and calculation method. We recommend to account for SOC and TN stocks on equivalent soil mass basis together with deep sampling. This study has significant implications on the projected land management in the degraded karst areas.

Beschreibung: Experimental sand burial affects seedling survivorship, morphological traits, and biomass allocation of Ulmus pumila var. sabulosa in the Horqin Sandy Land, China Jiao Tang, Carlos Alberto Busso, Deming Jiang, Ala Musa, Dafu Wu, Yongcui Wang, and Chunping Miao Solid Earth, 7, 1085-1094, doi:10.5194/se-7-1085-2016, 2016 In order to test the tolerance of sandy elm after emergence, an experiment was conducted to evaluate the changes of survivorship, morphological traits and biomass allocation buried by various experimental burial depths. The results showed that partial sand burial did not influence survivorship but increased seedling height, diameter, taproot length, total biomass, and relative growth rates. It decreased total leaf area and changed biomass allocation, transferring more biomass to aboveground.

Beschreibung: Characteristics of an avalanche-feeding and partially debris-covered glacier and its response to atmospheric warming in Mt. Tomor, Tian Shan, China Puyu Wang, Zhongqin Li, and Huilin Li The Cryosphere Discuss., doi:10.5194/tc-2016-138,2016 Manuscript under review for TC (discussion: open, 0 comments) A cirque-valley glacier with complex topography and partially debris-covered area was investigated in the Mt. Tomor, Tian Shan. The glacier is analogous to temperate one on movement and temperature regimes. The strongest ablation and most significant terminus retreat and area reduction occurred at the end of last century and the beginning of this century. Since inhibition of debris cover to melting, it is expected to keep shrinkage in the coming decades, but the terminus retreat is to be slower.

Beschreibung: On the temporal variability of the surface solar radiation by means of spectral representations Marc Bengulescu, Philippe Blanc, and Lucien Wald Adv. Sci. Res., 13, 121-127, doi:10.5194/asr-13-121-2016, 2016 The continuous wavelet (CWT) and the Hilbert–Huang transforms (HHT) are compared for the analysis of the temporal variability on ten years of daily means of the surface solar irradiance. In both cases, the variability exhibits a plateau between scales of two days and three months that has decreasing power with increasing scale, a spectral peak corresponding to the annual cycle, and a low power regime in-between. The HHT is shown to be suitable for inspecting the variability of the measurements.

Beschreibung: Development of high-resolution multi-scale modelling system for simulation of coastal-fluvial urban flooding Agnieszka Indiana Olbert, Joanne Comer, Stephen Nash, and Michael Hartnett Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2016-238,2016 Manuscript under review for NHESS (discussion: open, 0 comments) A novel nested flood model (MSN_Flood) is applied to simulate complex coastal-fluvial urban flooding in order to critically examine the model's capability to forecast evolution of urban inundation. The model demonstrates high accuracy of outputs without incurring the computational expense of high spatial resolution over the entire model domain. MSN_Flood provides full characteristics of water levels and flow regimes necessary for flood hazard identification and flood risk assessment.

Beschreibung: Development of high-resolution multi-scale modelling system for simulation of coastal-fluvial urban flooding Agnieszka Indiana Olbert, Joanne Comer, Stephen Nash, and Michael Hartnett Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2016-238,2016 Manuscript under review for NHESS (discussion: open, 0 comments) A novel nested flood model (MSN_Flood) is applied to simulate complex coastal-fluvial urban flooding in order to critically examine the model's capability to forecast evolution of urban inundation. The model demonstrates high accuracy of outputs without incurring the computational expense of high spatial resolution over the entire model domain. MSN_Flood provides full characteristics of water levels and flow regimes necessary for flood hazard identification and flood risk assessment.

Beschreibung: Turbulence kinetic energy budget during the afternoon transition – Part 2: A simple TKE model Erik Nilsson, Marie Lothon, Fabienne Lohou, Eric Pardyjak, Oscar Hartogensis, and Clara Darbieu Atmos. Chem. Phys., 16, 8873-8898, doi:10.5194/acp-16-8873-2016, 2016 A new simple model for turbulence kinetic energy (TKE) and its budget is presented for the sheared convective atmospheric boundary layer. It is used to study effects of buoyancy and shear on TKE evolution during the afternoon transition, especially near the surface. We also find a region of weak turbulence during unstable afternoon conditions below the inversion top, which we refer to as a "pre-residual layer".

Beschreibung: Turbulence kinetic energy budget during the afternoon transition – Part 1: Observed surface TKE budget and boundary layer description for 10 intensive observation period days Erik Nilsson, Fabienne Lohou, Marie Lothon, Eric Pardyjak, Larry Mahrt, and Clara Darbieu Atmos. Chem. Phys., 16, 8849-8872, doi:10.5194/acp-16-8849-2016, 2016 The evolution of near-surface turbulence kinetic energy (TKE) and its budget in the afternoon transition has been studied based on field measurements. The study shows that TKE transport is an important budget term that needs to be taken into account in modeling of TKE. A non-local parametrization of dissipation using a TKE–length scale model which takes into account of boundary layer depth also gave improved results compared to a local parametrization.

Beschreibung: Ice nucleation efficiency of AgI: review and new insights Claudia Marcolli, Baban Nagare, André Welti, and Ulrike Lohmann Atmos. Chem. Phys., 16, 8915-8937, doi:10.5194/acp-16-8915-2016, 2016 Silver iodide is one of the best-investigated ice nuclei. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Nevertheless, many open questions remain. This paper gives an overview of silver iodide as an ice nucleus and tries to identify the factors that influence the ice nucleation ability of silver iodide.

Beschreibung: A comprehensive biomass burning emission inventory with high spatial and temporal resolution in China Ying Zhou, Xiaofan Xing, Jianlei Lang, Dongsheng Chen, Shuiyuan Cheng, Lin Wei, Xiao Wei, and Chao Liu Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-560,2016 Manuscript under review for ACP (discussion: open, 0 comments) A 1-km gridded and comprehensive biomass burning emission inventory is developed for mainland China in 2012, based on the county-level activity data and updated source-specific emission factors. Several important parameters for emissions estimation are investigated. This paper presents the detailed emission inventory for air quality modelling and supports the development of a targeted control strategy for biomass pollution.

Beschreibung: How stratospheric are deep stratospheric intrusions? LUAMI 2008 Thomas Trickl, Hannes Vogelmann, Andreas Fix, Andreas Schäfler, Martin Wirth, Bertrand Calpini, Gilbert Levrat, Gonzague Romanens, Arnoud Apituley, Keith M. Wilson, Robert Begbie, Jens Reichardt, Holger Vömel, and Michael Sprenger Atmos. Chem. Phys., 16, 8791-8815, doi:10.5194/acp-16-8791-2016, 2016 A rather homogeneous deep stratospheric intrusion event was mapped by vertical sounding over central Europe and by model calculations along the transport path. The very low minimum H 2 O mixing ratios demonstrate almost negligible mixing with tropospheric air during the downward transport. The vertical distributions of O 3 and aerosol were transferred from the source region to Europe without major change. A rather shallow outflow from the stratosphere was found.

Beschreibung: Air–surface exchange of gaseous mercury over permafrost soil: an investigation at a high-altitude (4700 m a.s.l.) and remote site in the central Qinghai-Tibet Plateau Zhijia Ci, Fei Peng, Xian Xue, and Xiaoshan Zhang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-515,2016 Manuscript under review for ACP (discussion: open, 0 comments) We performed filed measurements and controlled field experiments to examine the flux, temporal variation and influencing factors of air–surface Hg(0) exchange at a high-altitude and remote site in the central Qinghai-Tibet Plateau. We found that the environmental conditions greatly influenced the air–surface Hg dynamics. Our results have important implications to the Hg biogeochemical cycle in the soils of Qinghai-Tibet Plateau under the rapid climate warming and environmental change.

Beschreibung: Ice nucleation efficiency of AgI: review and new insights Claudia Marcolli, Baban Nagare, André Welti, and Ulrike Lohmann Atmos. Chem. Phys., 16, 8915-8937, doi:10.5194/acp-16-8915-2016, 2016 Silver iodide is one of the best-investigated ice nuclei. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Nevertheless, many open questions remain. This paper gives an overview of silver iodide as an ice nucleus and tries to identify the factors that influence the ice nucleation ability of silver iodide.

Beschreibung: Controls on phase composition and ice water content in a convection-permitting model simulation of a tropical mesoscale convective system Charmaine N. Franklin, Alain Protat, Delphine Leroy, and Emmanuel Fontaine Atmos. Chem. Phys., 16, 8767-8789, doi:10.5194/acp-16-8767-2016, 2016 Simulations of tropical convection are used to investigate the processes that control the phase composition of tropical clouds. It is shown that the growth of ice is less dependent on vertical velocity than is liquid water, with the control on ice water content being the ice sizes and available liquid water. Results show that in the purely ice region of convective updraughts, the buoyancy is controlled by the ice sizes, demonstrating the importance of microphysical processes on convective dynamics.

Beschreibung: Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities Mijung Song, Pengfei F. Liu, Sarah J. Hanna, Rahul A. Zaveri, Katie Potter, Yuan You, Scot T. Martin, and Allan K. Bertram Atmos. Chem. Phys., 16, 8817-8830, doi:10.5194/acp-16-8817-2016, 2016 To improve predictions of air quality, visibility, and climate change, knowledge of the viscosities and diffusion rates within organic particulate matter consisting of secondary organic material (SOM) is required. Most qualitative and quantitative measurements of viscosity and diffusion rates within organic particulate matter have focused on SOM particles generated from biogenic volatile organic compounds (VOCs) such as α -pinene and isoprene. In this study, we quantify the relative humidity (RH)-dependent viscosities at 295 ± 1 K of SOM produced by photo-oxidation of toluene, an anthropogenic VOC. The viscosities of toluene-derived SOM were 2  ×  10 −1 to  ∼  6  ×  10 6  Pa s from 30 to 90 % RH, and greater than  ∼  2  ×  10 8  Pa s (similar to or greater than the viscosity of tar pitch) for RH  ≤  17 %. These viscosities correspond to Stokes–Einstein-equivalent diffusion coefficients for large organic molecules of  ∼  2  ×  10 −15  cm 2  s −1 for 30 % RH, and lower than  ∼  3  ×  10 −17  cm 2  s −1 for RH  ≤  17 %. Based on these estimated diffusion coefficients, the mixing time of large organic molecules within 200 nm toluene-derived SOM particles is 0.1–5 h for 30 % RH, and higher than  ∼  100 h for RH  ≤  17 %. As a starting point for understanding the mixing times of large organic molecules in organic particulate matter over cities, we applied the mixing times determined for toluene-derived SOM particles to the world's top 15 most populous megacities. If the organic particulate matter in these megacities is similar to the toluene-derived SOM in this study, in Istanbul, Tokyo, Shanghai, and São Paulo, mixing times in organic particulate matter during certain periods of the year may be very short, and the particles may be well-mixed. On the other hand, the mixing times of large organic molecules in organic particulate matter in Beijing, Mexico City, Cairo, and Karachi may be long and the particles may not be well-mixed in the afternoon (15:00–17:00 LT) during certain times of the year.

Beschreibung: Air–surface exchange of gaseous mercury over permafrost soil: an investigation at a high-altitude (4700 m a.s.l.) and remote site in the central Qinghai-Tibet Plateau Zhijia Ci, Fei Peng, Xian Xue, and Xiaoshan Zhang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-515,2016 Manuscript under review for ACP (discussion: open, 0 comments) We performed filed measurements and controlled field experiments to examine the flux, temporal variation and influencing factors of air–surface Hg(0) exchange at a high-altitude and remote site in the central Qinghai-Tibet Plateau. We found that the environmental conditions greatly influenced the air–surface Hg dynamics. Our results have important implications to the Hg biogeochemical cycle in the soils of Qinghai-Tibet Plateau under the rapid climate warming and environmental change.

Beschreibung: Aerosol source apportionment from 1-year measurements at the CESAR tower in Cabauw, the Netherlands Patrick Schlag, Astrid Kiendler-Scharr, Marcus Johannes Blom, Francesco Canonaco, Jeroen Sebastiaan Henzing, Marcel Moerman, André Stephan Henry Prévôt, and Rupert Holzinger Atmos. Chem. Phys., 16, 8831-8847, doi:10.5194/acp-16-8831-2016, 2016 This work provides chemical composition data of atmospheric aerosols acquired during 1 year in the rural site of Cabauw, the Netherlands. In some periods, we found unexpected high particle mass concentrations exceeding the WHO limits. Using these composition data, we found that reducing ammonia emissions in this region would largely reduce the main aerosol component ammonium nitrate, whereas the local mitigation of the organics turned out to be difficult due to the lack of a designated source.

Beschreibung: Turbulence kinetic energy budget during the afternoon transition – Part 2: A simple TKE model Erik Nilsson, Marie Lothon, Fabienne Lohou, Eric Pardyjak, Oscar Hartogensis, and Clara Darbieu Atmos. Chem. Phys., 16, 8873-8898, doi:10.5194/acp-16-8873-2016, 2016 A new simple model for turbulence kinetic energy (TKE) and its budget is presented for the sheared convective atmospheric boundary layer. It is used to study effects of buoyancy and shear on TKE evolution during the afternoon transition, especially near the surface. We also find a region of weak turbulence during unstable afternoon conditions below the inversion top, which we refer to as a "pre-residual layer".

Beschreibung: Comparing contact and immersion freezing from continuous flow diffusion chambers Baban Nagare, Claudia Marcolli, André Welti, Olaf Stetzer, and Ulrike Lohmann Atmos. Chem. Phys., 16, 8899-8914, doi:10.5194/acp-16-8899-2016, 2016 The relative importance of contact freezing and immersion freezing at mixed-phase cloud temperatures is the subject of debate. We performed experiments using continuous-flow diffusion chambers to compare the freezing efficiency of ice-nucleating particles for both these nucleation modes. Silver iodide, kaolinite and Arizona Test Dust were used as ice-nucleating particles. We could not confirm the dominance of contact freezing over immersion freezing for our experimental conditions.