WILBERT

Description: Change in frozen soils and its effect on regional hydrology, upper Heihe basin, northeastern Qinghai–Tibetan Plateau Bing Gao, Dawen Yang, Yue Qin, Yuhan Wang, Hongyi Li, Yanlin Zhang, and Tingjun Zhang The Cryosphere, 12, 657-673, https://doi.org/10.5194/tc-12-657-2018, 2018 This study developed a distributed hydrological model coupled with cryospherical processes and applied it in order to simulate the long-term change of frozen ground and its effect on hydrology in the upper Heihe basin. Results showed that the permafrost area shrank by 8.8%, and the frozen depth of seasonally frozen ground decreased. Runoff in cold seasons and annual liquid soil moisture increased due to frozen soils change. Groundwater recharge was enhanced due to the degradation of permafrost.

Description: NHM–SMAP: spatially and temporally high-resolution nonhydrostatic atmospheric model coupled with detailed snow process model for Greenland Ice Sheet Masashi Niwano, Teruo Aoki, Akihiro Hashimoto, Sumito Matoba, Satoru Yamaguchi, Tomonori Tanikawa, Koji Fujita, Akane Tsushima, Yoshinori Iizuka, Rigen Shimada, and Masahiro Hori The Cryosphere, 12, 635-655, https://doi.org/10.5194/tc-12-635-2018, 2018 We present a high-resolution regional climate model called NHM–SMAP applied to the Greenland Ice Sheet (GrIS). The model forced by JRA-55 reanalysis is evaluated using in situ data from automated weather stations, stake measurements, and ice core obtained from 2011 to 2014. By utilizing the model, we highlight that the choice of calculation schemes for vertical water movement in snow and firn has an effect of up to 200 Gt/year in the yearly accumulated GrIS-wide surface mass balance estimates.

Description: Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard Dorothée Vallot, Jan Åström, Thomas Zwinger, Rickard Pettersson, Alistair Everett, Douglas I. Benn, Adrian Luckman, Ward J. J. van Pelt, Faezeh Nick, and Jack Kohler The Cryosphere, 12, 609-625, https://doi.org/10.5194/tc-12-609-2018, 2018 This paper presents a new perspective on the role of ice dynamics and ocean interaction in glacier calving processes applied to Kronebreen, a tidewater glacier in Svalbard. A global modelling approach includes ice flow modelling, undercutting estimation by a combination of glacier energy balance and plume modelling as well as calving by a discrete particle model. We show that modelling undercutting is necessary and calving is influenced by basal friction velocity and geometry.

Description: Global glacier volume projections under high-end climate change scenarios Sarah Shannon, Robin Smith, Andy Wiltshire, Tony Payne, Matthias Huss, Richard Betts, John Caesar, Aris Koutroulis, Darren Jones, and Stephan Harrison The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-35,2018 Manuscript under review for TC (discussion: open, 0 comments) We present global glacier volume projections for the end of this century, under a range of high-end climate change scenarios, defined as exceeding 2 degrees global average warming. The ice loss contribution to sea level rise for all glaciers excluding those on the peripheral of the Antarctic ice sheet is 215.2 ± 21.3 mm. Such large ice losses will have consequences for sea-level rise and for water supply in glacier-fed river systems.

Description: Deglaciation and future stability of the Coats Land ice margin, Antarctica Dominic A. Hodgson, Kelly Hogan, James Smith, James A. Smith, Claus-Dieter Hillenbrand, Alastair G. C. Graham, Peter Fretwell, Claire Allen, Vicky Peck, Jan-Erik Arndt, Boris Dorschel, Christian Hübscher, Andy M. Smith, and Robert Larter The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-9,2018 Manuscript under review for TC (discussion: open, 0 comments) We studied the Coats Land ice margin, Antarctica providing: a multi-disciplinary geophysical assessment of the ice sheet configuration through its last advance and retreat; a description of the physical constraints on the stability of the past and present ice and future margin based on its submarine geomorphology and ice-sheet geometry; evidence that once detached from the bed, the ice shelves in this region were predisposed to rapid retreat back to coastal grounding lines.

Description: The European mountain cryosphere: a review of its current state, trends, and future challenges Martin Beniston, Daniel Farinotti, Markus Stoffel, Liss M. Andreassen, Erika Coppola, Nicolas Eckert, Adriano Fantini, Florie Giacona, Christian Hauck, Matthias Huss, Hendrik Huwald, Michael Lehning, Juan-Ignacio López-Moreno, Jan Magnusson, Christoph Marty, Enrique Morán-Tejéda, Samuel Morin, Mohamed Naaim, Antonello Provenzale, Antoine Rabatel, Delphine Six, Johann Stötter, Ulrich Strasser, Silvia Terzago, and Christian Vincent The Cryosphere, 12, 759-794, https://doi.org/10.5194/tc-12-759-2018, 2018 This paper makes a rather exhaustive overview of current knowledge of past, current, and future aspects of cryospheric issues in continental Europe and makes a number of reflections of areas of uncertainty requiring more attention in both scientific and policy terms. The review paper is completed by a bibliography containing 350 recent references that will certainly be of value to scholars engaged in the fields of glacier, snow, and permafrost research.

Description: Ice flow velocity as a sensitive indicator of glacier state Martin Stocker-Waldhuber, Andrea Fischer, Kay Helfricht, and Michael Kuhn The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-37,2018 Manuscript under review for TC (discussion: open, 0 comments) Climatic forcing affects glacier length changes, mass balance and ice flow dynamics on different time scales and also dependent on topography. The first two of these parameters are operationally used for glacier monitoring, whereas only a few time series of glacier dynamics exist with the potential to serve as long-term indicators of glacier response to climate change. With more than 100 years of measurements of ice flow velocities at stakes and stone lines on Hintereisferner (HEF) and more than 50 years on Kesselwandferner (KWF), records of annual velocity change are as long as records of glacier fluctuations. Interannual variations of ice flow velocities and shorter supporting interpretations of long-term records have been measured on Gepatschferner (GPF) and Taschachferner (TSF) for nearly 10 years. The ice flow velocities on Hintereisferner and especially on Kesselwandferner show great variations between advancing and retreating periods, with magnitudes increasing from the highest to the lowest stakes, making ice flow records at ablation stakes a very sensitive indicator of glacier state. Since the end of the latest glacier advances from the 1970s to the 1980s, the ice flow velocities have decreased continuously, a strong sign of the severe retreat of the glaciers in recent decades.

Description: Effects of short-term variability of meteorological variables on soil temperature in permafrost regions Christian Beer, Philipp Porada, Altug Ekici, and Matthias Brakebusch The Cryosphere, 12, 741-757, https://doi.org/10.5194/tc-12-741-2018, 2018 Idealized model experiments demonstrate that, in addition to a gradual climate change, changing daily to weekly variability of meteorological variables and extreme events will also have an impact on mean annual ground temperature in high-latitude permafrost areas. In fact, results of the land surface model experiments show that the projected increase of variability of meteorological variables leads to cooler permafrost soil in contrast to an otherwise soil warming in response to climate change.

Description: Calving relation for tidewater glaciers based on detailed stress field analysis Rémy Mercenier, Martin P. Lüthi, and Andreas Vieli The Cryosphere, 12, 721-739, https://doi.org/10.5194/tc-12-721-2018, 2018 This study investigates the effect of geometrical properties on the stress state and flow regime in the vicinity of the calving front of grounded tidewater glaciers. Our analysis shows that the stress state for simple geometries can be determined solely by the water depth relative to ice thickness. This scaled relationship allows for a simple parametrization to predict calving rates of grounded tidewater glaciers that is simple, physics-based and in good agreement with observations.

Description: Greenland Ice Mapping Project: Ice Flow Velocity Variation at submonthly to decadal time scales Ian Joughin, Ben E. Smith, and Ian Howat The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-40,2018 Manuscript under review for TC (discussion: open, 0 comments) We describe several new ice velocity maps produced using Landsat 8 and Copernicus Sentinel 1A/B data. We focus on several sites where we analyse these data in conjunction with earlier data from this project, which extend back to the year 2000. In particular, we find that Jakobshavn Isbrae began slowing substantially in 2017. The growing duration of these records will allow more robust analyses of the processes controlling fast flow and how they are affected by climate and other forcing.

Description: Mechanisms influencing seasonal to inter-annual prediction skill of sea ice extent in the Arctic Ocean in MIROC Jun Ono, Hiroaki Tatebe, Yoshiki Komuro, Masato I. Nodzu, and Masayoshi Ishii The Cryosphere, 12, 675-683, https://doi.org/10.5194/tc-12-675-2018, 2018 Sea ice in the Arctic Ocean has experienced rapid decline since the beginning of satellite observations. To assess the predictability of sea ice extent (SIE) in the Arctic Ocean and to clarify the underlying physical processes, we conducted prediction experiments using an initialized climate model (MIROC5). The present study suggests that subsurface ocean heat content originating from the North Atlantic contributes to the skillful prediction of winter SIE at lead times up to 11 months.

Description: Floe-size distributions in laboratory ice broken by waves Agnieszka Herman, Karl-Ulrich Evers, and Nils Reimer The Cryosphere, 12, 685-699, https://doi.org/10.5194/tc-12-685-2018, 2018 In regions close to the ice edge, sea ice is composed of many separate ice floes of different sizes and shapes. Strong fragmentation is caused mainly by ice breaking by waves coming from the open ocean. At present, this process, although recognized as important for many other physical processes, is not well understood. In this study we present results of a laboratory study of ice breaking by waves, and we provide interpretation of those results that may guide analysis of other similar datasets.

Description: NHM–SMAP: spatially and temporally high-resolution nonhydrostatic atmospheric model coupled with detailed snow process model for Greenland Ice Sheet Masashi Niwano, Teruo Aoki, Akihiro Hashimoto, Sumito Matoba, Satoru Yamaguchi, Tomonori Tanikawa, Koji Fujita, Akane Tsushima, Yoshinori Iizuka, Rigen Shimada, and Masahiro Hori The Cryosphere, 12, 635-655, https://doi.org/10.5194/tc-12-635-2018, 2018 We present a high-resolution regional climate model called NHM–SMAP applied to the Greenland Ice Sheet (GrIS). The model forced by JRA-55 reanalysis is evaluated using in situ data from automated weather stations, stake measurements, and ice core obtained from 2011 to 2014. By utilizing the model, we highlight that the choice of calculation schemes for vertical water movement in snow and firn has an effect of up to 200 Gt/year in the yearly accumulated GrIS-wide surface mass balance estimates.

Description: Climate warming over the past half century has led to thermal degradation of permafrost on the Qinghai–Tibet Plateau Youhua Ran, Xin Li, and Guodong Cheng The Cryosphere, 12, 595-608, https://doi.org/10.5194/tc-12-595-2018, 2018 Approximately 88 % of the permafrost area in the 1960s has been thermally degraded in the past half century over the Qinghai–Tibetan Plateau. The mean elevations of the very cold, cold, cool, warm, very warm, and likely thawing permafrost areas increased by 88 m, 97 m, 155 m, 185 m, 161 m, and 250 m, respectively. This degradation may lead to increases in risks to infrastructure, flood, reductions in ecosystem resilience, and positive climate feedback.

Description: Generalized nonlinear height–diameter models for a  Cryptomeria fortunei plantation in the Pingba region of Guizhou Province, China Zongzheng Chai, Wei Tan, Yuanyuan Li, Lan Yan, Hongbo Yuan, and Zhaojun Li Web Ecol., 18, 29-35, https://doi.org/10.5194/we-18-29-2018, 2018 Many years of forestry practice have confirmed that Cryptomeria fortunei can be cultivated in central Guizhou Province of China on a large scale, and this will continue due to its good growth performance and excellent development potential. The generalized height–diameter models proposed in the current paper will help forest managers to reduce costs and save time during the inventory, monitoring, and management for these forests.

Description: Pore morphology of polar firn around closure revealed by X-ray tomography Alexis Burr, Clément Ballot, Pierre Lhuissier, Patricia Martinerie, Christophe L. Martin, and Armelle Philip The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-14,2018 Manuscript under review for TC (discussion: open, 0 comments) 3D imaging of the pore network of polar firn from Antarctica was realized in order to relate the morphological evolution of pores with their progressive closure with depth. Evaluating the closed porosity was found to be very dependent of the size of samples and image reconstructions. A connectivity index, which is a parameter less dependent of such issues, was proposed, and proved to predict accurately the close-off depths and densities of two polar sites.

Description: Brief communication: "Oldest Ice" patches diagnosed 37 km southwest of Dome C, East Antarctica Olivier Passalacqua, Marie Cavitte, Olivier Gagliardini, Fabien Gillet-Chaulet, Frédéric Parrenin, Catherine Ritz, and Duncan Young The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-19,2018 Manuscript under review for TC (discussion: open, 0 comments) Locating a suitable drill site is a key step in the Antarctic Oldest-Ice challenge. We here led a 3D ice flow simulation in the region of Dome C using a refined bedrock description. Five selection criteria are computed that together provide an objective overview on the local ice flow conditions. These criteria delineates kilometer-scale favourable patches, that overlap with the ones recently proposed by another group. A few drill sites are proposed within these patches, located precisely.

Description: Change in frozen soils and its effect on regional hydrology, upper Heihe basin, northeastern Qinghai–Tibetan Plateau Bing Gao, Dawen Yang, Yue Qin, Yuhan Wang, Hongyi Li, Yanlin Zhang, and Tingjun Zhang The Cryosphere, 12, 657-673, https://doi.org/10.5194/tc-12-657-2018, 2018 This study developed a distributed hydrological model coupled with cryospherical processes and applied it in order to simulate the long-term change of frozen ground and its effect on hydrology in the upper Heihe basin. Results showed that the permafrost area shrank by 8.8%, and the frozen depth of seasonally frozen ground decreased. Runoff in cold seasons and annual liquid soil moisture increased due to frozen soils change. Groundwater recharge was enhanced due to the degradation of permafrost.

Description: Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard Dorothée Vallot, Jan Åström, Thomas Zwinger, Rickard Pettersson, Alistair Everett, Douglas I. Benn, Adrian Luckman, Ward J. J. van Pelt, Faezeh Nick, and Jack Kohler The Cryosphere, 12, 609-625, https://doi.org/10.5194/tc-12-609-2018, 2018 This paper presents a new perspective on the role of ice dynamics and ocean interaction in glacier calving processes applied to Kronebreen, a tidewater glacier in Svalbard. A global modelling approach includes ice flow modelling, undercutting estimation by a combination of glacier energy balance and plume modelling as well as calving by a discrete particle model. We show that modelling undercutting is necessary and calving is influenced by basal friction velocity and geometry.

Description: Implementing spatially explicit seed and pollen dispersal in the individual-based larch simulation model: LAVESI-WIND 1.0 Stefan Kruse, Alexander Gerdes, Nadja J. Kath, and Ulrike Herzschuh Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-31,2018 Manuscript under review for GMD (discussion: open, 0 comments) It is of major interest to estimate feedbacks of arctic ecosystems to global warming in the upcoming decades. However, the speed of this response is driven by the potential of species to migrate and the timing and spatial scale for this is rather uncertain. To close this knowledge gap, we updated a very detailed vegetation model by including seed and pollen dispersal driven by wind speed and direction. The new model can substantially help in unveiling the important drivers of migration dynamics.

Description: Exploring coral reef responses to millennial scale climatic forcings: insights from a 1-D numerical tool pyReef-Core v1.0 Tristan Salles, Jodie Pall, M. Jody Webster, and Belinda Dechnik Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-29,2018 Manuscript under review for GMD (discussion: open, 0 comments) We present a 1D model of coral reefs evolution over centennial to millennial timescales. The model enables to estimate the effects of environmental conditions (such as oceanic variability, sedimentation rate, sea-level fluctuations or tectonics) and ecological coral competition on reef vertical accretion and stratigraphic succession. The tool can quantitatively test carbonate platform development and efficiently interpret vertical growth under various forcing scenarios.

Description: Raindrop fall velocities from an optical array probe and 2-D video disdrometer Viswanathan Bringi, Merhala Thurai, and Darrel Baumgardner Atmos. Meas. Tech., 11, 1377-1384, https://doi.org/10.5194/amt-11-1377-2018, 2018 Raindrop fall velocities are important for rain rate estimation, soil erosion studies and in numerical modelling of rain formation in clouds. The assumption that the fall velocity is uniquely related to drop size is made inherently based on laboratory measurements under still air conditions from nearly 68 years ago. There have been very few measurements of drop fall speeds in natural rain under both still and turbulent wind conditions. We report on fall speed measurements in natural rain shafts.

Description: Non-methane organic gas emissions from biomass burning: identification, quantification, and emission factors from PTR-ToF during the FIREX 2016 laboratory experiment Abigail R. Koss, Kanako Sekimoto, Jessica B. Gilman, Vanessa Selimovic, Matthew M. Coggon, Kyle J. Zarzana, Bin Yuan, Brian M. Lerner, Steven S. Brown, Jose L. Jimenez, Jordan Krechmer, James M. Roberts, Carsten Warneke, Robert J. Yokelson, and Joost de Gouw Atmos. Chem. Phys., 18, 3299-3319, https://doi.org/10.5194/acp-18-3299-2018, 2018 Non-methane organic gases (NMOGs) were detected by proton-transfer-reaction mass spectrometry (PTR-ToF) during an extensive laboratory characterization of wildfire emissions. Identifications for PTR-ToF ion masses are proposed and supported by a combination of techniques. Overall excellent agreement with other instrumentation is shown. Scalable emission factors and ratios are reported for many newly reported reactive species. An analysis of chemical characteristics is presented.

Description: Characterization of blackbody inhomogeneity and its effect on the retrieval results of the GLORIA instrument Anne Kleinert, Isabell Krisch, Jörn Ungermann, Albert Adibekyan, Berndt Gutschwager, and Christian Monte Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-59,2018 Manuscript under review for AMT (discussion: open, 0 comments) This study investigates the required accuracy of radiometric calibration sources for remote sensing instruments to properly resolve decadal trends of climate relevant trace species like ozone, water vapor and temperature. The required temperature knowledge of the calibration source is in the order of 100 mK. This is demonstrated by a Monte-Carlo simulation. The results are confirmed using real measurements acquired by the GLORIA instrument.

Description: Wind Turbine Wake Measurements with Automatically Adjusting Scanning Trajectories in a Multi-Doppler Lidar Setup Norman Wildmann, Nikola Vasiljevic, and Thomas Gerz Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-55,2018 Manuscript under review for AMT (discussion: open, 0 comments) Wind turbines extract energy from the flow which manifests in a region of lower wind speeds and increased turbulence downstream of the rotor, the so-called wake. Understanding the characteristics of the wake is a key challenge for wind energy research. A new strategy to measure the wind in the wake with three synchronized lidar instruments is presented. The measurement points are automatically adapted to the prevailing wind direction to get a continuous monitoring of wake properties.

Description: The importance of surface reflectance anisotropy for cloud and NO 2 retrievals from GOME-2 and OMI Alba Lorente, K. Folkert Boersma, Piet Stammes, L. Gijsbert Tilstra, Andreas Richter, Huan Yu, Said Kharbouche, and Jan-Peter Muller Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-32,2018 Manuscript under review for AMT (discussion: open, 0 comments) Light reflected by Earth’s surface is different in each direction: surfaces appear brighter or darker in certain viewing directions. Currently this effect is not accounted for in satellite retrievals, thus surface reflectance climatologies and cloud fractions show an East-West bias across orbits (GOME2,OMI). The effect for NO 2 measurements in partly cloudy scenes is substantial. We recommend to coherently account for this effect in UV/Vis sensors, and will be especially beneficial for TROPOMI.

Description: On the distortions in calculated GW parameters during slanted atmospheric soundings Alejandro de la Torre, Peter Alexander, Torsten Schmidt, Pablo Llamedo, and Rodrigo Hierro Atmos. Meas. Tech., 11, 1363-1375, https://doi.org/10.5194/amt-11-1363-2018, 2018 This work is based on previous findings from our group of researchers, regarding the analysis of atmospheric data from slanted soundings during radiosoundings and GPS radio occulations. Several gravity wave climatologies may be found in the literature that to a certain extent are affected by considerable measurement distortions. We intend here to contribute to the interpretation of gravity waves analyses from slanted soundings in future climatologies.

Description: Characterization of blackbody inhomogeneity and its effect on the retrieval results of the GLORIA instrument Anne Kleinert, Isabell Krisch, Jörn Ungermann, Albert Adibekyan, Berndt Gutschwager, and Christian Monte Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-59,2018 Manuscript under review for AMT (discussion: open, 0 comments) This study investigates the required accuracy of radiometric calibration sources for remote sensing instruments to properly resolve decadal trends of climate relevant trace species like ozone, water vapor and temperature. The required temperature knowledge of the calibration source is in the order of 100 mK. This is demonstrated by a Monte-Carlo simulation. The results are confirmed using real measurements acquired by the GLORIA instrument.

Description: Reduction of ZTD outliers through improved GNSS data processing and screening strategies Katarzyna Stepniak, Olivier Bock, and Pawel Wielgosz Atmos. Meas. Tech., 11, 1347-1361, https://doi.org/10.5194/amt-11-1347-2018, 2018 Though Global Navigation Satellite System (GNSS) data processing has been significantly improved over the years, it is still commonly observed that zenith tropospheric delay (ZTD) estimates contain many outliers which are detrimental to meteorological and climatological applications. In this paper, we show that ZTD outliers in double-difference processing are mostly caused by sub-daily data gaps at reference stations, which cause disconnections of clusters of stations from the reference network and common mode biases due to the strong correlation between stations in short baselines. They can reach a few centimetres in ZTD and usually coincide with a jump in formal errors. The magnitude and sign of these biases are impossible to predict because they depend on different errors in the observations and on the geometry of the baselines. We elaborate and test a new baseline strategy which solves this problem and significantly reduces the number of outliers compared to the standard strategy commonly used for positioning (e.g. determination of national reference frame) in which the pre-defined network is composed of a skeleton of reference stations to which secondary stations are connected in a star-like structure. The new strategy is also shown to perform better than the widely used strategy maximizing the number of observations available in many GNSS programs. The reason is that observations are maximized before processing, whereas the final number of used observations can be dramatically lower because of data rejection (screening) during the processing. The study relies on the analysis of 1 year of GPS (Global Positioning System) data from a regional network of 136 GNSS stations processed using Bernese GNSS Software v.5.2. A post-processing screening procedure is also proposed to detect and remove a few outliers which may still remain due to short data gaps. It is based on a combination of range checks and outlier checks of ZTD and formal errors. The accuracy of the final screened GPS ZTD estimates is assessed by comparison to ERA-Interim reanalysis.

Description: The importance of surface reflectance anisotropy for cloud and NO 2 retrievals from GOME-2 and OMI Alba Lorente, K. Folkert Boersma, Piet Stammes, L. Gijsbert Tilstra, Andreas Richter, Huan Yu, Said Kharbouche, and Jan-Peter Muller Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-32,2018 Manuscript under review for AMT (discussion: open, 0 comments) Light reflected by Earth’s surface is different in each direction: surfaces appear brighter or darker in certain viewing directions. Currently this effect is not accounted for in satellite retrievals, thus surface reflectance climatologies and cloud fractions show an East-West bias across orbits (GOME2,OMI). The effect for NO 2 measurements in partly cloudy scenes is substantial. We recommend to coherently account for this effect in UV/Vis sensors, and will be especially beneficial for TROPOMI.

Description: Exploring coral reef responses to millennial scale climatic forcings: insights from a 1-D numerical tool pyReef-Core v1.0 Tristan Salles, Jodie Pall, M. Jody Webster, and Belinda Dechnik Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-29,2018 Manuscript under review for GMD (discussion: open, 0 comments) We present a 1D model of coral reefs evolution over centennial to millennial timescales. The model enables to estimate the effects of environmental conditions (such as oceanic variability, sedimentation rate, sea-level fluctuations or tectonics) and ecological coral competition on reef vertical accretion and stratigraphic succession. The tool can quantitatively test carbonate platform development and efficiently interpret vertical growth under various forcing scenarios.

Description: Dynamic magnification factors for tree blow-down by powder snow avalanche air blasts Perry Bartelt, Peter Bebi, Thomas Feistl, Othmar Buser, and Andrin Caviezel Nat. Hazards Earth Syst. Sci., 18, 759-764, https://doi.org/10.5194/nhess-18-759-2018, 2018 We study how short duration powder avalanche blasts break and overturn tall trees. Tree blow-down is often used to back-calculate avalanche pressure and therefore constrain avalanche flow velocity and motion. We find that tall trees are susceptible to avalanche air blasts because the duration of the air blast is near to the period of vibration of tall trees. Dynamic magnification factors should therefore be considered when back-calculating powder avalanche impact pressures.

Description: Thermodynamic Properties of Seawater, Ice and Humid Air: TEOS-10, Before and Beyond Rainer Feistel Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-19,2018 Manuscript under review for OS (discussion: open, 0 comments) TEOS-10 is the present international standard for thermodynamic properties of water, ice, seawater and humid air, recommended for geosciences by leading international organisations such as UNESCO/IOC and IUGG. TEOS-10 incorporates an extended manifold of different experimental data for those substances, collected from publications over many decades, in an unprecedentedly compact, consistent, comprehensive and accurate way.

Description: Constraints on Alpine Fault (New Zealand) Mylonitization Temperatures and Geothermal Gradient from Ti-in-quartz Thermobarometry Steven Kidder, Virginia Toy, Dave Prior, Tim Little, and Colin MacRae Solid Earth Discuss., https//doi.org/10.5194/se-2018-12,2018 Manuscript under review for SE (discussion: open, 0 comments) By quantifying trace concentrations of titanium in quartz (a known geologic thermometer ), we constrain the temperature profile for the deep crust along the Alpine Fault. We show there is a sharp change from fairly uniform temperatures at deep levels, to an extremely steep gradient in temperature in the upper kilometers of the crust. Presumably this gradient in temperature at shallow levels is due to the flux of fluids through cracks caused by earthquakes.

Description: Constraints on Alpine Fault (New Zealand) Mylonitization Temperatures and Geothermal Gradient from Ti-in-quartz Thermobarometry Steven Kidder, Virginia Toy, Dave Prior, Tim Little, and Colin MacRae Solid Earth Discuss., https//doi.org/10.5194/se-2018-12,2018 Manuscript under review for SE (discussion: open, 0 comments) By quantifying trace concentrations of titanium in quartz (a known geologic thermometer ), we constrain the temperature profile for the deep crust along the Alpine Fault. We show there is a sharp change from fairly uniform temperatures at deep levels, to an extremely steep gradient in temperature in the upper kilometers of the crust. Presumably this gradient in temperature at shallow levels is due to the flux of fluids through cracks caused by earthquakes.

Description: Magnetosheath jet properties and evolution as determined by a global hybrid-Vlasov simulation Minna Palmroth, Heli Hietala, Ferdinand Plaschke, Martin Archer, Tomas Karlsson, Xóchitl Blanco-Cano, David Sibeck, Primož Kajdič, Urs Ganse, Yann Pfau-Kempf, Markus Battarbee, and Lucile Turc Ann. Geophys. Discuss., https//doi.org/10.5194/angeo-2018-20,2018 Manuscript under review for ANGEO (discussion: open, 0 comments) We use a global hybrid-Vlasov simulation for the magnetosphere, Vlasiator, to investigate magnetosheath high-speed jets. Unlike many other hybrid-kinetic simulations, Vlasiator includes an unscaled geomagnetic dipole, indicating that the simulation spatial and temporal dimensions can be given without scaling. Thus, for the first time, this allows investigating the magnetosheath jet properties and comparing them directly with the observed jets within the Earth's magnetosheath. In the run shown in this paper, the interplanetary magnetic field (IMF) cone angle is 30°, and a foreshock develops upstream of the quasi-parallel magnetosheath. We visually detect a structure with high dynamic pressure propagating from the bow shock towards the magnetopause. The structure is confirmed as a jet using three different criteria, which have been adopted in previous observational studies. We compare these criteria against the simulation results. We find that the magnetosheath jet is an elongated structure extending Earthward of the bow shock by ~ 2.3 R E , while its size perpendicular to the direction of propagation is ~ 0.5 R E . We also investigate the jet evolution, and find that the jet originates due to the interaction of the foreshock Ultra Low Frequency (ULF) waves with the bow shock surface. The simulation shows that magnetosheath jets can develop also under steady IMF, as inferred by observational studies.

Description: Comparison and evaluation of anthropogenic emissions of SO 2 and NO x over China Meng Li, Zbigniew Klimont, Qiang Zhang, Randall V. Martin, Bo Zheng, Chris Heyes, Janusz Cofala, Yuxuan Zhang, and Kebin He Atmos. Chem. Phys., 18, 3433-3456, https://doi.org/10.5194/acp-18-3433-2018, 2018 In this paper, we conducted a comprehensive evaluation of two widely used anthropogenic emission inventories over China, ECLIPSE and MIX, to explore the potential sources of uncertainties and find clues to improving emission inventories. We found that SO 2 emission estimates are consistent between the two inventories (with 1 % differences), while NO x emissions in ECLIPSE's estimates are 16 % lower than those in MIX. Discrepancies at the sector and provincial levels are much higher.

Description: Monoterpene chemical speciation in a tropical rainforest:variation with season, height, and time of dayat the Amazon Tall Tower Observatory (ATTO) Ana María Yáñez-Serrano, Anke Christine Nölscher, Efstratios Bourtsoukidis, Eliane Gomes Alves, Laurens Ganzeveld, Boris Bonn, Stefan Wolff, Marta Sa, Marcia Yamasoe, Jonathan Williams, Meinrat O. Andreae, and Jürgen Kesselmeier Atmos. Chem. Phys., 18, 3403-3418, https://doi.org/10.5194/acp-18-3403-2018, 2018 This study shows the measurements of concentration of different monoterpene species in terms of height, time of day and season. Speciation seems similar during the dry seasons but changes with season. Furthermore, reactivity with the different oxidants demonstrated that a higher abundance of a monoterpene species does not automatically imply higher reactivity and that the most abundant monoterpene may not be the most atmospheric chemically relevant compound.

Description: Implications of potential future grand solar minimum for ozone layer and climate Pavle Arsenovic, Eugene Rozanov, Julien Anet, Andrea Stenke, Werner Schmutz, and Thomas Peter Atmos. Chem. Phys., 18, 3469-3483, https://doi.org/10.5194/acp-18-3469-2018, 2018 Global warming will persist in the 21st century, even if the solar activity undergoes an unusually strong and long decline. Decreased ozone production caused by reduction of solar activity and change of atmospheric dynamics due to the global warming might result in further thinning of the tropical ozone layer. Globally, total ozone would not recover to the pre-ozone hole values as long as the decline of solar activity lasts. This may let more ultra-violet radiation reach the Earth's surface.

Description: Emissions databases for polycyclic aromatic compounds in the Canadian Athabasca oil sands region – development using current knowledge and evaluation with passive sampling and air dispersion modelling data Xin Qiu, Irene Cheng, Fuquan Yang, Erin Horb, Leiming Zhang, and Tom Harner Atmos. Chem. Phys., 18, 3457-3467, https://doi.org/10.5194/acp-18-3457-2018, 2018 We developed emissions databases for polycyclic aromatic compounds (PACs) in the Athabasca oil sands region and evaluated the emissions databases by comparing CALPUFF-modelled concentrations with monitored data. Model–measurement agreement improved near oil sands mines due to updated PAC emissions from tailings ponds. Modelled concentrations were underestimated at remote sites and for alkylated PACs suggesting that the emissions of PACs particularly alkylated compounds are underestimated.

Description: Evaluation of stratospheric age of air from CF 4 , C 2 F 6 , C 3 F 8 , CHF 3 , HFC-125, HFC-227ea and SF 6 ; implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials Emma Leedham Elvidge, Harald Bönisch, Carl A. M. Brenninkmeijer, Andreas Engel, Paul J. Fraser, Eileen Gallacher, Ray Langenfelds, Jens Mühle, David E. Oram, Eric A. Ray, Anna R. Ridley, Thomas Röckmann, William T. Sturges, Ray F. Weiss, and Johannes C. Laube Atmos. Chem. Phys., 18, 3369-3385, https://doi.org/10.5194/acp-18-3369-2018, 2018 Chemical species measured in stratospheric air can be used as proxies for stratospheric circulation changes which cannot be measured directly. A range of tracers is important to understand changing stratospheric dynamics. We demonstrate the suitability of PFCs and HFCs as tracers and support recent work that reduces the current stratospheric lifetime of SF 6 . Updates to policy-relevant parameters (e.g. stratospheric lifetime) linked to this change are provided for O 3 -depleting substances.

Description: Diurnal, synoptic and seasonal variability of atmospheric CO 2 in the Paris megacity area Irène Xueref-Remy, Elsa Dieudonné, Cyrille Vuillemin, Morgan Lopez, Christine Lac, Martina Schmidt, Marc Delmotte, Frédéric Chevallier, François Ravetta, Olivier Perrussel, Philippe Ciais, François-Marie Bréon, Grégoire Broquet, Michel Ramonet, T. Gerard Spain, and Christophe Ampe Atmos. Chem. Phys., 18, 3335-3362, https://doi.org/10.5194/acp-18-3335-2018, 2018 Urbanized and industrialized areas are the largest source of fossil CO 2 . This work analyses the atmospheric CO 2 variability observed from the first in situ network deployed in the Paris megacity area. Gradients of several ppm are found between the rural, peri-urban and urban sites at the diurnal to the seasonal scales. Wind direction and speed as well as boundary layer dynamics, correlated to highly variable urban emissions, are shown to be key regulator factors of the observed CO 2 records.

Description: On the distortions in calculated GW parameters during slanted atmospheric soundings Alejandro de la Torre, Peter Alexander, Torsten Schmidt, Pablo Llamedo, and Rodrigo Hierro Atmos. Meas. Tech., 11, 1363-1375, https://doi.org/10.5194/amt-11-1363-2018, 2018 This work is based on previous findings from our group of researchers, regarding the analysis of atmospheric data from slanted soundings during radiosoundings and GPS radio occulations. Several gravity wave climatologies may be found in the literature that to a certain extent are affected by considerable measurement distortions. We intend here to contribute to the interpretation of gravity waves analyses from slanted soundings in future climatologies.

Description: Airborne limb-imaging measurements of temperature, HNO 3 , O 3 , ClONO 2 , H 2 O and CFC-12 during the Arctic winter 2015/16: characterization, in-situ validation and comparison to Aura/MLS Sören Johansson, Wolfgang Woiwode, Michael Höpfner, Felix Friedl-Vallon, Anne Kleinert, Erik Kretschmer, Thomas Latzko, Johannes Orphal, Peter Preusse, Jörn Ungermann, Michelle L. Santee, Tina Jurkat-Witschas, Andreas Marsing, Christiane Voigt, Andreas Giez, Martina Krämer, Christian Rolf, Andreas Zahn, Andreas Engel, Björn-Martin Sinnhuber, and Hermann Oelhaf Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-52,2018 Manuscript under review for AMT (discussion: open, 0 comments) We present two dimensional cross sections of temperature, HNO 3 , O 3 , ClONO 2 , H 2 O and CFC-12 from measurements of the GLORIA infrared limb imager during the POLSTRACC/GW-LCYCLE/SALSA aircraft campaigns in the Arctic winter 2015/16. GLORIA sounded the atmosphere between 5–14 km with vertical resolutions of 0.4–1 km. Estimated errors are in the range of 1–2 K (temperature) and 10–20 % (trace gases). Comparisons to in-situ instruments onboard the aircraft and to Aura/MLS are shown.

Description: Reduction of ZTD outliers through improved GNSS data processing and screening strategies Katarzyna Stepniak, Olivier Bock, and Pawel Wielgosz Atmos. Meas. Tech., 11, 1347-1361, https://doi.org/10.5194/amt-11-1347-2018, 2018 Though Global Navigation Satellite System (GNSS) data processing has been significantly improved over the years, it is still commonly observed that zenith tropospheric delay (ZTD) estimates contain many outliers which are detrimental to meteorological and climatological applications. In this paper, we show that ZTD outliers in double-difference processing are mostly caused by sub-daily data gaps at reference stations, which cause disconnections of clusters of stations from the reference network and common mode biases due to the strong correlation between stations in short baselines. They can reach a few centimetres in ZTD and usually coincide with a jump in formal errors. The magnitude and sign of these biases are impossible to predict because they depend on different errors in the observations and on the geometry of the baselines. We elaborate and test a new baseline strategy which solves this problem and significantly reduces the number of outliers compared to the standard strategy commonly used for positioning (e.g. determination of national reference frame) in which the pre-defined network is composed of a skeleton of reference stations to which secondary stations are connected in a star-like structure. The new strategy is also shown to perform better than the widely used strategy maximizing the number of observations available in many GNSS programs. The reason is that observations are maximized before processing, whereas the final number of used observations can be dramatically lower because of data rejection (screening) during the processing. The study relies on the analysis of 1 year of GPS (Global Positioning System) data from a regional network of 136 GNSS stations processed using Bernese GNSS Software v.5.2. A post-processing screening procedure is also proposed to detect and remove a few outliers which may still remain due to short data gaps. It is based on a combination of range checks and outlier checks of ZTD and formal errors. The accuracy of the final screened GPS ZTD estimates is assessed by comparison to ERA-Interim reanalysis.

Description: Raindrop fall velocities from an optical array probe and 2-D video disdrometer Viswanathan Bringi, Merhala Thurai, and Darrel Baumgardner Atmos. Meas. Tech., 11, 1377-1384, https://doi.org/10.5194/amt-11-1377-2018, 2018 Raindrop fall velocities are important for rain rate estimation, soil erosion studies and in numerical modelling of rain formation in clouds. The assumption that the fall velocity is uniquely related to drop size is made inherently based on laboratory measurements under still air conditions from nearly 68 years ago. There have been very few measurements of drop fall speeds in natural rain under both still and turbulent wind conditions. We report on fall speed measurements in natural rain shafts.

Description: PRIMAP-crf: UNFCCC CRF data in IPCC 2006 categories M. Louise Jeffery, Johannes Guetschow, Robert Gieseke, and Ronja Gebel Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-3,2018 Manuscript under review for ESSD (discussion: open, 0 comments) Developed countries are required to report detailed greenhouse gas emissions data to the UN on an annual basis. The reporting tables are complex, do not fit well with existing hierarchical reporting guidelines, and are not machine-readable. We present a processed version of the reported data in a consistent hierarchy and in a format that is machine-readable and easy-to-use. The emissions data is aggregated into 'baskets' of gases using equivalency metrics from IPCC reports.

Description: PRIMAP-crf: UNFCCC CRF data in IPCC 2006 categories M. Louise Jeffery, Johannes Guetschow, Robert Gieseke, and Ronja Gebel Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-3,2018 Manuscript under review for ESSD (discussion: open, 0 comments) Developed countries are required to report detailed greenhouse gas emissions data to the UN on an annual basis. The reporting tables are complex, do not fit well with existing hierarchical reporting guidelines, and are not machine-readable. We present a processed version of the reported data in a consistent hierarchy and in a format that is machine-readable and easy-to-use. The emissions data is aggregated into 'baskets' of gases using equivalency metrics from IPCC reports.

Description: Atmospheric electricity at Durham: the scientific contributions and legacy of J. A. (“Skip”) Chalmers (1904–1967) Karen L. Aplin Hist. Geo Space. Sci., 9, 25-35, https://doi.org/10.5194/hgss-9-25-2018, 2018 John Alan Chalmers spent almost 40 years working on atmospheric electricity at Durham University, UK. He is particularly remembered in the atmospheric physics community for his accessible and insightful textbook, Atmospheric Electricity. He also supervised over 35 research students. This article, inspired by a Royal Meteorological Society discussion meeting held at Durham, provides an overview of his background, scientific contributions, and legacy to modern atmospheric science.

Description: Real-time hydraulic interval state estimation for water transport networks: a case study Stelios G. Vrachimis, Demetrios G. Eliades, and Marios M. Polycarpou Drink. Water Eng. Sci., 11, 19-24, https://doi.org/10.5194/dwes-11-19-2018, 2018 Using real-time uncertain measurements from a real water transport network, the proposed Iterative Hydraulic Interval State Estimation algorithm generates bounds on hydraulic states, by taking into account the measurement uncertainty and modeling uncertainty in the form of uncertain pipe parameters. The applicability of this methodology was demonstrated by using it to estimate the unaccounted-for water in the network. This methodology can be used as a tool for fault detection in water networks.

Description: Inverting Rayleigh surface wave velocities for crustal thickness in eastern Tibet and the western Yangtze craton based on deep learning neural networks Xianqiong Cheng, Qihe Liu, Pingping Li, and Yuan Liu Nonlin. Processes Geophys. Discuss., https//doi.org/10.5194/npg-2018-11,2018 Manuscript under review for NPG (discussion: open, 0 comments) In this paper we resolve classic geophysical problem based on newly developed computer and information science. Since many classic geophysical problems are nonlinear, researches treating them as linearity are approximate. When we treat inverting moho depth as full nonlinearity we attain more satisfactory results with lower costs and higher accuracy. Results we have attained can provide important data for discussing origin and development of earthquake, also for distribution of mineral resources.

Description: Recent updates on the Copernicus Marine Service global ocean monitoring and forecasting real-time 1/12° high resolution system Jean-Michel Lellouche, Eric Greiner, Olivier Le Galloudec, Gilles Garric, Charly Regnier, Marie Drevillon, Mounir Benkiran, Charles-Emmanuel Testut, Romain Bourdalle-Badie, Florent Gasparin, Olga Hernandez, Bruno Levier, Yann Drillet, Elisabeth Remy, and Pierre-Yves Le Traon Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-15,2018 Manuscript under review for OS (discussion: open, 0 comments) In the coming decades, a strong growth of the ocean economy is expected. Scientific advances in operational oceanography will play a crucial role in addressing many of the environmental challenges and in the development of ocean-related economic activities. In this context, remarkable improvements have been achieved with the current Mercator ocean system. 3D water masses, sea level, sea ice and currents have been improved and thus, major oceanic variables are hard to distinguish from the data.

Description: Inverting Rayleigh surface wave velocities for crustal thickness in eastern Tibet and the western Yangtze craton based on deep learning neural networks Xianqiong Cheng, Qihe Liu, Pingping Li, and Yuan Liu Nonlin. Processes Geophys. Discuss., https//doi.org/10.5194/npg-2018-11,2018 Manuscript under review for NPG (discussion: open, 0 comments) In this paper we resolve classic geophysical problem based on newly developed computer and information science. Since many classic geophysical problems are nonlinear, researches treating them as linearity are approximate. When we treat inverting moho depth as full nonlinearity we attain more satisfactory results with lower costs and higher accuracy. Results we have attained can provide important data for discussing origin and development of earthquake, also for distribution of mineral resources.

Description: Carbonaceous material export from Siberian permafrost tracked across the Arctic Shelf using Raman spectroscopy Robert B. Sparkes, Melissa Maher, Jerome Blewett, Ayca Dogrul Selver, Örjan Gustafsson, Igor P. Semiletov, and Bart E. van Dongen The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-16,2018 Manuscript under review for TC (discussion: open, 0 comments) Ongoing climate change in the Siberian Arctic region has the potential to release large amounts of carbon, currently stored in permafrost, to the Arctic Shelf. Degradation can release this to the atmosphere as greenhouse gases. We used Raman spectroscopy to analyse a fraction of this carbon, carbonaceous material, a group that includes coal, lignite, and graphite. We were able to trace this carbon from the river mouths and coastal erosion sites across the Arctic shelf for hundreds of kilometres.

Description: Dissolved and particulate organic carbon in Icelandic proglacial streams Peter Chifflard, Christina Fasching, Martin Reiss, and Lukas Ditzel The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-32,2018 Manuscript under review for TC (discussion: open, 0 comments) For the first time, the concentration of dissolved and particulate organic carbon, as well as its optical properties in proglacial streams of Iceland, location of Europe’s largest nonpolar ice cap, was analyzed. Compared to the global annual release of 1.97 Tg C yr −1 POC, the estimation of annual release of 0.008 Tg C yr −1 (DOC) and 1.72 Tg C yr −1 (POC) from Icelandic glaciers underline the necessity to include the Icelandic glaciers in global organic carbon budget, which has not yet been done.

Description: An investigation of the thermomechanical features of Laohugou Glacier No. 12 on Qilian Shan, western China, using a two-dimensional first-order flow-band ice flow model Yuzhe Wang, Tong Zhang, Jiawen Ren, Xiang Qin, Yushuo Liu, Weijun Sun, Jizu Chen, Minghu Ding, Wentao Du, and Dahe Qin The Cryosphere, 12, 851-866, https://doi.org/10.5194/tc-12-851-2018, 2018 We combine in situ measurements and an ice flow model to study the thermomechanical features of Laohugou Glacier No. 12, the largest valley glacier on Qilian Shan. We reveal that this glacier, once considered to be extremely continental or cold, is actually polythermal with a lower temperate ice layer over a large region of the ablation area. Strain heating and latent heat due to meltwater refreezing in the firn zone play critical roles in controlling the thermal regime of this glacier.

Description: Impacts of bromine and iodine chemistry on tropospheric OH and HO 2 : comparing observations with box and global model perspectives Daniel Stone, Tomás Sherwen, Mathew J. Evans, Stewart Vaughan, Trevor Ingham, Lisa K. Whalley, Peter M. Edwards, Katie A. Read, James D. Lee, Sarah J. Moller, Lucy J. Carpenter, Alastair C. Lewis, and Dwayne E. Heard Atmos. Chem. Phys., 18, 3541-3561, https://doi.org/10.5194/acp-18-3541-2018, 2018 Halogen chemistry in the troposphere impacts oxidising capacity, but model studies assessing the nature of these impacts can vary according to the model framework used. In this work we present simulations of OH and HO 2 radicals using both box and global model frameworks, and compare to observations made at the Cape Verde Atmospheric Observatory. We highlight, and rationalise, differences between the model frameworks.

Description: Ice-nucleating particle concentrations unaffected by urban air pollution in Beijing, China Jie Chen, Zhijun Wu, Stefanie Augustin-Bauditz, Sarah Grawe, Markus Hartmann, Xiangyu Pei, Zirui Liu, Dongsheng Ji, and Heike Wex Atmos. Chem. Phys., 18, 3523-3539, https://doi.org/10.5194/acp-18-3523-2018, 2018 The ice nucleation activity of urban aerosols in the atmosphere of Beijing was detected in this study. Results showed that ice-nucleating particle (INP) concentrations were not influenced by the highly variable numbers of atmospheric particles, both in mass and particle number concentrations, implying that INP concentrations might not be influenced directly by anthropogenic activities, at least not down to roughly −25 °C and maybe even below.

Description: Temporally delineated sources of major chemical species in high Arctic snow Katrina M. Macdonald, Sangeeta Sharma, Desiree Toom, Alina Chivulescu, Andrew Platt, Mike Elsasser, Lin Huang, Richard Leaitch, Nathan Chellman, Joseph R. McConnell, Heiko Bozem, Daniel Kunkel, Ying Duan Lei, Cheol-Heon Jeong, Jonathan P. D. Abbatt, and Greg J. Evans Atmos. Chem. Phys., 18, 3485-3503, https://doi.org/10.5194/acp-18-3485-2018, 2018 The sources of key contaminants in Arctic snow may be an important factor in understanding the rapid climate changes observed in the Arctic. Fresh snow samples collected frequently through the winter season were analyzed for major constituents. Temporally refined source apportionment via positive matrix factorization in conjunction with FLEXPART suggested potential source characteristics and locations. The identity of these sources and their relative contribution to key analytes is discussed.

Description: Paleotsunami deposits along the coast of Egypt correlate with historical earthquake records of eastern Mediterranean Asem Salama, Mustapha Meghraoui, Mohamed El Gabry, Said Maouche, Hesham Moussa Hussein, and Ibrahim Korrat Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2018-62,2018 Manuscript under review for NHESS (discussion: open, 0 comments) We study the sedimentary record of past tsunamis along the coastal area west of Alexandria (NW Egypt) taking into account the occurrence of major historical earthquakes in the eastern Mediterranean. Dated charcoal and shell in sedimentary units allow the correlation with the 1870 (Mw 7.5), 1303 (Mw ~ 8) and 365 (Mw ~ 8) large tsunamigenic earthquakes. Our results point out the size and recurrence of past tsunamis and the potential for tsunami hazard over the Egyptian coastline.

Description: Paleotsunami deposits along the coast of Egypt correlate with historical earthquake records of eastern Mediterranean Asem Salama, Mustapha Meghraoui, Mohamed El Gabry, Said Maouche, Hesham Moussa Hussein, and Ibrahim Korrat Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2018-62,2018 Manuscript under review for NHESS (discussion: open, 0 comments) We study the sedimentary record of past tsunamis along the coastal area west of Alexandria (NW Egypt) taking into account the occurrence of major historical earthquakes in the eastern Mediterranean. Dated charcoal and shell in sedimentary units allow the correlation with the 1870 (Mw 7.5), 1303 (Mw ~ 8) and 365 (Mw ~ 8) large tsunamigenic earthquakes. Our results point out the size and recurrence of past tsunamis and the potential for tsunami hazard over the Egyptian coastline.

Description: The influence of sea surface temperature on the intensity and associated storm surge of tropical cyclone Yasi: a sensitivity study Sally L. Lavender, Ron K. Hoeke, and Deborah J. Abbs Nat. Hazards Earth Syst. Sci., 18, 795-805, https://doi.org/10.5194/nhess-18-795-2018, 2018 This study analyses the influence of sea surface temperature (SST) on the track and intensity of tropical cyclone (TC) Yasi and the associated precipitation and storm surge. A set of regional climate model simulations with SST anomalies varying from +4 to −4 °C are analysed and used to force a storm surge model. Increases in SST lead to an increase in the potential destructiveness of the TC (intensity, rainfall and storm surge), although this relationship is not linear.

Description: Evolution of fractality in space plasmas of interest to geomagnetic activity Víctor Muñoz, Macarena Domínguez, Juan Alejandro Valdivia, Simon Good, Giuseppina Nigro, and Vincenzo Carbone Nonlin. Processes Geophys., 25, 207-216, https://doi.org/10.5194/npg-25-207-2018, 2018 Fractals are self-similar objects (which look the same at all scales), whose dimensions can be noninteger. They are mathematical concepts, useful to describe various physical systems, as the fractal dimension is a measure of their complexity. In this paper we study how these concepts can be applied to some problems in space plasmas, such as the activity of the Earth's magnetosphere, simulations of plasma turbulence, or identification of magnetic structures ejected from the Sun.

Description: Evolution of fractality in space plasmas of interest to geomagnetic activity Víctor Muñoz, Macarena Domínguez, Juan Alejandro Valdivia, Simon Good, Giuseppina Nigro, and Vincenzo Carbone Nonlin. Processes Geophys., 25, 207-216, https://doi.org/10.5194/npg-25-207-2018, 2018 Fractals are self-similar objects (which look the same at all scales), whose dimensions can be noninteger. They are mathematical concepts, useful to describe various physical systems, as the fractal dimension is a measure of their complexity. In this paper we study how these concepts can be applied to some problems in space plasmas, such as the activity of the Earth's magnetosphere, simulations of plasma turbulence, or identification of magnetic structures ejected from the Sun.

Description: A Statistical Mechanical Approach for the Parametrization of the Coupling in a Fast-Slow System Gabriele Vissio and Valerio Lucarini Nonlin. Processes Geophys. Discuss., https//doi.org/10.5194/npg-2018-16,2018 Manuscript under review for NPG (discussion: open, 0 comments) Constructing accurate, flexible, and efficient parametrizations is one of the great challenges in the numerical modelling of geophysical fluids. We consider here the simple yet paradigmatic case of a Lorenz 84 model forced by a Lorenz 63 model and derive a parametrization using a recently developed statistical mechanical methodology based on the Ruelle response theory. We derive an expression for the deterministic and the stochastic component of the parametrization and we show that the approach allows for dealing seamlessly with the case of the Lorenz 63 being a fast as well as a slow forcing compared to the characteristic time scales of the Lorenz 84 model. We test our results using both standard metrics based on the moments of the variables of interest as well as Wasserstein distance between the projected measure of the original system on the Lorenz 84 model variables and the measure of the parametrized one. By testing our methods on reduced phase spaces obtained by projection, we find support to the idea that comparisons based on the Wasserstein distance might be of relevance in many applications despite the curse of dimensionality.

Description: A Statistical Mechanical Approach for the Parametrization of the Coupling in a Fast-Slow System Gabriele Vissio and Valerio Lucarini Nonlin. Processes Geophys. Discuss., https//doi.org/10.5194/npg-2018-16,2018 Manuscript under review for NPG (discussion: open, 0 comments) Constructing accurate, flexible, and efficient parametrizations is one of the great challenges in the numerical modelling of geophysical fluids. We consider here the simple yet paradigmatic case of a Lorenz 84 model forced by a Lorenz 63 model and derive a parametrization using a recently developed statistical mechanical methodology based on the Ruelle response theory. We derive an expression for the deterministic and the stochastic component of the parametrization and we show that the approach allows for dealing seamlessly with the case of the Lorenz 63 being a fast as well as a slow forcing compared to the characteristic time scales of the Lorenz 84 model. We test our results using both standard metrics based on the moments of the variables of interest as well as Wasserstein distance between the projected measure of the original system on the Lorenz 84 model variables and the measure of the parametrized one. By testing our methods on reduced phase spaces obtained by projection, we find support to the idea that comparisons based on the Wasserstein distance might be of relevance in many applications despite the curse of dimensionality.

Description: Ca-rich garnets and associated symplectites in mafic peraluminous granulites from the Gföhl Nappe System, Austria Konstantin Petrakakis, Nathalie Schuster-Bourgin, Gerlinde Habler, and Rainer Abart Solid Earth Discuss., https//doi.org/10.5194/se-2018-18,2018 Manuscript under review for SE (discussion: open, 0 comments) Aluminum-rich granulites from Austria contain large garnets with kyanite inclusions. Garnets are built up from compositionally different types. They are replaced partially by various symplectites. Thermodynamic analysis points to metasomatic alteration and rock decompression due to tectonic transport at high temperatures from deep to middle crustal levels. The various symplectites were formed after decompression during cooling within a short time interval of less than 500 years.

Description: Ca-rich garnets and associated symplectites in mafic peraluminous granulites from the Gföhl Nappe System, Austria Konstantin Petrakakis, Nathalie Schuster-Bourgin, Gerlinde Habler, and Rainer Abart Solid Earth Discuss., https//doi.org/10.5194/se-2018-18,2018 Manuscript under review for SE (discussion: open, 0 comments) Aluminum-rich granulites from Austria contain large garnets with kyanite inclusions. Garnets are built up from compositionally different types. They are replaced partially by various symplectites. Thermodynamic analysis points to metasomatic alteration and rock decompression due to tectonic transport at high temperatures from deep to middle crustal levels. The various symplectites were formed after decompression during cooling within a short time interval of less than 500 years.

Description: Improving gridded snow water equivalent products in British Columbia, Canada: multi-source data fusion by neural network models Andrew M. Snauffer, William W. Hsieh, Alex J. Cannon, and Markus A. Schnorbus The Cryosphere, 12, 891-905, https://doi.org/10.5194/tc-12-891-2018, 2018 Estimating winter snowpack throughout British Columbia is challenging due to the complex terrain, thick forests, and high snow accumulations present. This paper describes a way to make better snow estimates by combining publicly available data using machine learning, a branch of artificial intelligence research. These improved estimates will help water resources managers better plan for changes in rivers and lakes fed by spring snowmelt and will aid other research that supports such planning.

Description: How reliable are CMIP5 models in simulating dust optical depth? Bing Pu and Paul Ginoux Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-242,2018 Manuscript under review for ACP (discussion: open, 0 comments) Biases in dust modeling may result in biases in simulating energy budget and regional climate. Output of seven Coupled Model Intercomparison Project Phase 5 (CMIP5) models is examined. Seasonal cycle and spatial pattern of dust optical depth (DOD) in very dusty regions are largely captured by multi-model mean. But observed connections between DOD and local controlling factors such as bareness are not well represented. Future projections by CMIP5 models and a regression model are also analyzed.

Description: Theoretical analysis of mixing in liquid clouds – Part IV: DSD evolution and mixing diagrams Mark Pinsky and Alexander Khain Atmos. Chem. Phys., 18, 3659-3676, https://doi.org/10.5194/acp-18-3659-2018, 2018 In this paper it is shown that the difference between the mixing diagrams for homogeneous and inhomogeneous mixing is insignificant and decreases with an increase in the DSD width. If the normalized droplet concentration is used, mixing diagrams do not show any significant dependency on relative humidity in the dry volume. The main conclusion of the study is that traditional mixing diagrams cannot serve as a reliable tool in analysis of mixing type.

Description: Model simulations with COSMO-SPECS: impact of heterogeneous freezing modes and ice nucleating particle types on ice formation and precipitation in a deep convective cloud Karoline Diehl and Verena Grützun Atmos. Chem. Phys., 18, 3619-3639, https://doi.org/10.5194/acp-18-3619-2018, 2018 In deep convective clouds reaching altitudes of 14 km, heavy rain is often formed involving the ice phase. Ice nucleating particles (INPs) are responsible for heterogeneous freezing at middle and lower altitudes. Cloud model simulations indicate that INPs may effect a gradual increase in precipitation at early cloud stages instead of a strong increase at later cloud stages. Simultaneously, the local distribution of precipitation is changed, with more precipitation in the cloud center.

Description: Open fires in Greenland: an unusual event and its impact on the albedo of the Greenland Ice Sheet Nikolaos Evangeliou, Arve Kylling, Sabine Eckhardt, Viktor Myroniuk, Kerstin Stebel, Ronan Paugam, Sergiy Zibtsev, and Andreas Stohl Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-94,2018 Manuscript under review for ACP (discussion: open, 0 comments) We simulated the peatland fires that burned Western Greenland in summer 2017. Using satellite data we estimated that the total area burned was about 2345 hectares, the fuel amount consumed about 117 kt C and the emissions of BC about 23.5 t. Smoke plumes were often pushed towards the Greenland Ice Sheet and 30 % of the BC emissions was deposited on snow or ice. This caused a maximum albedo change of 0.006 and a surface radiative forcing of 0.03 W m −2 with local maxima of up to 0.63 W m −2 .

Description: Atmospheric water-soluble organic nitrogen (WSON) in the eastern Mediterranean: origin and ramifications regarding marine productivity Münevver Nehir and Mustafa Koçak Atmos. Chem. Phys., 18, 3603-3618, https://doi.org/10.5194/acp-18-3603-2018, 2018 Atmospheric samples of water-soluble organic nitrogen (WSON) obtained over the eastern Mediterranean have been investigated. Aerosol WSON concentrations exhibited large temporal variation, mainly due to rain and the origin of airflow. WSON originated from agricultural activities, secondary aerosol, nitrate, crustal material and sea salt. In the Cilician Basin, the WSON flux would sustain 33 % and 76 % of the new production of the plant-like organisms in coastal and open waters, respectively.

Description: Modeling reactive ammonia uptake by secondary organic aerosol in CMAQ: application to the continental US Shupeng Zhu, Jeremy R. Horne, Julia Montoya-Aguilera, Mallory L. Hinks, Sergey A. Nizkorodov, and Donald Dabdub Atmos. Chem. Phys., 18, 3641-3657, https://doi.org/10.5194/acp-18-3641-2018, 2018 For the first time, the interaction between ammonia and secondary organic aerosol (SOA) is integrated in an air quality model and investigated on a national scale. Our original analysis from simulation results indicates that a significant reduction in gas-phase ammonia is possible due to its uptake onto SOA. Significant impact is also observed in the concentration of particulate matter, with a distinct spatial pattern over different seasons.

Description: In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013 Jean-Baptiste Renard, François Dulac, Pierre Durand, Quentin Bourgeois, Cyrielle Denjean, Damien Vignelles, Benoit Couté, Matthieu Jeannot, Nicolas Verdier, and Marc Mallet Atmos. Chem. Phys., 18, 3677-3699, https://doi.org/10.5194/acp-18-3677-2018, 2018 A campaign was performed in the summer of 2013 above the Mediterranean basin, including in situ counting balloon-borne aerosol measurements (LOAC), for the detection of mineral dust. Three modes in the dust particle volume size distributions were detected, at roughly 0.2, 4, and 30 mm. Particles larger than 40 mm were often observed. They were lifted several days before and their persistence after transport over long distances is in conflict with dust sedimentation calculations.

Description: Ubiquitous influence of wildfire emissions and secondary organic aerosol on summertime atmospheric aerosol in the forested Great Lakes region Matthew J. Gunsch, Nathaniel W. May, Miao Wen, Courtney L. H. Bottenus, Daniel J. Gardner, Timothy M. VanReken, Steven B. Bertman, Philip K. Hopke, Andrew P. Ault, and Kerri A. Pratt Atmos. Chem. Phys., 18, 3701-3715, https://doi.org/10.5194/acp-18-3701-2018, 2018 During summer 2014, atmospheric particulate matter in northern Michigan was impacted by wildfire emissions under all air mass conditions (Canadian wildfires, US urban, and Canadian forest influences). Biomass burning particles coated with secondary organic aerosol contributed the majority of the submicron aerosol mass. Given increasing wildfires, the impacts of biomass burning on air quality must be assessed, particularly for downwind areas impacted by long-range transport.

Description: Gravity Waves excited during a Minor Sudden Stratospheric Warming Andreas Dörnbrack, Sonja Gisinger, Natalie Kaifler, Tanja Portele, Martina Bramberger, Markus Rapp, Micheal Gerding, Jens Söder, Nedjeljka Žagar, and Damjan Jelić Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-228,2018 Manuscript under review for ACP (discussion: open, 0 comments) A deep upper-air sounding stimulated the current investigation of internal gravity waves excited during a minor sudden stratospheric warming (SSW) in the Arctic winter 2015/16. The analysis of the radiosonde profile revealed large kinetic and potential energies in the upper stratosphere without any simultaneous enhancement of upper tropospheric and lower stratospheric values. In combination with high-resolution meteorological analyses we identified an elevated source of gravity wave excitation.

Description: Multi-generation chemical aging of α -pinene ozonolysis products by reactions with OH Ningxin Wang, Evangelia Kostenidou, Neil M. Donahue, and Spyros N. Pandis Atmos. Chem. Phys., 18, 3589-3601, https://doi.org/10.5194/acp-18-3589-2018, 2018 This study investigates aging in the α-pinene ozonolysis system with hydroxyl radicals (OH) through smog chamber experiments. After an equivalent of 2–4 days of typical atmospheric oxidation conditions, homogeneous OH oxidation of the α-pinene ozonolysis products resulted in a 20–40 % net increase in the organic aerosol concentration and an increase in aerosol O : C by up to 0.04. The relative humidity in the 5–50 % range had a minimum effect on aging.

Description: Contrasting behaviors of the atmospheric CO 2 interannual variability during two types of El Niños Jun Wang, Ning Zeng, Meirong Wang, Fei Jiang, Jingming Chen, Pierre Friedlingstein, Atul K. Jain, Ziqiang Jiang, Weimin Ju, Sebastian Lienert, Julia Nabel, Stephen Sitch, Nicolas Viovy, Hengmao Wang, and Andrew J. Wiltshire Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-208,2018 Manuscript under review for ACP (discussion: open, 0 comments) Based on the Mauna Loa CO 2 records and TRENDY multi-model historical simulations, we investigate the different impacts of EP and CP El Ninos on carbon cycle interannual variability. Composite analysis indicates that the evolutions of CO 2 growth rate anomalies have three clear differences in terms of precursors (negative & neutral), amplitudes (strong & weak), and durations of peak (Dec–Apr & Oct–Jan) during EP and CP El Ninos, respectively. Then we further discuss their terrestrial mechanisms.

Description: Is Mass Transfer in Secondary Organic Aerosol Particles Intrinsically Slow? Equilibration Timescales of Engine Exhaust and α-Pinene SOA Under Dry and Humid Conditions Khairallah Atwi, Mohamad Baassiri, Mariam Fawaz, and Alan Shihadeh Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-215,2018 Manuscript under review for ACP (discussion: open, 0 comments) Secondary organic aerosols (SOA) influence health and climate. A major simplifying assumption usually made in airshed models is that SOA particles attain instantaneous phase equilibrium with their surroundings. This assumption has been questioned by several recent studies. We generated engine exhaust and biogenic SOA and investigated their evaporation behavior upon dilution. Consistent with current practice, we found that SOA reestablish equilibrium on timescales small enough to be neglected.