ALBERT

Description: MicroHH 1.0: a computational fluid dynamics code for direct numerical simulation and large-eddy simulation of atmospheric boundary layer flows Chiel C. van Heerwaarden, Bart J. H. van Stratum, Thijs Heus, Jeremy A. Gibbs, Evgeni Fedorovich, and Juan-Pedro Mellado Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-41,2017 Manuscript under review for GMD (discussion: open, 0 comments) MicroHH ( ww.microhh.org ) is a new and open source computational fluid dynamics code for the simulation of turbulent flows in the atmosphere. It is made the simulate atmospheric flows up to the finest detail levels at very high resolution. It has been designed from scratch in order to use a modern design that allows the code to run on more than 10.000 cores, as well as on a Graphical Processing Unit.

Description: Historical (1750–2014) anthropogenic emissions of reactive gases and aerosols from the Community Emission Data System (CEDS) Rachel M. Hoesly, Steven J. Smith, Leyang Feng, Zbigniew Klimont, Greet Janssens-Maenhout, Tyler Pitkanen, Jonathan J. Seibert, Linh Vu, Robert J. Andres, Ryan M. Bolt, Tami C. Bond, Laura Dawidowski, Nazar Kholod, Jun-ichi Kurokawa, Meng Li, Liang Liu, Zifeng Lu, Maria Cecilia P. Moura, Patrick R. O'Rourke, and Qiang Zhang Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-43,2017 Manuscript under review for GMD (discussion: open, 0 comments) Historical emission trends are key inputs to earth systems and atmospheric chemistry models. We present a new data set of historical (1750–2014) anthropogenic gases (CO, CH 4 , NH 3 , NO X , SO 2 , NMVOC, BC, OC, and CO 2 ) developed with the Community Emissions Database System (CEDS). This improves on existing inventories as it uses consistent methods and data across emissions species, has annual resolution for a longer and more recent time series, and is designed to be transparent and reproducible.

Description: Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools and turnover in temperate forests Francesc Montané, Andrew M. Fox, Avelino F. Arellano, Natasha MacBean, M. Ross Alexander, Alex Dye, Daniel A. Bishop, Valerie Trouet, Flurin Babst, Amy E. Hessl, Neil Pederson, Peter D. Blanken, Gil Bohrer, Christopher M. Gough, Marcy E. Litvak, Kimberly A. Novick, Richard P. Phillips, Jeffrey D. Wood, and David J. P. Moore Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-74,2017 Manuscript under review for GMD (discussion: open, 0 comments) How carbon is allocated to different plant tissues (leaves, stem, and roots) determines carbon residence time and thus remains a central challenge for understanding the global carbon cycle. In this paper, we used a state-of-the-art land surface model (CLM4.5) with its standard carbon allocation scheme, and we implemented alternative carbon allocation schemes based on published papers. One of the alternative allocation schemes improved aboveground biomass estimates in most of our sites.

Description: The Fire Modeling Intercomparison Project (FireMIP), phase 1: experimental and analytical protocols with detailed model descriptions Sam S. Rabin, Joe R. Melton, Gitta Lasslop, Dominique Bachelet, Matthew Forrest, Stijn Hantson, Jed O. Kaplan, Fang Li, Stéphane Mangeon, Daniel S. Ward, Chao Yue, Vivek K. Arora, Thomas Hickler, Silvia Kloster, Wolfgang Knorr, Lars Nieradzik, Allan Spessa, Gerd A. Folberth, Tim Sheehan, Apostolos Voulgarakis, Douglas I. Kelley, I. Colin Prentice, Stephen Sitch, Sandy Harrison, and Almut Arneth Geosci. Model Dev., 10, 1175-1197, doi:10.5194/gmd-10-1175-2017, 2017 Global vegetation models are important tools for understanding how the Earth system will change in the future, and fire is a critical process to include. A number of different methods have been developed to represent vegetation burning. This paper describes the protocol for the first systematic comparison of global fire models, which will allow the community to explore various drivers and evaluate what mechanisms are important for improving performance. It also includes equations for all models.

Description: A Bayesian posterior predictive framework for weighting ensemble regional climate models Yanan Fan, Roman Olson, and Jason P. Evans Geosci. Model Dev., 10, 2321-2332, https://doi.org/10.5194/gmd-10-2321-2017, 2017 We develop a novel and principled Bayesian statistical approach to computing model weights in climate change projection ensembles of regional climate models. The approach accounts for uncertainty in model bias, trend and internal variability. The weights are easily interpretable and the ensemble weighted models are shown to provide the correct coverage and improve upon existing methods in terms of providing narrower confidence intervals for climate change projections.

Description: Tracking an Atmospheric River in a Warmer Climate: from Water Vapor to Economic Impacts Francina Dominguez, Sandy Dall'erba, Shuyi Huang, Andre Avelino, Ali Mehran, Huancui Hu, Arthur Schmidt, Lawrence Schick, and Dennis Lettenmaier Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-64,2017 Manuscript under review for ESD (discussion: open, 0 comments) Atmospheric rivers (ARs) account for most of the extreme flooding events in the northwestern coast of the US. In a warmer climate, ARs in this region are projected to become more frequent and intense. We present an integrated modeling system to quantify the atmospheric-hydrologic-hydraulic and economic impacts an AR event in western Washington. Our integrated modeling tool provides communities in the region a range of possible future physical and economic impacts associated with AR flooding.

Description: Estimating global cropland production from 1961 to 2010 Pengfei Han, Ning Zeng, Fang Zhao, and Xiaohui Lin Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-49,2017 Manuscript under review for ESD (discussion: open, 0 comments) Global cropland net primary production has tripled over the last fifty years. However, long-term comparisons across global croplands are scarce due to the lack of detailed management data. Here, we conducted a simulation study of global cropland production from 1961 to 2010 using VEGAS model. We modified the key parameter associated with the Green Revolution. The updated results decreased the root mean square error ~ 45 %, suggesting it is important to calibrate key parameters at regional scales.

Description: Sea-ice evaluation of NEMO-Nordic 1.0: a NEMO–LIM3.6 based ocean–sea ice model setup for the North Sea and Baltic Sea Per Pemberton, Ulrike Löptien, Robinson Hordoir, Anders Höglund, Semjon Schimanke, Lars Axell, and Jari Haapala Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-10,2017 Manuscript under review for GMD (discussion: open, 0 comments) The Baltic Sea is seasonally ice covered with intense wintertime ship traffic and a sensitive ecosystem. Understanding the sea-ice pack is important for climate effect studies and forecasting. Our work introduces a new model setup for the North Sea/Baltic Sea and a new method to handle ice in the coastal zone, an important feature in the Baltic Sea. We evaluate different sea ice parameters and overall finds that the model agrees well with the observation and is well suited for further studies.

Description: Implementation of methane cycling for deep time, global warming simulations with the DCESS Earth System Model (Version 1.2) Gary Shaffer, Esteban Fernández Villanueva, Roberto Rondanelli, Jens Olaf Pepke Pedersen, Steffen Malskær Olsen, and Matthew Huber Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-23,2017 Manuscript under review for GMD (discussion: open, 0 comments) We include methane cycling in the simplified but well-tested Danish Center for Earth System Science model. We now can deal with very large methane inputs to the Earth System that can lead to much methane in the atmosphere, extreme warming and ocean dead zones. We now can study ancient global warming events, probably forced by methane inputs. Some such events were accompanied by mass extinctions. We wish to understand such events, both for learning about the past and for looking into the future.

Description: Seasonal effects of irrigation on land–atmosphere latent heat, sensible heat, and carbon fluxes in semiarid basin Yujin Zeng, Zhenghui Xie, and Shuang Liu Earth Syst. Dynam., 8, 113-127, doi:10.5194/esd-8-113-2017, 2017 Irrigation constitutes 70 % of human water consumption. In this study, using the improved CLM4.5 with an active crop model, two 1 km simulations investigating the effects of irrigation on latent heat, sensible heat, and carbon fluxes in the Heihe River basin in northwestern China were conducted using a high-quality irrigation dataset compiled from 1981 to 2013. The results revealed the key role of irrigation in the control of land–atmosphere water, energy, and carbon fluxes in semiarid basin.

Description: Past and future influence of climate change on spatially heterogeneous vegetation activity in China Jiangbo Gao, Kewei Jiao, Shaohong Wu, Danyang Ma, Dongsheng Zhao, Yunhe Yin, and Erfu Dai Earth Syst. Dynam. Discuss., doi:10.5194/esd-2017-13,2017 Manuscript under review for ESD (discussion: open, 0 comments) We found the precipitation and temperature dominated vegetation activities were located in the north and south of China, respectively. Responding patterns to precipitation variation will move southward due to the hydrothermal mediation. In future, vegetation in north China may adapt to arid environment, but it will be repressed in south China. This work,extending time scales from past to future, can promote the understanding of climate–vegetation correlation, a frontier in global change research.

Description: Changes in the seasonal cycle of the Atlantic meridional heat transport in a RCP 8.5 climate projection in MPI-ESM Matthias Fischer, Daniela I. V. Domeisen, Wolfgang A. Müller, and Johanna Baehr Earth Syst. Dynam., 8, 129-146, doi:10.5194/esd-8-129-2017, 2017 In a climate projection experiment with the Max Planck Institute Earth System Model (MPI-ESM), we find that a decline in the Atlantic Ocean meridional heat transport (OHT) is accompanied by a change in the seasonal cycle of the total OHT and its components. We found a northward shift of 5° and latitude-dependent shifts between 1 and 6 months in the seasonal cycle that are mainly associated with changes in the meridional velocity field rather than the temperature field.

Description: Exploring new topography-based subgrid spatial structures for improving land surface modeling Teklu K. Tesfa and Lai-Yung Ruby Leung Geosci. Model Dev., 10, 873-888, doi:10.5194/gmd-10-873-2017, 2017 Motivated by the significant topographic influence on land surface processes, this study explored two methods to discretize watersheds into two types of subgrid structures to capture spatial heterogeneity for land surface models. Adopting geomorphologic concepts in watershed discretization yields improved capability in capturing subgrid topographic heterogeneity, which also allowed climatic and land cover variability to be better represented with a nominal increase in computational requirements.

Description: Efficiently modelling urban heat storage: an interface conduction scheme in an urban land surface model (aTEB v2.0) Mathew J. Lipson, Melissa A. Hart, and Marcus Thatcher Geosci. Model Dev., 10, 991-1007, doi:10.5194/gmd-10-991-2017, 2017 City-scale models describing the surface energy balance have difficulties representing heat storage in urban materials. This paper proposes an alternative method to discretise heat conduction through urban materials. We compare the new method with an approach commonly used in urban models and find the new method better matches exact solutions to heat transfer for a wide variety of urban material compositions. We also find the new method improves the bulk energy flux response of an urban model.

Description: How to represent human behavior and decision making in Earth system models? A guide to techniques and approaches Finn Müller-Hansen, Maja Schlüter, Michael Mäs, Rainer Hegselmann, Jonathan F. Donges, Jakob J. Kolb, Kirsten Thonicke, and Jobst Heitzig Earth Syst. Dynam. Discuss., doi:10.5194/esd-2017-18,2017 Manuscript under review for ESD (discussion: open, 0 comments) Today, human interactions with the Earth system lead to complex feedbacks between social and ecological dynamics. Modeling such feedbacks explicitly in Earth System Models (ESMs) requires making assumptions about individual decision making and behavior, social interaction and their aggregation. In this tutorial review, we compare different modeling approaches and techniques and highlight important consequences of modeling assumptions. We illustrate them with examples from land-use dynamics.

Description: Influence of bulk microphysics schemes upon Weather Research and Forecasting (WRF) version 3.6.1 nor'easter simulations Stephen D. Nicholls, Steven G. Decker, Wei-Kuo Tao, Stephen E. Lang, Jainn J. Shi, and Karen I. Mohr Geosci. Model Dev., 10, 1033-1049, doi:10.5194/gmd-10-1033-2017, 2017 This study evaluated the impact of five hydrometeor species physics schemes during seven intense winter storm events in the northeastern United States. Model simulations were evaluated against gridded analysis data, precipitation, and weather radar derived products. Results show minor differences in simulated precipitation and large-scale regional patterns, yet simulated weather radar fields were more accurate in physics schemes with less ice pellet content above the melting layer.

Description: Explicit and parametrised representation of under ice shelf seas in a z * coordinate ocean model Pierre Mathiot, Adrian Jenkins, Christopher Harris, and Gurvan Madec Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-37,2017 Manuscript under review for GMD (discussion: open, 0 comments) Ice shelf/ocean interactions are a major source of fresh water on the Antarctic continental shelf and have a strong impact on ocean properties, ocean circulation and sea ice. However, climate models based on the ocean/sea ice model NEMO currently do not include these interactions in any detail. The capability of explicitly simulating the circulation beneath ice shelves is introduced in the non-linear free surface model NEMO. Its implementation into the NEMO framework and its assessment in an idealised and realistic circum-Antarctic configuration is described in this study. Compared with the current prescription of ice shelf melting (i.e. at the surface) inclusion of open sub-ice-shelf leads to a decrease sea ice thickness along the coast, a weakening of the ocean stratification on the shelf, a decrease in salinity of HSSW on the Ross and Weddell Sea shelves and an increase in the strength of the gyres that circulate within the over-deepened basins on the West Antarctic continental shelf. Mimicking the under ice shelf seas overturning circulation by introducing the meltwater over the depth range of the ice shelf base, rather than at the surface is also tested. It yields similar improvements in the simulated ocean properties and circulation over the Antarctic continental shelf than the explicit ice shelf cavity representation. With the ice shelf cavities opened, the widely-used “3 equations” ice shelf melting formulation enables an interactive computation of melting that has been assessed. Comparison with observational estimates of ice shelf melting indicates realistic results for most ice shelves. However, melting rates for Amery, Getz and George VI ice shelves are considerably overestimated.

Description: Refining multi-model projections of temperature extremes by evaluation against land–atmosphere coupling diagnostics Sebastian Sippel, Jakob Zscheischler, Miguel D. Mahecha, Rene Orth, Markus Reichstein, Martha Vogel, and Sonia I. Seneviratne Earth Syst. Dynam., 8, 387-403, https://doi.org/10.5194/esd-8-387-2017, 2017 The present study (1) evaluates land–atmosphere coupling in the CMIP5 multi-model ensemble against an ensemble of benchmarking datasets and (2) refines the model ensemble using a land–atmosphere coupling diagnostic as constraint. Our study demonstrates that a considerable fraction of coupled climate models overemphasize warm-season moisture-limited climate regimes in midlatitude regions. This leads to biases in daily-scale temperature extremes, which are alleviated in a constrained ensemble.

Description: Prevailing climatic trends and runoff response from Hindukush–Karakoram–Himalaya, upper Indus Basin Shabeh Hasson, Jürgen Böhner, and Valerio Lucarini Earth Syst. Dynam., 8, 337-355, https://doi.org/10.5194/esd-8-337-2017, 2017 A first comprehensive and systematic hydroclimatic trend analysis for the upper Indus Basin suggests warming and drying of spring and rising early melt-season discharge over 1995–2012 period. In contrast, cooling and falling or weakly rising discharge is found within summer monsoon period that coincides well with main glacier melt season. Such seasonally distinct changes, indicating dominance of snow but suppression of glacial melt regime, address hydroclimatic explanation of Karakoram Anomaly .

Description: The Potential of using Remote Sensing data to estimate Air–Sea CO 2 exchange in the Baltic Sea Gaëlle Parard, Anna Rutgersson, Sindu Raj Parampil, and Anastase Alexandre Charantonis Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-33,2017 Manuscript under review for ESD (discussion: open, 1 comment) Coastal environments and shelf sea represent 7.6 % of the total oceanic surface area they are, however, biogeochemically more dynamic, and probably more vulnerable to climate change than the open ocean. Whatever the responses of the open ocean to climate change, they will propagate to the coastal ocean. We used the self-organizing multiple linear output (SOMLO) method to estimate the ocean surface pCO 2 in the Baltic Sea from the remotely sensed measurements and we estimates the air-sea CO 2 flux.

Description: More HomogeneousWind Conditions Under Strong Climate Change Decrease the Potential for Inter-State Balancing of Electricity in Europe Jan Wohland, Mark Reyers, Juliane Weber, and Dirk Witthaut Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-48,2017 Manuscript under review for ESD (discussion: open, 0 comments) Solar and wind energy generation are weather dependent and can not be switched on when needed. One option to obtain stable electricity generation despite this volatility is aggregation over large areas, for example Europe. We show that strong climate change impedes the integration of very high shares of renewables in Europe. This is because countries are more likely to suffer from simultaneous generation shortfall. As a consequence, local scarcity can less often be balanced by imports.

Description: Evaporative fractionation of H 2 18 O in the polar ocean and the invisibility of large changes of ice volume and sea level in the Saalian δ 18 O proxy records Robert G. Johnson Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-20,2017 Manuscript under review for ESD (discussion: open, 0 comments) Beginning about 150,000 yrs ago glacial ice blocked rivers flowing into the polar ocean and this prevented freezing of sea ice there. Evaporation of polar water then concentrated water containing H 2 18 O. In the proxy isotope record, this concealed a major world deglaciation that is contrary to the theory of direct control of glaciation by solar melting. This research began 26 yrs ago with a study of the fossil high sea level reefs on Barbados caused by that unexpected deglaciation.

Description: Online dynamical downscaling of temperature and precipitation within the iLOVECLIM model (version 1.1) Aurélien Quiquet, Didier M. Roche, Christophe Dumas, and Didier Paillard Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-116,2017 Manuscript under review for GMD (discussion: open, 0 comments) Earth system models of intermediate complexity have generally a simplified model physics and a coarse model resolution. In this work we present the inclusion of an online dynamical downscaling of temperature and precipitation in such a model. This downscaling explicitly takes into account sub-grid topography. With this new model functionality we are able to simulate temperature and precipitation on a 40 km grid for the whole Northern Hemisphere from the native model resolution.

Description: Evaluation of five dry particle deposition parameterizations for incorporation into atmospheric transport models Tanvir R. Khan and Judith A. Perlinger Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-93,2017 Manuscript under review for GMD (discussion: open, 0 comments) Despite considerable effort to develop mechanistic dry particle deposition parameterizations for atmospheric transport models, current knowledge has been inadequate to propose quantitative measures of the relative performance of available parameterizations. In this study, we evaluated the performance of five dry particle deposition parameterizations developed by Zhang et al. (2001) ( Z01 ), Petroff and Zhang (2010) ( PZ10 ), Kouznetsov and Sofiev (2012) ( KS12 ), Zhang and He (2014) ( ZH14 ), and Zhang and Sao (2014) ( ZS14 ), respectively. The evaluation was performed in three dimensions: model ability to reproduce observed deposition velocities, V d (accuracy), the influence of imprecision in input parameter values on the modeled V d (uncertainty), and identification of the most influential parameter(s) (sensitivity). The accuracy of the modeled V d was evaluated using observations obtained from five land use categories (LUCs): grass, coniferous and deciduous forests, natural water, and ice/snow. To ascertain the uncertainty in modeled V d , and quantify the influence of imprecision in key model input parameters, a Monte Carlo uncertainty analysis was performed. The Sobol' sensitivity analysis was conducted with the objective to determine the parameter ranking, from the most to the least influential. Comparing the normalized mean bias factors (indicator of accuracy), we find that the ZH14 parameterization is the most accurate for all LUCs except for coniferous forest, for which it is second most accurate (B NMBF  = −2.31). From Monte Carlo simulations, the estimated mean normalized uncertainties in the modeled Vd obtained for seven particle sizes (ranging from 0.005 to 2.5 μm) for the five LUCs are 17 %, 12 %, 13 %, 16 %, and 27 % for the Z01 , PZ10 , KS12 , ZH14 , and ZS14 parameterizations, respectively. From the Sobol' sensitivity results, we suggest that the parameter rankings vary by particle size and LUC for a given parameterization. Overall, for d p  = 0.001 to 1.0 μm, friction velocity was one of the three most influential parameters in all parameterizations. For giant particles ( d p  = 10 μm), relative humidity was the most influential parameter. Because it is the least complex of the five parameterizations, and it has the greatest accuracy and least uncertainty, we propose that the ZH14 parameterization is currently superior for incorporation into atmospheric transport models.

Description: The UKC2 regional coupled environmental prediction system Huw W. Lewis, Juan Manuel Castillo Sanchez, Jennifer Graham, Andrew Saulter, Jorge Bornemann, Alex Arnold, Joachim Fallmann, Chris Harris, David Pearson, Steven Ramsdale, Alberto Martínez de la Torre, Lucy Bricheno, Eleanor Blyth, Vicky Bell, Helen Davies, Toby R. Marthews, Clare O'Neill, Heather Rumbold, Enda O'Dea, Ashley Brereton, Karen Guihou, Adrian Hines, Momme Butenschon, Simon J. Dadson, Tamzin Palmer, Jason Holt, Nick Reynard, Martin Best, John Edwards, and John Siddorn Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-110,2017 Manuscript under review for GMD (discussion: open, 0 comments) In the real world the atmosphere, oceans and land surface are closely interconnected, and yet prediction systems tend to treat them in isolation. Those feedbacks are often illustrated in natural hazards, such as when strong winds lead to large waves and coastal damage, or when prolonged rainfall leads to saturated ground and high flowing rivers. For the first time, we have attempted to represent some of the feedbacks between sky, sea and land within a high resolution forecast system for the UK.

Description: A multi-species data assimilation system to retrieve information on land-atmosphere exchange processes Ivar R. van der Velde, John B. Miller, Michiel K. van der Molen, Pieter P. Tans, Bruce H. Vaughn, James W.C. White, Kevin Schaefer, and Wouter Peters Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-84,2017 Manuscript under review for GMD (discussion: open, 0 comments) We explored an inverse modeling technique to interpret global atmospheric measurements of CO 2 and the ratio of its stable carbon isotopes (δ 13 C). We detected the possible underestimation of drought stress in biosphere models after applying combined atmospheric CO 2 and δ 13 C constraints. This study highlights the importance to improve the representation of the biosphere in carbon-climate models, especially in a world where droughts become more extreme and more frequent.

Description: Correct boundary conditions for DNS models of nonlinear acoustic-gravity waves forced by atmospheric pressure variations Yuliya Kurdyaeva, Sergey Kshevetskii, Nikolay Gavrilov, and Sergey Kulichkov Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-76,2017 Manuscript under review for GMD (discussion: open, 0 comments) Various meteorological phenomena generate acoustic-gravity waves in the atmosphere and cause wave variations of atmospheric pressure. There are networks of microbarographs, which record pressure variations on the Earth's surface. The hydrodynamic problem of propagation of waves in the atmosphere from pressure variations on the Earth's surface is formulated. The problem wellposedness is proved. A supercomputer program for simulation of waves from pressure variations is developed and applied.

Description: Soil Methanotrophy Model (MeMo v1.0): a process-based model to quantify global uptake of atmospheric methane by soil Fabiola Murguia-Flores, Sandra Arndt, Anita L. Ganesan, Guillermo N. Murray-Tortarolo, and Edward R. C. Hornibrook Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-124,2017 Manuscript under review for GMD (discussion: open, 0 comments) Soil bacteria known as methanotrophs are the only biological sink for atmospheric methane (CH 4 ). Their activity depends on climatic and edaphic conditions, thus varies spatially and temporarily. Based on this, we developed a model (MeMo v1.0) to assess the global CH 4 consumption by soils.The global CH 4 uptake was 34.3 Tg CH 4  yr −1 for the period 1990–2009, with an increasing trend of 0.1 Tg CH 4  yr −2 . The regional analysis proved that warm and semiarid regions represent the most efficient CH 4 sink.

Description: High Performance Software Framework for the Calculation of Satellite-to-Satellite Data Matchups (MMS version 1.2) Thomas Block, Sabine Embacher, Christopher J. Merchant, and Craig Donlon Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-54,2017 Manuscript under review for GMD (discussion: open, 0 comments) For calibration and validation purposes it is nesessary to detect simultaneous data acquisitions from different space borne platforms. We present an algorithm and a software system which implements a general approach to resolve this problem. The Multisensor Matchup System (MMS) can detect simultaneous acquisitions in a large dataset (〉 100 TB) and extract data for matching locations for further analysis. The MMS implements a flexible software infrastructure and allows for high parallelisation.

Description: Carbon–nitrogen interactions in idealized simulations with JSBACH (version 3.10) Daniel S. Goll, Alexander J. Winkler, Thomas Raddatz, Ning Dong, Ian Colin Prentice, Philippe Ciais, and Victor Brovkin Geosci. Model Dev., 10, 2009-2030, https://doi.org/10.5194/gmd-10-2009-2017, 2017 The response of soil organic carbon decomposition to warming and the interactions between nitrogen and carbon cycling affect the feedbacks between the land carbon cycle and the climate. In the model JSBACH carbon–nitrogen interactions have only a small effect on the feedbacks, whereas modifications of soil organic carbon decomposition have a large effect. The carbon cycle in the improved model is more resilient to climatic changes than in previous version of the model.

Description: A non-linear Granger-causality framework to investigate climate–vegetation dynamics Christina Papagiannopoulou, Diego G. Miralles, Stijn Decubber, Matthias Demuzere, Niko E. C. Verhoest, Wouter A. Dorigo, and Willem Waegeman Geosci. Model Dev., 10, 1945-1960, https://doi.org/10.5194/gmd-10-1945-2017, 2017 Global satellite observations provide a means to unravel the influence of climate on vegetation. Common statistical methods used to study the relationships between climate and vegetation are often too simplistic to capture the complexity of these relationships. Here, we present a novel causality framework that includes data fusion from various databases, time series decomposition, and machine learning techniques. Results highlight the highly non-linear nature of climate–vegetation interactions.

Description: Variational assimilation of IASI SO 2 plume height and total column retrievals in the 2010 eruption of Eyjafjallajökull using the SILAM v5.3 chemistry transport model Julius Vira, Elisa Carboni, Roy G. Grainger, and Mikhail Sofiev Geosci. Model Dev., 10, 1985-2008, https://doi.org/10.5194/gmd-10-1985-2017, 2017 The vertical and temporal distributions of sulfur dioxide emissions during the 2010 eruption of Eyjafjallajökull were reconstructed by combining data from the IASI satellite instrument with a dispersion model. Unlike in previous studies, both column density (the total amount above a given point) and the plume height were derived from the satellite data. This resulted in more accurate simulated vertical distributions for the times when the emission was not constrained by the column densities.

Description: GLEAM v3: satellite-based land evaporation and root-zone soil moisture Brecht Martens, Diego G. Miralles, Hans Lievens, Robin van der Schalie, Richard A. M. de Jeu, Diego Fernández-Prieto, Hylke E. Beck, Wouter A. Dorigo, and Niko E. C. Verhoest Geosci. Model Dev., 10, 1903-1925, https://doi.org/10.5194/gmd-10-1903-2017, 2017 Terrestrial evaporation is a key component of the hydrological cycle and reliable data sets of this variable are of major importance. The Global Land Evaporation Amsterdam Model (GLEAM, www.GLEAM.eu ) is a set of algorithms which estimates evaporation based on satellite observations. The third version of GLEAM, presented in this study, includes an improved parameterization of different model components. As a result, the accuracy of the GLEAM data sets has been improved upon previous versions.

Description: Evaluation of high-resolution GRAMM/GRAL NO x simulations over the city of Zurich, Switzerland Antoine Berchet, Katrin Zink, Dietmar Oettl, Jürg Brunner, Lukas Emmenegger, and Dominik Brunner Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-102,2017 Manuscript under review for GMD (discussion: open, 0 comments) Hourly NO x concentrations were simulated for the city of Zurich, Switzerland, at 10 m resolution for the years 2013–2014. The simulations were generated with the nested mesoscale meteorology and microscale dispersion model system GRAMM/GRAL (versions v15.12/v14.8) by applying a catalogue-based approach. This approach was specifically designed to enable long-term city-wide building-resolving simulations with affordable computation costs. It relies on a discrete set of possible weather situations and corresponding steady-state flow and dispersion patterns that are pre-computed and then matched hourly with actual meteorological observations. The modelling system was comprehensively evaluated using eight sites continuously monitoring NO x concentrations and 65 passive samplers measuring NO 2 concentrations on a 2-weekly basis all over the city. The system was demonstrated to fulfil the European Commission standards for air pollution modelling at nearly all sites. The average spatial distribution was very well represented, despite a general tendency to overestimating the observed concentrations, possibly due to a crude representation of traffic-induced turbulence. The temporal variability of concentrations explained by varying emissions and weather situations was accurately reproduced on different time scales. The seasonal cycle of concentrations, mostly driven by stronger vertical dispersion in summer than in winter, was very well captured in the two year simulation period. Short-term events, such as episodes of particularly high and low concentrations, were detected in most cases by the system, although some unrealistic pollution peaks were occasionally generated, pointing at some limitations of the steady-state approximation. The different patterns of the diurnal cycle of concentrations observed in the city were generally well captured as well. The evaluation confirmed the adequacy of the catalogue-based approach in the context of city scale air pollution modelling. The ability to reproduce not only the spatial gradients but also the hourly temporal variability over multiple years makes the model system particularly suitable for investigating individualized air pollution exposure in the city.

Description: Exploring precipitation pattern scaling methodologies and robustness among CMIP5 models Ben Kravitz, Cary Lynch, Corinne Hartin, and Ben Bond-Lamberty Geosci. Model Dev., 10, 1889-1902, https://doi.org/10.5194/gmd-10-1889-2017, 2017 Pattern scaling is a way of approximating regional changes without needing to run a full, complex global climate model. We compare two methods of pattern scaling for precipitation and evaluate which methods is better in particular circumstances. We also decompose precipitation into a CO 2 portion and a non-CO 2 portion. The methodologies discussed in this paper can help provide precipitation fields for other models for a wide variety of scenarios of future climate change.

Description: Studying the Impact of Radioactive Charging on the Microphysical Evolution and Transport of Radioactive Aerosols with the TOMAS-RC v1 framework Petros Vasilakos, Yong-Ηa Kim, Jeffrey R. Pierce, Sotira Yiacoumi, Costas Tsouris, and Athanasios Nenes Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-96,2017 Manuscript under review for GMD (discussion: open, 2 comments) Radioactive charging can significantly impact the way radioactive aerosols behave, and as a result their lifetime, but such effects are neglected in predictive model studies of radioactive plumes. We extend a well-established model that simulates the evolution of atmospheric particulate matter to account for radioactive charging effects in an accurate and computationally efficient way. It is shown that radioactivity can strongly impact the deposition patterns of aerosol.

Description: The operational eEMEP model version 10.4 for volcanic SO 2 and ash forecasting Birthe M. Steensen, Michael Schulz, Peter Wind, Álvaro M. Valdebenito, and Hilde Fagerli Geosci. Model Dev., 10, 1927-1943, https://doi.org/10.5194/gmd-10-1927-2017, 2017 The operational emergency version of the EMEP MSC-W model for dispersion calculations of volcanic SO 2 and ash is described. Additions and changes to the standard EMEP MSC-W are presented. Grid resolution dependencies for meteorological data and numerical diffusion are studied by investigating model results driven by ensemble meteorological data for volcanic SO 2 emissions. The vertical ash layer sensitivity on gravitational settling is evaluated by comparing model results to lidar observations.

Description: Evaluation of the wind farm parameterization in the Weather Research and Forecasting model (version 3.8.1) with meteorological and turbine power data Joseph C. Y. Lee and Julie K. Lundquist Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-128,2017 Manuscript under review for GMD (discussion: open, 2 comments) We evaluate the the wind farm parameterization (WFP) in the Weather Research and Forecasting (WRF) model, a powerful tool to simulate wind farms and their meteorological impacts numerically. In our case study, the WFP-simulations with fine vertical grid resolution are skillful in matching the winds and the power production to the observations. Moreover, the WFP tends to underestimate power in windy conditions. We also illustrate the modeled wind speed is the critical factor influencing the WFP.

Description: A prognostic pollen emissions model for climate models (PECM1.0) Matthew C. Wozniak and Allison Steiner Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-105,2017 Manuscript under review for GMD (discussion: open, 0 comments) A new parameterization, Pollen Emissions for Climate Models (PECM), has been developed for use in climate models. New developments include 1) a new climate-sensitive, observation-based phenological model, 2) inclusion of the 13 highest-pollinating taxa in the United States, and 3) an option to compute pollen emissions by plant functional type (PFT). It can be used to address topics like impacts of climate change (e.g. on allergen exposure, on plant ecology) or pollen as an atmospheric aerosol.

Description: Inter-annual variability of mean sea level and its sensitivity to wind climate in an inter-tidal basin Theo Gerkema and Matias Duran-Matute Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-32,2017 Manuscript under review for ESD (discussion: open, 3 comments) The relation between the annual wind records from a weather station and annual mean sea level in an inter-tidal basin, the Dutch Wadden Sea, is examined. Only more recent, homogeneous wind records are used, covering the past two decades. It is demonstrated that even such a relatively short record is sufficient to find a convincing relation. The inter-annual variability of mean sea level can already be largely explained by the west–east component of the net wind energy vector, with some further improvement if one also includes the south–north component and theannual mean atmospheric pressure. For different tide-gauge stations in the Dutch Wadden Sea and along the coast, we find the same qualitative characteristics, although the precise values of the correlations vary. Correcting observed values of annual mean level for meteorological factors reduces the margin of error (expressed as 95 %-confidence interval) by about a factor of three in the trends of the 20-year sea level record. Model results illustrate the regional variability in annual mean sea level and its inter-annual variability. The sensitivity on wind direction varies spatially even on a small scale like the Dutch Wadden Sea. This study also implies that climatic changes in the strength of winds from a specific direction may affect local annual mean sea level quite significantly.

Description: Estimates of land and sea moisture contributions to the monsoonal rain over Kolkata, deduced based on isotopic analysis of rainwater Shaakir Shabir Dar and Prosenjit Ghosh Earth Syst. Dynam., 8, 313-321, https://doi.org/10.5194/esd-8-313-2017, 2017 Moisture sources responsible for rains over Kolkata during the summer monsoon can be traced using backward air-mass trajectory analysis. A summary of such trajectories between June and September suggest that these moisture parcels originate from the Arabian Sea and travel over the dry continental region and over the Bay of Bengal (BoB) prior to their arrival at Kolkata. We use monthly satellite and ground-based observations of the hydrometeorological variables together with isotopic data of rainwater from Bangalore and Kakinada to quantify the contributions of advected continental and oceanic water vapour in the Kolkata rains. The vapour mass is modified during its transit from its original isotopic value due to addition of evaporated moisture from the BoB, and further modification occurs due to the process of rainout during transport. The evaporated component is estimated using the Craig–Gordon equation. The rainout process is simulated using a Rayleigh fractionation model. In this simulation we assume that the initial isotopic composition of vapour originating from the continent is similar to the rainwater composition measured at Bangalore. In order to explain the monthly isotopic composition in southwest monsoon rainwater at Kolkata, we invoke 65–75 % moisture contribution from the BoB; the remaining moisture is from the continental land mass.

Description: Evaluation of Integrated Assessment Model hindcast experiments: A case study of the GCAM 3.0 land use module Abigail C. Snyder, Robert P. Link, and Katherine V. Calvin Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-97,2017 Manuscript under review for GMD (discussion: open, 0 comments) Experiments conducting a model forecast for a period in which observational data is available are rarely undertaken in the Integrated Assessment Model (IAM) community. When undertaken, results are often evaluated using global aggregates that mask deficiencies. Comparing land allocation simulations in GCAM with FAO observational data from 1990–2010, we find quantitative evidence that global aggregates alone are not sufficient for evaluating IAMs with global supply constraints similar to GCAM.

Description: CITRATE 1.0: Phytoplankton continuous trait-distribution model with one-dimensional physical transport applied to the Northwest Pacific Bingzhang Chen and S. Lan Smith Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-104,2017 Manuscript under review for GMD (discussion: open, 0 comments) Marine phytoplankton accounts for half of global primary production. Phytoplankton size is an important trait affecting its fitness and ecosystem functioning. We have developed a plankton model with continuous size distribution for phytoplankton and applied it in the North Pacific. This model is able to capture the general patterns of phytoplankton size distribution in the real ocean and can be used for understanding the mechanisms controlling phytoplankton size structure and diversity.

Description: A method to preserve trends in quantile mapping bias correction of climate modeled temperature Manolis G. Grillakis, Aristeidis G. Koutroulis, Ioannis N. Daliakopoulos, and Ioannis K. Tsanis Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-53,2017 Manuscript under review for ESD (discussion: open, 0 comments) We present a methodology to adjust the systematic errors of climate modeled temperature with a simultaneous long term trend preservation. The method considers the normalization of the temperature towards a reference period modeled temperature and the estimation of a residual signal, in order to apply adjustment only to the former. The skill of the methodology to reduce the systematic errors while simultaneously preserve the long term signal of the temperature is assessed in European scale.

Description: SedFoam-2.0: a 3D two-phase flow numerical model for sediment transport Julien Chauchat, Zhen Cheng, Tim Nagel, Cyrille Bonamy, and Tian-Jian Hsu Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-101,2017 Manuscript under review for GMD (discussion: open, 0 comments) This manuscript presents the development and validation of a community two-phase flow Eulerian-Eulerian model based on openFoam for sediment transport applications. The mathematical and numerical models are described in details. Two simple validation test cases, sedimentation and a pressure driven sediment transport in the laminar flow regime, are presented. Finally, the model is applied to two reallistic sediment transport configurations, intense bed-load transport and scour at an apron.

Description: Biogeochemical protocols and diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP) James C. Orr, Raymond G. Najjar, Olivier Aumont, Laurent Bopp, John L. Bullister, Gokhan Danabasoglu, Scott C. Doney, John P. Dunne, Jean-Claude Dutay, Heather Graven, Stephen M. Griffies, Jasmin G. John, Fortunat Joos, Ingeborg Levin, Keith Lindsay, Richard J. Matear, Galen A. McKinley, Anne Mouchet, Andreas Oschlies, Anastasia Romanou, Reiner Schlitzer, Alessandro Tagliabue, Toste Tanhua, and Andrew Yool Geosci. Model Dev., 10, 2169-2199, https://doi.org/10.5194/gmd-10-2169-2017, 2017 The Ocean Model Intercomparison Project (OMIP) is a model comparison effort under Phase 6 of the Coupled Model Intercomparison Project (CMIP6). Its physical component is described elsewhere in this special issue. Here we describe its ocean biogeochemical component (OMIP-BGC), detailing simulation protocols and analysis diagnostics. Simulations focus on ocean carbon, other biogeochemical tracers, air-sea exchange of CO2 and related gases, and chemical tracers used to evaluate modeled circulation.

Description: Seasonal prediction skill of East Asian summer monsoon in CMIP5-Models Bo Huang, Ulrich Cubasch, and Christopher Kadow Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-51,2017 Manuscript under review for ESD (discussion: open, 0 comments) We found that CMIP5-models show significant improvement in predicting zonal winds with initialization than that without initialization. Based on the knowledge that zonal wind indices can be used as potential predictors for the EASM. Given initial condition, two models improve the seasonal prediction skill of the EASM, while one model decreases it. Models have different response to the initialization due to their ability to depict the EASM-ESNO coupled mode.

Description: Recent changes of relative humidity: regional connection with land and ocean processes Sergio M. Vicente-Serrano, Raquel Nieto, Luis Gimeno, Cesar Azorin-Molina, Anita Drumond, Ahmed El Kenawy, Fernando Dominguez-Castro, Miquel Tomas-Burguera, and Marina Peña-Gallardo Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-43,2017 Manuscript under review for ESD (discussion: open, 0 comments) We analyzed changes in surface relative humidity (RH) at the global scale from 1979 to 2014 and compared the variability and trends of RH with those of land evapotranspiration and ocean evaporation in moisture source areas across a range of selected regions worldwide. Results demonstrate a strong agreement between the interannual variability of RH and the interannual variability of precipitation and land evapotranspiration in regions with continentally-originated humidity.

Description: Irreversible ocean thermal expansion under negative CO 2 emissions Dana Ehlert and Kirsten Zickfeld Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-45,2017 Manuscript under review for ESD (discussion: open, 1 comment) This study uses a global climate model to explore the extent to which sea level rise due to thermal expansion of the ocean is reversible if the atmospheric concentration of carbon dioxide (CO 2 ) declines. It is found that sea level continues to rise for several decades after atmospheric CO 2 starts to decline and does not return to the pre-industrial level for over thousand years after atmospheric CO 2 is restored to the pre-industrial concentration.

Description: Contrasting terrestrial carbon cycle responses to the two strongest El Niño events: 1997–98 and 2015–16 El Niños Jun Wang, Ning Zeng, Meirong Wang, Fei Jiang, Hengmao Wang, and Ziqiang Jiang Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-46,2017 Manuscript under review for ESD (discussion: open, 0 comments) Behaviors of terrestrial ecosystems differ in different El Niño events. We analyze terrestrial carbon cycle responses to the recent 2015–16 and earlier 1997–98 El Ninos, and find large differences. We find that global land-atmosphere C flux anomaly was about two times smaller in 2015–16 than in 1997–98 event, without the obvious lagged response. Then we illustrate the mechanisms of the different terrestrial carbon cycle responses in 2015–16 and 1997–98 El Ninos in regional biological processes.

Description: Current challenges of implementing anthropogenic land-use and land-cover change in models contributing to climate change assessments Reinhard Prestele, Almut Arneth, Alberte Bondeau, Nathalie de Noblet-Ducoudré, Thomas A. M. Pugh, Stephen Sitch, Elke Stehfest, and Peter H. Verburg Earth Syst. Dynam., 8, 369-386, https://doi.org/10.5194/esd-8-369-2017, 2017 Land-use change is still overly simplistically implemented in global ecosystem and climate models. We identify and discuss three major challenges at the interface of land-use and climate modeling and propose ways for how to improve land-use representation in climate models. We conclude that land-use data-provider and user communities need to engage in the joint development and evaluation of enhanced land-use datasets to improve the quantification of land use–climate interactions and feedback.

Description: A model study of warming-induced phosphorus–oxygen feedbacks in open-ocean oxygen minimum zones on millennial timescales Daniela Niemeyer, Tronje P. Kemena, Katrin J. Meissner, and Andreas Oschlies Earth Syst. Dynam., 8, 357-367, https://doi.org/10.5194/esd-8-357-2017, 2017 Observations indicate an expansion of oxygen minimum zones (OMZs) over the past 50 years, likely related to ongoing deoxygenation caused by reduced oxygen solubility, changes in stratification and circulation, and a potential acceleration of organic matter turnover in a warming climate. The overall area of ocean sediments that are in direct contact with low-oxygen bottom waters also increases with expanding OMZs. This leads to a release of phosphorus from ocean sediments. If anthropogenic carbon dioxide emissions continue unabated, higher temperatures will cause enhanced weathering on land, which, in turn, will increase the phosphorus and alkalinity fluxes into the ocean and therefore raise the ocean's phosphorus inventory even further. A higher availability of phosphorus enhances biological production, remineralisation and oxygen consumption, and might therefore lead to further expansions of OMZs, representing a positive feedback. A negative feedback arises from the enhanced productivity-induced drawdown of carbon and also increased uptake of CO 2 due to weathering-induced alkalinity input. This feedback leads to a decrease in atmospheric CO 2 and weathering rates. Here, we quantify these two competing feedbacks on millennial timescales for a high CO 2 emission scenario. Using the University of Victoria (UVic) Earth System Climate Model of intermediate complexity, our model results suggest that the positive benthic phosphorus release feedback has only a minor impact on the size of OMZs in the next 1000 years. The increase in the marine phosphorus inventory under assumed business-as-usual global warming conditions originates, on millennial timescales, almost exclusively (〉 80 %) from the input via terrestrial weathering and causes a 4- to 5-fold expansion of the suboxic water volume in the model.

Description: An explanation for the different climate sensitivities of land and ocean surfaces based on the diurnal cycle Axel Kleidon and Maik Renner Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-44,2017 Manuscript under review for ESD (discussion: open, 1 comment) We provide an explanation why land temperatures respond more strongly to global warming than ocean temperatures, a robust finding in climate models that has so far not been understood well. We explain it by the different ways by which ocean and land surfaces buffer the strong variation in solar radiation and demonstrate this with a simple, physically-based model. Our explanation also explains why nighttime temperatures warm more strongly, another robust finding of global warming.

Description: On the Future Role of the most Parsimonious Climate Module in Integrated Assessment Mohammad M. Khabbazan and Hermann Held Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-40,2017 Manuscript under review for ESD (discussion: open, 0 comments) We test the validity of a one-box climate model as an emulator for Atmosphere-Ocean General Circulation Models (AOGCMs) when the application is confined to the subset of scenarios approximately in-line with the 2° target. The one-box climate model is currently in use in the integrated assessment models FUND and MIND. For our assessment, we crucially rely on 14 recent CMIP5 AOGCM diagnostics of the total radiative forcing for various representative concentration pathways. Our findings are two-fold. Firstly, when directly prescribing AOGCMs’ respective equilibrium climate sensitivities (ECSs) and transient climate responses (TCRs) to the one-box model, global mean temperature (GMT) projections are generically too large by 0.5 K at peak temperature. Accordingly, corresponding integrated assessment studies might overestimate mitigation need and cost. Secondly, the one-box model becomes an excellent emulator of those AOGCMs once their ECS and TCR values are universally mapped onto effective one-box intrinsic counterparts. We suggest utilizing this one-box model in integrated assessment also in the future, in particular when computationally demanding decision-making under climate response uncertainty might be modelled. However, then the roles of ECS and TCR must be re-interpreted. For the MIND model as used over the past 5 years, even the transformed ECS values comply with the ranges explicated by IPCC AR5, however now at the high-end.

Description: Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap Yuri V. Konovalov and Oleg V. Nagornov Earth Syst. Dynam., 8, 283-294, https://doi.org/10.5194/esd-8-283-2017, 2017 The prognostic experiments conducted with the reference mass balance show that the grounding line would retreat by about 10 km in the three ice streams over a time period of 500 years. In the experiments, the ice flow velocities in the ice streams decreased with time. These trends in the ice flow velocities diminished the overall ice flux. The modeled evolution of the ice streams is in agreement with observations of ice mass loss in Severnaya Zemlya archipelago (Moholdt et al., 2012).

Description: The polar amplification asymmetry: role of Antarctic surface height Marc Salzmann Earth Syst. Dynam., 8, 323-336, https://doi.org/10.5194/esd-8-323-2017, 2017 The Arctic has been warming much faster than the rest of the globe, including Antarctica. Here it was shown that one of the important mechanisms that sets Antarctica apart from the Arctic is heat transport from lower latitudes, and it was argued that a decrease in land height due to Antarctic melting would be favorable for increased atmospheric heat transport from midlatitudes. Other factors related to the larger Antarctic land height were also investigated.

Description: Annual and semiannual cycles of midlatitude near-surface temperature and tropospheric baroclinicity: reanalysis data and AOGCM simulations Valerio Lembo, Isabella Bordi, and Antonio Speranza Earth Syst. Dynam., 8, 295-312, https://doi.org/10.5194/esd-8-295-2017, 2017 The study wishes to better characterize the annual and semiannual cycles of surface temperature and baroclinicity at midlatitudes as observed in ERA-Interim reanalysis data and AOGCM simulations. Results show that at the semiannual frequency model phases between surface temperature and baroclinicity have wide dispersion in both hemispheres with large errors in the estimates, denoting uncertainty and a degree of disagreement among models.

Description: Community Climate Simulations to assess avoided impacts in 1.5 °C and 2 °C futures Benjamin M. Sanderson, Yangyang Xu, Claudia Tebaldi, Michael Wehner, Brian O'Neill, Alexandra Jahn, Angeline G. Pendergrass, Flavio Lehner, Warren G. Strand, Lei Lin, Reto Knutti, and Jean Francois Lamarque Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-42,2017 Manuscript under review for ESD (discussion: final response, 3 comments) We present the results of a set of climate simulations designed to simulate futures in which the Earth's temperature is stabilized at the levels referred to in the 2015 Paris Agreement. We consider the necessary future emissions reductions and the aspects of extreme weather which differ significantly between the 2 degree and the 1.5 degree climate in the simulations.

Description: Desertification, Resilience and Re-greening in the African Sahel – A matter of the observation period? Hannelore Kusserow Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-4,2017 Manuscript under review for ESD (discussion: open, 2 comments) Since the turn of the millennium various publications have been discussinga re-greening of the Sahel after the 1980's drought mainly based on coarse-resolution satellite data. Recent field studies show a more differentiated picture questioning both paradigms, the Encroaching Sahara and the Re -greening Sahel . The author set out this article to discuss the concepts of Desertification, Resilience and Re-greening by addressing three main aspects: (i) relevance of edaphic factors for a vegetation re-greening, (ii) importance of the selected observation period in the debate of Sahel greening or browning, and (iii) modifications in vegetation pattern as possible indicators for ecosystem changes (shift from originally diffuse to contracted vegetation patterns). The data used in this article cover a period of more than 150 years and include the author's own research results from the early 1980s until today. A special emphasis, apart from field work and remote sensing, is laid on the analysis of historical documents. The key findings summarised at the end show the following: (i) a vegetation recovery predominantly depends on soil types; (ii) when discussing Sahel greening vs. browning, the majority of research articles only focuses on post-drought conditions. However, if pre-drought conditions (before 1980s) are analysed, remote sensing based time series and botanical investigations clearly show a substantial decline in diversity of woody species and cover density, compared to pre-drought conditions; (iii) self-organised patchiness of vegetation is considered to be an important indicator for ecosystem changes.

Description: Historical greenhouse gas concentrations for climate modelling (CMIP6) Malte Meinshausen, Elisabeth Vogel, Alexander Nauels, Katja Lorbacher, Nicolai Meinshausen, David M. Etheridge, Paul J. Fraser, Stephen A. Montzka, Peter J. Rayner, Cathy M. Trudinger, Paul B. Krummel, Urs Beyerle, Josep G. Canadell, John S. Daniel, Ian G. Enting, Rachel M. Law, Chris R. Lunder, Simon O'Doherty, Ron G. Prinn, Stefan Reimann, Mauro Rubino, Guus J. M. Velders, Martin K. Vollmer, Ray H. J. Wang, and Ray Weiss Geosci. Model Dev., 10, 2057-2116, https://doi.org/10.5194/gmd-10-2057-2017, 2017 Climate change is primarily driven by human-induced increases of greenhouse gas (GHG) concentrations. Based on ongoing community efforts (e.g. AGAGE and NOAA networks, ice cores), this study presents historical concentrations of CO 2 , CH 4 , N 2 O and 40 other GHGs from year 0 to year 2014. The data is recommended as input for climate models for pre-industrial, historical runs under CMIP6. Global means, but also latitudinal by monthly surface concentration fields are provided.

Description: Continuous high-resolution midlatitude-belt simulations for July–August 2013 with WRF Thomas Schwitalla, Hans-Stefan Bauer, Volker Wulfmeyer, and Kirsten Warrach-Sagi Geosci. Model Dev., 10, 2031-2055, https://doi.org/10.5194/gmd-10-2031-2017, 2017 Due to computational constraints, extended-range forecasts on the convection-permitting (CP) scale are often performed using a limited-area model. To overcome disturbances by lateral boundary conditions, a CP latitude belt simulation in the Northern Hemisphere was performed for July and August 2013. This approach allows for the study of resolution and parameterization impacts. The results demonstrate an improved representation of the general circulation and precipitation patterns.

Description: Sequential assimilation of satellite-derived vegetation and soil moisture products using SURFEX_v8.0: LDAS-Monde assessment over the Euro-Mediterranean area Clément Albergel, Simon Munier, Delphine Jennifer Leroux, Hélène Dewaele, David Fairbairn, Alina Lavinia Barbu, Emiliano Gelati, Wouter Dorigo, Stéphanie Faroux, Catherine Meurey, Patrick Le Moigne, Bertrand Decharme, Jean-Francois Mahfouf, and Jean-Christophe Calvet Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-121,2017 Manuscript under review for GMD (discussion: open, 0 comments) LDAS-Monde, A global Land Data Assimilation system, is tested over Europe and the Mediterranean basin to increase monitoring accuracy for land surface variables. It is able to ingest information from satellite-derived Surface Soil Moisture (SSM) and Leaf Area Index (LAI) observations to constrain the ISBA land surface model coupled with the CTRIP continental hydrological system. Assimilation of SSM and LAI leads to a better representation of evapotranspiration and gross primary production.

Description: Vorticity-divergence semi-Lagrangian global atmospheric model SL-AV20: dynamical core Mikhail Tolstykh, Vladimir Shashkin, Rostislav Fadeev, and Gordey Goyman Geosci. Model Dev., 10, 1961-1983, https://doi.org/10.5194/gmd-10-1961-2017, 2017 We present the hydrostatic dynamical core of the SL-AV20 global atmosphere model used for operational numerical weather prediction in Russia. The article describes model design, particularly vorticity-divergence formulation combined with the use of an unstaggerred grid. The model has an option to use a reduced latitude-longitude grid. The results for standard tests agree well with reference solutions.

Description: Influence of atmospheric internal variability on the long-term Siberian water cycle during the past two centuries Kazuhiro Oshima, Koto Ogata, Hotaek Park, and Yoshihiro Tachibana Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-54,2017 Manuscript under review for ESD (discussion: open, 0 comments) Long-term variations in the Siberian river discharges of the Lena in the east and the Ob in the west were investigated based on observations, tree-ring reconstructions and simulations with atmospheric and climate models. In conclusion, an east–west seesaw pattern of summertime large-scale atmospheric circulation frequently emerges over Siberia as an atmospheric internal variability, resulting in the negative correlation between the Lena and Ob River discharges.

Description: Synergy between land use and climate change increases future fire risk in Amazon forests Yannick Le Page, Douglas Morton, Hartin Corinne, Bond-Lamberty Ben, José Miguel Cardoso Pereira, George Hurtt, and Ghassem Asrar Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-55,2017 Manuscript under review for ESD (discussion: open, 0 comments) Fires damage large areas of eastern Amazon forests when ignitions from human activity coincide with droughts, while central and western regions – more humid – are less affected. Here, we use a fire model to estimate that fire activity could increase by an order of magnitude without climate mitigation. Our results show that avoiding further agricultural expansion can limit fire ignitions, but that tackling climate change is essential to insulate the interior Amazon through the 21st century.

Description: A global wetland methane emissions and uncertainty dataset for atmospheric chemical transport models (WetCHARTs version 1.0) A. Anthony Bloom, Kevin W. Bowman, Meemong Lee, Alexander J. Turner, Ronny Schroeder, John R. Worden, Richard Weidner, Kyle C. McDonald, and Daniel J. Jacob Geosci. Model Dev., 10, 2141-2156, https://doi.org/10.5194/gmd-10-2141-2017, 2017 Wetland emissions are a principal source of uncertainty in the global atmospheric methane budget due to poor knowledge of wetland processes. We construct a wetland methane emission and uncertainty dataset for use in global atmospheric methane models. Our wetland model ensemble is based on static wetland maps, satellite-derived inundation and carbon cycle models. The ensemble performs favourably against regional flux estimates and atmospheric methane measurements relative to previous studies.

Description: JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere Darren Engwirda Geosci. Model Dev., 10, 2117-2140, https://doi.org/10.5194/gmd-10-2117-2017, 2017 A new algorithm for the generation of very high-quality staggered unstructured grids for multi-resolution ocean and atmospheric modelling is described. Through use of unstructured triangulation and grid-optimisation techniques, it is shown that meshes satisfying a number of important a priori grid-quality constraints can be constructed. This new algorithm is expected to be of interest to both developers and users of unstructured general circulation models.

Description: Sensitivity Analysis of a Coupled Hydrodynamic-Vegetation Model Using the Effectively Subsampled Quadratures Method Tarandeep S. Kalra, Alfredo Aretxabaleta, Pranay Seshadri, Neil K. Ganju, and Alexis Beudin Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-107,2017 Manuscript under review for GMD (discussion: open, 0 comments) The manuscript details the sensitivity of vegetation properties that are input to a 3D submerged aquatic vegetation model within a coupled hydrodynamics and wave model. It describes a novel strategy to perform sensitivity analysis efficiently by using a combination of Effective Quadratures method and Sobol' indices. This method reduces the number of simulations to understand the sensitivity patterns and also quantifies the amount of sensitivity.

Description: Impacts of microtopographic snow-redistribution and lateral subsurface processes on hydrologic and thermal states in an Arctic polygonal ground ecosystem Gautam Bisht, William J. Riley, Haruko M. Wainwright, Baptiste Dafflon, Yuan Fengming, and Vladimir E. Romanovsky Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-71,2017 Manuscript under review for GMD (discussion: open, 0 comments) The land model integrated in the ACME Earth System Model (ESM) was extended to include snow redistribution (SR) and lateral subsurface hydrologic and thermal processes. Simulation results at a polygonal tundra site near Barrow, Alaska showed inclusion of SR resulted in a better agreement with observations. Excluding lateral subsurface processes had a small impact on mean states but a large overestimation of spatial variability in soil moisture and temperature.

Description: A single-column particle-resolved model for simulating the vertical distribution of aerosol mixing state: WRF-PartMC-MOSAIC-SCM v1.0 Jeffrey H. Curtis, Nicole Riemer, and Matthew West Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-112,2017 Manuscript under review for GMD (discussion: open, 0 comments) Traditional aerosol representations rely on simplifying assumptions regarding aerosol composition in order to reduce computational cost. This affects the estimate of macroscale properties of the atmosphere. In contrast, the WRF-PartMC-MOSAIC-SCM model, presented here, uses a particle-resolved aerosol representation. It is made feasible by the development of efficient numerical methods, and allows for the capturing of complex aerosol mixing states with altitude.

Description: DCMIP2016: A Review of Non-hydrostatic Dynamical Core Design and Intercomparison of Participating Models Paul A. Ullrich, Christiane Jablonowski, James Kent, Peter H. Lauritzen, Ramachandran Nair, Kevin A. Reed, Colin M. Zarzycki, David M. Hall, Don Dazlich, Ross Heikes, Celal Konor, David Randall, Thomas Dubos, Yann Meurdesoif, Xi Chen, Lucas Harris, Christian Kühnlein, Vivian Lee, Abdessamad Qaddouri, Claude Girard, Marco Giorgetta, Daniel Reinert, Joseph Klemp, Sang-Hun Park, William Skamarock, Hiroaki Miura, Tomoki Ohno, Ryuji Yoshida, Robert Walko, Alex Reinecke, and Kevin Viner Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-108,2017 Manuscript under review for GMD (discussion: open, 0 comments) Atmospheric dynamical cores are a fundamental component of global atmospheric modeling systems, and are responsible for capturing the dynamical behavior of the Earth's atmosphere. To better understand modern dynamical cores, this paper aims to provide a comprehensive review of eleven dynamical cores, drawn from modeling centers and groups that participated in the 2016 Dynamical Core Model Intercomparison Project (DCMIP) workshop and summer school.

Description: Plume-SPH 1.0: A three-dimensional, dusty-gas volcanic plume model based on smoothed particle hydrodynamics Zhixuan Cao, Abani Patra, Marcus Bursik, E. Bruce Pitman, and Matthew Jones Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-119,2017 Manuscript under review for GMD (discussion: open, 0 comments) Plume-SPH provides the first particle based simulation of volcanic plumes. Smooth particle hydrodynamics used here has several advantages over mesh based methods for multiphase free boundary flows like volcanic plumes. This tool will provide more accurate eruption source terms to users of Volcanic ash transport and dispersion models greatly improving volcanic ash forecasts.The Plume-SPH code incorporates several newly developed techniques in SPH needed multiphase compressible turbulent flow.

Description: Defining metrics of the Quasi-Biennial Oscillation in global climate models Verena Schenzinger, Scott Osprey, Lesley Gray, and Neal Butchart Geosci. Model Dev., 10, 2157-2168, https://doi.org/10.5194/gmd-10-2157-2017, 2017 The Quasi-Biennial Oscillation (QBO) is a pattern of winds in the equatorial stratosphere that has been observed for the past 60 years. It is thought to have long-range influences, e.g. on the Northern Hemisphere winter polar vortex and therefore Europe's winter weather. Since its period is about 2 years, being able to predict the QBO might also improve weather forecasting. Using a set of characteristic metrics, this paper examines how reliable current climate models are in simulating the QBO.

Description: Fractional Governing Equations of Transient Groundwater Flow in Confined Aquifers with Multi-Fractional Dimensions in Fractional Time M. Levent Kavvas, Tongbi Tu, Ali Ercan, and James Polsinelli Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-47,2017 Manuscript under review for ESD (discussion: open, 0 comments) A dimensionally-consistent governing equation of transient, saturated groundwater flow in fractional time in a multi-fractional confined aquifer is developed. First a continuity equation for groundwater flow in fractional time and in a multi-fractional, multi-dimensional confined aquifer is developed. An equation of water flux is also developed. The governing equation of transient groundwater flow in a multi-fractional, multi-dimensional confined aquifer in fractional time is then obtained.

Description: Evaluating the atmospheric drivers leading to the December 2014 flood in Schleswig-Holstein, Germany Nils H. Schade Earth Syst. Dynam., 8, 405-418, https://doi.org/10.5194/esd-8-405-2017, 2017 Atmospheric conditions at the onset of the December 2014 flood in Schleswig-Holstein, Germany, are described. Results show that the antecedent precipitation index (API) is able to reflect soil moisture conditions and, in combination with the maximum 3–day precipitation sum (R3d), to capture the main drivers ultimately leading to this flood. Trend analyses indicate an increasing risk of flood-prone situations over the last decades in this region. Further analyses are planned at the German coasts.

Description: A 4D-Var inversion system based on the icosahedral grid model (NICAM-TM 4D-Var v1.0) – Part 2: Optimization scheme and identical twin experiment of atmospheric CO 2 inversion Yosuke Niwa, Yosuke Fujii, Yousuke Sawa, Yosuke Iida, Akihiko Ito, Masaki Satoh, Ryoichi Imasu, Kazuhiro Tsuboi, Hidekazu Matsueda, and Nobuko Saigusa Geosci. Model Dev., 10, 2201-2219, https://doi.org/10.5194/gmd-10-2201-2017, 2017 A new 4D-Var inversion system based on the icosahedral grid model, NICAM, is introduced and tested. Adding to the offline forward and adjoint models, this study has introduced the optimization method of POpULar; it does not require difficult decomposition of a matrix that establishes the correlation among the prior flux errors. In identical twin experiments of atmospheric CO 2 inversion, the system successfully reproduces the spatiotemporal variations of the surface fluxes.

Description: rpe v5: an emulator for reduced floating-point precision in large numerical simulations Andrew Dawson and Peter D. Düben Geosci. Model Dev., 10, 2221-2230, https://doi.org/10.5194/gmd-10-2221-2017, 2017 Weather and climate models must become more efficient if they continue growing in complexity. One option for reducing computational cost is to reduce numerical precision. We present a tool that allows users to study how models perform with reduced numerical precision. The tool is applied to a geophysical use case where precision is heavily reduced while maintaining suitable accuracy. The tool can be applied to other models to determine whether they can be made more computationally efficient.

Description: Modeling regional air quality and climate: improving organic aerosol and aerosol activation processes in WRF/Chem version 3.7.1 Khairunnisa Yahya, Timothy Glotfelty, Kai Wang, Yang Zhang, and Athanasios Nenes Geosci. Model Dev., 10, 2333-2363, https://doi.org/10.5194/gmd-10-2333-2017, 2017 Air quality and climate influence each other through the uncertain processes of aerosol formation and cloud droplet activation. In this study, both processes are improved in the Weather, Research and Forecasting model with Chemistry (WRF/Chem) version 3.7.1. The existing Volatility Basis Set (VBS) treatments for organic aerosol (OA) formation in WRF/Chem are improved by considering the following: the secondary OA (SOA) formation from semi-volatile primary organic aerosol (POA), a semi-empirical formulation for the enthalpy of vaporization of SOA, and functionalization and fragmentation reactions for multiple generations of products from the oxidation of VOCs. Over the continental US, 2-month-long simulations (May to June 2010) are conducted and results are evaluated against surface and aircraft observations during the Nexus of Air Quality and Climate Change (CalNex) campaign. Among all the configurations considered, the best performance is found for the simulation with the 2005 Carbon Bond mechanism (CB05) and the VBS SOA module with semivolatile POA treatment, 25 % fragmentation, and the emissions of semi-volatile and intermediate volatile organic compounds being 3 times the original POA emissions. Among the three gas-phase mechanisms (CB05, CB6, and SAPRC07) used, CB05 gives the best performance for surface ozone and PM 2. 5 concentrations. Differences in SOA predictions are larger for the simulations with different VBS treatments (e.g., nonvolatile POA versus semivolatile POA) compared to the simulations with different gas-phase mechanisms. Compared to the simulation with CB05 and the default SOA module, the simulations with the VBS treatment improve cloud droplet number concentration (CDNC) predictions (normalized mean biases from −40.8 % to a range of −34.6 to −27.7 %), with large differences between CB05–CB6 and SAPRC07 due to large differences in their OH and HO 2 predictions. An advanced aerosol activation parameterization based on the Fountoukis and Nenes (2005) series reduces the large negative CDNC bias associated with the default Abdul Razzak and Ghan (2000) parameterization from −35.4 % to a range of −0.8 to 7.1 %. However, it increases the errors due to overpredictions of CDNC, mainly over the northeastern US. This work indicates a need to improve other aerosol–cloud–radiation processes in the model, such as the spatial distribution of aerosol optical depth and cloud condensation nuclei, in order to further improve CDNC predictions.

Description: STRAPS v1.0: evaluating a methodology for predicting electron impact ionisation mass spectra for the aerosol mass spectrometer David O. Topping, James Allan, M. Rami Alfarra, and Bernard Aumont Geosci. Model Dev., 10, 2365-2377, https://doi.org/10.5194/gmd-10-2365-2017, 2017 Our ability to model the chemical and thermodynamic processes that lead to secondary organic aerosol (SOA) formation is thought to be hampered by the complexity of the system. In this proof of concept study, the ability to train supervised methods to predict electron impact ionisation (EI) mass spectra for the AMS is evaluated to facilitate improved model evaluation. The study demonstrates the use of a methodology that would be improved with more training data and data from simple mixed systems.

Description: Intensity of geodynamic processes in the Lithuanian part of the Curonian Spit Algimantas Česnulevičius, Regina Morkūnaitė, Artūras Bautrėnas, Linas Bevainis, and Donatas Ovodas Earth Syst. Dynam., 8, 419-428, https://doi.org/10.5194/esd-8-419-2017, 2017 The article analysed the problems of aeolian relief changes. The changes are determined by climate, neo-tectonics, and human impact. The most important climate factors are wind speed and wind direction. Strong permanent winds induced fast sand drying and activated deflation processes, which were further accelerated by a constant stream of visitors to the dunes. The neo-tectonic movements formed micro-terraces on the eastern dune slope, which changes on wet sand pressure.

Description: The importance of terrestrial weathering changes in multimillennial recovery of the global carbon cycle: a two-dimensional perspective Marc-Olivier Brault, H. Damon Matthews, and Lawrence A. Mysak Earth Syst. Dynam., 8, 455-475, https://doi.org/10.5194/esd-8-455-2017, 2017 In this paper we describe the development and application of a new spatially explicit weathering scheme within the University of Victoria Earth System Climate Model (UVic ESCM). We integrated a dataset of modern-day lithology with a number of previously devised parameterizations for weathering dependency on temperature, primary productivity, and runoff. We tested the model with simulations of future carbon cycle perturbations and confirmed the importance of silicate weathering in the long term.

Description: Source-receptor matrix calculation for deposited mass with the Lagrangian particle dispersion model FLEXPART v10.2 in backward mode Sabine Eckhardt, Massimo Cassiani, Nikolaos Evangeliou, Espen Sollum, Ignacio Pisso, and Andreas Stohl Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-131,2017 Manuscript under review for GMD (discussion: open, 0 comments) We extend the backward modelling technique in an existing model (FLEXPART), to substances deposited at the Earth's surface by wet scavenging and dry deposition. This means that for existing measurements of a substance in snow, ice cores or rain samples the source regions can be determined. This will help the interpretation of the measurement as well as gaining information of emission strength at the source of the deposited substance.

Description: Synthesizing long-term sea level rise projections – the MAGICC sea level model v2.0 Alexander Nauels, Malte Meinshausen, Matthias Mengel, Katja Lorbacher, and Tom M. L. Wigley Geosci. Model Dev., 10, 2495-2524, https://doi.org/10.5194/gmd-10-2495-2017, 2017 The MAGICC sea level model projects global sea level rise by emulating process-based estimates for all major sea level drivers and applying them to available climate scenarios and their extensions to 2300. The MAGICC sea level projections are well within the ranges of the fifth IPCC assessment report. Due to its efficient structure, this emulator is a powerful tool for exploring sea level uncertainties and investigating sea level responses for a wide range of climate mitigation pathways.

Description: Sensitivity experiments on the response of Vb cyclones to sea surface temperature and soil moisture changes Martina Messmer, Juan José Gómez-Navarro, and Christoph C. Raible Earth Syst. Dynam., 8, 477-493, https://doi.org/10.5194/esd-8-477-2017, 2017 Low-pressure systems of type Vb may trigger heavy rainfall events over central Europe. This study aims at analysing the relative role of their moisture sources. For this, a set of sensitivity experiments encompassing changes in soil moisture and Atlantic Ocean and Mediterranean Sea SSTs are carried out with WRF. The latter moisture source stands out as the most relevant one. Furthermore, the regions most affected by Vb events in the future might be shifted from the Alps to the Balkan Peninsula.

Description: Earth system model simulations show different carbon cycle feedback strengths under glacial and interglacial conditions Markus Adloff, Christian H. Reick, and Martin Claussen Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-67,2017 Manuscript under review for ESD (discussion: open, 1 comment) Computer simulations show that during an ice age a strong atmospheric CO 2 increase would have resulted in a stronger carbon uptake of the continents than today. Causes are the larger potential of glacial vegetation to increase its photosynthetic efficiency under increasing CO 2 and the much less carbon stored in extratropical soils during an ice age that can be released under greenhouse warming. Hence, for different climates the Earth system is differently sensitive to carbon cycle perturbations.

Description: A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5 Juno Hsu, Michael J. Prather, Philip Cameron-Smith, Alex Veidenbaum, and Alex Nicolau Geosci. Model Dev., 10, 2525-2545, https://doi.org/10.5194/gmd-10-2525-2017, 2017 Solar-J is a high-fidelity solar radiative transfer Fortran 90 code. It has been developed for consistently calculating both the photolysis rates of important chemical species and the heating rates of the atmosphere and the Earth's surface. Its spectral range spans from 177 nm to 12 microns. It can be easily dropped in as a module in global climate–chemistry models.

Description: Recent Trends in Frequency and Duration of Global Floods Nasser Najibi and Naresh Devineni Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-59,2017 Manuscript under review for ESD (discussion: open, 0 comments) Frequency and duration of flood events are analyzed using Dartmouth Flood Observatory's (DFO) global flood database to detect significant trends and regime shifts during 1985–2015 at global and latitudinal scales. Three classes of flood duration (i.e. short: 1–7, moderate: 8–20, and long: 21 days and above) are also considered for this analysis. The non-parametric Mann-Kendall trend test and Pettitt change-point analysis are used to evaluate three hypotheses (H1, H2, and H3) addressing potential monotonic trends and regime shifts in flood frequency, moments of the duration, and the frequency of a specific flood duration type. The results show that long duration flood frequency has increased across most spatial scales with significant change-point observed in the 2000s. In the tropics, floods have increased four-fold since the 2000s. This increase is 2.5 fold in the north mid-latitudes. There is no monotonic trend in the frequency of short duration floods across all global and latitudinal scales. There is also a significant increasing trend in the annual median and tails of flood durations globally and in each latitudinal belt. The possible causes of these trends are analyzed using a Generalized Linear Model framework and also discussed qualitatively. This analysis provides the framework for understanding simultaneously changing climate and socioeconomic conditions and how they relate to the frequency and persistence in the organization of global and local dynamical systems that cause hydrologic extremes.

Description: The carbon cycle in the Australian Community Climate and Earth System Simulator (ACCESS-ESM1) – Part 1: Model description and pre-industrial simulation Rachel M. Law, Tilo Ziehn, Richard J. Matear, Andrew Lenton, Matthew A. Chamberlain, Lauren E. Stevens, Ying-Ping Wang, Jhan Srbinovsky, Daohua Bi, Hailin Yan, and Peter F. Vohralik Geosci. Model Dev., 10, 2567-2590, https://doi.org/10.5194/gmd-10-2567-2017, 2017 The paper describes a version of the Australian Community Climate and Earth System Simulator that has been enabled to simulate the carbon cycle, which is designated ACCESS-ESM1. The model performance for pre-industrial conditions is assessed and land and ocean carbon fluxes are found to be simulated realistically.

Description: A multi-diagnostic approach to cloud evaluation Keith D. Williams and Alejandro Bodas-Salcedo Geosci. Model Dev., 10, 2547-2566, https://doi.org/10.5194/gmd-10-2547-2017, 2017 The simulation of cloud is problematic for general circulation models. As clouds come in differing types, areal coverage, altitude and reflectivity, it is possible for a model to appear to perform well against a particular observational dataset through a compensation of errors. Here we evaluate a model's cloud simulation against a range of observational datasets, globally and across weather–climate timescales, in order to provide a comprehensive assessment.

Description: Development of an inorganic and organic aerosol model (Chimere2017 β v1.0): seasonal and spatial evaluation over Europe Florian Couvidat, Bertrand Bessagnet, Marta Garcia-Vivanco, Elsa Real, Laurent Menut, and Augustin Colette Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-120,2017 Manuscript under review for GMD (discussion: open, 0 comments) This paper includes the development of a new aerosol module in the air quality model Chimere to improve Particulate Matter (PM) simulation. The results of the model are compared to numerous measurements over Europe to evaluate the strengths and weaknesses of the model.

Description: Projected changes in crop yield mean and variability over West Africa in a world 1.5 K warmer than the pre-industrial Ben Parkes, Dimitri Defrance, Benjamin Sultan, Philippe Ciais, and Xuhui Wang Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-66,2017 Manuscript under review for ESD (discussion: open, 0 comments) We present an analysis of three crops in West Africa and their response to short term climate change in a world where temperatures are 1.5 K above the preindustrial levels. We show that the number of crop failures for all crops is due to increase in the future climate. We further show the difference in yield change across several West African countries and show that the yields are not expected to increase fast enough to prevent food shortages.

Description: AMM15: A new high resolution NEMO configuration for operational simulation of the European North West Shelf Jennifer A. Graham, Enda O’Dea, Jason Holt, Jeff Polton, Helene T. Hewitt, Rachel Furner, Karen Guihou, Ashley Brereton, Alex Arnold, Sarah Wakelin, Juan Manuel Castillo Sanchez, and C. Gabriela Mayorga Adame Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-127,2017 Manuscript under review for GMD (discussion: open, 0 comments) This paper describes the next generation ocean forecast model for the European NW Shelf, AMM15 (Atlantic Margin Model, 1.5 km resolution). The current forecast system has a resolution of 7 km. While this is sufficient to represent large-scale circulation, many dynamical features (such as eddies, frontal-jets and internal tides) can only begin to be resolved at O(1 km) resolution. Here we introduce AMM15, and demonstrate its ability to represent the mean state and variability of the region.

Description: Source apportionment and sensitivity analysis: two methodologies with two different purposes Alain Clappier, Claudio A. Belis, Denise Pernigotti, and Philippe Thunis Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-161,2017 Manuscript under review for GMD (discussion: open, 0 comments) This work demonstrates that when the relationship between emissions and concentrations is non-linear, sensitivity approaches, generally used for air quality planning are not suitable to retrieve source contributions and source apportionment methods are not appropriate to evaluate the impact of abatement strategies on air quality. A simple theoretical example is used highlighting differences and potential implications for policy.

Description: On the Predictability of Land Surface Fluxes from Meteorological Variables Ned Haughton, Gab Abramowitz, and Andy J. Pitman Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-153,2017 Manuscript under review for GMD (discussion: open, 0 comments) Previous studies indicate that fluxes of heat, water, and carbon between the land surface and atmosphere are substantially more predictable than the performance of the current crop of land surface models would indicate. This study uses simple empirical models to estimate the amount of useful information in meteorological forcings that is available for predicting land surface fluxes. These models can be used as benchmarks for land surface models, and may help identify areas ripe for improvement.

Description: Modelling feedbacks between human and natural processes in the land system Derek T. Robinson, Alan Di Vittorio, Peter Alexander, Almut Arneth, C. Michael Barton, Daniel G. Brown, Albert Kettner, Carsten Lemmen, Brian C. O'Neill, Marco Janssen, Thomas A. M. Pugh, Sam S. Rabin, Mark Rounsevell, James P. Syvitski, Isaac Ullah, and Peter H. Verburg Earth Syst. Dynam. Discuss., https//doi.org/10.5194/esd-2017-68,2017 Manuscript under review for ESD (discussion: open, 0 comments) The unprecedented use of Earth's resources by humans, in combination with the increasing natural variability in natural processes over the past century, is affecting evolution of the Earth system. To better understand natural processes and their potential future trajectories requires improved integration with and quantification of human processes. Similarly, to mitigate risk and facilitate socio-economic development requires a better understanding of how the natural system (e.g., climate variability and change, extreme weather events, and processes affecting soil fertility) affects human processes. To capture and formalize our understanding of the interactions and feedback between human and natural systems a variety of modelling approaches are used. While integrated assessment models are widely recognized as supporting this goal and integrating representations of the human and natural system for global applications, an increasing diversity of models and corresponding research have focused on coupling models specializing in specific human (e.g., decision-making) or natural (e.g., erosion) processes at multiple scales. Domain experts develop these specialized models with a greater degree of detail, accuracy, and transparency, with many adopting open-science norms that use new technology for model sharing, coupling, and high performance computing. We highlight examples of four different approaches used to couple representations of the human and natural system, which vary in the processes represented and in the scale of their application. The examples illustrate how groups of researchers have attempted to overcome the lack of suitable frameworks for coupling human and natural systems to answer questions specific to feedbacks between human and natural systems. We draw from these examples broader lessons about system and model coupling and discuss the challenges associated with maintaining consistency across models and representing feedback between human and natural systems in coupled models.

Description: A parameterisation for the co-condensation of semi-volatile organics into multiple aerosol particle modes Matthew Crooks, Paul Connolly, and Gordon McFiggans Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2017-123,2017 Manuscript under review for GMD (discussion: open, 0 comments) Clouds form when water condenses onto particles in the atmosphere and the size and chemical composition of these particles can have a large influence over how much water condenses and the subsequent formation of cloud. Additional gases exist in the atmosphere that can condense onto the aerosol particles and change their composition. We present a fast and efficient method of calculating the effect of atmospheric gases on the formation of cloud that can be used in climate and weather models.

Description: The iFlow modelling framework v2.4: a modular idealized process-based model for flow and transport in estuaries Yoeri M. Dijkstra, Ronald L. Brouwer, Henk M. Schuttelaars, and George P. Schramkowski Geosci. Model Dev., 10, 2691-2713, https://doi.org/10.5194/gmd-10-2691-2017, 2017 The iFlow modelling framework is a width-averaged model for the systematic analysis of the water motion and sediment transport processes in estuaries and tidal rivers. The distinctive solution method, a mathematical perturbation method, used in the model allows for identification of the effect of individual physical processes on the water motion and sediment transport and study of the sensitivity of these processes to model parameters. This distinction between processes provides a unique tool for interpreting and explaining hydrodynamic interactions and sediment trapping. iFlow also includes a large number of options to configure the model geometry and multiple choices of turbulence and salinity models. Additionally, the model contains auxiliary components, including one that facilitates easy and fast sensitivity studies. iFlow has a modular structure, which makes it easy to include, exclude or change individual model components, called modules. Depending on the required functionality for the application at hand, modules can be selected to construct anything from very simple quasi-linear models to rather complex models involving multiple non-linear interactions. This way, the model complexity can be adjusted to the application. Once the modules containing the required functionality are selected, the underlying model structure automatically ensures modules are called in the correct order. The model inserts iteration loops over groups of modules that are mutually dependent. iFlow also ensures a smooth coupling of modules using analytical and numerical solution methods. This way the model combines the speed and accuracy of analytical solutions with the versatility of numerical solution methods. In this paper we present the modular structure, solution method and two examples of the use of iFlow. In the examples we present two case studies, of the Yangtze and Scheldt rivers, demonstrating how iFlow facilitates the analysis of model results, the understanding of the underlying physics and the testing of parameter sensitivity. A comparison of the model results to measurements shows a good qualitative agreement. iFlow is written in Python and is available as open source code under the LGPL license.

Description: A wind proxy based on migrating dunes at the Baltic coast: statistical analysis of the link between wind conditions and sand movement Svenja E. Bierstedt, Birgit Hünicke, Eduardo Zorita, and Juliane Ludwig Earth Syst. Dynam., 8, 639-652, https://doi.org/10.5194/esd-8-639-2017, 2017 We statistically analyse the relationship between the structure of migrating dunes in the southern Baltic and the driving wind conditions over the past 26 years, with the long-term aim of using migrating dunes as a proxy for past wind conditions at an interannual resolution.

Description: Drought identification in the eastern Baltic region using NDVI Egidijus Rimkus, Edvinas Stonevicius, Justinas Kilpys, Viktorija Maciulyte, and Donatas Valiukas Earth Syst. Dynam., 8, 627-637, https://doi.org/10.5194/esd-8-627-2017, 2017 Drought effect on vegetation in the eastern part of the Baltic Sea region was determined using satellite data. The impact of precipitation deficit on vegetation on arable land and in broadleaved and coniferous forests was analysed. The precipitation deficit in the first part of the growing season only has a significant impact on the vegetation on arable land, while this impact becomes more evident in all types of vegetation in the second half of the season.

Description: BRICK v0.2, a simple, accessible, and transparent model framework for climate and regional sea-level projections Tony E. Wong, Alexander M. R. Bakker, Kelsey Ruckert, Patrick Applegate, Aimée B. A. Slangen, and Klaus Keller Geosci. Model Dev., 10, 2741-2760, https://doi.org/10.5194/gmd-10-2741-2017, 2017 We present the Building blocks for Relevant Ice and Climate Knowledge (BRICK) model v0.2. BRICK is a model for hindcasting past and projecting future surface temperature and sea-level rise, resolving the sea-level contributions from glaciers and ice caps, the Greenland and Antarctic ice sheets, and thermal expansion. BRICK is specifically designed to support decision analyses through its transparency, and includes functionality to scale global sea-level estimates to regional projections.