ALBERT

Description: Singular vector based targeted observations of chemical constituents: description and first application of the EURAD-IM-SVA Geoscientific Model Development Discussions, 8, 6267-6307, 2015 Author(s): N. Goris and H. Elbern Measurements of the large dimensional chemical state of the atmosphere provide only sparse snapshots of the state of the system due to their typically insufficient temporal and spatial density. In order to optimize the measurement configurations despite those limitations, the present work describes the identification of sensitive states of the chemical system as optimal target areas for adaptive observations. For this purpose, the technique of singular vector analysis (SVA), which has been proved effective for targeted observations in numerical weather predication, is implemented into the chemical transport model EURAD-IM (EURopean Air pollution and Dispersion – Inverse Model) yielding the EURAD-IM-SVA. Besides initial values, emissions are investigated as critical simulation controlling targeting variables. For both variants, singular vectors are applied to determine the optimal placement for observations and moreover to quantify which chemical compounds have to be observed with preference. Based on measurements of the airship based ZEPTER-2 campaign, the EURAD-IM-SVA has been evaluated by conducting a comprehensive set of model runs involving different initial states and simulation lengths. Since the considered cases are restricted in terms of considered chemical compounds and selected areas, they allow for a retracing of the results and a confirmation of their correctness. Our analysis shows that the optimal placement for observations of chemical species is not entirely determined by mere transport and mixing processes. Rather, a combination of initial chemical concentrations, chemical conversions, and meteorological processes determine the influence of chemical compounds and regions. We furthermore demonstrate that the optimal placement of observations of emission strengths is highly dependent on the location of emission sources and that the benefit of including emissions as target variables outperforms the value of initial value optimisation with growing simulation length. The obtained results confirm the benefit of considering both initial values and emission strengths as target variables and of applying the EURAD-IM-SVA for measurement decision guidance with respect to chemical compounds.

Description: A global scale mechanistic model of the photosynthetic capacity Geoscientific Model Development Discussions, 8, 6217-6266, 2015 Author(s): A. A. Ali, C. Xu, A. Rogers, R. A. Fisher, S. D. Wullschleger, N. G. McDowell, E. C. Massoud, J. A. Vrugt, J. D. Muss, J. B. Fisher, P. B. Reich, and C. J. Wilson Although plant photosynthetic capacity as determined by the maximum carboxylation rate (i.e., V c, max25 ) and the maximum electron transport rate (i.e., J max25 ) at a reference temperature (generally 25 °C) is known to vary substantially in space and time in response to environmental conditions, it is typically parameterized in Earth system models (ESMs) with tabulated values associated to plant functional types. In this study, we developed a mechanistic model of leaf utilization of nitrogen for assimilation (LUNA V1.0) to predict the photosynthetic capacity at the global scale under different environmental conditions, based on the optimization of nitrogen allocated among light capture, electron transport, carboxylation, and respiration. The LUNA model was able to reasonably well capture the observed patterns of photosynthetic capacity in view that it explained approximately 55 % of the variation in observed V c, max25 and 65 % of the variation in observed J max25 across the globe. Our model simulations under current and future climate conditions indicated that V c, max25 could be most affected in high-latitude regions under a warming climate and that ESMs using a fixed V c, max25 or J max25 by plant functional types were likely to substantially overestimate future global photosynthesis.

Description: Evaluation of an operational ocean model configuration at 1/12° spatial resolution for the Indonesian seas – Part 2: Biogeochemistry Geoscientific Model Development Discussions, 8, 6669-6706, 2015 Author(s): E. Gutknecht, G. Reffray, M. Gehlen, I. Triyulianti, D. Berlianty, and P. Gaspar In the framework of the INDESO (Infrastructure evelopment of Space Oceanography) project, an operational ocean forecasting system was developed to monitor the state of the Indonesian seas in terms of circulation, biogeochemistry and fisheries. This forecasting system combines a suite of numerical models connecting physical and biogeochemical variables to population dynamics of large marine predators (tunas). The physical/biogeochemical coupled component (INDO12BIO configuration) covers a large region extending from the western Pacific Ocean to the Eastern Indian Ocean at 1/12° resolution. The OPA/NEMO physical ocean model and the PISCES biogeochemical model are coupled in "on-line" mode without degradation in space and time. The operational global ocean forecasting system (1/4°) operated by Mercator Ocean provides the physical forcing while climatological open boundary conditions are prescribed for the biogeochemistry. This paper describes the skill assessment of the INDO12BIO configuration. Model skill is assessed by evaluating a reference hindcast simulation covering the last 8 years (2007–2014). Model results are compared to satellite, climatological and in situ observations. Diagnostics are performed on chlorophyll a , primary production, mesozooplankton, nutrients and oxygen. Model results reproduce the main characteristics of biogeochemical tracer distributions in space and time. The seasonal cycle of chlorophyll a is in phase with satellite observations. The northern and southern parts of the archipelago present a distinct seasonal cycle, with higher chlorophyll biomass in the southern (northern) part during SE (NW) monsoon. Nutrient and oxygen concentrations are correctly reproduced in terms of horizontal and vertical distributions. The biogeochemical content of water masses entering in the archipelago as well as the water mass transformation across the archipelago conserves realistic vertical distribution in Banda Sea and at the exit of the archipelago.

Description: Decadal evaluation of regional climate, air quality, and their interactions using WRF/Chem Version 3.6.1 Geoscientific Model Development Discussions, 8, 6707-6756, 2015 Author(s): K. Yahya, K. Wang, P. Campbell, T. Glotfelty, J. He, and Y. Zhang The Weather Research and Forecasting model with Chemistry (WRF/Chem) v3.6.1 with the Carbon Bond 2005 (CB05) gas-phase mechanism is evaluated for its first decadal application during 2001–2010 using the Representative Concentration Pathway (RCP 8.5) emissions to assess its capability and appropriateness for long-term climatological simulations. The initial and boundary conditions are downscaled from the modified Community Earth System Model/Community Atmosphere Model (CESM/CAM5) v1.2.2. The meteorological initial and boundary conditions are bias-corrected using the National Center for Environmental Protection's Final (FNL) Operational Global Analysis data. Climatological evaluations are carried out for meteorological, chemical, and aerosol-cloud-radiation variables against data from surface networks and satellite retrievals. The model performs very well for the 2 m temperature (T2) for the 10 year period with only a small cold bias of −0.3 °C. Biases in other meteorological variables including relative humidity at 2 m, wind speed at 10 m, and precipitation tend to be site- and season-specific; however, with the exception of T2, consistent annual biases exist for most of the years from 2001 to 2010. Ozone mixing ratios are slightly overpredicted at both urban and rural locations but underpredicted at rural locations. PM 2.5 concentrations are slightly overpredicted at rural sites, but slightly underpredicted at urban/suburban sites. In general, the model performs relatively well for chemical and meteorological variables, and not as well for aerosol-cloud-radiation variables. Cloud-aerosol variables including aerosol optical depth, cloud water path, cloud optical thickness, and cloud droplet number concentration are generally underpredicted on average across the continental US. Overpredictions of several cloud variables over eastern US result in underpredictions of radiation variables and overpredictions of shortwave and longwave cloud forcing which are important climate variables. While the current performance is deemed to be acceptable, improvements to the bias-correction method for CESM downscaling and the model parameterizations of cloud dynamics and thermodynamics, as well as aerosol-cloud interactions can potentially improve model performance for long-term climate simulations.

Description: The GEWEX LandFlux project: evaluation of model evaporation using tower-based and globally-gridded forcing data Geoscientific Model Development Discussions, 8, 6809-6866, 2015 Author(s): M. F. McCabe, A. Ershadi, C. Jimenez, D. G. Miralles, D. Michel, and E. F. Wood Determining the spatial distribution and temporal development of evaporation at regional and global scales is required to improve our understanding of the coupled water and energy cycles and to better monitor any changes in observed trends and variability of linked hydrological processes. With recent international efforts guiding the development of long-term and globally distributed flux estimates, continued product assessments are required to inform upon the selection of suitable model structures and also to establish the appropriateness of these multi-model simulations for global application. In support of the objectives of the GEWEX LandFlux project, four commonly used evaporation models are evaluated against data from tower-based eddy-covariance observations, distributed across a range of biomes and climate zones. The selected schemes include the Surface Energy Balance System (SEBS) approach, the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model, the Penman-Monteith based Mu model (PM-Mu) and the Global Land Evaporation: the Amsterdam Methodology (GLEAM). Here we seek to examine the fidelity of global evaporation simulations by examining the multi-model response to varying sources of forcing data. To do this, we perform parallel and collocated model simulations using tower-based data together with a global-scale grid-based forcing product. Through quantifying the multi-model response to high-quality tower data, a better understanding of the subsequent model response to coarse-scale globally gridded data that underlies the LandFlux product can be obtained, while also providing a relative evaluation and assessment of model performance. Using surface flux observations from forty-five globally distributed eddy-covariance stations as independent metrics of performance, the tower-based analysis indicated that PT-JPL provided the highest overally statistical performance (0.72; 61 W m −2 ; 0.65), followed closely by GLEAM (0.68; 64 W m −2 ; 0.62), with values in parenthesis representing the R 2 , RMSD and Nash-Sutcliffe Efficiency (NSE) and respectively. PM-Mu (0.51; 78 W m −2 ; 0.45) tended to underestimate fluxes, while SEBS (0.72; 101 W m −2 ; 0.24) overestimated values relative to observations. A focused analysis across specific biome types and climate zones showed considerable variability in the performance of all models, with no single model consistently able to outperform any other. Results also indicated that the global gridded data tended to reduce the performance for all of the studied models when compared to the tower data, likely a response to scale mismatch and issues related to forcing quality. Rather than relying on any single model simulation, the spatial and temporal variability at both the tower- and grid-scale highlighted the potential benefits of developing an ensemble or blended evaporation product for global scale LandFlux applications. Challenges related to the robust assessment of the LandFlux product are also discussed.

Description: GO2OGS: a versatile workflow to integrate complex geological information with fault data into numerical simulation models Geoscientific Model Development Discussions, 8, 6309-6348, 2015 Author(s): T. Fischer, M. Walther, S. Sattler, D. Naumov, and O. Kolditz We offer a versatile workflow to convert geological models built with the software Paradigm™ GOCAD © into the open-source VTU format for the usage in numerical simulation models. Tackling relevant scientific questions or engineering tasks often involves multidisciplinary approaches. Conversion workflows are needed as a way of communication between the diverse tools of the various disciplines. Our approach offers an open-source, platform independent, robust, and comprehensible method that is potentially useful for a multitude of similar environmental studies. With two application examples in the Thuringian Syncline, we show how a heterogeneous geological GOCAD model including multiple layers and faults can be used for numerical groundwater flow modelling. The presented workflow offers the chance to incorporate increasingly detailed data, utilizing growing availability of computational power to simulate numerical models.

Description: WRF4G: WRF experiment management made simple Geoscientific Model Development Discussions, 8, 6551-6582, 2015 Author(s): V. Fernández-Quiruelas, J. Fernández, A. S. Cofiño, C. Blanco, M. García-Díez, M. Magariño, L. Fita, and J. M. Gutiérrez This work presents a framework, WRF4G, to manage the experiment workflow of the Weather Research and Forecasting (WRF) modelling system. WRF4G provides a flexible design, execution and monitoring for a general class of scientific experiments. It has been designed with the aim of facilitating the management and reproducibility of complex experiments. Furthermore, the concepts behind the design of this framework can be straightforwardly extended to other models. We describe the user interface and the new concepts required to design parameter-sweep, hindcast and climate simulation experiments. A number of examples are provided, based on the design used for existing (published) WRF experiments. This software is open-source and publicly available http://www.meteo.unican.es/software/wrf4g ).

Description: Implementation of the Community Earth System Model (CESM1, version 1.2.1) as a new basemodel into version 2.50 of the MESSy framework Geoscientific Model Development Discussions, 8, 6523-6550, 2015 Author(s): A. J. G. Baumgaertner, P. Jöckel, A. Kerkweg, R. Sander, and H. Tost The Community Earth System Model (CESM1), maintained by the United States National Centre for Atmospheric Research (NCAR) is connected with the Modular Earth Submodel System (MESSy). For the MESSy user community, this offers many new possibilities. The option to use the CESM1(CAM) atmospheric dynamical cores, especially the spectral element (SE) core, as an alternative to the ECHAM5 spectral transform dynamical core will provide scientific and computational advances for atmospheric chemistry and climate modelling with MESSy. The SE dynamical core does not require polar filters since the grid is quasi-uniform. By advecting the surface pressure rather then the logarithm of surface pressure the SE core locally conserves energy and mass. Furthermore, it has the possibility to scale to up to 10 5 compute cores, which is useful for current and future computing architectures. The well-established finite volume core from CESM1(CAM) is also made available. This offers the possibility to compare three different atmospheric dynamical cores within MESSy. Additionally, the CESM1 land, river, sea ice, glaciers and ocean component models can be used in CESM1/MESSy simulations, allowing to use MESSy as a comprehensive Earth System Model. For CESM1/MESSy setups, the MESSy process and diagnostic submodels for atmospheric physics and chemistry are used together with one of the CESM1(CAM) dynamical cores; the generic (infrastructure) submodels support the atmospheric model component. The other CESM1 component models as well as the coupling between them use the original CESM1 infrastructure code and libraries, although in future developments these can also be replaced by the MESSy framework. Here, we describe the structure and capabilities of CESM1/MESSy, document the code changes in CESM1 and MESSy, and introduce several simulations as example applications of the system. The Supplements provide further comparisons with the ECHAM5/MESSy atmospheric chemistry (EMAC) model and document the technical aspects of the connection in detail.

Description: DebrisInterMixing-2.3: a Finite Volume solver for three dimensional debris flow simulations based on a single calibration parameter – Part 2: Model validation Geoscientific Model Development Discussions, 8, 6379-6415, 2015 Author(s): A. von Boetticher, J. M. Turowski, B. W. McArdell, D. Rickenmann, M. Hürlimann, C. Scheidl, and J. W. Kirchner Here we present the validation of the fluid dynamic solver presented in part one of this work (von Boetticher et al., 2015), simulating laboratory-scale and large-scale debris-flow experiments. The material properties of the experiments, including water content, sand content, clay content and its mineral composition, and gravel content and its friction angle, were known. We show that given these measured properties, a single free model parameter is sufficient for calibration, and a range of experiments with different material compositions can be reproduced by the model without recalibration. The model validation focuses on different case studies illustrating the sensitivity of debris flows to water and clay content, channel curvature, channel roughness and the angle of repose of the gravel. We characterize the accuracy of the model using experimental observations of flow head positions, front velocities, run-out patterns and basal pressures.

Description: Modeling global water use for the 21st century: Water Futures and Solutions (WFaS) initiative and its approaches Geoscientific Model Development Discussions, 8, 6417-6521, 2015 Author(s): Y. Wada, M. Flörke, N. Hanasaki, S. Eisner, G. Fischer, S. Tramberend, Y. Satoh, M. T. H. van Vliet, P. Yillia, C. Ringler, and D. Wiberg To sustain growing food demand and increasing standard of living, global water use increased by nearly 6 times during the last 100 years and continues to grow. As water demands get closer and closer to the water availability in many regions, each drop of water becomes increasingly valuable and water must be managed more efficiently and intensively. However, soaring water use worsens water scarcity condition already prevalent in semi-arid and arid regions, increasing uncertainty for sustainable food production and economic development. Planning for future development and investments requires that we prepare water projections for the future. However, estimations are complicated because the future of world's waters will be influenced by a combination of environmental, social, economic, and political factors, and there is only limited knowledge and data available about freshwater resources and how they are being used. The Water Futures and Solutions initiative (WFaS) coordinates its work with other on-going scenario efforts for the sake of establishing a consistent set of new global water scenarios based on the Shared Socioeconomic Pathways (SSPs) and the Representative Concentration Pathways (RCPs). The WFaS "fast-track" assessment uses three global water models, namely H08, PCR-GLOBWB, and WaterGAP. This study assesses the state of the art for estimating and projecting water use regionally and globally in a consistent manner. It provides an overview of different approaches, the uncertainty, strengths and weaknesses of the various estimation methods, types of management and policy decisions for which the current estimation methods are useful. We also discuss additional information most needed to be able to improve water use estimates and be able to assess a greater range of management options across the water-energy-climate nexus.

Description: Influence of grid aspect ratio on planetary boundary layer turbulence in large-eddy simulations Geoscientific Model Development Discussions, 8, 6021-6094, 2015 Author(s): S. Nishizawa, H. Yashiro, Y. Sato, Y. Miyamoto, and H. Tomita We examine the influence of the grid aspect ratio of horizontal to vertical grid spacing on turbulence in the planetary boundary layer (PBL) in a large-eddy simulation (LES). In order to distinguish them as much as possible from other artificial effects caused by numerical schemes, we used a fully compressible meteorological LES model with a fully explicit scheme of temporal integration. The influences are investigated with a series of sensitivity tests with parameter sweeps of spatial resolution and grid aspect ratio. We confirmed that the mixing length of the eddy viscosity and diffusion due to sub-grid scale turbulence plays an essential role in reproducing the theoretical −5/3 slope of the energy spectrum. If we define the filter length in LES modeling based on consideration of the numerical scheme, and introduce a corrective factor for the grid aspect ratio into the mixing length, the theoretical slope of the energy spectrum can be obtained; otherwise, spurious energy piling appears at high wavenumbers. We also found that the grid aspect ratio has influence on the turbulent statistics, especially the skewness of the vertical velocity near the top of the PBL, which becomes spuriously large with large aspect ratio, even if a reasonable spectrum is obtained.

Description: The role of ecosystem function and emergent relationships in the assessment of global marine ecosystem models: a case study with ERSEM Geoscientific Model Development Discussions, 8, 6095-6141, 2015 Author(s): L. de Mora, M. Butenschön, and J. I. Allen Ecosystem models are often assessed using quantitative metrics of absolute ecosystem state, but these model-data comparisons are disproportionately vulnerable to discrepancies in the location of important circulation features. An alternative method is to demonstrate the models capacity to represent ecosystem function; the emergence of a coherent natural relationship in a simulation is a strong indication that the model has a appropriate representation of the ecosystem functions that lead to the emergent relationship. Furthermore, as emergent properties are large scale properties of the system, model validation with emergent properties is possible even when there is very little or no appropriate data for the region under study, or when the hydrodynamic component of the model differs significantly from that observed in nature at the same location and time. A selection of published meta-analyses are used to establish the validity of a complex marine ecosystem model and to demonstrate the power of validation with emergent properties. These relationships include the phytoplankton community structure, the ratio of carbon to chlorophyll in phytoplankton and particulate organic matter, the ratio of particulate organic carbon to particulate organic nitrogen and the stoichiometric balance of the ecosystem. These metrics can also inform aspects of the marine ecosystem model not available from traditional quantitative and qualitative methods. For instance, these emergent properties can be used to validate the design decisions of the model, such as the range of phytoplankton functional types and their behaviour, the stoichiometric flexibility with regards to each nutrient, and the choice of fixed or variable carbon to nitrogen ratios.

Description: A semi-Lagrangian advection scheme for radioactive tracers in a regional spectral model Geoscientific Model Development Discussions, 8, 4221-4243, 2015 Author(s): E.-C. Chang and K. Yoshimura In this study, the non-iteration dimensional-split semi-Lagrangian (NDSL) advection scheme is applied to the National Centers for Environmental Prediction (NCEP) regional spectral model (RSM) to alleviate the Gibbs phenomenon. The Gibbs phenomenon is a problem wherein negative values of positive-definite quantities (e.g., moisture and tracers) are generated by the spectral space transformation in a spectral model system. To solve this problem, the spectral prognostic specific humidity and radioactive tracer advection scheme is replaced by the NDSL advection scheme, which considers advection of tracers in a grid system without spectral space transformations. A regional version of the NDSL is developed in this study and is applied to the RSM. Idealized experiments show that the regional version of the NDSL is successful. The model runs for an actual case study suggest that the NDSL can successfully advect radioactive tracers (iodine-131 and cesium-137) without noise from the Gibbs phenomenon. The NDSL can also remove negative specific humidity values produced in spectral calculations without losing detailed features.

Description: Open-source modular solutions for flexural isostasy: gFlex v1.0 Geoscientific Model Development Discussions, 8, 4245-4292, 2015 Author(s): A. D. Wickert Isostasy is one of the oldest and most widely applied concepts in the geosciences, but the geoscientific community lacks a coherent, easy-to-use tool to simulate flexure of a realistic (i.e. laterally heterogeneous) lithosphere under an arbitrary set of surface loads. Such a model is needed for studies of mountain-building, sedimentary basin formation, glaciation, sea-level change, and other tectonic, geodynamic, and surface processes. Here I present gFlex, an open-source model that can produce analytical and finite difference solutions for lithospheric flexure in one (profile) and two (map view) dimensions. To simulate the flexural isostatic response to an imposed load, it can be used by itself or within GRASS GIS for better integration with field data. gFlex is also a component with the Community Surface Dynamics Modeling System (CSDMS) and Landlab modeling frameworks for coupling with a wide range of Earth-surface-related models, and can be coupled to additional models within Python scripts. As an example of this in-script coupling, I simulate the effects of spatially variable lithospheric thickness on a modeled Iceland ice cap. Finite difference solutions in gFlex can use any of five types of boundary conditions: 0-displacement, 0-slope (i.e. clamped); 0-slope, 0-shear; 0-moment, 0-shear (i.e. broken plate); mirror symmetry; and periodic. Typical calculations with gFlex require ≪ 1s to ~1 min on a personal laptop computer. These characteristics – multiple ways to run the model, multiple solution methods, multiple boundary conditions, and short compute time – make gFlex an effective tool for flexural isostatic modeling across the geosciences.

Description: A new multiscale air quality transport model (Fluidity, 4.1.9) using fully unstructured anisotropic adaptive mesh technology Geoscientific Model Development Discussions, 8, 4337-4374, 2015 Author(s): J. Zheng, J. Zhu, Z. Wang, F. Fang, C. C. Pain, and J. Xiang A new anisotropic hr-adaptive mesh technique has been applied to modelling of multiscale transport phenomena, which is based on a discontinuous Galerkin/control volume discretization on unstructured meshes. Over existing air quality models typically based on static-structured grids using a locally nesting technique, the advantage of the anisotropic hr-adaptive model has the ability to adapt the mesh according to the evolving pollutant distribution and flow features. That is, the mesh resolution can be adjusted dynamically to simulate the pollutant transport process accurately and effectively. To illustrate the capability of the anisotropic adaptive unstructured mesh model, three benchmark numerical experiments have been setup for two-dimensional (2-D) transport phenomena. Comparisons have been made between the results obtained using uniform resolution meshes and anisotropic adaptive resolution meshes.

Description: SHIMMER (1.0): a novel mathematical model for microbial and biogeochemical dynamics in glacier forefield ecosystems Geoscientific Model Development Discussions, 8, 6143-6216, 2015 Author(s): J. A. Bradley, A. M. Anesio, J. S. Singarayer, M. R. Heath, and S. Arndt SHIMMER (Soil biogeocHemIcal Model for Microbial Ecosystem Response) is a new numerical modelling framework which is developed as part of an interdisciplinary, iterative, model-data based approach fully integrating fieldwork and laboratory experiments with model development, testing, and application. SHIMMER is designed to simulate the establishment of microbial biomass and associated biogeochemical cycling during the initial stages of ecosystem development in glacier forefield soils. However, it is also transferable to other extreme ecosystem types (such as desert soils or the surface of glaciers). The model mechanistically describes and predicts transformations in carbon, nitrogen and phosphorus through aggregated components of the microbial community as a set of coupled ordinary differential equations. The rationale for development of the model arises from decades of empirical observation on the initial stages of soil development in glacier forefields. SHIMMER enables a quantitative and process focussed approach to synthesising the existing empirical data and advancing understanding of microbial and biogeochemical dynamics. Here, we provide a detailed description of SHIMMER. The performance of SHIMMER is then tested in two case studies using published data from the Damma Glacier forefield in Switzerland and the Athabasca Glacier in Canada. In addition, a sensitivity analysis helps identify the most sensitive and unconstrained model parameters. Results show that the accumulation of microbial biomass is highly dependent on variation in microbial growth and death rate constants, Q 10 values, the active fraction of microbial biomass, and the reactivity of organic matter. The model correctly predicts the rapid accumulation of microbial biomass observed during the initial stages of succession in the forefields of both the case study systems. Simulation results indicate that primary production is responsible for the initial build-up of substrate that subsequently supports heterotrophic growth. However, allochthonous contributions of organic matter are identified as important in sustaining this productivity. Microbial production in young soils is supported by labile organic matter, whereas carbon stocks in older soils are more refractory. Nitrogen fixing bacteria are responsible for the initial accumulation of available nitrates in the soil. Biogeochemical rates are highly seasonal, as observed in experimental data. The development and application of SHIMMER not only provides important new insights into forefield dynamics, but also highlights aspects of these systems that require further field and laboratory research. The most pressing advances need to come in quantifying nutrient budgets and biogeochemical rates, in exploring seasonality, the fate of allochthonous deposition in relation to autochthonous production, and empirical studies of microbial growth and cell death, to increase understanding of how glacier forefield development contributes to the global biogeochemical cycling and climate in the future.

Description: DebrisInterMixing-2.3: a Finite Volume solver for three dimensional debris flow simulations based on a single calibration parameter – Part 1: Model description Geoscientific Model Development Discussions, 8, 6349-6378, 2015 Author(s): A. von Boetticher, J. M. Turowski, B. W. McArdell, D. Rickenmann, and J. W. Kirchner Here we present a three-dimensional fluid dynamic solver that simulates debris flows as a mixture of two phases (gravel and fine material suspension) with a third unmixed phase representing the air and the free surface. We link all rheological parameters to the material composition, i.e., to water content, clay content and mineral composition, content of sand and gravel, and the gravel's friction angle; the user must specify only a single free model parameter. The Volume-Of-Fluid (VOF) approach is used to combine the three phases into a single cell-averaged Navier–Stokes equation for incompressible flow, based on code adapted from standard solvers of the Open-Source CFD software OpenFOAM. We present a stable implementation of a Coulomb-Viscoplastic model that represents the pressure-dependent flow behavior of the granular phase, and a Herschel–Bulkley representation of the interstitial fluid. The VOF method saves computational costs compared to drag-force based multiphase models. Thus depth-averaging is not necessary and complex three-dimensional flow structures can be simulated.

Description: Representativeness errors in comparing chemistry transport and chemistry climate models with satellite UV/Vis tropospheric column retrievals Geoscientific Model Development Discussions, 8, 7821-7877, 2015 Author(s): K. F. Boersma, G. C. M. Vinken, and H. J. Eskes UV/Vis satellite retrievals of trace gas columns of nitrogen dioxide (NO 2 ), sulphur dioxide (SO 2 ), and formaldehyde (HCHO) are useful to test and improve models of atmospheric composition, for data assimilation, air quality hindcasting and forecasting, and to provide top-down constraints on emissions. However, because models and satellite measurements do not represent the exact same geophysical quantities, the process of confronting model fields with satellite measurements is complicated by representativeness errors, which degrade the quality of the comparison beyond contributions from modelling and measurement errors alone. Here we discuss three types of representativeness errors that arise from the act of carrying out a model-satellite comparison: (1) horizontal representativeness errors due to imperfect collocation of the model grid cell and an ensemble of satellite pixels called superobservation, (2) temporal representativeness errors originating mostly from differences in cloud cover between the modelled and observed state, and (3) vertical representativeness errors because of reduced satellite sensitivity towards the surface accompanied with necessary retrieval assumptions on the state of the atmosphere. To minimize the impact of these representativeness errors, we recommend that models and satellite measurements be sampled as consistently as possible, and our paper provides a number of recipes to do so. A practical confrontation of tropospheric NO 2 columns simulated by the TM5 chemistry transport model (CTM) with Ozone Monitoring Instrument (OMI) tropospheric NO 2 retrievals suggests that horizontal representativeness errors, while unavoidable, are limited to within 5–10 % in most cases and of random nature. These errors should be included along with the individual retrieval errors in the overall superobservation error. Temporal sampling errors from mismatches in cloud cover, and, consequently, in photolysis rates, are on the order of 10 % for NO 2 and HCHO, and systematic, but partly avoidable. In the case of air pollution applications where sensitivity down to the ground is required, we recommend that models should be sampled on the same mostly cloud-free days as the satellite retrievals. The most relevant representativeness error is associated with the vertical sensitivity of Ultraviolet-visible (UV/Vis) satellite retrievals. Simple vertical integration of modelled profiles leads to systematically different model columns compared to application of the appropriate averaging kernel. In comparing OMI NO 2 to GEOS-Chem NO 2 simulations, these systematic differences are as large as 15–20 % in summer, but, again, avoidable.

Description: LIMA (v1.0): a two-moment microphysical scheme driven by a multimodal population of cloud condensation and ice freezing nuclei Geoscientific Model Development Discussions, 8, 7767-7820, 2015 Author(s): B. Vié, J.-P. Pinty, S. Berthet, and M. Leriche The paper describes the 2-moment microphysical scheme LIMA (Liquid Ice Multiple Aerosols), which relies on the prognostic evolution of a three-dimensional (3-D) aerosol population, and the careful description of the nucleating properties that enable cloud droplets and pristine ice crystals to form. LIMA uses the aerosol nucleating properties to form cloud droplets and pristine ice crystals. Several modes of Cloud Condensation Nuclei (CCN) and Ice Freezing Nuclei (IFN) are considered individually. A special class of partially soluble IFN is also introduced. These "aged" IFN act first as CCN and then as IFN by immersion nucleation at low temperatures. All the CCN modes are in competition with each other, as expressed by the single equation of maximum supersaturation. The IFN are insoluble aerosols that nucleate ice in several ways (condensation, deposition and immersion freezing) assuming the singular hypothesis. The scheme also includes the homogeneous freezing of cloud droplets, the Hallett–Mossop ice multiplication process and the freezing of haze at very low temperature. LIMA assumes that water vapour is in thermodynamic equilibrium with the population of cloud droplets (adjustment to saturation in warm clouds). In ice clouds, the prediction of the number concentration of the pristine ice crystals is used to compute explicit deposition and sublimation rates (leading to free under/supersaturation over ice). The formation of hydrometeors is standard. The autoconversion, accretion and self-collection processes shape the raindrop spectra. The initiation of the large crystals and aggregates category is the result of the depositional growth of large crystals beyond a critical size. Aggregation and riming are computed explicitly. Heavily rimed crystals (graupel) can experience a dry or wet growth mode. An advanced version of the scheme includes a separate hail category of particles forming and growing exclusively in the wet growth mode. The sedimentation of all particle types is included. The LIMA scheme is inserted in the cloud-resolving mesoscale model Meso-NH. The flexibility of LIMA is illustrated by two 2-D experiments. The first one highlights the sensitivity of orographic ice clouds to IFN types and IFN concentrations. Then a squall line case discusses the microstructure of a mixed-phase cloud and the impacts of pure CCN and IFN polluting plumes. The experiments show that LIMA captures the complex nature of aerosol-cloud interactions leading to different pathways for cloud and precipitation formation.

Description: Evaluation of improved land use and canopy representation in BEIS v3.61 with biogenic VOC measurements in California Geoscientific Model Development Discussions, 8, 8117-8154, 2015 Author(s): J. O. Bash, K. R. Baker, and M. R. Beaver Biogenic volatile organic compounds (BVOC) participate in reactions that can lead to secondarily formed ozone and particulate matter (PM) impacting air quality and climate. BVOC emissions are important inputs to chemical transport models applied on local to global scales but considerable uncertainty remains in the representation of canopy parameterizations and emission algorithms from different vegetation species. The Biogenic Emission Inventory System (BEIS) has been used to support both scientific and regulatory model assessments for ozone and PM. Here we describe a new version of BEIS which includes updated input vegetation data and canopy model formulation for estimating leaf temperature and vegetation data on estimated BVOC. The Biogenic Emission Landuse Database (BELD) was revised to incorporate land use data from the Moderate Resolution Imaging Spectroradiometer (MODIS) land product and 2006 National Land Cover Database (NLCD) land coverage. Vegetation species data is based on the US Forest Service (USFS) Forest Inventory and Analysis (FIA) version 5.1 for years from 2002 to 2013 and US Department of Agriculture (USDA) 2007 census of agriculture data. This update results in generally higher BVOC emissions throughout California compared with the previous version of BEIS. Baseline and updated BVOC emissions estimates are used in Community Multiscale Air Quality Model (CMAQ) simulations with 4 km grid resolution and evaluated with measurements of isoprene and monoterpenes taken during multiple field campaigns in northern California. The updated canopy model coupled with improved land use and vegetation representation resulted in better agreement between CMAQ isoprene and monoterpene estimates compared with these observations.

Description: IL-GLOBO (1.0) – development and verification of the moist convection module Geoscientific Model Development Discussions, 8, 8239-8261, 2015 Author(s): D. Rossi, A. Maurizi, and M. Fantini The development and verification of the convective module of IL-GLOBO, a Lagrangian transport model coupled online with the Eulerian general circulation model GLOBO, is described. The online-coupling promotes the full consistency between the Eulerian and the Lagrangian components of the model. The Lagrangian convective scheme is derived based on the Kain–Fritsch convective parameterisation used in GLOBO. A transition probability matrix is computed using the fluxes provided by the Eulerian KF parameterisation. Then, the convection redistribution of Lagrangian particles is implemented via a Monte Carlo scheme. The formal derivation is described in details and, consistently with the Eulerian module, includes the environmental flux in the transition probability matrix to avoid splitting of the convection and subsidence processes. Consistency of the Lagrangian implementation with its Eulerian counterpart is verified by computing environment fluxes from the transition probability matrix and comparing them to those computed by the Eulerian module. Assessment of the impact of the module is made for different latitudinal belts, showing that the major impact is found in the tropics, as expected. Concerning vertical distribution, the major impact is observed in the boundary layer at every latitude, while in the tropical area, the influence extends to very high levels.

Description: Simulating the thermal regime and thaw processes of ice-rich permafrost ground with the land-surface model CryoGrid 3 Geoscientific Model Development Discussions, 8, 6931-6986, 2015 Author(s): S. Westermann, M. Langer, J. Boike, M. Heikenfeld, M. Peter, B. Etzelmüller, and G. Krinner Thawing of permafrost in a warming climate is governed by a complex interplay of different processes, of which only conductive heat transfer is taken into account in most model studies. However, observations in many permafrost landscapes demonstrate that lateral and vertical movement of water can have a pronounced influence on the thaw trajectories, creating distinct landforms like thermokarst ponds and lakes even in areas where permafrost is otherwise thermally stable. Novel process parameterizations are required to include such phenomena in future projections of permafrost thaw and hereby triggered climatic feedbacks. In this study, we present a new land-surface scheme designed for permafrost applications, CryoGrid 3, which constitutes a flexible platform to explore new parameterizations for a range of permafrost processes. We document the model physics and employed parameterizations for the basis module CryoGrid 3, and compare model results with in-situ observations of surface energy balance, surface temperatures, and ground thermal regime from the Samoylov permafrost observatory in NE Siberia. The comparison suggests that CryoGrid 3 can not only model the evolution of the ground thermal regime in the last decade, but also consistently reproduce the chain of energy transfer processes from the atmosphere to the ground. In addition, we demonstrate a simple 1-D parameterization for thaw process in permafrost areas rich in ground ice, which can phenomenologically reproduce both formation of thermokarst ponds and subsidence of the ground following thawing of ice-rich subsurface layers. Long-term simulation from 1901–2100 driven by reanalysis data and climate model output demonstrate that the hydrological regime can both accelerate and delay permafrost thawing. If meltwater from thawed ice-rich layers can drain, the ground subsides while at the same time the formation of a talik is delayed. If the meltwater pools at the surface, a pond is formed which enhances heat transfer in the ground and leads to the formation of a talik. The model results suggest that the trajectories of future permafrost thaw are strongly influenced by the cryostratigraphy, as determined by the late quaternary history of a site.

Description: Towards a representation of priming on soil carbon decomposition in the global land biosphere model ORCHIDEE (version 1.9.5.2) Geoscientific Model Development Discussions, 8, 9193-9227, 2015 Author(s): B. Guenet, F. E. Moyano, P. Peylin, P. Ciais, and I. A. Janssens Priming of soil carbon decomposition encompasses different processes through which the decomposition of native (already present) soil organic matter is amplified through the addition of new organic matter, with new inputs typically being more labile than the native soil organic matter. Evidence for priming comes from laboratory and field experiments, but to date there is no estimate of its impact at global scale and under the current anthropogenic perturbation of the carbon cycle. Current soil carbon decomposition models do not include priming mechanisms, thereby introducing uncertainty when extrapolating short-term local observations to ecosystem and regional to global scale. In this study we present a simple conceptual model of decomposition priming, called PRIM, able to reproduce laboratory (incubation) and field (litter manipulation) priming experiments. Parameters for this model were first optimized against data from 20 soil incubation experiments using a Bayesian framework. The optimized parameter values were evaluated against another set of soil incubation data independent from the ones used for calibration and the PRIM model reproduced the soil incubations data better than the original, CENTURY-type soil decomposition model, whose decomposition equations are based only on first order kinetics. We then compared the PRIM model and the standard first order decay model incorporated into the global land biosphere model ORCHIDEE. A test of both models was performed at ecosystem scale using litter manipulation experiments from 5 sites. Although both versions were equally able to reproduce observed decay rates of litter, only ORCHIDEE-PRIM could simulate the observed priming ( R 2 = 0.54) in cases where litter was added or removed. This result suggests that a conceptually simple and numerically tractable representation of priming adapted to global models is able to capture the sign and magnitude of the priming of litter and soil organic matter.

Description: Treatment of non-ideality in the multiphase model SPACCIM – Part 1: Model development Geoscientific Model Development Discussions, 8, 4155-4219, 2015 Author(s): A. J. Rusumdar, R. Wolke, A. Tilgner, and H. Herrmann Ambient tropospheric deliquesced particles generally comprise a complex mixture of electrolytes, organic compounds, and water. Dynamic modeling of physical and chemical processes in this complex matrix is challenging. Thus, up-to-date multiphase chemistry models do generally not consider non-ideal solution effects. Therefore, the present study was aimed at the further development of the SPACCIM model to treat both complex multiphase chemistry and phase transfer processes considering newly non-ideality properties of concentrated aerosol solutions. The present paper describes firstly, the performed model development including (i) the kinetic implementation of the non-ideality in the SPACCIM framework, (ii) the advancements in the coupling scheme of microphysics and multiphase chemistry and (iii) the required adjustments of the numerical schemes, especially in the sparse linear solver and the calculation of the Jacobian. Secondly, results of performed sensitivity investigations are outlined aiming at the evaluation of different activity coefficient modules and the examination of the contributions of different intermolecular forces to the overall activity coefficients. Finally, first results obtained with the new model framework are presented. The main product of the performed model development is the new kinetic model approach SPACCIM-SpactMod, which utilizes activities in reaction terms instead of aqueous concentrations. Based on an intercomparison of different activity coefficient models and the comparison with experimental data, AIOMFAC was selected as base model and extended by additional interaction parameters from literature for mixed organic–inorganic systems. Moreover, the performance and the capability of the applied activity coefficient module were evaluated by means of water activity measurements, literature data and results of other thermodynamic equilibrium models. Comprehensive comparison studies showed that the SpactMod (SPACCIM activity coefficient module) is valuable to predict the thermodynamic behavior of complex mixtures of multicomponent atmospheric aerosol particles. First simulations with a detailed chemical mechanism have demonstrated the applicability of SPACCIM-SpactMod. The simulations have implied that the treatment of non-ideality should be mandatory for modeling multiphase chemistry processes in deliquesced particles. The modeled activity coefficients implicate that turnovers of chemical processes in deliquesced particles can be both decreased and increased depending on the particular species involved in the reactions. For key ions, activity coefficients on the order of 0.1–0.8 and a strong dependency on the charge state as well as the RH conditions are modeled implicating a lowered chemical ion processing in concentrated solutions. In contrast, modeled activity coefficients of organic compounds are partly 〉 1 and suggest the possibility of an increased organic processing. Moreover, the model runs have shown noticeable differences in the pH values calculated with and without consideration of non-ideality. On average, the predicted pH values of the simulations considering non-ideality are −0.27 and −0.44 pH units lower under 90 and 70% RH conditions, respectively. More comprehensive results of detailed SPACCIM-SpactMod studies on the multiphase processing in organic–inorganic mixtures of deliquesced particles are described in a companion paper.

Description: Integration of nitrogen dynamics into the Noah-MP land model v1.1 for climate and environmental predictions Geoscientific Model Development Discussions, 8, 4113-4153, 2015 Author(s): X. Cai, Z.-L. Yang, J. B. Fisher, X. Zhang, M. Barlage, and F. Chen Climate and terrestrial biosphere models consider nitrogen an important factor in limiting plant carbon uptake, while operational environmental models view nitrogen as the leading pollutant causing eutrophication in water bodies. The community Noah land surface model with multi-parameterization options (Noah-MP) is unique in that it is the next generation land surface model for the Weather Research and Forecasting meteorological model and for the operational weather/climate models in the National Centers for Environmental Prediction. In this study, we add capability to Noah-MP to simulate nitrogen dynamics by coupling the Fixation and Uptake of Nitrogen (FUN) plant model and the Soil and Water Assessment Tool (SWAT) soil nitrogen dynamics. This incorporates FUN's state-of-the-art concept of carbon cost theory and SWAT's strength in representing the impacts of agricultural management on the nitrogen cycle. Parameterizations for direct root and mycorrhizal-associated nitrogen uptake, leaf retranslocation, and symbiotic biological nitrogen fixation are employed from FUN, while parameterizations for nitrogen mineralization, nitrification, immobilization, volatilization, atmospheric deposition, and leaching are based on SWAT. The coupled model is then evaluated at the Kellogg Biological Station – a Long-term Ecological Research site within the U.S. Corn Belt. Results show that the model performs well in capturing the major nitrogen state/flux variables (e.g., soil nitrate and nitrate leaching). Furthermore, the addition of nitrogen dynamics improves the modeling of the carbon and water cycles (e.g., net primary productivity and evapotranspiration). The model improvement is expected to advance the capability of Noah-MP to simultaneously predict weather and water quality in fully coupled Earth system models.

Description: Improved simulation of precipitation in the tropics using a modified BMJ scheme in WRF model Geoscientific Model Development Discussions, 8, 4019-4049, 2015 Author(s): R. Fonseca, T. Zhang, and T. Y. Koh The successful modelling of the observed precipitation, a very important variable for a wide range of climate applications, continues to be one of the major challenges that climate scientists face today. When the Weather Research and Forecasting (WRF) model is used to dynamically downscale the Climate Forecast System Reanalysis (CFSR) over the Indo-Pacific region, with analysis (grid-point) nudging, it is found that the cumulus scheme used, Betts–Miller–Janjić (BMJ), produces excessive rainfall suggesting that it has to be modified for this region. Experimentation has shown that the cumulus precipitation is not very sensitive to changes in the cloud efficiency but varies greatly in response to modifications of the temperature and humidity reference profiles. A new version of the scheme, denominated "modified BMJ" scheme, where the humidity reference profile is more moist, was developed and in tropical belt simulations it was found to give a better estimate of the observed precipitation, as given by the Tropical Rainfall Measuring Mission (TRMM) 3B42 dataset, than the default BMJ scheme for the whole tropics and both monsoon seasons. In fact, in some regions the model even outperforms CFSR. The advantage of modifying the BMJ scheme to produce better rainfall estimates lies in the final dynamical consistency of the rainfall with other dynamical and thermodynamical variables of the atmosphere.

Description: S 4 CAST v2.0: sea surface temperature based statistical seasonal forecast model Geoscientific Model Development Discussions, 8, 3971-4018, 2015 Author(s): R. Suárez-Moreno and B. Rodríguez-Fonseca Sea Surface Temperature is the key variable when tackling seasonal to decadal climate forecast. Dynamical models are unable to properly reproduce tropical climate variability, introducing biases that prevent a skillful predictability. Statistical methodologies emerge as an alternative to improve the predictability and reduce these biases. Recent studies have put forward the non-stationary behavior of the teleconnections between tropical oceans, showing how the same tropical mode has different impacts depending on the considered sequence of decades. To improve the predictability, the Sea Surface Temperature based Statistical Seasonal foreCAST model (S 4 CAST) introduces the novelty of considering the non-stationary links between the predictor and predictand fields. This paper describes the development of S 4 CAST model whose operation is focused on the study of the predictability of any variable related to sea surface temperature. An application focused on West African rainfall predictability has been implemented as a benchmark example.

Description: A new test statistic for climate models that includes field and spatial dependencies using Gaussian Markov random fields Alvaro Nosedal-Sanchez, Charles S. Jackson, and Gabriel Huerta Geosci. Model Dev., 9, 2407-2414, doi:10.5194/gmd-9-2407-2016, 2016 We have developed a new metric for climate model evaluation that quantifies the significance of modeling errors across multiple fields. Our approach dramatically reduces the amount of data that is required to evaluate field and space dependencies and increases the community's potential to make use of the extremely valuable but limited satellite observational record. Our objective is to improve the strategies that currently exist for more formal data-driven model development.

Description: Exploring global surface temperature pattern scaling methodologies and assumptions from a CMIP5 model ensemble Cary Lynch, Corinne Hartin, Ben Bond-Lamberty, and Ben Kravitz Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-170,2016 Manuscript under review for GMD (discussion: open, 0 comments) Pattern scaling is used to explore uncertainty in future forcing scenarios and assess local climate sensitivity to global temperature change. This paper examines the two dominant pattern scaling methods using a multi-model ensemble with two future socio-economic storylines. We find that high latitudes show the strongest sensitivity to global temperature change and that the simple least squared regression approach to generation of patterns is a better fit to projected global temperature.

Description: Evaluation of NorESM-OC (versions 1 and 1.2), the ocean carbon-cycle stand-alone configuration of the Norwegian Earth System Model (NorESM1) Jörg Schwinger, Nadine Goris, Jerry F. Tjiputra, Iris Kriest, Mats Bentsen, Ingo Bethke, Mehmet Ilicak, Karen M. Assmann, and Christoph Heinze Geosci. Model Dev., 9, 2589-2622, doi:10.5194/gmd-9-2589-2016, 2016 We present an evaluation of the ocean carbon cycle stand-alone configuration of the Norwegian Earth System Model. A re-tuning of the ecosystem parameterisation improves surface tracer fields between versions 1 and 1.2 of the model. Focus is placed on the evaluation of newly implemented parameterisations of the biological carbon pump (i.e. the sinking of particular organic carbon). We find that the model previously underestimated the carbon transport into the deep ocean below 2000 m depth.

Description: Global 7-km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIP-G7): Experimental design and preliminary results Masuo Nakano, Akiyoshi Wada, Masahiro Sawada, Hiromasa Yoshimura, Ryo Onishi, Shintaro Kawahara, Wataru Sasaki, Tomoe Nasuno, Munehiko Yamaguchi, Takeshi Iriguchi, Masato Sugi, and Yoshiaki Takeuchi Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-184,2016 Manuscript under review for GMD (discussion: open, 0 comments) Recent advances in high-performance computers facilitate operational numerical weather prediction by global hydrostatic atmospheric models with horizontal resolution ~ 10 km. Given further advances in such computers and the fact that the hydrostatic balance approximation becomes invalid for spatial scales

Description: A sub-grid model for improving the spatial resolution of air quality modelling at a European scale Mark R. Theobald, David Simpson, and Massimo Vieno Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-160,2016 Manuscript under review for GMD (discussion: open, 0 comments) Impacts of air pollution at a continental scale estimated using air quality models can potentially be greatly under- or overestimated due to the low spatial resolution used (grid cells of 10–50 km). We present a method to estimate the spatial variations in air quality within a model grid cell by combining high resolution emission data with estimates of short range dispersion. This simple but robust technique has the potential to improve estimates of air quality impacts at a continental scale.

Description: Evaluating statistical consistency in the ocean model component of the Community Earth System Model (pyCECT v2.0) Allison H. Baker, Yong Hu, Dorit M. Hammerling, Yu-heng Tseng, Haiying Xu, Xiaomeng Huang, Frank O. Bryan, and Guangwen Yang Geosci. Model Dev., 9, 2391-2406, doi:10.5194/gmd-9-2391-2016, 2016 Software quality assurance is critical to detecting errors in large, complex climate simulation codes. We focus on ocean model simulation data in the context of an ensemble-based statistical consistency testing approach developed for atmospheric data. Because ocean and atmosphere models have differing characteristics, we develop a new statistical tool to evaluate ocean model simulation data that provide a simple, subjective, and systematic way to detect errors and instil model confidence.

Description: AerChemMIP: Quantifying the effects of chemistry and aerosols in CMIP6 William J. Collins, Jean-François Lamarque, Michael Schulz, Olivier Boucher, Veronika Eyring, Michaela I. Hegglin, Amanda Maycock, Gunnar Myhre, Michael Prather, Drew Shindell, and Steven J. Smith Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-139,2016 Manuscript under review for GMD (discussion: open, 0 comments) We have designed a set of climate model experiments called the "Aerosol Chemistry Model Intercomparison Project" (AerChemMIP). These are designed to quantify the climate and air quality impacts of aerosols and chemically-reactive gases in the climate models that are used to simulate past and future climate. We hope that many climate modelling centres will choose to run these experiments to help understand the contribution of aerosols and chemistry to climate change.

Description: Biogeochemical protocols and diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP) James C. Orr, Raymond G. Najjar, Olivier Aumount, 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. Discuss., doi:10.5194/gmd-2016-155,2016 Manuscript under review for GMD (discussion: open, 0 comments) 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 CO 2 and related gases, and chemical tracers used to evaluate modeled circulation.

Description: The new implementation of a computationally efficient modeling tool (STOPS v1.5) into CMAQ v5.0.2 and its application for a more accurate prediction of Asian dust Wonbae Jeon, Yunsoo Choi, Peter Percell, Amir Hossein Souri, Chang-Keun Song, Soon-Tae Kim, and Jhoon Kim Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-180,2016 Manuscript under review for GMD (discussion: open, 0 comments) This study suggests a new hybrid Lagrangian-Eulerian modeling tool (the Screening Trajectory Ozone Prediction System, STOPS) for a more accurate prediction of Asian dust event. The STOPS is a moving nest (Lagrangian approach) between the source and the receptor inside Eulerian model. We run STOPS, instead of running time-consuming Eulerian model, using constrained PM concentration from remote sensing aerosol optical depth, reflecting real-time dust particles. The STOPS is for unexpected events.

Description: Quantitative evaluation of numerical integration schemes for Lagrangian particle dispersion models Huda Mohd. Ramli and J. Gavin Esler Geosci. Model Dev., 9, 2441-2457, doi:10.5194/gmd-9-2441-2016, 2016 A rigorous methodology is presented to assess numerical integration schemes for stochastic models in atmospheric dispersion known as Lagrangian particle dispersion models. A series of one-dimensional test problems modelling dispersion in the atmospheric boundary layer is used to evaluate commonly used stochastic integration schemes. The results allow for optimal time-step selection for each scheme and recommendations to be made for use in operational models.

Description: Experimental design for three interrelated marine ice sheet and ocean model intercomparison projects: MISMIP v. 3 (MISMIP +), ISOMIP v. 2 (ISOMIP +) and MISOMIP v. 1 (MISOMIP1) Xylar S. Asay-Davis, Stephen L. Cornford, Gaël Durand, Benjamin K. Galton-Fenzi, Rupert M. Gladstone, G. Hilmar Gudmundsson, Tore Hattermann, David M. Holland, Denise Holland, Paul R. Holland, Daniel F. Martin, Pierre Mathiot, Frank Pattyn, and Hélène Seroussi Geosci. Model Dev., 9, 2471-2497, doi:10.5880/PIK.2016.002, 2016 Coupled ice sheet–ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of ice sheets and glaciers, including assessing their contributions to sea level change. Here we describe the idealized experiments that make up three interrelated Model Intercomparison Projects (MIPs) for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities.

Description: High-resolution land surface fluxes from satellite and reanalysis data (HOLAPS v1.0): evaluation and uncertainty assessment Alexander Loew, Jian Peng, and Michael Borsche Geosci. Model Dev., 9, 2499-2532, doi:10.5194/gmd-9-2499-2016, 2016 Surface water and energy fluxes are essential components of the Earth system. The present paper introduces a new framework for the estimation of surface energy and water fluxes at the land surface, which allows for temporally and spatially high resolved flux estimates at the global scale. The framework maximizes the usage of existing long-term satellite data records. Overall the results indicate very good agreement with in situ observations when compared against 49 FLUXNET stations worldwide.

Description: A diagram for evaluating multiple aspects of model performance in simulating vector fields Zhongfeng Xu, Zhaolu Hou, Ying Han, and Weidong Guo Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-172,2016 Manuscript under review for GMD (discussion: open, 0 comments) The paper devises a new diagram, termed vector field evaluation (VFE) diagram, which is very similar to Taylor diagram but to provide a concise evaluation of model performance in simulating vector fields. The diagram can measure how well of two vector fields match each other in terms of three statistical variables. The VFE diagram is a generalized Taylor diagram, which can be applied to multi-dimensional variables (e.g. vector winds, pressure gradient) evaluation.

Description: Implementation of street trees in solar radiative exchange parameterization of TEB in SURFEX v8.0 Emilie Redon, Aude Lemonsu, Valéry Masson, Benjamin Morille, and Marjorie Musy Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-157,2016 Manuscript under review for GMD (discussion: open, 0 comments) In order to assess the potential of cooling of urban vegetation in cities we need to refine some processes in the microclimate models running on cities as the TEB model. The shading effects of trees on roads, low vegetation (grass) or walls are key processes impacting both air and surfaces temperatures in the streets by reducing them and improving the thermal comfort of inhabitants. They have been implemented into the TEB model and simulations have been evaluated by a fine scale model, SOLENE.

Description: Simple Plumes: A parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for climate studies Bjorn Stevens, Stephanie Fiedler, Stefan Kinne, Karsten Peters, Sebastian Rast, Jobst Müsse, Steven J. Smith, and Thorsten Mauritsen Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-189,2016 Manuscript under review for GMD (discussion: open, 0 comments) A simple analytic description of aerosol optical properties and their main effects on clouds is developed and described. The analytic description is easy to use and easy to modify and should aid experimentation to help understand how aerosol radiative and cloud interactions effect climate and circulation. The climatology is recommended for adoption by models participating in the sixth phase of the coupled model intercomparision project.

Description: Development of a new gas flaring emission data set for southern West Africa Konrad Deetz and Bernhard Vogel Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-110,2016 Manuscript under review for GMD (discussion: open, 0 comments) A new gas flaring emission parameterization has been developed which combines remote sensing observations with combustion equations. This parameterization can easily be applied to different research domains and allows the creation of a flaring emission dataset (e.g. for chemistry models). This research is part of the project DACCIWA (Dynamics-aerosol-cloud interactions in West Africa) in which among other sources of air pollution also the gas flaring plays an important role.

Description: Air quality modelling in the Berlin-Brandenburg region using WRF-Chem v3.7.1: sensitivity to resolution of model grid and input data Friderike Kuik, Axel Lauer, Galina Churkina, Hugo A. C. Denier van der Gon, Daniel Fenner, Kathleen A. Mar, and Tim M. Butler Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-190,2016 Manuscript under review for GMD (discussion: open, 0 comments) Air pollution is the number one environmental cause of premature deaths in Europe. Despite extensive regulations, air pollution remains a challenge, especially in urban areas. For studying summertime air quality in the Berlin-Brandenburg region of Germany, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) is set up and evaluated against meteorological and air quality observations from monitoring stations as well as from a field campaign conducted in 2014. The objective is to assess which resolution and level of detail in the input data is needed for simulating urban background air pollutant concentrations and their spatial distribution in the Berlin-Brandenburg area. The model setup includes three nested domains with horizontal resolutions of 15 km, 3 km, and 1 km and anthropogenic emissions from the TNO-MACC III inventory. We use RADM2 chemistry and the MADE/SORGAM aerosol scheme. Three sensitivity simulations are conducted updating input parameters to the single-layer urban canopy model based on structural data for Berlin, specifying land use classes on a sub-grid scale (mosaic option) and downscaling the original emissions to a resolution of ca. 1 km × 1 km for Berlin based on proxy data including traffic density and population density. The results show that the model simulates meteorology well, though urban 2 m temperature and urban wind speeds are biased high and nighttime mixing layer height is biased low in the base run. We show that the simulation of urban meteorology can be improved when specifying the input parameters to the urban model, and to a lesser extent when using the mosaic option. On average, ozone is simulated reasonably well, but maximum daily eight hour mean concentrations are underestimated, which is consistent with the results from previous modelling studies using the RADM2 chemical mechanism. Particulate matter is underestimated, which is partly due to an underestimation of secondary organic aerosols. NO x (= NO + NO 2 ) concentrations are simulated reasonably well on average, but nighttime concentrations are overestimated due to the model's underestimation of the mixing layer height, and urban daytime concentrations are underestimated. The daytime underestimation is improved when using downscaled, and thus locally higher emissions, suggesting that part of this bias is due to deficiencies in the emission input data and their resolution. The results further demonstrate that a horizontal resolution of 3 km improves the results and spatial representativeness of the model compared to a horizontal resolution of 15 km. With the input data (land use classes, emissions) at the level of detail of the base run of this study we find that a horizontal resolution of 1 km does not improve the results compared to a resolution of 3 km. However, our results suggest that a 1 km horizontal model resolution could enable a detailed simulation of local pollution patterns in the Berlin-Brandenburg region if the urban land use classes together with the respective input parameters to the urban canopy model are specified with a higher level of detail and if urban emissions of higher spatial resolution are used.

Description: Historical greenhouse gas concentrations Malte Meinshausen, Elisabeth Vogel, Alexander Nauels, Katja Lorbacher, Nicolai Meinshausen, David Etheridge, Paul Fraser, Stephen A. Montzka, Peter Rayner, Cathy Trudinger, Paul Krummel, Urs Beyerle, Josep G. Cannadell, John S. Daniel, Ian Enting, Rachel M. Law, Simon O'Doherty, Ron G. Prinn, Stefan Reimann, Mauro Rubino, Guus J. M. Velders, Martin K. Vollmer, and Ray Weiss Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-169,2016 Manuscript under review for GMD (discussion: open, 0 comments) Climate change is primarily driven by human-induced increases of greenhouse gas (GHG) concentrations. Based on ongoing community efforts in the AGAGE and NOAA measurement networks, 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 in their historical concentration-driven runs for the intercomparison project CMIP6. Global means, but also latitudinal and seasonal variations are provided.

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 Férnandez-Prieto, Hylke E. Beck, Wouter A. Dorigo, and Niko E. C. Verhoest Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-162,2016 Manuscript under review for GMD (discussion: open, 0 comments) Terrestrial evaporation is a key component of the hydrological cycle and reliable datasets of this variable are of major importance. The Global Land Evaporation Amsterdam Model (GLEAM, http://GLEAM.eu ) is a set of algorithms which estimates evaporation based on satellite observations. The 3rd version of GLEAM, presented in this study, includes an improved parameterization of different model components. As a result, the accuracy of the GLEAM datasets has been improved upon previous versions.

Description: Constraining the strength of the terrestrial CO 2 fertilization effect in the Canadian Earth system model version 4.2 (CanESM4.2) Vivek K. Arora and John F. Scinocca Geosci. Model Dev., 9, 2357-2376, doi:10.5194/gmd-9-2357-2016, 2016 This paper uses observed features of the global carbon cycle to constrain how much carbon the land should take up in an Earth system model in response to increasing fossil fuel CO 2 emissions since the start of the industrial era. These models are the only tool available to us for projecting future climate change. Despite their uncertainties, if current observations can be used to constrain models then more confidence can be places in models' future climate change projections.

Description: Northern Hemisphere storminess in the Norwegian Earth System Model (NorESM1-M) Erlend M. Knudsen and John E. Walsh Geosci. Model Dev., 9, 2335-2355, doi:10.5194/gmd-9-2335-2016, 2016 In this paper, two global climate models (NorESM1-M and CCSM4) are compared to an observational-based data set (ERA-Interim) for their ability to simulate historical Arctic storminess in autumn. With this in hand, the models are run through the 21st century. We find an overall significant increase in precipitation expected, with generally fewer and weaker storms in midlatitudes and partly more and stronger storms in high-latitudes. The tendencies are strongest in areas of Arctic sea ice retreat.

Description: A diagnostic interface for the ICOsahedral Non-hydrostatic (ICON) modelling framework based on the Modular Earth Submodel System (MESSy, 2.50) Bastian Kern and Patrick Jöckel Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-126,2016 Manuscript under review for GMD (discussion: open, 0 comments) Input and output of large data limit the performance of numerical models on supercomputers. We present an interface for the calculation of on-line diagnostics in a weather and climate model. These diagnostics are calculated on-line during the simulation instead of as subsequent post-processing. Depending on the diagnostic we can reduce the amount of model output.

Description: Evaluation of Monte Carlo tools for high energy atmospheric physics Casper Rutjes, David Sarria, Alexander Broberg Skeltved, Alejandro Luque, Gabriel Diniz, Nikolai Østgaard, and Ute Ebert Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-147,2016 Manuscript under review for GMD (discussion: open, 0 comments) High energy atmospheric physics includes Terrestrial Gamma-ray Flashes, electron-positron beams and gamma-ray glows from thunderstorms. It requires appropriate models for the interaction of energetic particles with the atmosphere. We benchmark general purpose and custom made codes against each other. We focus on basic tests, namely on the evolution of particles through air in the absence of electric and magnetic fields, providing a first benchmark for present and future custom made codes.

Description: A new radiation infrastructure for the Modular Earth Submodel System (MESSy, based on version 2.51) Simone Dietmüller, Patrick Jöckel, Holger Tost, Markus Kunze, Catrin Gellhorn, Sabine Brinkop, Christine Frömming, Michael Ponater, Benedikt Steil, Axel Lauer, and Johannes Hendricks Geosci. Model Dev., 9, 2209-2222, doi:10.5194/gmd-9-2209-2016, 2016 Four new radiation related submodels (RAD, AEROPT, CLOUDOPT, and ORBIT) are available within the MESSy framework now. They are largely based on the original radiation scheme of ECHAM5. RAD simulates radiative transfer, AEROPT calculates aerosol optical properties, CLOUDOPT calculates cloud optical properties, and ORBIT is responsible for Earth orbit calculations. Multiple diagnostic calls of the radiation routine are possible, so radiative forcing can be calculated during the model simulation.

Description: DeepMIP: experimental design for model simulations of the EECO, PETM, and pre-PETM Daniel J. Lunt, Matthew Huber, Michiel L. J. Baatsen, Rodrigo Caballero, Rob DeConto, Yannick Donnadieu, David Evans, Ran Feng, Gavin Foster, Ed Gasson, Anna S. von der Heydt, Chris J. Hollis, Sandy Kirtland Turner, Robert L. Korty, Reinhardt Kozdon, Srinath Krishnan, Jean-Baptiste Ladant, Petra Langebroek, Caroline H. Lear, Allegra N. LeGrande, Kate Littler, Paul Markwick, Bette Otto-Bliesner, Paul Pearson, Chris Poulsen, Ulrich Salzmann, Christine Shields, Kathryn Snell, Michael Starz, James Super, Clay Tabour, Jess Tierney, Gregory J. L. Tourte, Gary R. Upchurch, Bridget Wade, Scott L. Wing, Arne M. E. Winguth, Nicky Wright, James C. Zachos, and Richard Zeebe Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-127,2016 Manuscript under review for GMD (discussion: open, 0 comments) In this paper we describe the experimental design for a set of simulations which will be carried out by a range of climate models, all investigating the climate of the Eocene, about 50 million years ago. The intercomparison of model results is called "DeepMIP", and we anticipate that we will contribute to the next IPCC report through an analysis of these simulations and the geological data to which we will compare them.

Description: Microphysics parameterization sensitivity of the WRF Model version 3.1.7 to extreme precipitation: evaluation of the 1997 New Year’s flood of California Elcin Tan Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-94,2016 Manuscript under review for GMD (discussion: open, 0 comments) California is vulnerable to extreme precipitation, which occurs due to atmospheric rivers. This study is an attempt to evaluate the performance of the WRF Model for the extreme precipitation event that caused the 1997 New Year’s flood in California. The results show that the accuracy of the WRF Model is much higher for the 72-hr total basin-averaged evaluations than for the hourly and point-wise comparisons. The Thompson Scheme indicates more trustworthy results than others, with a 3.1 % error.

Description: Automatic delineation of geomorphological slope-units and their optimization for landslide susceptibility modelling Massimiliano Alvioli, Ivan Marchesini, Paola Reichenbach, Mauro Rossi, Francesca Ardizzone, Federica Fiorucci, and Fausto Guzzetti Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-118,2016 Manuscript under review for GMD (discussion: open, 0 comments) Slope-Unit are morphological mapping units bounded by drainage and divide lines that maximize within-unit homogeneity and between-unit heterogeneity. We present r.slopeunits , a software for the automatic delination of Slope-Units. We outline an objective procedure to optimize the software input parameters for Landslide Susceptibility (LS) zonation. Optimization is achieved maximizing an objective function that simultaneously evaluates terrain aspect segmentation quality and LS model performance.

Description: The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) contribution to CMIP6: Investigation of sea-level and ocean climate change in response to CO 2 forcing Jonathan M. Gregory, Nathaelle Bouttes-Mauhourat, Stephen M. Griffies, Helmuth Haak, William J. Hurlin, Johann Jungclaus, Maxwell Kelley, Warren G. Lee, John Marshall, Anastasia Romanou, Oleg A. Saenko, Detlef Stammer, and Michael Winton Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-122,2016 Manuscript under review for GMD (discussion: open, 0 comments) As a consequence of greenhouse gas emissions, changes in ocean temperature, salinity, circulation and sea-level are expected in coming decades. Among the models used for climate projections for the 21st century, there is a large spread in projections of these effects. The Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) aims to investigate and explain this spread by prescribing a common set of changes in the input of heat, water and windstress to the ocean in the participating models.

Description: The compact Earth system model OSCAR v2.2: description and first results Thomas Gasser, Philippe Ciais, Olivier Boucher, Yann Quilcaille, Maxime Tortora, Laurent Bopp, and Didier Hauglustaine Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-149,2016 Manuscript under review for GMD (discussion: open, 0 comments) Simple models of the Earth system are useful, especially because of their high computing efficiency. This work describes the OSCAR model: a new simple Earth system model calibrated on state-of-the-art complex models. It will add to the pool of the few simple models currently used by the community, and it will therefore improve the robustness of future studies. Its source code will be made publicly available upon final release of this description paper.

Description: mizuRoute version 1: a river network routing tool for a continental domain water resources applications Naoki Mizukami, Martyn P. Clark, Kevin Sampson, Bart Nijssen, Yixin Mao, Hilary McMillan, Roland J. Viger, Steve L. Markstrom, Lauren E. Hay, Ross Woods, Jeffrey R. Arnold, and Levi D. Brekke Geosci. Model Dev., 9, 2223-2238, doi:10.5194/gmd-9-2223-2016, 2016 mizuRoute version 1 is a stand-alone runoff routing tool that post-processes runoff outputs from any distributed hydrologic models to produce streamflow estimates in large-scale river network. mizuRoute is flexible to river network representation and includes two different river routing schemes. This paper demonstrates mizuRoute's capability of multi-decadal streamflow estimations in the river networks over the entire contiguous Unites States, which contains over 54 000 river segments.

Description: Climate SPHINX: evaluating the impact of resolution and stochastic physics parameterisations in climate simulations Paolo Davini, Jost von Hardenberg, Susanna Corti, Hannah M. Christensen, Stephan Juricke, Aneesh Subramanian, Peter A. G. Watson, Antje Weisheimer, and Tim N. Palmer Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-115,2016 Manuscript under review for GMD (discussion: open, 0 comments) The Climate SPHINX (Stochastic Physics HIgh resolutioN eXperiments) project is a comprehensive set of ensemble simulations aimed at evaluating the sensitivity of present and future climate to model resolution and stochastic parameterisation. The EC-Earth Earth-System Model is used to explore the impact of stochastic physics in a large ensemble of 30-year climate integrations at five different atmospheric horizontal resolutions (from 125 km up to 16 km). The project includes more than 120 simulations in both a historical scenario (1979–2008) and a climate change projection (2039–2068), together with coupled transient runs (1850–2100). A total of 20.4 million core hours have been used, made available from a single year grant from PRACE (the Partnership for Advanced Computing in Europe), and close to 1.5 PBytes of output data have been produced on SuperMUC IBM Petascale System at the Leibniz Supercomputing Center (LRZ) in Garching, Germany. About 140 TBytes of post-processed data are stored on the CINECA supercomputing center archives and are freely accessible to the community thanks to an EUDAT Data Pilot project. This paper presents the technical and scientific setup of the experiments, including the details on the forcing used for the simulations performed, defining the SPHINX v1.0 protocol. In addition, an overview of preliminary results is given: an improvement in the simulation of Euro-Atlantic atmospheric blocking following resolution increases is observed. It is also shown that including stochastic parameterisation in the low resolution runs helps to improve some aspects of the tropical climate – specifically the Madden-Julian Oscillation and the tropical rainfall variability. These findings show the importance of representing the impact of small scale processes on the large scale climate variability either explicitly (with high resolution simulations) or stochastically (in low resolution simulations).

Description: Large ensemble modeling of the last deglacial retreat of the West Antarctic Ice Sheet: comparison of simple and advanced statistical techniques David Pollard, Won Chang, Murali Haran, Patrick Applegate, and Robert DeConto Geosci. Model Dev., 9, 1697-1723, doi:10.5194/gmd-9-1697-2016, 2016 Computer modeling of variations of the Antarctic Ice Sheet help to understand the ice sheet's sensitivity to climate change. We apply a numerical model to its retreat over the last 20 000 years, from its maximum glacial extent to modern. An ensemble of 625 simulations is performed with systematic combinations of uncertain model parameter values. Results are analyzed using (1) simple averaging, and (2) advanced statistical techniques, and reasonable agreement is found between the two.

Description: The carbon cycle in the Australian Community Climate and Earth System Simulator (ACCESS-ESM1). 2. Historical simulations Tilo Ziehn, Andrew Lenton, Rachel M. Law, Richard J. Matear, and Matthew A. Chamberlain Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-14,2016 Manuscript under review for GMD (discussion: open, 0 comments) Our work presents the evaluation of the Australian Community Climate and Earth System Simulator (ACCESS-ESM1) over the historical period (1850–2005). The main focus is on climate and carbon related variables. Globally integrated land-atmosphere and ocean-atmosphere fluxes and flux patterns are well reproduced and show good agreement with most recent observations. This makes ACCESS-ESM1 a useful tool to explore the change in land and oceanic carbon uptake in the future.

Description: ESMValTool (v1.0) – a community diagnostic and performance metrics tool for routine evaluation of Earth system models in CMIP Veronika Eyring, Mattia Righi, Axel Lauer, Martin Evaldsson, Sabrina Wenzel, Colin Jones, Alessandro Anav, Oliver Andrews, Irene Cionni, Edouard L. Davin, Clara Deser, Carsten Ehbrecht, Pierre Friedlingstein, Peter Gleckler, Klaus-Dirk Gottschaldt, Stefan Hagemann, Martin Juckes, Stephan Kindermann, John Krasting, Dominik Kunert, Richard Levine, Alexander Loew, Jarmo Mäkelä, Gill Martin, Erik Mason, Adam S. Phillips, Simon Read, Catherine Rio, Romain Roehrig, Daniel Senftleben, Andreas Sterl, Lambertus H. van Ulft, Jeremy Walton, Shiyu Wang, and Keith D. Williams Geosci. Model Dev., 9, 1747-1802, doi:10.5194/gmd-9-1747-2016, 2016 A community diagnostics and performance metrics tool for the evaluation of Earth system models (ESMs) in CMIP has been developed that allows for routine comparison of single or multiple models, either against predecessor versions or against observations.

Description: Ice Sheet Model Intercomparison Project (ISMIP6) contribution to CMIP6 Sophie M. J. Nowicki, Tony Payne, Eric Larour, Helene Seroussi, Heiko Goelzer, William Lipscomb, Jonathan Gregory, Ayako Abe-Ouchi, and Andrew Shepherd Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-105,2016 Manuscript under review for GMD (discussion: open, 0 comments) This paper describes an experimental protocol designed to quantify and understand the global sea level that arises due to past, present and future changes in the Greenland and Antarctic ice sheets, along with investigating ice sheet–climate feedbacks. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) protocol includes targeted experiments, and a set of output diagnostic related to ice sheets, that are part of the 6th phase of the Coupled Model Intercomparison Project (CMIP6).

Description: Inconsistent strategies to spin up models in CMIP5: implications for ocean biogeochemical model performance assessment Roland Séférian, Marion Gehlen, Laurent Bopp, Laure Resplandy, James C. Orr, Olivier Marti, John P. Dunne, James R. Christian, Scott C. Doney, Tatiana Ilyina, Keith Lindsay, Paul R. Halloran, Christoph Heinze, Joachim Segschneider, Jerry Tjiputra, Olivier Aumont, and Anastasia Romanou Geosci. Model Dev., 9, 1827-1851, doi:10.5194/gmd-9-1827-2016, 2016 This paper explores how the large diversity in spin-up protocols used for ocean biogeochemistry in CMIP5 models contributed to inter-model differences in modeled fields. We show that a link between spin-up duration and skill-score metrics emerges from both individual IPSL-CM5A-LR's results and an ensemble of CMIP5 models. Our study suggests that differences in spin-up protocols constitute a source of inter-model uncertainty which would require more attention in future intercomparison exercises.

Description: Coupling aerosol optics to the MATCH (v5.5.0) chemical transport model and the SALSA (v1) aerosol microphysics module Emma Andersson and Michael Kahnert Geosci. Model Dev., 9, 1803-1826, doi:10.5194/gmd-9-1803-2016, 2016 Modelling aerosol optical properties is a notoriously difficult task due to the particles' complex morphologies and compositions. Yet aerosol particles and their optical properties are important for chemistry-climate modelling and remote sensing applications. In this study we aim to find answers to whether or not a detailed description of aerosol particles gives a significant impact on modelled radiative properties.

Description: The Cloud Feedback Model Intercomparison Project (CFMIP) contribution to CMIP6 Mark J. Webb, Timothy Andrews, Alejandro Bodas-Salcedo, Sandrine Bony, Christopher S. Bretherton, Robin Chadwick, Hélène Chepfer, Hervé Douville, Peter Good, Jennifer E. Kay, Stephen A. Klein, Roger Marchand, Brian Medeiros, A. Pier Siebesma, Christopher B. Skinner, Bjorn Stevens, George Tselioudis, Yoko Tsushima, and Masahiro Watanabe Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-70,2016 Manuscript under review for GMD (discussion: open, 0 comments) The Cloud Feedback Model Intercomparison Project (CFMIP) aims to inform future climate change assessments by improving the understanding and evaluation of cloud-climate feedback mechanisms and regional changes in atmospheric circulation and precipitation. CFMIP is supporting ongoing model inter-comparison activities by coordinating a hierarchy of targeted experiments with a set of cloud related output diagnostics as part of the 6th phase of the Coupled Model Intercomparison Project (CMIP6).

Description: The weather@home regional climate modelling project for Australia and New Zealand Mitchell T. Black, David J. Karoly, Suzanne M. Rosier, Sam M. Dean, Andrew D. King, Neil R. Massey, Sarah N. Sparrow, Andy Bowery, David Wallom, Richard G. Jones, Friederike E. L. Otto, and Myles R. Allen Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-100,2016 Manuscript under review for GMD (discussion: open, 0 comments) This study presents a citizen science computing project, known as weather@home Australia-New Zealand, which runs climate models on thousands of home computers. By harnessing the power of volunteers' computers, this project is capable of simulating extreme weather events over Australia and New Zealand under different climate scenarios.

Description: Multi-sensor cloud and aerosol retrieval simulator and remote sensing from model parameters – Part 2: Aerosols Galina Wind, Arlindo M. da Silva, Peter M. Norris, Steven Platnick, Shana Mattoo, and Robert C. Levy Geosci. Model Dev., 9, 2377-2389, doi:10.5194/gmd-9-2377-2016, 2016 The MCARS code creates sensor radiances using model-generated atmospheric columns and actual sensor and solar geometry. MCARS output looks like real data, so it is usable by any code that reads MODIS data. MCARS output can be used to test remote-sensing retrieval algorithms. Users know what went into creating the radiance: atmosphere, surface, clouds, and aerosols. Models can use MCARS output to create new parameterizations of relations of atmospheric physical quantities and measured radiances.

Description: Application of the adjoint approach to optimise the initial conditions of a turbidity current Samuel D. Parkinson, Simon W. Funke, Jon Hill, Matthew D. Piggott, and Peter A. Allison Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-136,2016 Manuscript under review for GMD (discussion: open, 0 comments) Turbidity currents are one of the main drivers for sediment transport from the continental shelf to the deep ocean. The resulting sediment deposits can reach hundreds of kilometres into the ocean. Computer models that simulate turbidity currents and the resulting sediment deposit can help to understand their general behaviour. However, in order to recreate real-world scenarios, the challenge is to find the turbidity current parameters that reproduce the observations of sediment deposits. This paper demonstrates a solution to the inverse sediment transportation problem: for a known sedimentary deposit, the developed model reconstructs details about the turbidity current that produced these deposits. The reconstruction is constrained here by a shallow water sediment-laden density current model, which is discretised by the finite element method and an adaptive time-stepping scheme. The model is differentiated using the adjoint approach and an efficient gradient-based optimisation method is applied to identify turbidity parameters which minimise the misfit between modelled and observed field sediment deposits. The capabilities of this approach are demonstrated using measurements taken in the Miocene-age Marnoso Arenacea Formation (Italy). We find that whilst the model cannot match the deposit exactly due to limitations in the physical processes simulated, it provides valuable insights into the depositional processes and represents a significant advance in our toolset for interpreting turbidity current deposits.

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

Description: Calibrating a global three-dimensional biogeochemical ocean model (MOPS-1.0) Iris Kriest, Volkmar Sauerland, Samar Khatiwala, Anand Srivastav, and Andreas Oschlies Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-173,2016 Manuscript under review for GMD (discussion: open, 0 comments) Global biogeochemical ocean models are subject to a high level of parametric uncertainty. This may be of consequence for their skill with respect to accurately describing features of the present ocean, and their sensitivity to possible environmental changes. We present first results from a framework that combines an offline biogeochemical tracer transport model with an Estimation of Distribution Algorithm, calibrating six biogeochemical model parameters against observed oxygen and nutrients.

Description: Improved representation of plant functional types and physiology in the Joint UK Land Environment Simulator (JULES v4.2) using plant trait information Anna B. Harper, Peter M. Cox, Pierre Friedlingstein, Andy J. Wiltshire, Chris D. Jones, Stephen Sitch, Lina M. Mercado, Margriet Groenendijk, Eddy Robertson, Jens Kattge, Gerhard Bönisch, Owen K. Atkin, Michael Bahn, Johannes Cornelissen, Ülo Niinemets, Vladimir Onipchenko, Josep Peñuelas, Lourens Poorter, Peter B. Reich, Nadjeda A. Soudzilovskaia, and Peter van Bodegom Geosci. Model Dev., 9, 2415-2440, doi:10.5194/gmd-9-2415-2016, 2016 Dynamic global vegetation models (DGVMs) are used to predict the response of vegetation to climate change. We improved the representation of carbon uptake by ecosystems in a DGVM by including a wider range of trade-offs between nutrient allocation to photosynthetic capacity and leaf structure, based on observed plant traits from a worldwide data base. The improved model has higher rates of photosynthesis and net C uptake by plants, and more closely matches observations at site and global scales.

Description: A consistent prescription of stratospheric aerosol for both radiation and chemistry in the Community Earth System Model (CESM1) Ryan Reynolds Neely III, Andrew J. Conley, Francis Vitt, and Jean-François Lamarque Geosci. Model Dev., 9, 2459-2470, doi:10.5194/gmd-9-2459-2016, 2016 We describe an updated scheme for prescribing stratospheric aerosol in the Community Earth System Model (CESM1). The inadequate response of the CESM1 to large volcanic disturbances to the stratospheric aerosol layer (such as the 1991 Pinatubo eruption) in comparison to observations motivates the need for a new parameterization. Simulations utilizing the new scheme successfully reproduce the observed global mean and local stratospheric temperature response to the Pinatubo eruption.

Description: Evaluating Lossy Data Compression on Climate Simulation Data within a Large Ensemble Allison H. Baker, Dorit M. Hammerling, Sheri A. Mickleson, Haiying Xu, Martin B. Stolpe, Phillipe Naveau, Ben Sanderson, Imme Ebert-Uphoff, Savini Samarasinghe, Francesco De Simone, Francesco Carbone, Christian N. Gencarelli, John M. Dennis, Jennifer E. Kay, and Peter Lindstrom Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-146,2016 Manuscript under review for GMD (discussion: open, 0 comments) We apply lossy data compression to output from the Community Earth System Model Large Ensemble Community Project. We challenge climate scientists to examine features of the data relevant to their interests and identify which of the ensemble members have been compressed, and we perform direct comparisons on features critical to climate science. We find that applying lossy data compression to climate model data effectively reduces data volumes with minimal effect on scientific results.

Description: Numerical framework and performance of the new multiple-phase cloud microphysics scheme in RegCM4.5: precipitation, cloud microphysics, and cloud radiative effects Rita Nogherotto, Adrian Mark Tompkins, Graziano Giuliani, Erika Coppola, and Filippo Giorgi Geosci. Model Dev., 9, 2533-2547, doi:10.5194/gmd-9-2533-2016, 2016 The paper presents a new cloud scheme for regional climate model RegCM4.5. The new scheme treats microphysical processes occurring within stratiform clouds and with respect to the pre-existing scheme is able to allow a more physically realistic representation of cloud microphysics and distribution, improving the representation of the longwave and shortwave components of the cloud radiative forcing.

Description: Comparison of adjoint and nudging methods to initialise ice sheet model basal conditions Cyrille Mosbeux, Fabien Gillet-Chaulet, and Olivier Gagliardini Geosci. Model Dev., 9, 2549-2562, doi:10.5194/gmd-9-2549-2016, 2016 Model projections of ice sheet contribution to 21st century sea level rise are greatly affected by initial conditions. Solutions have been developed to infer the friction of the ice on its bedrock using observed surface velocities. A drawback of these methods is that remaining uncertainties, especially in the bedrock elevation, lead to non-physical ice flux divergence anomalies. Here, we compare two different solutions able to infer both bedrock friction and elevation with good performance.

Description: Transient climate simulations of the deglaciation 21–9 thousand years before present (version 1) – PMIP4 Core experiment design and boundary conditions Ruza F. Ivanovic, Lauren J. Gregoire, Masa Kageyama, Didier M. Roche, Paul J. Valdes, Andrea Burke, Rosemarie Drummond, W. Richard Peltier, and Lev Tarasov Geosci. Model Dev., 9, 2563-2587, doi:10.5194/gmd-9-2563-2016, 2016 This manuscript presents the experiment design for the PMIP4 Last Deglaciation Core experiment: a transient simulation of the last deglaciation, 21–9 ka. Specified model boundary conditions include time-varying orbital parameters, greenhouse gases, ice sheets, ice meltwater fluxes and other geographical changes (provided for 26–0 ka). The context of the experiment and the choices for the boundary conditions are explained, along with the future direction of the working group.

Description: Finding the Goldilocks zone: Compression-error trade-off for large gridded datasets Jeremy D. Silver and Charles S. Zender Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-177,2016 Manuscript under review for GMD (discussion: open, 0 comments) Many modern scientific research projects generate large amounts of data. Storage space is valuable and may be limited, hence compression is vital. We tested different compression methods for large gridded datasets, assessing the space savings and the amount of precision lost. We found a general trade-off between precision and compression, and that the method that optimises this trade-off depends on the dataset. A method introduced here proved to be a competitive archive format for gridded data.

Description: PLUME-MoM 1.0: a new 1-D model of volcanic plumes based on the method of moments Geoscientific Model Development Discussions, 8, 3745-3790, 2015 Author(s): M. de' Michieli Vitturi, A. Neri, and S. Barsotti In this paper a new mathematical model for volcanic plumes, named PlumeMoM, is presented. The model describes the steady-state 1-D dynamics of the plume in a 3-D coordinate system, accounting for continuous variability in particle distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. Proper description of such a multiparticle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of properties of the continuous size-distribution of the particles. This is achieved by formulation of fundamental transport equations for the multiparticle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables investigation of the response of four key output variables (mean and standard deviation (SD) of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and SD) characterizing the pyroclastic mixture at the base of the plume. Results show that, for the range of parameters investigated, the grain-size distribution at the top of the plume is remarkably similar to that at the base and that the plume height is only weakly affected by the parameters of the grain distribution.

Description: ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation Geoscientific Model Development Discussions, 8, 3653-3743, 2015 Author(s): G. Forget, J.-M. Campin, P. Heimbach, C. N. Hill, R. M Ponte, and C. Wunsch This paper presents the ECCO v4 non-linear inverse modeling framework and its baseline solution for the evolving ocean state over the period 1992–2011. Both components are publicly available and highly integrated with the MITgcm. They are both subjected to regular, automated regression tests. The modeling framework includes sets of global conformal grids, a global model setup, implementations of model-data constraints and adjustable control parameters, an interface to algorithmic differentiation, as well as a grid-independent, fully capable Matlab toolbox. The reference ECCO v4 solution is a dynamically consistent ocean state estimate (ECCO-Production, release 1) without un-identified sources of heat and buoyancy, which any interested user will be able to reproduce accurately. The solution is an acceptable fit to most data and has been found physically plausible in many respects, as documented here and in related publications. Users are being provided with capabilities to assess model-data misfits for themselves. The synergy between modeling and data synthesis is asserted through the joint presentation of the modeling framework and the state estimate. In particular, the inverse estimate of parameterized physics was instrumental in improving the fit to the observed hydrography, and becomes an integral part of the ocean model setup available for general use. More generally, a first assessment of the relative importance of external, parametric and structural model errors is presented. Parametric and external model uncertainties appear to be of comparable importance and dominate over structural model uncertainty. The results generally underline the importance of including turbulent transport parameters in the inverse problem.

Description: An automatic and effective parameter optimization method for model tuning Geoscientific Model Development Discussions, 8, 3791-3822, 2015 Author(s): T. Zhang, L. Li, Y. Lin, W. Xue, F. Xie, H. Xu, and X. Huang Physical parameterizations in General Circulation Models (GCMs), having various uncertain parameters, greatly impact model performance and model climate sensitivity. Traditional manual and empirical tuning of these parameters is time consuming and ineffective. In this study, a "three-step" methodology is proposed to automatically and effectively obtain the optimum combination of some key parameters in cloud and convective parameterizations according to a comprehensive objective evaluation metrics. Different from the traditional optimization methods, two extra steps, one determines parameter sensitivity and the other chooses the optimum initial value of sensitive parameters, are introduced before the downhill simplex method to reduce the computational cost and improve the tuning performance. Atmospheric GCM simulation results show that the optimum combination of these parameters determined using this method is able to improve the model's overall performance by 9%. The proposed methodology and software framework can be easily applied to other GCMs to speed up the model development process, especially regarding unavoidable comprehensive parameters tuning during the model development stage.

Description: A new ensemble-based consistency test for the Community Earth System Model Geoscientific Model Development Discussions, 8, 3823-3859, 2015 Author(s): A. H. Baker, D. M. Hammerling, M. N. Levy, H. Xu, J. M. Dennis, B. E. Eaton, J. Edwards, C. Hannay, S. A. Mickelson, R. B. Neale, D. Nychka, J. Shollenberger, J. Tribbia, M. Vertenstein, and D. Williamson Climate simulations codes, such as the Community Earth System Model (CESM), are especially complex and continually evolving. Their on-going state of development requires frequent software verification in the form of quality assurance to both preserve the quality of the code and instill model confidence. To formalize and simplify this previously subjective and computationally-expensive aspect of the verification process, we have developed a new tool for evaluating climate consistency. Because an ensemble of simulations allows us to gauge the natural variability of the model's climate, our new tool uses an ensemble approach for consistency testing. In particular, an ensemble of CESM climate runs is created, from which we obtain a statistical distribution that can be used to determine whether a new climate run is statistically distinguishable from the original ensemble. The CESM Ensemble Consistency Test, referred to as CESM-ECT, is objective in nature and accessible to CESM developers and users. The tool has proven its utility in detecting errors in software and hardware environments and providing rapid feedback to model developers.

Description: A new sub-grid surface mass balance and flux model for continental-scale ice sheet modelling: validation and last glacial cycle Geoscientific Model Development Discussions, 8, 3037-3077, 2015 Author(s): K. Le Morzadec, L. Tarasov, M. Morlighem, and H. Seroussi To investigate ice sheet evolution over the time scale of a glacial cycle, 3-D ice sheet models (ISMs) need to be run at grid resolutions (10 to 50 km) that do not resolve individual mountains. This will introduce to-date unquantified errors in sub-grid (SG) transport, accumulation and ablation for regions of rough topography. In the past, synthetic hypsometric curves, a statistical summary of the topography, have been used in ISMs to describe the variability of these processes. However, there has yet to be detailed uncertainty analysis of this approach. We develop a new SG model using a 1 km resolution digital elevation model to compute each local hypsometric curve and to determine local parameters to represent the hypsometric levels' slopes and widths. 1-D mass-transport for the SG model is computed with the shallow ice approximation. We test this model against simulations produced by the 3-D Ice Sheet System Model (ISSM) run at 1 km grid resolution. Results show that no simple parameterization can totally capture SG surface mass balance and flux processes. Via glacial cycle ensemble results for North America, we quantify the impact of SG model coupling in an ISM and the associated parametric uncertainties related to the exchange of ice between the SG and coarse grid levels. Via glacial cycle ensemble results for North America, we quantify the impact of SG model coupling in an ISM. We show that SG process representation and associated parametric uncertainties, related to the exchange of ice between the SG and coarse grid levels, can have significant impact on modelled ice sheet evolution.

Description: Validation of reactive gases and aerosols in the MACC global analysis and forecast system Geoscientific Model Development Discussions, 8, 1117-1169, 2015 Author(s): H. Eskes, V. Huijnen, A. Arola, A. Benedictow, A.-M. Blechschmidt, E. Botek, O. Boucher, I. Bouarar, S. Chabrillat, E. Cuevas, R. Engelen, H. Flentje, A. Gaudel, J. Griesfeller, L. Jones, J. Kapsomenakis, E. Katragkou, S. Kinne, B. Langerock, M. Razinger, A. Richter, M. Schultz, M. Schulz, N. Sudarchikova, V. Thouret, M. Vrekoussis, A. Wagner, and C. Zerefos The European MACC (Monitoring Atmospheric Composition and Climate) project is preparing the operational Copernicus Atmosphere Monitoring Service (CAMS), one of the services of the European Copernicus Programme on Earth observation and environmental services. MACC uses data assimilation to combine in-situ and remote sensing observations with global and regional models of atmospheric reactive gases, aerosols and greenhouse gases, and is based on the Integrated Forecast System of the ECMWF. The global component of the MACC service has a dedicated validation activity to document the quality of the atmospheric composition products. In this paper we discuss the approach to validation that has been developed over the past three years. Topics discussed are the validation requirements, the operational aspects, the measurement data sets used, the structure of the validation reports, the models and assimilation systems validated, the procedure to introduce new upgrades, and the scoring methods. One specific target of the MACC system concerns forecasting special events with high pollution concentrations. Such events receive extra attention in the validation process. Finally, a summary is provided of the results from the validation of the latest set of daily global analysis and forecast products from the MACC system reported in November 2014.

Description: Taking off the training wheels: the properties of a dynamic vegetation model without climate envelopes Geoscientific Model Development Discussions, 8, 3293-3357, 2015 Author(s): R. A. Fisher, S. Muszala, M. Verteinstein, P. Lawrence, C. Xu, N. G. McDowell, R. G. Knox, C. Koven, J. Holm, B. M. Rogers, D. Lawrence, and G. Bonan We describe an implementation of the Ecosystem Demography (ED) concept in the Community Land Model. The structure of CLM(ED) and the physiological and structural modifications applied to the CLM are presented. A major motivation of this development is to allow the prediction of biome boundaries directly from plant physiological traits via their competitive interactions. Here we investigate the performance of the model for an example biome boundary in Eastern North America. We explore the sensitivity of the predicted biome boundaries and ecosystem properties to the variation of leaf properties determined by the parameter space defined by the GLOPNET global leaf trait database. Further, we investigate the impact of four sequential alterations to the structural assumptions in the model governing the relative carbon economy of deciduous and evergreen plants. The default assumption is that the costs and benefits of deciduous vs. evergreen leaf strategies, in terms of carbon assimilation and expenditure, can reproduce the geographical structure of biome boundaries and ecosystem functioning. We find some support for this assumption, but only under particular combinations of model traits and structural assumptions. Many questions remain regarding the preferred methods for deployment of plant trait information in land surface models. In some cases, plant traits might best be closely linked with each other, but we also find support for direct linkages to environmental conditions. We advocate for intensified study of the costs and benefits of plant life history strategies in different environments, and for the increased use of parametric and structural ensembles in the development and analysis of complex vegetation models.

Description: Revision of the convective transport module CVTRANS 2.4 in the EMAC atmospheric chemistry–climate model Geoscientific Model Development Discussions, 8, 3117-3145, 2015 Author(s): H. G. Ouwersloot, A. Pozzer, B. Steil, H. Tost, and J. Lelieveld The convective transport module, CVTRANS, of the ECHAM/MESSy Atmospheric Chemistry (EMAC) model has been revised to better represent the physical flows and incorporate recent findings on the properties of the convective plumes. The modifications involve (i) applying intermediate time stepping based on a settable criterion, (ii) using an analytic expression to account for the intra time step mixing ratio evolution below cloud base, and (iii) implementing a novel expression for the mixing ratios of atmospheric compounds at the base of an updraft. Even when averaged over a year, the predicted mixing ratios of atmospheric compounds are significantly affected by the intermediate time stepping. For example, for an exponentially decaying atmospheric tracer with a lifetime of 1 day, the zonal averages can locally differ by more than a factor of 6 and the induced root mean square deviation from the original code is, weighted by the air mass, higher than 40% of the average mixing ratio. The other modifications result in smaller differences. However, since they do not require additional computational time, their application is also recommended.

Description: Using field observations to inform thermal hydrology models of permafrost dynamics with ATS (v0.83) Geoscientific Model Development Discussions, 8, 3235-3292, 2015 Author(s): A. L. Atchley, S. L. Painter, D. R. Harp, E. T. Coon, C. J. Wilson, A. K. Liljedahl, and V. E. Romanovsky Climate change is profoundly transforming the carbon-rich Arctic tundra landscape, potentially moving it from a carbon sink to a carbon source by increasing the thickness of soil that thaws on a seasonal basis. However, the modeling capability and precise parameterizations of the physical characteristics needed to estimate projected active layer thickness (ALT) are limited in Earth System Models (ESMs). In particular, discrepancies in spatial scale between field measurements and Earth System Models challenge validation and parameterization of hydrothermal models. A recently developed surface/subsurface model for permafrost thermal hydrology, the Advanced Terrestrial Simulator (ATS), is used in combination with field measurements to calibrate and identify fine scale controls of ALT in ice wedge polygon tundra in Barrow, Alaska. An iterative model refinement procedure that cycles between borehole temperature and snow cover measurements and simulations functions to evaluate and parameterize different model processes necessary to simulate freeze/thaw processes and ALT formation. After model refinement and calibration, reasonable matches between simulated and measured soil temperatures are obtained, with the largest errors occurring during early summer above ice wedges (e.g. troughs). The results suggest that properly constructed and calibrated one-dimensional thermal hydrology models have the potential to provide reasonable representation of the subsurface thermal response and can be used to infer model input parameters and process representations. The models for soil thermal conductivity and snow distribution were found to be the most sensitive process representations. However, information on lateral flow and snowpack evolution might be needed to constrain model representations of surface hydrology and snow depth.

Description: An evaluation of current capabilities of modelling low-frequency climate variability Heikki Järvinen, Teija Seitola, Johan Silén, and Jouni Räisänen Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-61,2016 Manuscript under review for GMD (discussion: open, 0 comments) In this study we compare the inter-annual to multi-decadal climate variability modes in 12 climate model simulations and two reanalysis data sets using the randomised multi-channel singular spectrum analysis. The two reanalysis data sets are remarkably similar on all time scales, except for some differences on the decadal scale. None of the climate models closely reproduce all aspects of the reanalysis data sets, although some models represent many aspects well.

Description: The location of the thermodynamic atmosphere–ice interface in fully coupled models – a case study using JULES and CICE Alex E. West, Alison J. McLaren, Helene T. Hewitt, and Martin J. Best Geosci. Model Dev., 9, 1125-1141, doi:10.5194/gmd-9-1125-2016, 2016 This study compares two methods of coupling a sea ice model to an atmospheric model in a series of idealized one-dimensional experiments. The JULES method calculates surface variables in the atmosphere; the CICE method calculates surface variables in the sea ice. It is found that simulations of all variables are more accurate in the JULES method, likely because of the shorter time step of the atmosphere.

Description: Air quality modeling with WRF-Chem v3.5 in East Asia: sensitivity to emissions and evaluation of simulated air quality Min Zhong, Eri Saikawa, Yang Liu, Vaishali Naik, Larry W. Horowitz, Masayuki Takigawa, Yu Zhao, Neng-Huei Lin, and Elizabeth A. Stone Geosci. Model Dev., 9, 1201-1218, doi:10.5194/gmd-9-1201-2016, 2016 Large discrepancies exist among emission inventories (e.g., REAS and EDGAR) at the provincial level in China. We use WRF-Chem to evaluate the impact of the difference in existing emission inventories and find that emissions inputs significantly affect our air pollutant simulation results. Our study highlights the importance of constraining emissions at the provincial level for regional air quality modeling over East Asia.

Description: Implementation of a Marauding Insect Module (MIM, version 1.0) in the Integrated BIosphere Simulator (IBIS, version 2.6b4) dynamic vegetation–land surface model Jean-Sébastien Landry, David T. Price, Navin Ramankutty, Lael Parrott, and H. Damon Matthews Geosci. Model Dev., 9, 1243-1261, doi:10.5194/gmd-9-1243-2016, 2016 Insect-induced plant damage affects the land-atmosphere exchanges of carbon, energy, and water. We developed a module to quantify such effects in process-based models suitable for climate studies. The module can simulate damage from broadleaf defoliators, needleleaf defoliators, and bark beetles. When coupled to an existing terrestrial vegetation model, the module produced reasonable results for vegetation dynamics and land-atmosphere exchanges, from daily to centennial timescales.

Description: Discrete-Element bonded-particle Sea Ice model DESIgn, version 1.3a – model description and implementation Agnieszka Herman Geosci. Model Dev., 9, 1219-1241, doi:10.5194/gmd-9-1219-2016, 2016 Recent developments in observational and modeling techniques allow us to analyze sea ice with increasingly higher resolution. Instead of a continuous ice cover we observe a complex, constantly changing medium composed of interacting floes. Understanding these aspects of sea ice behavior requires new modeling methods, like the Discrete-Element Sea Ice model (DESIgn) in which sea ice is treated as an assemblage of grains that freeze together or break apart in response to wind and ocean currents.

Description: Overview of the Global Monsoons Model Inter-comparison Project (GMMIP) Tianjun Zhou, Andrew Turner, James Kinter, Bin Wang, Yun Qian, Xiaolong Chen, Bin Wang, Bo Liu, Bo Wu, and Liwei Zou Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-69,2016 Manuscript under review for GMD (discussion: open, 0 comments) This paper tells why to launch the Global Monsoons Model Inter-comparison Project (GMMIP) and how to achieve its scientific goals on monsoon variability. It addresses the scientific questions to be answered, describes three tiered experiments comprehensively and proposes a basic analysis framework to guide future research. It will help the monsoon research communities to understand the objectives of the GMMIP and the modelling groups involved in the GMMIP conduct the experiments successfully.

Description: Assimilating compact phase space retrievals of atmospheric composition with WRF-Chem/DART: a regional chemical transport/ensemble Kalman filter data assimilation system Arthur P. Mizzi, Avelino F. Arellano Jr., David P. Edwards, Jeffrey L. Anderson, and Gabriele G. Pfister Geosci. Model Dev., 9, 965-978, doi:10.5194/gmd-9-965-2016, 2016 This paper introduces (i) WRF-Chem/DART – a state-of-the-art chemical transport/data assimilation system, and (ii) compact phase space retrievals (CPSRs). WRF-Chem/DART is NCAR's regional chemical weather forecasting prototype. Such systems require assimilation of chemical composition observations, such as trace gas retrievals. Retrievals are expensive to assimilate. CPSRs reduce those assimilation costs (~ 35 % for MOPITT CO) without loss in forecast skill by removing redundant information.

Description: Addressing numerical challenges in introducing a reactive transport code into a land surface model: a biogeochemical modeling proof-of-concept with CLM–PFLOTRAN 1.0 Guoping Tang, Fengming Yuan, Gautam Bisht, Glenn E. Hammond, Peter C. Lichtner, Jitendra Kumar, Richard T. Mills, Xiaofeng Xu, Ben Andre, Forrest M. Hoffman, Scott L. Painter, and Peter E. Thornton Geosci. Model Dev., 9, 927-946, doi:10.5194/gmd-9-927-2016, 2016 We demonstrate that CLM-PFLOTRAN predictions are consistent with CLM4.5 for Arctic, temperate, and tropical sites. A tight relative tolerance may be needed to avoid false convergence when scaling, clipping, or log transformation is used to avoid negative concentration in implicit time stepping and Newton-Raphson methods. The log transformation method is accurate and robust while relaxing relative tolerance or using the clipping or scaling method can result in efficient solutions.

Description: Empirical Bayes approach to climate model calibration Charles S. Jackson and Gabriel Huerta Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-20,2016 Manuscript under review for GMD (discussion: open, 0 comments) Climate data is highly correlated which can make it difficult from a statistical perspective to quantify the significance of differences that arise between a model and observations. Here we explore a common device in Bayesian inference for assessing the statistical significance of a fit between a model and data and suggest how this approach may be applied to the calibration of a climate model.

Description: Couplerlib : a metadata-driven library for the integration of multiple models of higher and lower trophic level marine systems with inexact functional group matching Jonathan Beecham, Jorn Bruggeman, John Aldridge, and Steven Mackinson Geosci. Model Dev., 9, 947-964, doi:10.5194/gmd-9-947-2016, 2016 This paper is a description of how very different higher and lower trophic level models (Ecopath with Ecosim) and ERSEM, respectively, can be coupled together using a metadata coupling system together with a number of examples of short- and long-range projections for end to end modelling.

Description: The 1-way on-line coupled model system MECO(n) – Part 4: Chemical evaluation (based on MESSy v2.52) Mariano Mertens, Astrid Kerkweg, Patrick Jöckel, Holger Tost, and Christiane Hofmann Geosci. Model Dev. Discuss., doi:10.5194/gmd-2015-269,2016 Manuscript under review for GMD (discussion: open, 0 comments) This fourth part in a series of publications describing the newly developed regional chemistry-climate system MECO(n) is dedicated to the evaluation of MECO(n) with respect to tropospheric gas-phase chemistry. For this a simulation incorporating two regional instances, one over Europe with 50 km resolution and one over Germany with 12 km resolution, is conducted. The model results are compared with satellite-, ground-based- and aircraft in situ observations.

Description: Modeling the diurnal cycle of conserved and reactive species in the convective boundary layer using SOMCRUS Donald H. Lenschow, David Gurarie, and Edward G. Patton Geosci. Model Dev., 9, 979-996, doi:10.5194/gmd-9-979-2016, 2016 We have developed a one-dimensional second-order closure numerical model to study the vertical turbulent transport of trace reactive species in the convective (daytime) planetary boundary layer (CBL), which we call the Second-Order Model for Conserved and Reactive Unsteady Scalars (SOMCRUS). The temporal variation of the CBL depth is calculated using a simple mixed-layer model with a constant entrainment coefficient and zero-order discontinuity at the CBL top. We then calculate time-varying continuous profiles of mean concentrations and vertical turbulent fluxes, variances, and covariances of both conserved and chemically reactive scalars in a diurnally varying CBL. The set of reactive species is the O 3 –NO–NO 2 triad. The results for both conserved and reactive species are compared with large-eddy simulations (LES) for the same free-convection case using the same boundary and initial conditions. For the conserved species, we compare three cases with different combinations of surface fluxes, and CBL and free-troposphere concentrations. We find good agreement of SOMCRUS with LES for the mean concentrations and fluxes of both conserved and reactive species except near the CBL top, where SOMCRUS predicts a somewhat shallower depth, and has sharp transitions in both the mean and turbulence variables, in contrast to more smeared-out variations in the LES due to horizontal averaging. Furthermore, SOMCRUS generally underestimates the variances and species–species covariances. SOMCRUS predicts temperature–species covariances similar to LES near the surface, but much smaller magnitude peak values near the CBL top, and a change in sign of the covariances very near the CBL top, while the LES predicts a change in sign of the covariances in the lower half of the CBL. SOMCRUS is also able to estimate the intensity of segregation (the ratio of the species–species covariance to the product of their means), which can alter the rates of second-order chemical reactions; however, for the case considered here, this effect is small. The simplicity and extensibility of SOMCRUS means that it can be utilized for a broad range of turbulence-mixing scenarios and sets of chemical reactions in the planetary boundary layer; it therefore holds great promise as a tool to incorporate these processes within air quality and climate models.

Description: C-IFS-CB05-BASCOE: Stratospheric Chemistry in the Integrated Forecasting System of ECMWF Vincent Huijnen, Johannes Flemming, Simon Chabrillat, Quentin Errera, Yves Christophe, Anne-Marlene Blechschmidt, Andreas Richter, and Henk Eskes Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-40,2016 Manuscript under review for GMD (discussion: open, 0 comments) We present a model description and benchmark evaluation of an extension of the tropospheric chemistry module in the ECMWF Integrated Forecasting System (IFS) with stratospheric chemistry. The stratospheric chemistry originates from the one used in the Belgian Assimilation System for Chemical ObsErvations (BASCOE), and is here combined with the modified CB05 chemistry module for the troposphere as currently used operationally in the Copernicus Atmosphere Monitoring Service (CAMS).

Description: Open-source modular solutions for flexural isostasy: gFlex v1.0 A. D. Wickert Geosci. Model Dev., 9, 997-1017, doi:10.5194/gmd-9-997-2016, 2016 Earth's lithosphere bends beneath surface loads, such as ice, sediments, and mountain belts. The pattern of this bending, or flexural isostatic response, is a function of both the loads and the spatially variable strength of the lithosphere. gFlex is an easy-to-use program to calculate flexural isostastic response, and may be used to better understand how ice sheets, glaciers, large lakes, sedimentary basins, volcanoes, and other surface loads interact with the solid Earth.