8th GEWEX Science Conference: Extremes and Water on the Edge

May 6 - 11, 2018 | Canmore, Alberta, Canada

The program over the 6-day conference will cover topics related to the two WCRP Grand Challenges on “Extremes” and “Water for the Food Baskets of the World,” as well as the main themes of the GEWEX project. Sessions are divided between seven themes and are listed below.


  • Nexus of Water, Energy and Food
  • Climate Extremes
  • Extreme Weather
  • Atmospheric Modeling and Observations
  • Land Modeling and Observations
  • Mountain and High-Latitude Hydrology
  • Global Energy and Water Cycles


Co-conveners are listed in alphabetical order.

  1. Open Session on Water and Extremes Research
    Graeme Stephens, Sonia Seneviratne, and Peter van Oevelen

    Open Session
  2. Regional Hydroclimate Projects
    Philippe Drobinsky, Jason Evans, Brian Golding, Branka Ivancan-Picek, and Howard Wheater

    GEWEX Regional Hydroclimate Projects (RHPs) are generally large, regionally focused multidisciplinary projects that aim to improve the understanding and prediction of a particular region’s weather, climate and hydrology. All RHPs address the physical processes surrounding water and energy exchanges within a region, thus addressing the GEWEX Science Questions. Most RHPs are broader than this, often addressing questions related to the biosphere and carbon cycle, human interaction in the landscape, and even socio-economic factors. RHPs are globally unique in providing observatories to address a set of large-scale science challenges, which include land-atmosphere interactions, but also large basin scale hydrology and water management. This session will provide an overview of currently active RHPs, highlighting science advances and capability developments, identifying new large-scale science questions to be addressed, as well as proposing some new RHPs for discussion.
  3. Evapotranspiration Determination
    Helen Cleugh, Joan Cuxart, Pierre Gentine, and Jan Polcher

    Evapotranspiration (ET) links the water, energy and carbon cycles, and it is quantitatively very important in their respective budgets. The determination of its actual value for a given location remains a major challenge. This session calls for experimental scientists to critically evaluate their measurement methodologies, specifically micrometeorologists using eddy-correlation and gradient methods and hydrologists, agronomers, plant and soil scientists using lysimeters, water balance methods and leaf transpiration or sap flow measurements. The session also welcomes contributions revising the critical assumptions made in the estimations of ET by remote sensing and the uncertainties related, and evaluations of the performance of parameterizations in models currently in use against observations.
  4. Understanding Sub-daily Rainfall Extremes and the Diurnal Cycle of Precipitation
    Andrea Flossmann, Hayley Fowler, Elizabeth Lewis, and Nathalie Schaller

    Extremes of short duration precipitation can cause severe flooding which can lead to substantial damages to infrastructure and ecosystems and can result in loss of life. It is still uncertain how such hydrological extremes will change with global warming, as we do not fully understand the processes that cause extreme precipitation under current climate variability. Progress in this area is severely limited by the lack of sub-daily rainfall data available to researchers. This session focuses on the availability and analysis of sub-daily rain-gauge observations and improving the understanding of drivers of extreme events by linking these observations with other data sets. We therefore welcome contributions that:

    • Examine the development and availability of new sub-daily rainfall observations and their analysis. This includes novel approaches for the quality control of rain-gauge data, climatological analyses of data sets (spatial and temporal characteristics, particularly, extremes) and examining observed trends and variability
    • Identify and assess relevant sub-daily indices or generate other derived sub-daily data products (e.g., products which combine rain-gauge observations with other types of measurement including radar, gridded rain-gauge products)
    • Improve understanding of the drivers of extreme sub-daily events, including both large-scale circulation conditions and local scale thermodynamics
    • Integrate the analysis of outputs from very high resolution climate and NWP models with observational datasets; for example, in terms of model validation or critically improved understanding of atmospheric/meteorological processes
  5. Advances in Irrigation Hydrology and Irrigation Impact on Water Cycle: Measurements, Modeling, and Multi-Scale Impacts on Water Resources
    Hyungjun Kim, Patricia M. Lawston, Joseph Santanello, and Wim Thiery

    Anthropogenic water management activities, such as irrigation and dam regulation, can impact groundwater resources, the land surface energy balance, and atmospheric feedbacks. Understanding and responding to these effects is critical for sustaining water resources and improving hydrological drought forecasting in a changing climate. To address these needs, water management schemes, such as irrigation parameterizations, have been actively developed for weather and climate models. However, work remains to be done in monitoring water management, in understanding the processes that drive impacts on the water cycle, and in refining models and parameterizations to accurately represent these activities and impacts.

    This session seeks to unify research focused on human water management to facilitate the quantification of anthropogenic impacts to the water and energy cycles. Contributions are invited on topics including, but not limited to, applications of remote sensing for monitoring irrigated areas and inland water bodies linked to human activities, advancements in Earth system models and water management schemes, assessments of irrigation-induced groundwater loss and land subsidence, and changes in water balance across spatial scales resulting from water management.
  6. Changes in Rainfall Intensity and Distribution in Time and Space and Their Effect on Surface Water Partitioning
    Gianpaolo Balsamo, Eleanor Blyth, Aaron Boone, and Remko Uijlenhoet

    Changes in rainfall intensity and distribution in time and space are taking place as a result of changes in climate. The impact of this needs to be included in models if we are to accurately predict changes in floods and water resources, as well as changes to soil moisture and land-atmosphere fluxes. Currently, large-scale atmospheric models still exhibit strong biases of intensity in convective rainfall with drizzle, too frequently triggered. These intensity biases are absolutely critical over land regions and strongly affect our ability to predict extreme hydrologic events, the onset of drought and water resources. We need to be able to model the effect of changes of rainfall intensity on partitioning the surface water into interception; soil moisture, river flow and groundwater recharge independent of model spatial resolutions and time step size.

    Abstracts covering the following subjects in both observational and modeling studies are welcome:

    • Runoff generation from intense rainfall
    • Response of soil moisture and groundwater recharge to spatial and temporal rainfall distributions
    • Changes to land-atmosphere feedbacks due to changes in rainfall intensity
    • Impact of climate change on rainfall rate distributions in both time and space
    • Site-based, regional, or global studies welcome
  7. Cold Regions Earth Systems Change, Including Precipitation Occurring Near 0°C
    Pavel Groisman, Gerhard Krinner, Ronald Stewart, and Howard Wheater

    Cold regions are at the forefront of global warming and undergoing rapid Earth system change. For hydrology, the major events are typically related to storage and melting of snow and ice, and the related energetics of phase change. These events are governed by interacting atmospheric, cryospheric, and ecological processes, resulting in a unique assemblage of hydrological processes that produce complex and spatially and temporally variable responses. This session is concerned with recent advances in understanding, diagnosis, and prediction of past and future changes in these Earth systems. The development and use of numerical models to diagnose past change and predict future sensitivity and response under various climate and land cover scenarios will be a particular focus. Key issues include changes in cold regions hydrological processes and their interactions in response to climatic drivers, feedbacks and thresholds leading Earth system changes, and/or factors imparting hydrological resilience or sensitivity to change. For the atmosphere, dramatic variations in the types of precipitation are associated with temperatures near 0°C in these regions. This precipitation includes snow, freezing rain, freezing drizzle, ice pellets, and wet snow, and it is also linked with phenomena such as icing and rain-on-snow events. It is often difficult to quantitatively measure critical aspects of this precipitation and models need to be very sophisticated to handle its complex formation. Key issues to be considered include its measurement (from in situ to satellite), climatology (regionally and globally), simulation, and future occurrence.
  8. Modeling for Extremes
    Gaby Hegerl, Andrew Pitman, and Robert Vautard

    Climate models are used to project changes in extremes on an assumption that they are fit for purpose. Most evaluation of climate models focuses on their ability to capture averages and parameterizations are built with this goal in mind. Where climate models are evaluated explicitly for skill in extremes (rainfall, heat waves, droughts), individual models commonly perform poorly. What are the attributes required of a climate model with skill in simulating extremes? Does spatial resolution help a lot or a little? Do processes-based parameterizations have to be modified or revolutionized? What metrics do we need to measure model skill? Are there processes not captured at all that will become critical to the simulation of extremes (e.g., topographic influences, rivers, lateral flows)? In short, what are the challenges, strategies, and priorities to ensure our climate models are fit-for-purpose in the simulation of human-relevant climate extremes?
  9. Energy and Water Budget Closure, and Advances in Assessment Techniques
    Tristan L’Ecuyer, Karina von Schuckmann, and Kevin Trenberth

    The Earth’s energy imbalance and its partitioning between atmospheric, ocean, cryosphere, and land heat reservoirs govern the rate at which the global climate evolves. Regional energy and water imbalances drive heat transport, in part through ocean currents, evaporation, precipitation, and runoff. This session seeks contributions that synthesize multiple energy and water variables derived from observations (in situ, satellite), reanalyses, or climate models to examine energy and water cycle closure on regional through global scales. Studies of systematic or structural uncertainties using closure tests in flows of heat and water are also solicited. Approaches for utilizing top of atmosphere radiation, atmospheric and oceanic mass and heat transports, air-sea fluxes, direct and indirect ocean heat content analyses, and estimates of surface ice mass, heat content, and water storage to establish consistency between estimates of planetary heat balance and ocean heat storage are especially encouraged. This session seeks contributions that synthesize multiple energy and water variables derived from observations (in situ, satellite), reanalyses, or climate models to examine energy and water cycle closure on regional through global scales.
  10. Global Energy and Water Cycles, Clouds, and Radiation
    Rémy Roca, Graeme Stephens, and Claudia Stubenrauch

    Water on earth exists in three thermodynamic phases. Water vapor is source of clouds and of precipitation. Changes of phase in the atmosphere are a source of energy that fuels storms and help drive the atmospheric circulation. Changes in energy and water cycles, induced by climate change, depend on the interaction of all components. To reliably prediction weather and climate, it is essential to identify and understand key processes of the relationships that connect and define the flow of water through the atmosphere, from tropical convection to higher latitude storms. Contributions that focus on process-scale interactions that connect energy, water and radiation are encourages including those studies that contribute to the framework of the recently formed GEWEX Process Evaluation Studies.
    Specific topics of this session are:

    • Understanding the Earth’s climate from an Earth observational perspective;
    • Aerosol, cloud, precipitation and radiation processes and interactions in the climate system
    • Synergetic use of observations to improve the representation of key processes in climate models
  11. Water Cycle over the Breadbaskets: Cities, Agriculture, and Environment
    Richard Harding, Taikan Oki, and Yoshihide Wada

    Humans have a major impact on our freshwater systems and water has been and will be a major constraint on food production and development. Papers are invited on the anthropogenic impacts on the global and regional terrestrial water cycles, future water scarcities, and the feedbacks to the climate system. Half our major rivers are moderately or severely impacted by anthropogenic activities. Irrigated areas, although globally small, supply 40 percent of our food and are the major users of water from rivers, reservoirs, and groundwater. The area and intensity of irrigation is likely to increase as we struggle to feed up to 11 billion people in the future. Water use for our cities is growing rapidly and will increasingly constrain human development and wellbeing. These pressures will exacerbate with climate change – although global precipitation is likely to increase, regionally we may see decreasing rainfall coupled with increasing variability and more intensity – which will put yet more pressure on areas where water resources are already stretched.There are many impacts of human interventions that are more indirect in the terrestrial water cycle. Approximately one fourth of the observed sea level rise to date can be attributed to dewatering of aquifers, ameliorated to an extent by increases in impoundments in reservoirs. Reduced outflows to the oceans lead to erosion of delta regions. Feedbacks between a changed land surface and the atmosphere may also be important – with local and large-scale impacts on climate. Our projections of future climate and water resources will increasingly need to include anthropogenic interventions in land cover, freshwater systems, and the environment at large. To manage these scarce resources, with changing demands and climate, we need a detailed understanding of the systems, impacts, and feedbacks.
  12. Satellite Observations for Climate Extremes, Water Cycle Processes, and Land-Atmosphere Interactions
    Nick Rayner, Matthew Rodell, and Christopher Taylor

    Satellite remote sensing has revolutionized our ability to quantify, understand, and predict climate extremes, water cycle processes, and land-atmosphere interactions. While ground based observations will always be important for local, in situ understanding of extremes, for calibration and evaluation of remote sensing datasets, and to provide a connection to the historical record, it would be infeasible to monitor all of the relevant states and fluxes everywhere, all the time, using ground based observations alone. Satellite remote sensing, as part of a combined, complementary observing system, often enables spatially and temporally continuous observation and consistency of measurement, all of which are crucial for characterizing and identifying extremes and understanding hydrological processes and land-atmosphere interactions. This session will explore the latest satellite observation based datasets and discoveries and discuss upcoming and future remote sensing capabilities. In particular, we seek contributions that apply satellite observations for

    • Identification, quantification, and prediction of water cycle and other extremes
    • Improved understanding of water cycle processes and land-atmosphere interactions
    • Development of new datasets
    • Future prospects for remote sensing relevant to this topic area.
  13. The Human-Climate Water Nexus, Climate Change, and Water Security
    Katja Frieler, Carole Dalin, Anil Mishra, and Jan Polcher

    Human livelihoods and well-being both essentially rely on and significantly affect global water resources. Water withdrawals for agriculture, industry, and domestic purposes have sharply increased in the past few decades, driven by population growth and socio-economic development. Moreover, associated anthropogenic changes in land use and land cover also affect the quantity and quality of available water resources in many regions worldwide. The dynamics of the hydrological cycle and water availability are impacted by climate variability, climate change, and anthropogenic activities across regions. This session will cover recent scientific advances in the understanding of human-water-climate interactions (or “nexus”), which can help implement changes towards the water-related Sustainable Development Goals (SDGs) and the Paris Climate Agreement.

    This session welcomes contributions on:

    • Human and climate impacts on the global water cycle (quantity and quality): population growth; environmental, demographical and agricultural land use changes; climate-related uncertainty and hydrological disasters impacts
    • Anthropocene and water security challenges
    • Water security, a key challenge for human development: how to address unsustainable surface and groundwater use, and interactions between water security and food security
    • Case studies from hotspots (vulnerable regions): identify global and climate change impacts and showcase innovative solutions and adaptation strategies to address water security challenges (e.g., studies of climate adaptation/mitigation strategies and their effects, particularly on relevant sustainable development indicators)
    • Scientific challenges to achieve the water-related SDGs and the Paris Climate Agreement

A synthesis of these ideas and a panel discussion will focus on the challenge questions related to Water Security and Climate Change.

  1. The Mountain Water Cycle
    Roy Rasmussen, John Pomeroy, and Chris DeBeer

    Mountains receive and produce a disproportionately large fraction of global precipitation and stream flow, including contributions to floods and essential water supplies for vast downstream areas that include at least one-half of humanity and most of its irrigated food production. Most mountain regions are undergoing dramatic cryospheric and ecological change from global warming. Advances in modeling, remote sensing, big data techniques, and process understanding are developed for application to continental to local scale water sheds and often verified using observations such as snow telemetry (SNOTEL) or instrumented alpine research catchments and then used to inform mountain water-cycling predictions. However, research in alpine catchments is complicated by data scarcity in mountain regions, and most Earth system models have insufficient spatial detail to resolve mountain processes that govern its water cycling. This session welcomes contributions that:

    • Support research efforts related to GEWEX’s International Network for Alpine Research Catchment Hydrology (INARCH)
    • Show the value of enhanced mountain hydrometeorological and cryospheric observations and process understanding to inform mountain water cycle modeling
    • Provide results of high resolution modeling efforts regarding the mountain water cycle
    • Describe the results of recently completed field efforts, such as the WMO Solid Precipitation Intercomparison Experiment (SPICE) project on measurement of snowfall, in mountain terrain
    • Quantify and improve the diagnostic and prognostic potential of models, including those that use big data techniques and large computers and models to predict water and energy cycling in mountain regions
    • Show how improved and hybrid downscaling methods can drive fine scale “snowdrift resolving” models from large scale atmospheric models, including convective-permitting modeling that assimilates high-resolution satellite data
    • Show how changing cryospheric states are influencing water and energy cycling in mountain headwater catchments
  1. Land-Atmosphere Interactions and Water Cycle over the Third Pole Region
    Aili Ailikun, Xin Li, Bob Su, Yongkang Xue, and Tandong Yao

    The Third Pole Region, which covers the huge area of Hindu-Kush, Karakorum, the Himalayas, and the Tibetan Plateau, is facing severe sustainability challenges to water scarcity, land degradation, and natural disasters in recent decades. Warming acceleration after the 1990s in this region has resulted in crucial changes in glacier, snow cover, permafrost, lakes, rivers, wetlands, and pastures that affect the livelihoods of millions of people from local and regional to global scales. For a long period of time, the harsh environment and lack of continuous observations in this area kept scientists from understanding the processes and mechanisms of changes in the cryosphere, atmosphere, hydrosphere, and ecosystem. In the past decades, scientists and funding agencies from all over the world have made great efforts to establish projects and networks to encourage the joint interdisciplinary research in this region. This session will present the latest scientific achievements on observations, analysis, and modeling related to land-atmosphere Interactions and the water cycle in the Third Pole Region.

    The main topics of this session are:

    • Glacier, snow dynamics, and local/regional hydrological cycle in the Third Pole Region
    • Land surface characteristics, parameterizations, and their application in regional climate modeling over the highlands of the Third Pole
    • Regional Earth system (multisphere) modeling for the Third Pole Region and its impact on the adjacent regions at different scales
    • Ground/satellite observations and data assimilation for the highlands of the Third Pole Region
  1. Heat Waves and Heat Extremes in the Past, Present, and Future Climates
    Frédérique Cheruy, Erich Fischer, and Francis Zwiers

    Extreme heat events are synoptic phenomena with regional and or even local footprints whose characteristics are expected to be modified in the context of anthropogenic climate change. However, future climate projections of heat events and the assessment of the severity of their impacts are still challenging. Several reasons can be cited: their regional signature, the role of poorly represented land-atmosphere interactions in models (e.g., urban heat islands, soil moisture-atmosphere coupling), the numerous possible feedbacks that might amplify heat and drought, the non-unique characteristics of the heat waves (e.g., moist versus dry heat waves) that modulate their health and ecosystem impacts, and their rarity, which complicates any statistical analysis. This session will host contributions that help to narrow uncertainties in these fields.

    The objective of this session is therefore to examine heat waves and heat extremes from both statistical and process based perspectives in the light of links to the water cycle at scales ranging from urban to sub-continental. This includes indicators of heat stress on humans, agriculture and ecosystems, the evaluation of extreme cooling loads for air-conditioning and industrial processes, the assessment of extreme wildfire risk, which is affected by the moisture content of the fuel and the land surface, coupled land-atmosphere processes that exacerbate heat extremes and prolong heat waves and droughts, the role of circulation features such as blocking in heat wave development, duration and intensity, and spatial drought propagation processes that may prolong agricultural drought and extend its spatial footprint over the life cycle of a given drought event. It is anticipated that papers in this session will be broadly representative of three areas, including: (i) improvements in process based understanding of extreme heat, relevant feedback processes, the ability of numerical weather prediction and climate models to represent key processes at a range of scales, and model improvements; (ii) methodological improvements in the analysis of heat extremes, including advanced applications of extreme value theory, improvements in detection, trend attribution, and event attribution approaches specifically focused on heat extremes, and improvements in the ability to identify and apply emergent constraints; and (iii) the assessment and analysis of historical observations, including improvements in extreme temperature and humidity datasets based on in situ data and/or temperature and humidity data products that integrate remote sensing data, assessments of historical change simulated by models of varying levels of detail and complexity, and projections of future change based on models alone, or that are obtained through the application of various types of observational constraints to models.
  2. Storms and High-Impact Weather
    Michael Kunz, Olivia Romppainen-Martius, and Paolo Ruti

    In most regions across the globe, extreme meteorological events are expected to increase in their intensity and probability in future decades. Therefore, a key part of society’s adaptation is to improve preparedness for future hazards over a wide range of applications and actors. This should start with evaluation of the resilience of current society, identifying potential weaknesses and crucial thresholds – for specific sectors and society as a whole – beyond which environmental, social, or economic stability are endangered. We welcome contributions on improving forecasting of high impact weather systems and storms on all spatial scales and on applying new knowledge and developments in information content, language, format, public awareness, and dissemination to increase resilience today and to enable the preparation of future adaptation strategies. This prominently includes the evolution of severe weather in a changing climate and the effects of a changing hydrological cycle on the occurrence and characteristics of severe weather.

    Contributions may include modeling experiments and/or observations and can focus on statistical analyses or the description of relevant dynamics. A special focus will be on the core themes of WWRP’s High Impact Weather research project: key hazards (urban flooding, wildfires, localized extreme winds, disruptive winter weather, urban heatwaves and air pollution); predictability and processes; multi-scale forecasting of weather-related hazards; human impacts, vulnerability and risk; communication; user-oriented evaluation.
  3. Addressing the Challenge of Compound Events
    Amir AghaKouchak, Bart van den Hurk, Seth Westra, and Jakob Zscheischler

    Hazards such as floods, wildfires, heat waves, and droughts often result from a combination of interacting physical processes that take place across a wide range of spatial and temporal scales. The combination of physical processes leading to an impact is referred to as a “compound event.” The session seeks case studies, conceptual frameworks, model simulations, or data analyses addressing both current understanding and research gaps related to compound events, focusing on the following areas:

    • Document: Which climate variables need to be assessed jointly in order to characterize the relevant class of a compound event? How much is currently known about the dependence between these variables? Are the observations sufficient to underpin the assessment of these variables and their dependencies?
    • Attribute: To what extent are historical and/or projected changes in the identified compound events attributable to particular causes? Are the available modeling tools appropriate to enable attribution of compound events? Does forcing change the physical mechanisms involved in compound events, leading to stronger or weaker connections?
    • Understand: What are the processes that lead to dependence between the identified climate variables? What is the role of the spatial and temporal scale at which the processes are analyzed in influencing the strength of dependence between variables? How are these processes expected to change as a result of anthropogenic climate change?
    • Simulate: Are models able to reliably simulate the dependence between climate variables and how they might change in a future climate? What methods are available to evaluate the capacity of models to simulate an appropriate level of dependence between variables?
  4. Detection and Attribution of Climate Extremes
    Friederike Otto, Michael Wehner, and Xuebin Zhang

    Hazardous climate impacts on human society and natural systems are often realized through weather and climate extremes. Understanding what the main contributors are to the observed weather and climate extremes and to the changes in the frequency and intensity of the observed extremes is critically important to policy and decision makers. As there is an increasing interest in using attribution to inform risk assessment and in guiding future adaptation strategies, it is important to quantify the relative roles of hazard, exposure, and vulnerability when assessing impacts. This session aims to examine recent developments in the science of attribution of the human contribution to climate extremes including attribution of the impacts of severe weather to inform the forthcoming IPCC 6th Assessment. The session welcomes contributions in all areas related to attribution of climate and weather extremes.
  5. Droughts in Present and Future Climate
    Christel Prudhomme, Sonia Seneviratne, Jacob Schewe, Lena Tallaksen, and Justin Sheffield

    As recent events in East Africa, Western North America, or Southern Europe have once more demonstrated, droughts are among the most devastating climate phenomena. At the same time, they are complex processes, involving feedbacks between atmosphere, soil, vegetation, and human interventions that can strongly influence drought duration and intensity. An improved understanding of these interactions can aid both the short-term forecasting of droughts, as well as an effective assessment of future drought risk under longer-term scenarios of global climate change.

    This session welcomes contributions using observations, theoretical methods, climate, hydrological, or other modeling tools to investigate drought representation, processes, their drivers, and their impacts in both present and future climate.
  6. Climate Extremes, Ecosystems, and Society: Impacts, Feedbacks, and Emergent Risks
    Markus Reichstein, Jana Sillmann, and Dáithí Stone

    Climate extremes can have substantial impacts on natural and managed ecosystems and on different societal groups. In turn, these impacts can in some cases influence the nature of the climate extremes, and they almost always affect the vulnerability of the impacted system. Within a changing world, the nature of climate extremes, feedbacks, exposure, and vulnerability are all subject to change, leading to potentially complex changes in risk.

    This session explores in particular the linkages between climate extremes, ecosystems, and societal groups. Emphasis is on a) impacts that are caused by climate extremes on various aspects of ecosystems (including natural and managed ecosystems) and society (e.g. livelihoods, policy, insurance, health, economics, equity); b) feedbacks that modify climate extremes and/or ecosystem and societal vulnerability and exposure; c) climate extremes related-hazards, ecosystem and societal exposure and vulnerability, and associated feedbacks that are changing through time, and d) multi-hazard interactions and cascading impacts (including technological, political, and socio-economic) and risks emerging from existing development pathways or emission scenarios. Empirical, theoretical, and modeling studies from local to global scales are all highly welcome.
  7. Soils in Water and Climate Models
    Dani Or, Harry Vereecken, and Anne Verhoef

    Land use changes and intensification in soil-supported agricultural and forest ecosystems give rise to land-climate feedbacks that may affect precipitation characteristics, and the occurrence of extreme events such as droughts and heat waves. There is a large disparity between small-scale and short-term processes of interest in traditional soil models, and long-term climatic processes at regional and continental scales. New modeling approaches and data sets are required to bridge these spatio-temporal scale gaps, while retaining key information that is pertinent to all scales. Some of the most pressing modeling challenges involve a better representation of the role of soil in triggering, maintaining, and ending extreme events. This involves comprehensive coupling of the water, surface energy, and carbon balance across scales. Improved modeling of land use, ecosystem, and climate interactions under future climate scenarios would enable us to provide more reliable predictions of groundwater recharge in future climates, and of soil carbon dynamics and storage. We welcome contributions that highlight improved descriptions of soil processes in hydrological and climate models, and related land surface models, that analyze experimental and observational soil data with relevance to these models or that provide improved and novel global data sets of key soil parameters and properties in the context of land-surface-atmosphere exchange and possible feedbacks on extremes.
  8. Land-Atmosphere Interactions and Climate Predictability, Including Subseasonal to Seasonal (S2S) Prediction
    Paul Dirmeyer, Michael Ek, and Xubin Zeng

    Land-atmosphere coupling is a key component of the Earth system, and it directly affects weather, water, and climate prediction, including subseasonal-to-seasonal (S2S) prediction. Progress in this area requires interdisciplinary collaborations among scientists working on modeling, observations, theoretical studies, and synthesis. This session is intended as a platform for interdisciplinary exchange of ideas in several focus areas:

    • Mechanisms of land-atmosphere coupling at various time scales ranging from the diurnal cycle to interannual and decadal scales
    • Quantification of local land feedbacks versus non-local land/atmospheric impacts on atmospheric processes (e.g., precipitation)
    • Impact of land processes (e.g., snowpack, soil moisture, soil temperature, frozen soil, vegetation) on weather, S2S, and climate prediction
    • Role of land-atmosphere interactions in climate variability and change, including extreme events (e.g., heat waves, droughts, and flooding)
    • Impacts of land-cover and land use change on weather and climate variability and change
  9. Benchmarking and Metrics
    Gab Abramovitz, David Lawrence, and James Randerson

    This session will focus on how the community can ensure that broad, comprehensive, standardized model evaluation becomes an automated part of model development internationally. Publicly available tools, such as ILAMB, PMP, ESMValTool, and PALS have begun this process, but their use is still not widespread. Further, they have tended to focus on higher level metrics that integrate many processes rather than directly inform individual process representations within models. We invite a broad range of contributions of relevance to energy and water cycle evaluation of land surface, atmospheric, and coupled modeling systems, including, but not limited to:

    • Novel implementations and development of community evaluation packages, such as those listed above
    • Examples where underutilized observational sources provide enough constraint to evaluate specific model process representations in large-scale applications, including lessons and metrics from GEWEX-PROES type studies
    • New observational datasets of use to global scale model evaluation
    • Novel approaches to benchmarking – quantifying a priori model performance expectations
  10. High-Resolution Modeling and Resolved/Permitted Convection
    Elizabeth Kendon, Daniel Klocke, Nicole van Lipzig, and Andreas Prein

    This session focuses on high-resolution climate and weather modeling experiments with global or limited area models that assess benefits, challenges, and limitations in this rapidly evolving research area, including:

    • Convection-permitting/resolving simulations
    • Global high-resolution simulations (e.g., HighResMIP)
    • Variable resolution simulations
    • High-resolution process studies (e.g., feedbacks, extremes)
    • High-resolution observations for model evaluation

    High-resolution modeling has the potential to resolve long-standing challenges in weather and climate simulations such as the representation of deep convection, land-atmosphere interactions, or orographic processes. Convection-permitting models are commonly used in short-range weather forecasting where they have been shown to forecast localized extreme events not captured at coarser resolutions. Applied to climate time scales, convection-permitting models allow unprecedented insights into the role of mesoscale processes in the climate system and their interaction with larger-scales, which is hoped to improve climate projections on seasonal to decadal timescales.

    This session aims to explore recent advances and challenges in high resolution modeling from process to global scales. We welcome contributions that assess the added-value of high-resolution simulations, differences in climate change projections between high-resolution and traditional climate simulations, process-studies about mesoscale phenomena and feedback processes, and high-resolution observational data sets for model evaluation. Studies that focus on solutions for major challenges in high-resolution modeling such as the high demand of computational resources, the management of big data volumes, the assessments of uncertainties in high-resolution simulations, or improvements in model physics are also welcome.

  11. Documenting Extremes
    Lisa Alexander, Ali Behrangi, Lukas Gudmundsson, and Albert Klein Tank

    This session deals with observational issues and uncertainties associated with climate extremes. Observations are the key foundation for understanding long-term climate variability and change. However, observations are often not well constrained, and critical gaps exist in the amount, quality, consistency and availability of observations, especially with respect to extremes. The current suite of datasets for assessing climate extremes is generally inadequate to properly assess climate variability and change. Consequently, the datasets also cannot provide the required underpinning for detection and attribution studies and model evaluation. This is due to limited spatial and temporal coverage, differences in how extremes are defined, the spatial representativeness of point-based measurements, scaling issues between observations and models, and uncertainties in in situ observations and estimates from remote sensing retrievals. This session welcomes contributions that address these and other issues that affect how extremes are observed or documented on both regional and global scales. This could include issues and uncertainties that are important for extremes related to data rescue, quality control and homogenization, and dataset development (in situ, remote sensing, and complex observational data products).

    Abstract topics include:

    • data set development and intercomparison (in situ, remote sensing, and complex observational data products)
    • quality control and homogenization
    • scaling issues
    • model evaluation
    • long-term climate variability and change