Session programme

UP – Understanding Weather & Climate Processes

PSE key.3

Sue Grimmond, Met Office Joint Chair, Professor of Urban Meteorology and Climate, University of Reading (confirmed)

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Co-organized by UP
Conveners: Frank Beyrich, Barbara Chimani, Martina Junge

UP1 – Atmospheric processes and severe weather

UP1.1

Weather prediction has improved tremendously over the last decades. Ultimately, however, there are limits in predictability due to the multi-scale, non-linear nature of atmospheric dynamics.
To further improve our mechanistic understanding of atmospheric dynamics and to further improve numerical weather forecasting it is increasingly important to better understand the physical and dynamical processes connecting atmospheric motions across temporal and spatial scales. This includes, for example, the identification of the limits of predictability of different weather systems. For longer time scales, identifying and understanding sources of predictability and variability is of crucial importance. This session will therefore discuss the current understanding of physical and dynamical processes determining predictability and variability on different scales.

Contributions are invited that attempt to improve our understanding of atmospheric dynamics or that link process-based, dynamical understanding and predictability aspects. Atmospheric phenomena on all spatial and temporal scales are of interest. Particularly welcome are contributions that focus on high-impact weather, the sub-seasonal to seasonal (S2S) timescale, and related extremes. This may include, but is not limited to, the influence of remote factors (e.g., the stratosphere, the Artic, or the tropics) on the midlatitudes, predictability in the tropics and polar regions, stationary and recurrent systems (e.g. associated with heat waves, cyclone clustering, heavy precipitation), or processes driving seasonal or interannual variability.

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Convener: Sebastian Schemm | Co-Conveners: Christian M. Grams, Alessandro Dell'Aquila, Michael Riemer
UP1.2

Atmospheric boundary-layer (ABL) processes and their interactions with the underlying surface are crucial for weather, climate, air-quality and renewable-energy forecasts. The multitude of interacting processes act on a variety of temporal and spatial scales and include atmospheric turbulence, atmosphere-soil-vegetation interactions, gravity waves, boundary-layer interactions with dry and moist convection, mesoscale flows, submeso motions, etc.

Although significant advances have been achieved during the last decades, an appropriate comprehension of ABL processes and their interactions under different conditions is still a challenge in meteorology. Improving this knowledge will help to correctly represent ABL processes in weather and climate models, allowing to provide more accurate numerical weather prediction (NWP) forecasts and climate scenarios.

This session welcomes conceptual, observational and modeling research related to the physical processes that appear in the ABL, including those devoted to study the interactions with the free atmosphere above and with the surface below. Current contributions evaluating existing models and schemes are also welcome, as well as the presentation of new implementation in numerical modelling.

The following topics are especially encouraged to be submitted to the session:

• Theoretical and experimental studies of the turbulence-closure problem with emphasis on very stable stratification and convection, accounting for interactions between the mean flow, turbulence, internal waves and large-scale self-organized structures.

• Boundary-layer clouds (including fog) and marine, cloud-topped boundary layers: physics and parameterization within NWP and climate models and observational studies.

• Orographic effects: form drag, wave drag and flow blocking, gravity waves.

• Challenges on the surface-exchange processes, including soil-vegetation-atmosphere transfers. Flux aggregation in atmospheric boundary layers over heterogeneous terrain.

• Representation of boundary layers and land-surface interaction in atmospheric models.

• Organization of deep convection across differing atmospheric scales.

• Large-eddy simulation and direct numerical simulation of turbulent flows.

• PBL and surface-layer studies using long-term data (climatology), detailed analysis of case studies and field campaigns presentation.

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Convener: Gert-Jan Steeneveld | Co-Conveners: Bert Holtslag, Carlos Román-Cascón, Nikki Vercauteren, Sergej Zilitinkevich
UP1.3

This session will welcome all technical and scientific contributions devoted to increase our understanding of atmospheric phenomena that might represent a hazard for people, property and environment. Studies devoted to enhance physical understanding of severe weather phenomena (for example deep convection or intense straight lines winds) are of particular interest even if the severe weather phenomena are not linked directly to a specific hazard (multihazard events).
Embracing the proposal given by the organizers, this year will be particularly welcome contributions dealing (directly or indirectly) with severe droughts in Europe or connecting droughts events and atmospheric hazards.
Moreover, in line with the spirit of EMS, we would encourage contributions devoted to underline the intercultural aspects of methods and findings, and to point the attention not only to the physical and meteorological characteristics of atmospheric hazards and severe droughts, but also to their relevance in a changing climate, including possible impacts on human activities and the environment.
Contributions dealing with studies of specific episodes (case studies) will be welcome, provided they further increase physical understanding and are representative at least for the area where these events took place.
Particularly welcome will be contributions incorporating both numerical and conceptual modelling to improve our understanding of severe weather phenomena.
In general we will encourage the exchange of expertise and experiences related to the various topics connected to hazardous atmospheric phenomena and severe weather events. For this reason an interdisciplinary approach will be particularly welcome.
Potential topics for this session include i.a.:
• Severe droughts;
• Flash-floods and heavy rain events;
• Hail;
• Freezing rain, icing and intense snow falls;
• Cold/heat events, even those occurring at small time scales;
• Fog;
• Tornadoes, waterspouts, derechos and downbursts;
• Severe wind storms;
• Intense Mediterranean cyclones;
• Tropical like cyclones;
• Lightning;
• Polar lows, their evolution and impacts;
• Severe katabatic or foehn winds;
• Gap and orographic flows;
• Breaking of gravity waves, as well as severe turbulence;
The above-listed topics are of course not exclusive and the session’s Conveners eagerly anticipate papers on new ideas and approaches and novel understanding covering all aspects of atmospheric hazards and severe weather events.

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Conveners: Fulvio Stel, Arne Spekat | Co-Conveners: Dario Giaiotti, Mario Marcello Miglietta, Sante Laviola, Jordi Mazon, Victoria Sinclair
UP1.4

During the last years, the worldwide interaction between the Metrology and Meteorology communities has improved and increased. The EURAMET, the European association of national Institutes of Metrology, is presently funding several projects aiming at delivering results of valuable impact for the meteorology and climatology sciences. The key aspect of these projects is to establish traceability of measurements and uncertainties of measured physical and chemical quantities and Essential Climate Variables.

The session on Metrology for Meteorology and Climate is organized to give an opportunity to present and discuss needs, methods, expertise and devices with objective to cooperate in producing more reliable data. It will be an occasion to reciprocally increase knowledge and understanding for these two fields, semantically so similar but each one representing problems of different nature.
A special focus on climate reference stations and networks will be included.

Topics for the session are
• Traceability and uncertainty in weather observations.
• Metrology applied to Ground based systems. Temperature, humidity and pressure sensors. Wind speed and direction, solar radiation.
• Requirements and instrumental features of climate reference stations
• Quantities of influence and mutual influences. Sensors dynamics.
• Special calibration procedures for upper air measurements and aircraft-based measurements.
• Ocean research: metrological traceability to the SI system for the measurement of the key variables salinity, pH, composition and dissolved oxygen content of sea water.
• Water: water vapour, liquid water, ice, hygrometry, soil moisture.
• Calibration and traceability for rain and snow gauges.
• Permafrost temperature measurements: instruments, procedures and calibrations.
• Assessment of the historical temperature measurement data with respect to uncertainties on instruments used.
• Thermal metrology for meteorology and climate.
• Chemical metrology for environment and climate.
• Instruments and measurements capabilities, calibration procedures, best practice and regulations.

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Convener: Andrea Merlone | Co-Conveners: Fabio Madonna, Peter Pavlasek
UP1.5

Measurements are essential to provide information on the actual state of the atmosphere for nowcasting purposes, for climate monitoring, for assimilation into numerical weather prediction (NWP) systems and to improve our understanding of atmospheric processes and their role in the climate system. In particular, there is a strong need for complex observations suitable to develop, improve and validate parameterizations used in NWP and climate models and to provide ground-truth against which to compare atmospheric parameters derived from satellite data. With a new generation of high-resolution forecast models (1-3 km) used for the prediction of high-impact weather, dense observational networks focusing on measurements in the lower few kilometers of the atmosphere are required.
This session is intended to give a forum to discuss recent developments and achievements in local to regional measurement concepts and technology. There will be a special emphasis on measurements which seek to improve our understanding of complex atmospheric processes – especially those characterizing interactions in the climate system – through obtaining comprehensive data sets. The focus is on measurements of atmospheric dynamics and thermodynamics, energy and water cycle components, and on the interaction of the atmosphere with the underlying surface. With respect to the special conference focus on droughts, contributions on measurements of precipitation, soil moisture, and evaporation are specifically invited.
The session will also include consideration of novel measurement approaches and networks under development for future operational use, e.g., within the frame of the Eumetnet observations program, and the performance of new measurement techniques. Manufacturers of hydro-meteorological instruments and system solutions are thus explicitly invited to present news on sensor development, sensor performance and system integration.
Techniques may cover in-situ and remote sensing measurements from various platforms. Special attention will be given to the creation of a new generation of reliable unmanned instrument networks across Europe that provide calibrated and controlled data on the boundary layer structure in near-real time. Contributions are also invited that make use of advanced data sets for satellite data validation.

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Convener: Frank Beyrich | Co-Conveners: Fred C. Bosveld, Jens Bange, Domenico Cimini
UP1.6

This session provides a platform for contributions on high-resolution precipitation measurements, analyses, and applications in real-time as well as climate studies. Monitoring and statistical analyses of precipitation at small spatial and temporal scales are challenging. Therefore, special focus is placed on documenting the benefit of highly spatially and temporally resolved observations of different measurement platforms, e.g. satellites, radar networks, or opportunistic sensing, e.g. retrieving rainfall from microwave links. Papers on monitoring and analyzing extreme precipitation events including extreme value statistics, multi-scale analysis, and event-based data analyses are especially welcome, comprising definitions and applications of indices to characterize extreme precipitation events, e.g. in public communication. Contributions on long-term observations of precipitation and correlations to meteorological and non-meteorological data with respect to climate change studies are cordially invited. In addition, contributions on the development and improvement of gridded reference data sets based on in-situ and remote sensing precipitation measurements (e.g., GPCC, OPERA) are welcome.
Extreme events in precipitation monitoring do not solely comprise heavy precipitation but equally low precipitation periods and droughts. According to the special focus of the 2020 Annual Meeting contributions on drought monitoring and impact are especially encouraged.
High-resolution measurements and analyses of precipitation are crucial, especially in urban areas with high vulnerabilities, in order to describe the hydrological response and improve water risk management. Thus, this session also addresses contributions on the application of high-resolution precipitation data in hydrological impact and design studies.
Summarizing, one or more of the following topics shall be addressed:
• Precipitation measurement techniques
• High-resolution precipitation observations from different platforms (e.g., gauges, disdrometers, radars, satellites, microwave links) and their combination
• Precipitation reference data sets (e.g., GPCC, OPERA)
• Drought monitoring and impact
• Statistical analysis of extreme precipitation (events)
• Statistical analysis of changes/trends in precipitation totals (monthly, seasonal, annual)
• Multi-scale analysis, including sub-kilometer scale statistical precipitation description and downscaling methods
• Definition and application of indices to characterize extreme precipitation events
• Climate change studies on extreme precipitation (events)
• Urban hydrology and hydrological impact as well as design studies
• New concepts of adaptation to climate change with respect to extreme precipitation in urban areas

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Conveners: Miloslav Müller, Tanja Winterrath | Co-Conveners: Elsa Cattani, Auguste Gires, Katharina Lengfeld, Marie-Claire ten Veldhuis, Massimiliano Zappa, Markus Ziese

UP2 – Interactions within the Earth System

UP2.1

The session will cover a wide range of atmospheric and oceanographic phenomena occurring in coastal areas, from synoptic and mesoscale patterns down to local scale processes, both for research purposes and applications, including operational oceanography and related services (e.g., coastal resource management, wind-waves and circulation monitoring and predictions for the sake of maritime safety and navigation, marine environmental protection, coastal erosion).

Observational studies will be considered, including in-situ measurements, ground-based and space-borne remote sensing techniques (scatterometers, synthetic aperture radar, ...), focusing in particular on recent mission data (e.g., SENTINEL), operational campaigns (e.g., HyMeX), and European project results (e.g., CEASELESS).

Modeling studies, based on stand-alone atmospheric, waves and ocean circulation models, will be of interest for the session. However, the main focus will be on the new area of numerical coupled modeling, which combines the dynamics of ocean, atmosphere and waves in a fully two-way exchange context. Coupled model results will be analyzed on the climate scale, validated against observations, but also applied to specific case studies in short-to-medium range simulations. Within this framework, specific attention will be allocated to high-impact weather and related marine events affecting coastal areas, such as intense cyclones, severe wind storms and storm surges, heavy rain events, flash floods, and supercells, analyzed both from a meteorological, marine and climate change perspective.

Activities of interest for stakeholders, related to renewable energy spatial planning both onshore and offshore, coastal management, urbanization planning for smart coastal cities, are also very welcome.

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Convener: Joanna Staneva | Co-Conveners: Frank Beyrich, Barbara Chimani
UP2.2

This session is devoted to basic and applied research on atmospheric processes, phenomena and impacts linking the chemical and physical states of the atmosphere. Particular interest lies in the observations and modelling of the transport, dispersion, transformation and deposition of atmospheric compounds (including air pollutants, pollen, GHGs, radionuclides and other substances naturally or accidentally released) and how they interact with the local and global climate and weather.

Within this scope, the session draws from diverse elements of atmospheric science research related to weather, atmospheric composition and climate, and includes theoretical, numerical modelling and experimental studies on scales extending from local to global, including the urban areas. Contributions on the development of observations and modelling techniques as well as on mitigation strategies varying from nature-based solutions to emission reductions also fit the scope of the session.

Targeted towards both disciplinary and interdisciplinary audiences, this session invites oral and poster contributions on topics including, but not limited to, the following:
• Feedback processes between atmospheric compounds, meteorology, and climate
• Characterization of the effect of urban planning choices and other interventions on the emissions, transport, dispersion and concentrations of atmospheric compounds
• Observations and modelling of urban meteorology including street canyon circulation, heat and mass fluxes within and over cities
• The impact of boundary layer processes on the transport and dispersion of atmospheric compounds
• Novel air pollution and atmospheric composition monitoring networks and platforms
• Air quality and transport model development using meteorological and chemical observations
• Air quality forecasting/assesment (incl. online modelling integrating chemical weather with NWP modelling) and chemical data assimilation.

The session also serves as a dissemination forum for relevant projects, including the Copernicus Atmosphere Monitoring Service (CAMS), COST Actions, WMO Global Atmosphere Watch (GAW) SAG-GURME & SAG-APP, FAIRMODE, as well as national- and European-scale consortium projects and research infrastructures.

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Convener: Leena Järvi | Co-Conveners: Alexander Baklanov, Vincent-Henri Peuch, Zita Ferenczi
UP2.3

We are planning to use the SPARK concept for this session. See https://www.ems2020.eu/programme_and_abstracts/on_the_programme/spark_sessions.html for further info.

This session is open for abstracts on all aspects of solar radiation, terrestrial radiation, cloud microphysics and aerosols. We welcome talks and posters on measurements and measurement campaigns, physics parametrizations, modelling on all time-scales from nowcasting to short-range numerical weather predication to decadal predictions and climate simulations, verification and applications such as renewable energy and agriculture among many others. This session is also open to contributions on any other relevant topic not explicitly listed here.

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Conveners: Emily Gleeson, Kristian Pagh Nielsen, Laura Rontu
UP2.4

The cryosphere represents one of the Earth system compartments showing strong signs of dramatic changes due to climate forcing.
If global warming is the main common driver causing such changes, the rates, impacts, and processes acting in the mountain and Polar regions can differ markedly.
Estimating the response of the global cryosphere to climate change as well as the response of the components of the climate system to changes in the cryosphere relies on the understanding of climate-cryosphere interactions and processes in different regions and along with different spatial and temporal scales.

Mountain regions:
The seasonal snow cover, mountain glaciers, permafrost and permanent ice deposits in caves are the main parts of the mountains cryosphere.
They affect the hydrology of a vast range of river systems in the world and are vital for water availability particularly in arid high mountain regions.
The water volume stored in mountain glaciers is small compared to the water storage in Polar Regions, but increasing rates of glacier mass loss result in a significant contribution to recent sea-level rise.
The observed permafrost degradation in mountain regions has severe implications on rock stability and increases the risk of natural hazards.
Permanent ice deposits in caves are probably the lesser-known as well as the smallest part of the earth’s cryosphere, but it has been shown recently that they can store important palaeoenvironmental information.
Investigating the micro-climate over snow and ice surfaces and its linkage to large-scale weather conditions and model climate is fundamental for tackling the mass and energy balance of the mountain cryosphere.

Polar regions:
Sea ice and ice sheets in both polar regions are sensitive to atmospheric forcing. Changes in these cryosphere components influence the climate through changes in atmospheric and ocean circulation, sea level, albedo, vegetation, and several related feedbacks.
In the Arctic, sea ice concentration and volume have recently experienced a sharp declining trend, and the Greenland Ice Sheet has similarly been losing mass at an increasing pace. Atmospheric forcing has played a crucial role in driving these trends and triggering positive feedbacks within the Arctic cryosphere-ocean-atmosphere system. These changes to the cryosphere may further feedback into large-scale climate variability through atmospheric and oceanic pathways.
At the other pole, sea and land ice in the Antarctic have heretofore experienced changes that strongly depend on the geographic location (e.g., east vs. west) and, overall, are less dramatic when compared to the changes observed in the Arctic cryosphere. Atmospheric influences on sea ice retreat and ice sheet/shelf surface melt are projected to become more prominent with continued climate warming.

Session:
Understanding the spatial and temporal variability of snow accumulation, storage and transport of ice and ice ablation in mountains and Polar Regions, and the interaction of the snow surface with the atmosphere within the boundary layer, are crucial for interpreting proxy records from various archives such as ice cores.
This session invites contributions addressing all aspects of cold regions meteorology and the cryosphere interacting with the past, present and future climate system from both modeling and observations.
We encourage submissions from multiple approaches, i.e. past records, meteorological and geophysical observations, numerical modeling and downscaling methods aiming to advance the current knowledge of the feedbacks between the cryosphere and the climate system.
Presentations of interdisciplinary studies, as well as detailed process surveys, are highly welcome.

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Conveners: Renato R. Colucci, Andrea Fischer, Marco Tedesco, Lise Lotte Sørensen | Co-Conveners: kay Helfricht, Costanza Del Gobbo, Timo Vihma
UP2.5

The Sun is the main energy source for the Earth's atmosphere. The main manifestations of external forcing from space to the atmosphere are in variations in solar parameters such as the solar irradiance (including solar UV) and solar particle fluxes. These parameters can induce changes in the atmosphere both at local and global scales, and can influence over a large range of altitudes. Some of these changes have the potential to affect the troposphere through atmospheric coupling processes, particularly through the stratosphere-troposphere connection, and thus have the potential to influence weather and climate.
The field of space weather, that is the change in the environment between the Sun and the Earth, has seen a rapid increase in research activity in recent years and in associated large scientific advances. It is clear that the weather and climate community can benefit from this via better representation of space weather effects and their associated impacts on the Earth’s atmosphere.

The aim of this session is to provide a framework for reviewing the state-of-the-art on these issues and to identify possible interrelationships between Earth and the Sun and space weather by assessing the level of coupling in the relevant physical systems and processes.

Contributions from the following topics (but not exclusively) are welcome:
• Solar irradiance and energetic particle impacts on the atmosphere
• Upper atmospheric dynamical variability and coupling between atmospheric layers
• Solar variations and stratosphere-troposphere coupling
• Solar influence on climate variability
• Solar irradiance (spectral and total irradiance) variations

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Convener: Mauro Messerotti | Co-Conveners: David R. Jackson, Suzy Bingham, Jan Laštovička
UP2.6

Meteorology and hydrology act in tandem across the interface of the earth's surface, and as our understanding and predictive capabilities grow this interface is becoming increasingly important. For the good of society, the need to meld together the two disciplines is now stronger than ever. Indeed many national meteorological services around the world have been evolving, formally or informally, into national hydro-meteorological services. The aim of this session, which was new in 2019, is to provide a large and all-embracing hydro-meteorological forum where experts from both disciplines can join forces, to combine and exploit expertise, and to accelerate the integration process. We invite contributions across a wide-range of spatial scales (from 10s of metres up to global), and a wide-range of time scales (from ~1 hour up to seasonal and climate change), including, but not limited to, the following topics:
- land-atmosphere interaction and hydrological processes, including feedback mechanisms;
- understanding the meteorological processes driving hydrological extremes;
- tools, techniques, and expertise in forecasting hydro-meteorological extremes (e.g. river flooding, flash floods etc.);
- fully integrated numerical earth system modelling;
- quantification/propagation of uncertainties in hydro-meteorological models;
- quantification of (past/future) hydrological trends in observations and climate models;
- hydro-meteorological prediction that includes the associated impacts;
- related cryospheric processes;
- environmental variable monitoring by remote sensing.
- droughts (in tandem with the 2020 conference theme)

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Conveners: Timothy Hewson, Fatima Pillosu
UP2.7

The European continent is in the lucky situation of hosting three Regional Hydroclimate Projects (RHPs) sponsored by the Global Energy and Water Exchanges Project (GEWEX) of the World Climate Research Programme (WCRP). These projects, though at various stage of their implementation, have the same objectives of providing a multi-disciplinary understanding of the water cycle under a changing climate and evolving human water usages. These RHPs cover three relatively different climates of Europe with their specific water challenges:
• HyMex: The Mediterranean region with extreme rainfall events and long droughts.
• BalticEarth: The Baltic region with its evolving cold conditions and biogeochemical linkages.
• PannEx: A transition climate in which humans have shaped the water usage during the last centuries.
The budgets between the various processes of the water balance (precipitation distribution and intensity, evaporation characteristics or contribution of surface and ground transports) are very different within each region and thus impacts of climate change will also differ. Two of these regions furthermore include the coupling to a closed sea. Human water usages have over the centuries adapted to the physical characteristics of the water cycle within each regional climate and are thus very different in all three regions.

In order to help prepare our societies to a different climate and ensure adequate water resources, we need to advance our process understanding and enhance our forecasting capabilities at all scales from days to centuries. Thanks to these RHPs we can bring together the critical mass of scientists of various disciplines to illuminate the different aspects of the water cycle and our water resources in each region. Focusing on certain regions also allows developing specific solutions for each of the regions and communicate more directly our knowledge to decision makers and the public at large.

This session invites oral and poster presentations dealing with the main scientific questions identified in these European RHPs. Several of these questions are common to other part of Europe and the world. Thus, this session will focus on the specific scientific, observational, forecasting, impact, application, collaboration and socio-economic issues:

• Water balance at the basin scale;
• Forecasting extreme rainfall events and their evolution in a warmer climate;
• Forecasting of Basin floods and flash floods: water for societal security under changing climate conditions;
• Understanding drought formation and improving early warning systems;
• Impact of irrigation on the water cycle;
• Agro-climatological and biological systems: Agriculture response to climate changes and weather extremes;
• Local climate interactions with energy fluxes: agronomical process modelling and micrometeorology,;
• Urban issues: urban metabolism, energy flows and interactions with surrounding areas;
• Regional climate modelling: Extreme weather and climate events as a risk to sustainable development;
• Regional Earth System processes which couple physical, biological and chemical cycles of the atmosphere, land and ocean.
• Impact and vulnerability assessments of climate changes and extreme weather events on different socio-economic sectors;
• Outreach, exploitation and education.

The conveners will also organise a short panel discussion within the session to examine which coordinated actions could be undertaken between the three European RHPs.

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Convener: Monika Lakatos | Co-Conveners: Jan Polcher, Anna Rutgersson, Joan Cuxart
UP2.8

Cities and urban environments become increasingly important in both scientific and socio-economic perspectives. As urbanization processes continue across the world, its representation, impact, and understanding need to be further studied in order to fully comprehend the extent of their impact on weather and/or climate and their extremes. Key challenges to this task are the level of complexity and multi-scale dimension of diverse urban environments.

Urban environment, in general, includes industrial zones which are on one hand limited by existing climate but on the other hand they make an impact on the surrounding environment including climate. Further to the air and water quality issues connected with industrial production water consumption, energy production and low level of resilience to climate extremes increase the general risks in industrialized urban areas. Climate change impacts are obvious and adaptation strategies have to include explicit recognition between climate issues and industrialization. All this makes an issue regarding the urban climate in terms of living conditions.

This session presents and explores aspects of cities and urban environments within the Earth system. We welcome modeling and observational studies that aim to investigate different aspects of urbanization (e.g. urban heat island, population vulnerability, urban/peri-urban agriculture) and their feedback on the climate system and extremes. Novel methods that aim to assess urban representation and/or to bridge the different scales of representation within numerical models are encouraged. The impact of cities on weather, climate and/or their extremes (e.g. drought, precipitation), as well as on climate change and on population and adaptation will also be discussed in this session.

Topics may include:
• new urban parameterizations, methods to derive urban parameters for numeric models
• implementation of climate mitigations, adaptation strategies and self-government policies in cities and urban context
• impact of the different urban parameterizations on the atmosphere dynamics and on the different scales
• the impact of the urbanization including estate industrial on weather and/or climate extremes
• field measurements of urban climate, e.g. urban heat island
• impact of different surfaces (green areas, impermeable outer surfaces etc.) on climate and/or its extremes in build-up areas
• population vulnerability to urban climate and climate change
• extreme events (e.g. drought, rainfall events) impacts on town agglomeration
• urban and peri-urban agriculture

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Conveners: Pavol Nejedlik, Arianna Valmassoi | Co-Conveners: Silvana Di Sabatino, Juraj Holec, Jan Keller, Marina Neophytou

UP3 – Climate modelling, analyses and predictions

UP3.1

Society will feel the impacts of climate change mainly through extreme weather and climate events, such as heat waves and droughts, heavy rainfall and associated flooding, and extreme winds. Determining from the observational record whether there have been significant changes in the frequency, amplitude and persistence of extreme events poses considerable challenges. Changes in the distributional tails of climate variables may not necessarily be coherent with the changes in their mean values. Also, attributing any such changes to natural or anthropogenic drivers is a challenge.

The aim of this session will be studies that bridge the spatial scales and reach the timescales of extreme events that impact all our lives. Papers are solicited on advancing the understanding of causes of observed changes in mean climate, in its variability and in the frequency and intensity of extreme events. In particular, papers are invited on trends in the regional climate of Europe, not just the mean, but variability and extremes, often for the latter measured through well-chosen indices.

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Convener: Martine Rebetez | Co-Conveners: Simona Fratianni, Albert M.G. Klein Tank, Monika Lakatos
UP3.2

Covariability between remote regions – often named teleconnections – are at the basis of our current knowledge of a large part of Earth’s climate variations and represent an important source of weather and climate predictability. Tropospheric and stratospheric pathways have been suggested to play a role in connecting internally-generated and radiatively-forced anomalies at mid-latitudes, as well as in settling tropical-extratropical and polar-nonpolar interactions. However, the underlying processes behind these linkages are still not properly understood, misled by different metrics and diagnostics, and/or generally poorly simulated by global climate models (GCMs). A continuous assessment of these atmospheric teleconnections is thus necessary, since advances in process understanding could translate into improving climate models and predictions.

This session aims at gathering studies on both empirical and modelling approaches, dealing with a dynamical characterization of mid-latitude atmospheric teleconnections. It invites contributions using observational datasets; coupled and uncoupled (atmosphere-only) GCM simulations; pre-industrial, present, and future climate conditions; idealised sensitivity experiments; or theoretical models.

Keynote talk:

(to be defined)

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Convener: Javier Garcia-Serrano | Co-Conveners: Paolo Davini, Yannick Peings
UP3.3

Synoptic climatology examines all aspects of relationships between large-scale atmospheric circulation on one side, and surface climate and environmental variables on the other. The session addresses all topics of synoptic climatology; nevertheless, we would like to concentrate on the following areas: statistical (empirical) downscaling, circulation and weather classifications, teleconnections and circulation regimes, and climatology of cyclones and other pressure formations, including effects of the circulation features on surface climate conditions. We also encourage submissions on recent climate variability and change studied by tools of synoptic climatology or otherwise related to synoptic-climatological concepts.

We invite contributions on theoretical developments of classification methods as well as on their use in various tasks of atmospheric sciences, such as climate zonation, identification and analysis of circulation and weather types, and synoptic catalogues. Climatological, meteorological, and environmental applications of circulation classifications are particularly welcome.

The session will also include presentations on statistical (empirical) downscaling as a tool for evaluation and reconstruction of historical climate, gap filling in time series, analysis of extremes and non-climatic variables. Also intercomparisons among downscaling methods and their validation belong to this session.

Contributions on teleconnections (modes of low-frequency variability) and circulation regimes are expected to cover particularly their impacts on surface weather, climate, and environment.

The contributions on climatology of cyclones and other pressure formations will include analyses of cyclone tracks, life time and intensity of cyclones, as well as analyses of anticyclones and blockings. We also invite studies on impacts of the pressure formations on the environment and society, their relationships with large scale circulation patterns, as well as analyses of their recent trends and behavior in possible future climates.

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Conveners: Radan Huth, Rasmus Benestad
UP3.4

The exceptional amplitude and rate of warming recorded at global, hemispherical and regional scales within contemporary instrumental records should be placed in the context of longer-term multi-centennial and millennial climate variability in order to both assess its uniqueness and better understand the mechanisms that contribute to the background of natural climate variability. Systematic meteorological measurements only span over a relatively short time interval. Thus, documentary evidence and natural climate proxies are used for the reconstruction and understanding of longer term past climate variability.

This session welcomes presentations related to various topics related to this frame:
• early instrumental meteorological measurements, their history and use for the long-term series
• documentary evidence and its features (advantages, disadvantages limits)
• natural climate proxies and its features (advantages, disadvantages, limits)
• methodological improvements and analysis of climate reconstruction approaches both from documentary evidence and natural climatic proxies
• results of climate reconstructions over different regions based on various climatic sources
• hydrological and meteorological extremes (e.g. floods, hurricanes, windstorms, tornadoes, hailstorms, frosts) and their human impacts in relation to climate variability beyond the instrumental period.
• climate modelling of the last 2K and comparison of model outputs with reconstructed/observed climatological data
• past impacts of climate variability on natural processes and human society
• past and recent perception of the climate and its variability
• history of meteorology and meteorological and climatological knowledge
• discussion of natural and anthropogenic forcings as well as recent warming at global, regional and local scales in a long-term context.

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Convener: Rudolf Brazdil | Co-Conveners: Ricardo García-Herrera, Fidel González-Rouco
UP3.5

Climate models have become a widespread tool to simulate the behavior of the climate system over longer periods (e.g., multi-decadal to centennial). They are also increasingly employed to obtain climate predictions on timescales of seasons to decades. And as computational power has increased, the ability to run these models at so-called convection-permitting scales (<4km grid spacing) has lead to an explosion of activity that targets explicitly resolving multi-scalar aspects of the climate system and opens new lines of inquiry. Climate modeling contributes to the understanding of the complex interaction processes in the earth system and provides scenarios for future climate conditions. The results of climate modeling form the basis for recommendations and decisions on how to prepare for and adapt to climate change and form the backbone of downstream development of many climate services. This session will be devoted to different aspects of new frontiers in climate modeling, including:
• advances and challenges in convection-permitting atmospheric modeling,
• numerical aspects of climate models,
• ensemble climate modeling,
• representation of physical earth system processes in climate models,
• sources and drivers of biases in climate models from subgrid-scale parameterizations to higher-level physical interactions,
• verification and intercomparison of climate model results, including new evaluation methods/metrics,
• data treatment and visualization of climate model results.

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Convener: Bodo Ahrens | Co-Conveners: Barbara Chimani, Stefan Sobolowski
UP3.6

Improved reanalyses of past weather can be obtained by retrospectively assimilating reprocessed observational datasets ranging from surface stations and satellites with a up-to-date Numerical Weather Prediction (NWP) model. The resulting time series of the atmospheric state is both dynamically consistent and close to observations. The interest in extracting climate information from reanalysis is rising and creating a request for reanalysis uncertainty estimation at various temporal-spatial scales.
These research questions have been addressed in EU-funded research projects (e.g.ERA-CLIM, EURO4M and UERRA). Regional reanalyses are now available for Europe and specific sub-domains, e.g. produced by national meteorological services. Global and regional reanalyses are also an important element of the Copernicus Climate Change Services.

This session invites papers that:
• Explore and demonstrate the capability of global and regional reanalysis data for climate applications
• Compare different reanalysis (global, regional) with each other and/or observations
• Improve recovery, quality control and uncertainty estimation of related observations
• Analyse the uncertainty budget of the reanalyses and relate to user applications

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Convener: Frank Kaspar | Co-Conveners: Eric Bazile, Jan Keller

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