Session programme

UP – Understanding Weather & Climate Processes

Programme Stream Moderators: Frank Beyrich, Barbara Chimani

PSE key.3

Public information:

Julia Schmale is assistant professor at École Polytechnique fédérale de Lausanne, Switzerland, where she heads the Extreme Environments Research Laboratory (EERL) since 2019. Her research focuses on how the ocean, land, cryosphere and human activities influence the chemical and microphysical composition of the atmosphere, and the resulting effects on climate and air quality. The main study regions are the Arctic, Antarctica, Southern Ocean and high altitudes, where she deploys aerosol and trace gas instrumentation on aircraft, research vessels, ground-based observatories and tethered balloons. Prior to founding the EERL, Julia was part of the Laboratory of Atmospheric Chemistry at the Paul Scherrer Institute, Switzerland, where she started as a postdoc and then headed the molecular cluster and particle processes research group.
Throughout her career, Julia has been engaged in science-policy interaction, a direction she pursued in particular as scientist at the Institute for Advanced Sustainability Studies, Germany, after having obtained her PhD from the Max Planck Institute for Chemistry, Mainz, Germany. Currently Julia represents Switzerland in the international steering group of the MOSAiC expedition, the Atmosphere Working Group of the International Arctic Science Committee, and she is a lead author on the forthcoming report by the Arctic Monitoring and Assessment Programme’s expert group on short-lived climate forcers.

Julia Schmale will give the Keynote Presentation of the Programme Stream Understanding Weather & Climate Processes:

Measurements of Atmospheric Variability during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition

Co-organized by UP
| Tue, 07 Sep, 16:00–16:30 (CEST)

UP1 – Atmospheric processes and severe weather


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.

Convener: Gert-Jan Steeneveld | Co-conveners: Bert Holtslag, Carlos Román-Cascón, Nikki Vercauteren
Lightning talks
| Mon, 06 Sep, 09:00–15:30 (CEST)

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.

Conveners: Fulvio Stel, Arne Spekat | Co-conveners: Dario Giaiotti, Mario Marcello Miglietta, Victoria Sinclair, Sante Laviola, Jordi Mazon
Lightning talks
| Tue, 07 Sep, 09:00–12:30 (CEST)

Forecasting wind gusts may become the next major challenge in numerical weather prediction. With increasing computer power, operational NWP systems just entered the convective scale, allowing the model physics to simulate convective processes more explicitly. While this is very beneficial for precipitation forecasting, wind gusts are still a sub-grid scale phenomenon relying on crude parametrizations. Furthermore, wind gusts cause large socio-economic damages every year. Wind gust predictions are getting higher relevance and load, e.g. for transport, aviation, urban development or public weather warnings. Yet forecast verification exhibits exceptionally low skill for wind gust predictions compared to other meteorological variables, which might also be impacted by a very sparse observational network. The spatial variability of wind gusts is probably as large as that of precipitation, but the observational network is much less dense and no equivalent to the spatial coverage of radar derived precipitation exists.

This session welcomes contributions which lead to a better understanding of the physical processes that determine wind gusts, and novel ideas/methods to improve wind gust forecasting and warnings in the future. More specifically, contributions on the following topics are welcome:

- Observations: The development of novel measurement tools for wind gusts (e.g. WindLIDARS) and suggestions for an optimized observational network in the future. Descriptions of the spatio-temporal variations of gusts.

- Explicit modelling: Small-scale model simulations (e.g. LES simulations) are a prerequisite to explicitly resolve the processes leading to wind gusts. Beside a better understanding of the physical processes they can be utilized to improve empirical approaches to approximate wind gusts more accurately.

- Wind gust forecasting and warnings: Methods to obtain guidance for wind gusts forecasts and warnings from operational weather forecasts, e.g. using historical observations by statistical postprocessing or forecast assimilation techniques. Prediction uncertainty of wind gusts.

- Climate monitoring: Long-term data sets for wind gusts as well as techniques for spatial wind gust analysis which are necessary for climate change adaptation and mitigation strategies

- Evaluation: The high-resolution model simulations on the one side and a sparse observational network on the other side require novel ideas in the verification of wind gusts simulations and warnings.

Convener: Irene Suomi | Co-convener: Sabrina Wahl
Lightning talks
| Tue, 07 Sep, 14:00–15:30 (CEST)

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.
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. This also includes metrological aspects of sensor characterization. Contributions are also invited that make use of advanced data sets for satellite data validation.

Convener: Frank Beyrich | Co-conveners: Fred C. Bosveld, Jens Bange, Domenico Cimini
Lightning talks
| Wed, 08 Sep, 09:00–12:30 (CEST), 14:00–15:30 (CEST)

This session provides a platform for contributions on high-resolution precipitation measurements, analyses, and applications in real-time as well as climate studies. Special focus is placed on documenting the benefit of highly spatially and temporally resolved observations of different measurement platforms, e.g. satellites and radar networks. This also comprises the growing field of opportunistic sensing such as 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 are welcome.
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.
According to the special focus of the 2021 Annual Meeting contributions on climate research and services for the achievement of Sustainable Development Goals are especially encouraged, such as contributions on research and services devoted to strengthening resilience and adaptive capacity, awareness raising and capacity, as well as disaster reduction (SDG 13) and application studies within the framework of inclusive, safe, resilient and sustainable cities (SDG 11) with respect to extreme precipitation in a changing climate.
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
• Climate research and services for the achievement of Sustainable Development Goals

Convener: Tanja Winterrath | Co-conveners: Elsa Cattani, Auguste Gires, Katharina Lengfeld, Miloslav Müller, Marie-Claire ten Veldhuis, Massimiliano Zappa, Markus Ziese
Lightning talks
| Thu, 09 Sep, 11:00–15:30 (CEST)

UP2 – Interactions within the Earth System


Cities and urban environments are a key aspect of the United Nations (UN) Agenda for Sustainable Development, as well as in recent the 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. These aspects are crucial both for the advancing of the current knowledge and the creation of effective sustainable solutions. Key challenges to this task are the level of complexity and multi-scale dimension of diverse urban environments.

Urban environments have a complex structure as they include different typologies, e.g. industrial, residential, and recreational/green areas, which have a different impact on the Earth system and can vary over time. These typologies have a diverse impact on the air and water quality and consumption issues, energy consumption/production. Further, urban environments have a low resilience to changes in climate change and extremes, which affects the overall population 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, with a particular focus on application for sustainable adaptation plans. 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

Including Tromp Foundation Conference Award to Young Scientists winner
Conveners: Pavol Nejedlik, Arianna Valmassoi | Co-conveners: Silvana Di Sabatino, Jan Keller, Marina Neophytou
Lightning talks
| Fri, 10 Sep, 11:00–15:30 (CEST)

The ongoing COVID-19 pandemic affects many aspects of the earth system and the society-environment interactions. In a world where most of the population is living in urban areas, the COVID-19 pandemic and associated restrictions have led to significantly change the pollution levels and exposure levels across the world. Also, the influence of external environmental parameters on the spread of the virus is still unclear. This session is calling for abstract submissions covering aspects of interactions between air pollution, meteorology and the spread of COVID-19. The submissions focus should cover one or more of the three proposed topics:
• Studies quantifying emissions and pollution changes associated to the countries and regions lockdowns stringency, but also accounting for changes in meteorological and environmental variables relevant to explain accurately the variability observed during the COVID-19 lockdowns. Abstracts focusing on air quality and possibly climate (expected effects due to potential long term emission reductions) are welcome.
• Studies on the influence of different atmospheric conditions (e.g. air quality, solar radiation, atmospheric dynamics, relative humidity and temperature) in the spread of COVID-19 and linking it with seasonality of the transmission rate.
• Studies assessing the associated comorbidity factors at the micro, local and large scales due to atmospheric conditions. The influence of meteorology, air quality and environmental factors and their relative weight in the spread of COVID-19, as compared against other relevant factors, such as viral variants, population density, social habits, stringency of confinement measures, and urban characteristics.

Including Tromp Foundation Conference Award to Young Scientists winner
Convener: Jérôme Barré | Co-conveners: Francesca Costabile, Leena Järvi, Jan Semenza
Lightning talks
| Thu, 09 Sep, 09:00–10:30 (CEST)

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.

We are planning to use the SPARK concept for this session. See for further info.

Conveners: Emily Gleeson, Kristian Pagh Nielsen
Lightning talks
| Wed, 08 Sep, 14:00–15:30 (CEST)

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)

Conveners: Timothy Hewson, Fatima Pillosu
Lightning talks
| Thu, 09 Sep, 09:00–10:30 (CEST)

UP3 – Climate modelling, analyses and predictions


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.

Including EMS Young Scientist Conference Award winner
Convener: Martine Rebetez | Co-conveners: Albert M.G. Klein Tank, Monika Lakatos
Lightning talks
| Tue, 07 Sep, 11:00–15:30 (CEST), Wed, 08 Sep, 09:00–12:30 (CEST)

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:

Elisa Manzini - "Troposphere-Stratosphere Coupling and Global Warming"

Including EMS Young Scientist Conference Award winner
Convener: Javier Garcia-Serrano | Co-conveners: Paolo Davini, Yannick Peings
Lightning talks
| Tue, 07 Sep, 09:00–10:30 (CEST)

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.

Including EMS Young Scientist Award winner
Conveners: Radan Huth, Rasmus Benestad
Lightning talks
| Mon, 06 Sep, 14:00–15:30 (CEST)

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

Convener: Frank Kaspar | Co-conveners: Eric Bazile, Jan Keller
Lightning talks
| Mon, 06 Sep, 09:00–12:30 (CEST)

Supporters & sponsors