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UP – Understanding Weather & Climate Processes
Programme Stream Moderators:
Climate change detection, assessment of trends, variability and extremes
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.
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.
Tido Semmler - Arctic influence on mid-latitude weather and climate: recent progress and future prospects
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.
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.
Climate models have become a widespread tool to simulate the behavior of the climate system over longer time 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 forms the backbone of downstream development of many climate services. This session will be devoted to different aspects of climate modeling, including:
• advances and challenges in convection-permitting atmospheric modeling,
• development and refinement of global and regional climate models,
• 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.
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 are adressed in the ERA-CLIM, EURO4M and UERRA projects which are supporting the development 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
Analysis and predictions of tropical cyclones from subseasonal to decadal time scales
Tropical cyclones (TCs) are devastating weather phenomena that can cause vast socio-economic impacts. Here the term TC encompasses tropical depressions, tropical storms, hurricanes and typhoons. Each TC is predominantly influenced by synoptic-scale conditions, whereas, TC activity from sub-seasonal to decadal timescales is influenced by large-scale climate variability. Advances in understanding and prediction of TC activity enable us to make meaningful TC predictions with longer lead time. Since TCs in different basins have similarities and differences in terms of how large-scale conditions modulate TC activity, comprehensive understanding of TC variability in different basins helps deepen our knowledge of TC predictability and enhances our capability for TC prediction. This session offers a unique opportunity for research and operational communities to share recent progress in climate monitoring and prediction of TCs in all basins from sub-seasonal to decadal timescales. Both prediction and process understanding studies are welcomed.