Virtual workshop| 10-12 March 2020
Due to the measures associated with the COVID-19 virus, this workshop was held virtually for all external participants.
Workshop description
Warm conveyor belts (WCBs) are cloudy regions of ascent and strong diabatic forcing along the cold front of a synoptic depression. They can lead to heavy local precipitation and can have downstream impacts such as the onset and maintenance of blocking. They are therefore important in both weather and climate prediction. However, WCBs are also associated with inherently increased error growth-rates, and are difficult to constrain in analyses - due partly to clouds having a strong non-linear impact on satellite observations and moist processes leading to larger model errors. Indeed, forecast “busts” are often associated with the existence of WCBs. In the climate context, model deficiencies in WCBs and in their large-scale drivers are likely to be particularly relevant; with implications for the future statistics of precipitation, heatwaves and droughts for example. This workshop brought together observation, assimilation, model, forecast and research communities to explore these aspects. The aim was to improve understanding and to help develop optimal strategies to improve weather and climate prediction - a goal which would be very difficult for a single such community to achieve on its own. The workshop included invited and submitted talks, and had a strong focus on posters.
Programme and key questions
1. WCBs and downstream impacts
What do we know about the formation, dynamics and physics of WCBs and their downstream impacts? Is convection and upscale error growth important for the evolution and predictability of WCBs – with implications for the scales we need to represent in the model and constrain in data assimilation? Relationship to Atmospheric Rivers. Conceptual models.
2. Observations
Numerical weather prediction assimilates a wealth of observations; some sensitive to cloud and precipitation through the use of "all sky" methods. What are the key observations which currently constrain WCBs? What are the limits to how well they could constrain the relevant scales and parameters? Do WCBs strengthen the case for additional observations in future? EarthCARE, Aeolus. Learn from NAWDEX and AR campaigns.
3. Models and model uncertainty
How well do model climates represent the dynamics and physics of WCBs? What are the key sensitivities in model formulation and resolution (in the absence of initialisation)? Comparison with observations and reanalyses. Multi-model comparisons. Formulation and impact of model uncertainty.
4. Data assimilation
While WCBs might not highlight useful developments in DA methodology per se, there is a lot that diagnostics of data assimilation can tell us. How well do current assimilation schemes constrain WCBs? Where might the largest achievable improvements be made amongst the prior (background), model (non-linear, tangent linear and model uncertainty) and observational components? Ensemble data assimilation. Adjoint sensitivity. Forecast Sensitivity - Observation Impact (FSOI). Initial process tendencies and analysis increments. Multi-analysis comparisons.
5. Weather forecasting
How well are the dynamical evolution (including downstream impacts) and physical aspects predicted at present? Comparison with observational campaign data. Evaluation of ensemble forecast reliability, refinement and sharpness. Role of model uncertainty. What are the limits and challenges? Multi-model comparisons of ensemble forecasts (including TIGGE).
6. Climate variability and change
From observations/reanalyses what broader-scale features are associated with variations in WCB statistics? How well do models at seasonal/climate resolution represent these links? What can we infer about the statistics of WCBs (and their downstream impacts) in seasonal/climate predictions?
7. Break out groups and plenary
Further consideration of the above questions (in the light of talks and posters) and report back.
Presentations and recordings
Tuesday 10 March 2020
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Introduction |
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An overview on the concept of warm conveyor belts |
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Aspirations for the workshop - Bringing WCB understanding into forecast system development |
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Airborne active remote-sensing observations of warm conveyor belts |
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Embedded convection in the warm conveyor belt of a North Atlantic cyclone and its relevance for large-scale dynamics |
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The importance of warm conveyor belts for (upscale) error growth |
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The role of cloud diabatic processes in the life cycle of Atlantic-European weather regimes |
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Examining model error in potential temperature and potential vorticity via weather forecasts at different lead times |
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The Impact of Warm Conveyor Belt Forecast Uncertainty on Variability in the Downstream Waveguide |
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Linking atmospheric rivers and warm conveyor belt airflows |
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Influence of Warm Conveyor Belts on the Predictability of Downstream High-Impact Weather |
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West Coast Forecast Challenges and Development of Atmospheric River Reconnaissance |
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Adjoint Sensitivity and the Impact of Atmospheric River Reconnaissance Observations for North Pacific Forecasts |
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Workshop photo - Bluejeans Gallery |
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Wednesday 11 March 2020
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How well do current observations observe key features of warm conveyor belts? |
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Assimilation of water vapour, cloud and precipitation observations in extratropical cyclones |
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The prospects for radars on satellites to provide better observations of warm conveyor belts |
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How do diabatic processes in warm conveyor belts influence circulation and Rossby waves at tropopause level? |
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Revisiting the isentropic view of PV modification in warm conveyor belts |
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Three-dimensional radiative transfer around a tropopause fold |
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Rapid ascents embedded in a warm conveyor belt observed and modeled at kilometer-scale resolution |
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Impact of different microphysics on the warm conveyor belt of a deep extratropical cyclone observed during the NAWDEX campaign and on its associated ridge building. |
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Diabatic processes in the Warm Conveyor Belt of the Stalactite Cyclone: sensitivity to two convective parametrization schemes of the global Météo-France model ARPEGE |
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Microphysics and dynamics of snowfall associated to a warm conveyor belt over Korea |
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The effect of clouds, radiation and turbulence on upper-level PV |
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Linking Predictability barriers and diabatic processes |
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Impact of model upgrades on diabatic processes in extratropical cyclones and downstream forecast evolution |
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GPM Satellite Radar Observations of Precipitation Mechanisms in Atmospheric Rivers |
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Observational analysis of atmospheric rivers from dropsondes |
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Thursday 12 March 2020
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Development of a logistic model to study warm conveyor belts on subseasonal time-scales |
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Verification of warm conveyor belts in ECMWF IFS reforecasts |
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Exceptional air mass transport and dynamical drivers of an extreme wintertime Arctic warm event |
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Warm Conveyor Belts and Their Role for Cloud Radiative Forcing in the Extratropical Storm Tracks |
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Introduction to break out groups |
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Working group summaries and final plenary discussions |
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Posters
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Vertical cloud structure of warm conveyor belts – a comparison and evaluation of ECMWF operational analyses, CloudSat and CALIPSO data |
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Flow-dependent sub-seasonal forecast skill for Euro-Atlantic weather regimes and the role of warm conveyor belts |
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Association of the atmospheric rivers over Southern Ocean/Antarctica with warm conveyor belts |
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A novel masking technique to investigate atmosphere-ocean interaction over Western Boundary Currents |
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The Origin and Lifecycle of Diabatically Modified PV Anomalies in Atmospheric Blocks: A Case Study |
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Multi-layer cloud conditions in trade wind shallow cumulus – confronting models with airborne observations |
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Sensitivity of the warm conveyor belt of a deep cyclone to microphysics and turbulence schemes of the mesoscale model |
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Illustrating Multi-model Ensemble Predictability Across Scales Associated with the Valentine’s Day 2019 Storm |
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Dependence of the energy market players on ECMWF weather forecasts |
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Sensitivity of Diabatic Outflow of Warm Conveyor Belts on Ensemble Configuration |
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Quantifying the role of warm conveyor belts and PV cutoffs for the growth of ensemble spread over the North Atlantic |
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PV- and Warm Conveyor Belt Analysis of a North Atlantic Cyclone |
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Properties of warm conveyor belts along the flights of the SAFIRE Falcon during NAWDEX : comparison between airborne remote sensing observations and simulations of the global Météo-France model |
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The sensitivity of atmospheric blocking to changes in upstream latent heating |
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A portrayal of an orographic Warm Conveyor Belt using observations from aircraft, lidar and radar |
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A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe |
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Organising committee
Stephen English, Laura Ferranti, Richard Forbes, Christian Grams, David Lavers, Linus Magnusson, Mark Rodwell, Irina Sandu, Heini Wernli