Workshop: Stratospheric predictability and impact on the troposphere

ECMWF | Reading | 18-21 November 2019

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Workshop description

This workshop brought together experts to discuss and propose ways forward in representing the stratosphere in current and future numerical weather prediction models (1-50 km resolution, forecast lead times from medium-range to seasonal), and pathways by which better treatment of the stratosphere can improve predictive skill in the troposphere. The topics included understanding and diagnosing stratosphere-troposphere interactions, improved parametrizations and numerical schemes, the role of water vapour and ozone, observational evaluation and data assimilation. The aim of the workshop was to provide guidance to ECMWF on the priorities for representing the stratosphere in the coming decade.

Presentations and recordings

Monday 18 November 2019

Welcome and opening
Nils Wedi (ECMWF)

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Importance of the stratosphere for extended-range prediction
Ted Shepherd (University of Reading)

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The representation of stratosphere-troposphere coupling in S2S models
Amy Butler (CIRES/NOAA)

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A signal and noise analysis of stratosphere-troposphere coupling in sub-seasonal prediction models
Andrew Charlton-Perez (University of Reading)

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The importance of stratospheric initial conditions for winter North Atlantic Oscillation predictability
Christopher O'Reilly (University of Oxford)

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Subseasonal-to-seasonal predictability of the Southern Hemisphere eddy-driven jet during austral spring and early summer
Nick Byrne (University of Reading)

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On the dynamics of stratosphere-troposphere planetary-wave coupling
Etienne Dunn-Sigouin (Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research)

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Subseasonal Forecasting of Sudden Stratospheric Warming Events and their Influence on the Troposphere in the NASA-GEOS-S2S Forecast System
Joan Alexander (NWRA)

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Tuesday 19 November 2019

Stratospheric impact on surface climate on seasonal time scales
Steven Hardiman (Met Office)

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The dynamics and predictability of sudden stratospheric warmings and their surface impacts
Daniela Domeisen (ETH Zurich)

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Causes and fixes for stratospheric temperature biases in IFS and their impact on predictability
Inna Polichtchouk (ECMWF)

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Sudden stratospheric warmings in reanalyses and their tropospheric fingerprint
Blanca Ayarzagüena (Universidad Complutense de Madrid)

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The impact of Arctic sea-ice anomalies on the stratospheric polar vortex
William Seviour (University of Bristol)

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What influences the timing of Sudden Stratospheric Warmings?
Lesley Gray (NCAS / University of Oxford)

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Remote presentation: Future trends in stratosphere-to-troposphere transport in CCMI models
Marta Abalos (Universidad Complutense de Madrid)

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Remote presentation: Trace Gas Transport in the Stratosphere: Opportunities and Challenges
Edwin Gerber (Courant Institute, New York University)

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Chemical, radiative and dynamics interactions in the stratosphere using a hierarchy of models
Alison Ming (University of Cambridge)

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Panel discussion with Joan Alexander, Amy Butler, Ted Shepherd and Günther Zängl

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Wednesday 20 November 2019

Recent work at DWD to improve model dynamics and physics in the stratosphere and mesosphere
Günther Zängl (Deutscher Wetterdienst)

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A new approach to linear ozone modelling
Tim Stockdale (ECMWF)

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Dependence of simulated atmospheric teleconnections on biases in stratospheric circulation
Alexey Karpechko (Finnish Meteorological Institute)

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Dynamics of Sudden Stratospheric Warmings
Presenting on behalf of Thomas Birner (University of Munich): Álvaro de la Cámara (Universidad Complutense de Madrid)

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Stratospheric data assimilation at ECMWF
Elias Holm (ECMWF)

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How does the Troposphere Amplify Stratospheric Variability?
Mark Baldwin (University of Exeter)

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Using causal discovery algorithms to evaluate troposphere-stratosphere linkages in reanalyses and modelling experiments
Marlene Kretschmer (PIK)

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Remote presentation: Propagating annular modes
Aditi Sheshadri (Stanford University)

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Investigation of ECMWF IFS Arctic winter 2015/16 lowermost stratosphere moist bias using airborne limb-imaging infrared observations
Wolfgang Woiwode (Karlsruhe Institute of Technology, IMK-ASF)

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Thursday 21 November 2019

Global gravity wave distributions observed from satellites and resolved in the ECMWF-IFS
Peter Preusse (Forschungszentrum Juelich)

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Stratospheric waves over the Southern Andes
Andreas Dörnbrack (DLR Oberpfaffenhofen, Institute of Atmospheric Physics)

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Beyond Traditional Limits of Gravity-Wave Parameterizations: Transient Wave-Mean-Flow Interactions and Unbalanced Mean Flows
Ulrich Achatz (Goethe Universität Frankfurt)

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How does knowledge of atmospheric gravity waves guide their parametrizations?
Riwal Plougonven (LMD/IPSL, Ecole Polytechnique)

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Stratospheric impacts of a source-based parameterization of gravity waves generated by flow imbalance
Álvaro de la Cámara (Universidad Complutense de Madrid)

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Posters

The zonally-asymmetric response to stratospheric forcing in the Atlantic and Pacific storm tracks
Hilla Afargan Gerstman (ETH Zurich)

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Eliassen Palm Fluxes and Stratospheric circulations - Teleconnections as forcing
Jens Bonewitz (DWD)

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Towards a transient gravity wave drag parameterization
Gergely Bölöni (Goethe University Frankfurt)

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Seasonal Forecasting of the Quasi-Biennial Oscillation
Lawrence Coy (NASA/GSFC)

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The Combined Influence of the MJO and the Stratospheric Polar Vortex on Subseasonal Northern Hemisphere Winter Weather Patterns
Jason Furtado (University of Oklahoma)

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Zonally asymmetric tropospheric signatures of polar vortex splits and displacements
Michael Goss (Stanford University)

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ENSO influence on the North Atlantic: Quantifying nonlinearity and relative role of the stratospheric and the tropospheric pathways
Bernat Jiménez-Esteve (ETH Zurich)

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Coupling convective sources to a transient gravity-wave parametrization in ICON
Young-Ha Kim (Goethe University Frankfurt)

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Homogeneity of the temperature data from renalyses
Michal Kozubek (Institute of Atmospheric Physic ASCR)

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Abrupt stratospheric vortex weakening associated with North Atlantic anticyclonic wave breaking
Simon Lee (University of Reading)

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Evaluation of revised gravity wave parametrizations using statistics of first-guess departures
Chihiro Matsukawa (Japan Meteorological Agency)

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Storyline Description of Southern Hemisphere Midlatitude Regional Climate Change
Julia Mindlin (Universidad Nacional de Buenos Aires)

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Impact of satellite observations on forecasting sudden stratospheric warmings
Shunsuke Noguchi (JAMSTEC/Meteorological Research Institute)

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Real-time predictions of the 2019 New Year Stratospheric Sudden Warming in Multiple S2S Models
Jian Rao (Fredy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem)

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Downward Influence of the 2018 and 2019 SSW events in S2S Models
Jian Rao (Fredy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem)

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Can Solar cyclic variability modulate winter Arctic climate?
Indrani Roy (University College London)

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On the development of NCEP 127-L GFS with its top extending to the mesopause
Fanglin Yang (NOAA/NWS/NCEP/EMC)

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Do sudden stratospheric warmings boost convective activity in the tropics?
Kohei Yoshida (Meteorological Research Institute)

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Working group questions

Processes

  • Which stratospheric processes are important to represent accurately for improved tropospheric predictability on medium-range to seasonal timescales?
  • Which tropospheric processes are important to represent accurately for improved stratospheric predictability?
  • Can we quantify the strength of stratospheric impact on the troposphere (e.g., following weak and/or strong vortex events) versus the impact of other remote forcers such as MJO and ENSO?
  • What are the best tools and metrics to objectively evaluate the strength of the stratosphere-troposphere coupling, and, the skill provided by the stratosphere for tropospheric predictability?


Model design and development

  • What can be done to eradicate persistent stratospheric biases shared by many models? Is there an indication that certain biases are more important than others for tropospheric predictability?
  • What is the most efficient testing protocol for assessing if model changes result in an enhanced tropospheric skill as a result of a better stratospheric representation? For example, should we be focusing on the time periods around “windows of opportunity” (e.g., SSWs, final warmings in the Southern Hemisphere) when stratosphere is known to impact the troposphere?
  • How important is adding more complexity to parametrization design is for stratospheric circulation? E.g., should we be building source dependency into nonorographic gravity wave drag parametrizations in high resolution models? Should we be incorporating 3D propagation into gravity wave drag schemes?
  • Are there certain dynamical core designs that are known to better represent stratospheric processes (e.g., gravity waves, transport, QBO) and/or stratosphere-troposphere coupling?
  • Does the location of model top matter for stratospheric and/or tropospheric predictability? If so, where should the model top be located?

Role of observations

  • Are there any additional observations which are needed to enable model improvements relevant for weather prediction?
  • Are observational data sufficient to initialize the stratosphere?
  • How much do (or should) modellers trust stratospheric re-analyses?

Organising committee

Inna Polichtchouk, Peter Bechtold, Michail Diamantakis, Robin Hogan, Irina Sandu, Tim Stockdale, Nils Wedi

Programme

Workshop photos

Contact


#StratosphericWS