ECMWF | Reading | 18-21 November 2019
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
Importance of the stratosphere for extended-range prediction
The representation of stratosphere-troposphere coupling in S2S models
A signal and noise analysis of stratosphere-troposphere coupling in sub-seasonal prediction models
The importance of stratospheric initial conditions for winter North Atlantic Oscillation predictability
Subseasonal-to-seasonal predictability of the Southern Hemisphere eddy-driven jet during austral spring and early summer
On the dynamics of stratosphere-troposphere planetary-wave coupling
Subseasonal Forecasting of Sudden Stratospheric Warming Events and their Influence on the Troposphere in the NASA-GEOS-S2S Forecast System
Tuesday 19 November 2019
Wednesday 20 November 2019
Recent work at DWD to improve model dynamics and physics in the stratosphere and mesosphere
A new approach to linear ozone modelling
Dependence of simulated atmospheric teleconnections on biases in stratospheric circulation
Dynamics of Sudden Stratospheric Warmings
Stratospheric data assimilation at ECMWF
How does the Troposphere Amplify Stratospheric Variability?
Using causal discovery algorithms to evaluate troposphere-stratosphere linkages in reanalyses and modelling experiments
Remote presentation: Propagating annular modes
Investigation of ECMWF IFS Arctic winter 2015/16 lowermost stratosphere moist bias using airborne limb-imaging infrared observations
Thursday 21 November 2019
Global gravity wave distributions observed from satellites and resolved in the ECMWF-IFS
Stratospheric waves over the Southern Andes
Beyond Traditional Limits of Gravity-Wave Parameterizations: Transient Wave-Mean-Flow Interactions and Unbalanced Mean Flows
How does knowledge of atmospheric gravity waves guide their parametrizations?
Stratospheric impacts of a source-based parameterization of gravity waves generated by flow imbalance
The zonally-asymmetric response to stratospheric forcing in the Atlantic and Pacific storm tracks
Eliassen Palm Fluxes and Stratospheric circulations - Teleconnections as forcing
Towards a transient gravity wave drag parameterization
Seasonal Forecasting of the Quasi-Biennial Oscillation
The Combined Influence of the MJO and the Stratospheric Polar Vortex on Subseasonal Northern Hemisphere Winter Weather Patterns
Zonally asymmetric tropospheric signatures of polar vortex splits and displacements
ENSO influence on the North Atlantic: Quantifying nonlinearity and relative role of the stratospheric and the tropospheric pathways
Coupling convective sources to a transient gravity-wave parametrization in ICON
Homogeneity of the temperature data from renalyses
Abrupt stratospheric vortex weakening associated with North Atlantic anticyclonic wave breaking
Evaluation of revised gravity wave parametrizations using statistics of first-guess departures
Storyline Description of Southern Hemisphere Midlatitude Regional Climate Change
Impact of satellite observations on forecasting sudden stratospheric warmings
Real-time predictions of the 2019 New Year Stratospheric Sudden Warming in Multiple S2S Models
Downward Influence of the 2018 and 2019 SSW events in S2S Models
Can Solar cyclic variability modulate winter Arctic climate?
On the development of NCEP 127-L GFS with its top extending to the mesopause
Do sudden stratospheric warmings boost convective activity in the tropics?
Working group questions
- 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?
Inna Polichtchouk, Peter Bechtold, Michail Diamantakis, Robin Hogan, Irina Sandu, Tim Stockdale, Nils Wedi