Workshop: Stratospheric predictability and impact on the troposphere
Session
Conveners
Session 5 : Model development, impact of model biases
- Michail Diamantakis (ECMWF)
This presentation reports on recent and ongoing model development work at DWD to improve the dynamical core and the physics parameterizations for model tops above the middle mesosphere, and to reduce systematic model biases in the lower stratosphere.
In the framework of a research group on multi-scale dynamics of gravity waves funded by the German Science Foundation (DFG), the dynamical...
Full stratospheric chemistry models are moderately expensive, and not suitable for high resolution ensemble forecasting at long lead times. Linear ozone models are cheap, but can suffer from biases compared to the latest ozone reanalyses, since they are traditionally calculated by linearizing a full chemistry model which is itself imperfect. These biases are an obstacle to using interactive...
Atmospheric teleconnections play a key role in long-range climate predictability. Important question is how well these teleconnections are represented in forecast models which usually have biased climate with respect to observations. Here we investigate the effect of systematic model biases on teleconnections influencing the Northern Hemisphere wintertime circulation. We perform a two-step...
Abrupt breakdowns of the polar winter stratospheric circulation such as sudden stratospheric warmings (SSWs) are a manifestation of strong two-way interactions between upward propagating planetary waves and the mean flow. While tropospheric precursors to SSWs have often been noted, SSWs have also been shown to spontaneously arise due to fortuitous coupling of a fixed wave field provided by the...
The stratosphere presents several challenges to the assimilation system, including systematic biases in models and observations, gravity wave dynamics affecting the balance of the analysis and limited amount of humidity observations. Recent developments have made it possible to address some of these challenges more directly, leading to improvements in the stratospheric analysis.
Model...