Predictability and Dynamics of tropopause Rossby-waves and high-impact weather

English

Predictability and Dynamics of tropopause Rossby-waves and high-impact weather

Conny Schwierz, Arwen Twitchett

Aims:

The aim of  research is to investigate the predictability of Rossby-wave trains, the processes by which they are triggered and amplified and through which their propagation is modified. We will investigate these Rossby wave properties climatologically using reanalyses, as well as assess their predictability in operational forecast data (e.g. TIGGE). Numerical sensitivity experiments of selected case studies will be conducted to study the role of the components and processes (diabatic processes, triggers, wave guide) involved with the Rossby wave development leading to high-impact weather events. The outcome will inform PANDOWAE partners and aid in the planning of the European THORPEX experiment T-NAWDEX.

Summary

In this project we investigate the predictability of RWs and RW breaking (RWB, streamers), with a specific focus on the representation of processes by which they are triggered and through which their propagation and breaking is modified. The related forecast errors will be attributed and the effect of these errors for downstream impacts will also be addressed. The investigation will consider the predictability of tropopause RWs and streamers in deterministic and ensemble prediction systems, as well as by carrying out case studies for select events. Dynamical insight will be sought also by comparison with existing RW and streamer climatologies from the ERA40 data set and subsequent operational analyses. A specific component of the project makes use of the forseen T-PARC targeting and predictability experiment and the newly available TIGGE multi-model-multi-ensemble data base. Specific objectives of the project The overall aim of our work is to identify and analyse the factors and dynamical processes that influence predictability of RWs and wave breaking in current forecasting suites, with a focus on generation, propagation and wave-breaking, and to quantify the role that RW take in the predictability of high-impact weather. In relation to PANDOWAE, the following objectives are relevant:

A) Undertake a climatological assessment of the predictability of some salient features involved in RW propagation and breaking using forecast data and comparing them to a corresponding, existing longterm climatology (ERA40, ECMWF analyses). These features include frequency, shape, wave-guide properties, amplification properties.

B) Identify and quantify systematic model errors of the above RW features, in particular errors for subgroups of forecasts for specific cases of, e.g. high-impact weather, or background flows of interest (conditional verification). C) Quantify the impact of moist/diabatic processes on the development of RWs and their importance in explaining forecast errors.

D) Quantify the predictive capabilites for RW features in multi-model-multi-ensemble TIGGE data.