Annette Müller, Freie Universität Berlin
"What is... the Dynamic State Index?"
The Dynamic State Index (DSI) is a scalar diagnostic field that quantifies local deviations from a steady and adiabatic wind solution. Thus, this parameter indicates non-stationarity as well as diabaticity. The DSI-concept has originally been developed through the Energy-Vorticity Theory based on the full compressible flow equations.
Additional Dynamic State Indices that are based on reduced models of atmospheric motions, the quasi-geostrophic (QG-) theory and the Rossby-model, provide the opportunity for a scale-dependent diagnoses of various atmospheric processes. Applying the COSMO-DE data set of the German Weather Service and ECMWF’s ERA-INTERIM data set, it can be shown that each DSI captures different characteristics of scale-dependent atmospheric processes. The DSI for the primitive equations is highly correlated to precipitation on convective scale, whereas the DSI for the QG-model indicates precipitation clusters up to ‚Großwetterlagen‘ on synoptic scale. Finally, the DSI for the Rossby model can be used to diagnose larger scale weather situations on the synoptic scale, such as atmospheric blockings.