Laborhalle 3D - Foyer

Dipl.Met. Nico Becker, Institut für Meteorologie, FU Berlin, D

Wed, June 18th 2014, 3:30 pm

Orography-driven large scale secondary circulations in a regional climate model


Simulations with regional climate models (RCMs) often show large scale deviations from the driving model simulation. We show, that these deviations of the climatological averaged fields are the “footprints” of a secondary circulation (SC) that develops within the RCM domain relative to the driving data. A clustering approach is used in order to analyse the characteristics of the SC for different large scale flow situations. It is shown that large vortices with scales larger than 3000 km occur in the SC fields, which change location, intensity and shape depending on the large scale flow. These vortices are mainly caused by the different topographies of the RCM and the driving model. Higher mountains in the RCM modify the circulation of the driving data. However, these modifications cannot exit the model boundary due to the prescribed boundary conditions. Therefore, a closed circulation has to occur within the domain, leading to strong artificial balancing flows along the RCM boundaries.