8 October 26, 2009 8 th COPS Workshop, Cambridge, UK Achievements, challenges, and strategy:  3DVAR (Arome, Meteo France) and 3DVAR/4DVAR (WRF, IPM) with GPS and radar data  Nudging (DWD reanalyses, ARPA SIMC)  Strong impact of the assimilation of humidity, Doppler wind, and radar reflectivity data but no comparison of data assimilation methodology (e.g., VAR versus EnKF), so far data assimilation efforts not coordinated.
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