Andreas Rhodin, German Weather Service

Choice of localisation length scales in a hybrid EnVar/LETKF


At DWD a hybrid global data assimilation system (13 km deterministic EnVar coupled to a 40 km LETKF) is operational since January 20th 2016. The initial configuration is based on fixed localisation length scales (300 km horizontally, 0.3 to 0.8 scale heights vertically) in both components.

This talk examines the range of correlation length scales present in the background ensemble and explores options for a more sophisticated consideration of the range of scales in the setup of the hybrid system.