Experiments with Atmospheric Motion Vectors at Ecmwf

Two new developments in extracting wind information by tracking of clouds or water vapour features are increasing the spatial coverage and providing quality estimates for individual observations. The transition from low density to high density wind observations of both GOES satellites led to first experiences with increased spatial coverage in NWP centres. The relative impact of low density and high density wind observations on the ECMWF assimilation and forecast system was tested. The rms vector difference against the background of the high density data is increased by up to 20 % for high level winds where the number of observations has increased by one order of magnitude. An initial negative forecast impact in the Northern Hemisphere was removed by introducing a thinning step for SATOB data as part of the observation screening. High density winds from GMS and GOES 9 during the NORPEX field study reveal potential for forecast improvements but confirms the complications with increased coverage. Secondly the monitoring of experimental Meteosat 7 wind products indicates the usefulness of the MPEF Quality Indicator (QI). The observation screening of SATOB winds was extended using this quality indicator as an additional selection criterium. Application of this approach leads to improvement for the NORPEX study.