Martin Weissmann, Hans-Ertel-Centre for Weather Research, LMU Munich
Height correction for the assimilation of atmospheric motion vectors based on satellite lidar observations from CALIPSO
Coauthors
Kathrin Folger, Harald Anlauf, Alexander CressAbstract:
Atmospheric Motion Vectors (AMVs) provide valuable wind information for the initial conditions of numerical weather prediction models. However, height assignment issues and horizontal error correlations require a rigid thinning of the available AMVs in current data assimilation systems. The aim of this study is to investigate the feasibility of correcting the pressure heights of operational AMVs from the geostationary satellites Meteosat-9 and Meteosat-10 with cloud top heights derived from lidar observations by the polar orbiting satellite CALIPSO. The study shows that the wind error of AMVs above 700 hPa is reduced by 12 17% when AMV winds are assigned to 120 hPa deep layers below the lidar cloud tops. In addition to this direct correction that requires collocated CALIPSO and AMV observations, CALIPSO observations can also be used to derive monthly height bias correction functions to AMVs. These are now applied in data assimilation experiments with the modelling system of Deutscher Wetterdienst and first results indicate that the CALIPSO-based height bias correction for AMVs leads to significantly lower first guess departures of AMV winds as well as a reduction of forecast errors.