Infrared brightness temperature assimilation using an LETKF at convection-resolving resolutions

The German Weather Service (DWD) is making efforts to assimilate cloud and water vapor sensitive infrared brightness temperatures in the regional COSMO model using an LETKF data assimilation system. Observations from several infrared channels from the SEVIRI instrument onboard the Meteosat geostationary satellite are chosen for the assimilation. However, it has a number of challenges. These are, among others, the adequate forward modeling of clouds to obtain the model equivalent radiances, an effective treatment of both clear-sky and cloudy areas, and the evaluation and correction of systematic differences between measured and modeled brightness temperatures. Ongoing work is presented as steps towards the processing and assimilation of cloud-affected SEVIRI radiances in the COSMO model. The brightness temperature departures of observations and model equivalent are monitored to develop a cloud-dependent bias correction. Pre-operational results from the monitoring procedures and bias correction experiments are shown.