Impact of NOAA16 and NOAA17 AMSU-A in the DMI-HIRLAM 3DVar analysis and forecasting system J. Grove-Rasmussen

Until recently (A)TOVS data have mainly been assimilated into global numerical weather models, but the study of their impact on a regional model is of great relevance for many weather services, especially if data can be made available with sufficiently short delay. A study of the impact of adding NOAA16 and NOAA17 ATOVS AMSU-A radiances to the DMI-HIRLAM system is carried out. The analysis is performed with both locally received data from the two stations Smidsbjerg (Denmark) and Sdr. Strmfjord/Kangerlussuaq (Greenland), and with data from EARS . The data used are from the temperature sounding channels (channels 4-10) from the AMSU-A instrument. A positive impact is observed in the winter time when using the satellite data, whereas the conclusion on summertime use of the data is less certain. 1. OBSERVATIONS With polar orbiting satellites used for Earth/atmosphere observation a global coverage is reached within reasonable time. At present three satellites (NOAA15, NOAA16 and NOAA17) deliver data from the nadir viewing ATOVS package of instruments. From this package observation at infrared wavelengths is performed with the HIRS instrument and in the microwave regime with AMSU -A and AMSU-B