Impact study of Aeolus/ALADIN bias correction in the KIM data assimilation system

The Aeolus Atmospheric Laser Doppler Instrument (ALADIN) sensor onboard Aeolus provides the Horizontal Line Of Sight (HLOS) wind. The satellite-based HLOS wind profile data is significant because it complements the southern hemisphere, tropical and polar regions where existing wind observations are insufficient. The KMA also assimilates the HLOS wind for the operational data assimilation (DA) system since 2021, showing slightly positive impacts on average in the analysis field. However, it was confirmed that the impacts were relatively lower than those of the leading centers and limited due to systematic or random errors in the observation. 
In this study, we tested if we could enhance the positive impacts by applying the bias correction (BC) method to the HLOS wind observation. To this end, the Total Least Squares (TLS) were tested to conduct on the KIM Package for Observation Processing (KPOP) system, which is a system to provide well-qualified observations to the DA system. It shows better statistics in the mean and standard deviation of the first guess departures (O-B) by applying the TLS BC method with -0.19 m/s and 3.30 m/s from -0.44 m/s and 6.22 m/s, relatively. Detailed impacts on the analysis and forecast fields from the cycling experiments will be presented.