Multi-year analysis using the NICAM-LETKF data assimilation system

Abstract

This study investigates the long-term stability of the global atmospheric data assimilation system, incorporating the Local Ensemble Transform Kalman Filter (LETKF) with the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The NICAMLETKF system assimilates conventional observations, advanced microwave sounding unit-A (AMSU-A) radiances, and global satellite mapping of precipitation (GSMaP) data. The longterm stability of the data assimilation system can be investigated only by running an expensive long-term experiment. This study successfully performed a data assimilation experiment with more than 2 years of data, using the relaxation to prior spread (RTPS) method for covariance inflation. Analysis fields indicate a stable physical performance compared with the ERA-interim data for the entire experimental period.