An update on the 4D-LETKF data assimilation system for the whole neutral atmosphere

Abstract. The four-dimensional local ensemble transform Kalman filter (4D-LETKF) data assimilation system for the whole neutral atmosphere is updated to better represent disturbances with wave periods shorter than 1 d in mesosphere and lower thermosphere (MLT) region. First, incremental analysis update (IAU) filtering introduced reduce generation of spurious waves arising from insertion updates. IAU other methods, also commonly used middle atmospheric assimilation. Second, order horizontal diffusion forecast model changed reproduce more realistic tidal amplitudes that were observed by satellites. Third, Sounding Atmosphere using Broadband Emission Radiometry (SABER) Special Sensor Microwave Imager/Sounder (SSMIS) observations stratosphere are assimilated. performance resultant analyses evaluated comparing them mesospheric winds meteor radars, which not representation products greatly improved only zonal mean field but short-period and/or horizontally small-scale disturbances.