11:15 AM - 11:30 AM
[AAS03-02] Assimilation experiment by using localizations considering horizontal scale of error correlation in rainfall area
Keywords:GPS derived PWV, Data assimilation, LETKF, Localization
JMA-NHM (Japan Meteorological Agency Non-Hydrostatic Model) (Saito et al., 2007) and a nested NHM-LETKF system (Seko et al., 2013) which consists of outer (15 km grid) and inner (1.875 km grid) LETKFs were used. We targeted to reproduce rain bands which caused Uji heavy rainfall on 13-14 August 2012. GPS derived PWV (precipitable water vapor) data observed by our hyper-dense network installed in Uji with 1 km resolution (Sato et al., 2013) and GPS receivers of GEONET (GPS Earth Observation NETwork) were assimilated. Intense precipitating areas where rain rates are more than 10 mm/h were detected from radar data. We adopted 1 grid scale of localization radius for intense precipitating region and 5 grid scale for the other regions in inner LETKF. RMSEs of 1 hour rainfall of first guess averaged around rain band were calculated for 8 cycles of inner LETKF.
As a result of using smaller localization radius for intense precipitating area, RMSE became smaller in 5 cycles and became large only in 1 cycle. In 8th cycle when intensity of the rain band was at its peak, RMSE was improved about 10%.