[A-AS02] 台風研究の新展開～過去・現在・未来

[AAS02-P02] Observing system simulation experiment for tropical cyclone prediction using SAMRAI

*青野 憲史¹、Nguyen Trung²、前田 崇²、冨井 直弥²、岡﨑 淳史³ (1.国立大学法人千葉大学　環境リモートセンシング研究センター、2.宇宙航空研究開発機構、3.国立大学法人千葉大学　国際高等研究基幹)

キーワード：データ同化、数値天気予報、観測システムシミュレーション実験、台風

The improvement of numerical weather prediction is essential for management of weather disaster. In the numerical weather prediction, obtaining better initial values is an important issue. Although satellites are powerful tool for observing atmospheric condition, conventional sensor has missing values due to the radio frequency interference (RFI). The new microwave radiometer called SAMRAI, which is under development by JAXA, has higher spatial, temporal and frequency resolution compared to conventional systems and technologies. SAMRAI will provide observation without missing values from the RFI because of high frequency resolution. This study investigates the potential of SAMRAI for tropical cyclone (TC) forecast by the observing system simulation experiment (OSSE). We conducted a forecast experiment which assimilates sea surface winds and column-integrated water vapor over the sea retrieved by SAMRAI and compared with forecast without SAMRAI observation to assess the impacts of SAMRAI.

In this OSSE, we chose 18-km grid spacings although it was coarser than observation. We applied local ensemble transform Kalman filter (LETKF) as a data assimilation system. The SAMRAI-observed variables were assimilated under a horizontal localization length of 400 km and a vertical localization length of 5 km. We performed forecast experiments using mean of analysis from 30-member data assimilation. Results suggested that SAMRAI improved a 5-day forecast of track and intensity though it depended on the initial date. The future issues are to increase horizontal resolution and the number of data assimilation cycles.