Himawari-8/9 Follow-on Satellite Program and Impacts of Potential Usage of Hyperspectral IR Sounder

In FY 2018, the Japan Meteorological Agency (JMA) has started considering the next geostationary satellite program. JMA will pursue a seamless geostationary Earth orbit satellite system, including in particular the deployment of hyperspectral infrared sounder (HSS) across the full GEO ring. In the study reported here, the impacts of the hyperspectral sounder on a geostationary satellite (GeoHSS) were assessed via the observing system simulation experiment (OSSE) to help evaluate the Himawari follow-on program. Hypothetical GeoHSS observations were simulated using an accurate reanalysis dataset for 2018 heavy rainfall and typhoon events in western Japan. The global data assimilation experiment demonstrated that the assimilated GeoHSS clear-sky radiances improved representative meteorological field forecasts and significantly reduced typhoon positional errors. A regional data assimilation experiment showed that assimilated temperature and relative humidity profiles derived from GeoHSS data improved information on heavy rainfall associated with enhanced southwesterly moisture flow off the northwestern coast of Kyushu Island. These results indicate that the GeoHSS provides valuable information on frequently provided data regarding vertically resolved temperature and humidity, thereby helping to improve forecasting of extreme meteorological events.