[p2] Observational issues


Data assimilation experiment of SSR mode-s downlink data

Hiromu Seko (Meteorological Research Institute), Takayuki Yoshihara, and Atsushi Senoguchi (Electronic Navigation Research Institute)


New air control radars provide the high-frequent data (4-10 seconds) of horizontal wind and temperature, as well as the positions of airplanes. This data, which is known as SSR mode-s downlink data, is expected as assimilation data of operational numerical prediction systems. In this study, the impact of downlink data on a heavy rainfall that occurred in the Kanto region, Japan on 26th August 2011 was investigated with the data assimilation systems by using a Local Transform Ensemble Kalman Filter (LETKF). The data assimilation experiment shows that the low-level convergence that caused the heavy rainfall was intensified by the downlink data and that the reproduced distribution of rainfall regions became similar to the observed one. This result indicates that the downlink data has potential to improve rainfall forecasts.