ハイパースペクトル赤外サウンダを用いた台風中心部の大気プロファイル解析

Abstract

Warm-core structure featured by positive temperature anomalies at the center of tropical cyclones (TCs) is related to TC intensity defined by minimum sea-level pressure mostly determined by the hydrostatic balance. Microwave (MW) sounders such as Advanced Microwave Sounding Unit (AMSU) and Atmospheric Infrared Sounder (AIRS) Level-2 product (using Infrared + MW) have been used to investigate the warm-core structure. However, these observations might have a difficulty to resolve the detail of the warm-core structure due to its resolution (~50km). In order to retrieve the profiles more accurately, we developed a 1-dimensional variational method (1D-Var) that retrieved the temperature and humidity profiles at the eye of TCs using full-resolution (~15km) Hyper Spectral Infrared Sounder (HSIS) observations. A case study was conducted in the mature phase of Typhoon Trami (2018). Dropsonde observations by a Japanese airborne observation project called T-PARCII for Trami were collocated to validate the retrieved profiles from the Cross-Track Infrared Sounder (CrIS). The retrieved temperature and humidity profiles were close to the dropsonde observations compared to those obtained from the predictions by the global Numerical Weather Production (NWP) model of Japan Meteorological Agency (JMA). On 25th September when Trami had a peak intensity, the positive temperature anomaly, approximately 14 K temperature anomaly observed by dropsonde observation, was well reconstructed by 1D-Var with the CrIS observation compared to that estimated from the global NWP model output and the AIRS Level-2 product.