Application of multi-source spaceborne microwave sensors in the analysis of intensity and wind structure of Typhoon Koinu

Spaceborne microwave sensors can penetrate clouds and fog to directly measure 10 m ocean sea surface wind in any weather condition and at any time with a wide swath. These advantages provide an opportunity for monitoring the variation of typhoon intensity and wind field structure. Taking super typhoon Koinu (2023) as the research object, this paper estimates the typhoon intensity, radius of maximum wind (RMW) and wind radii from the long time series of measurements of active spaceborne synthetic aperture radar (SAR) and passive microwave radiometer. The International Best Track Archive for Climate Stewardship (IBTrACS) data and National Meteorological Center (NMC) real time meteorological data are used to validate our retrieval results. The results indicate that typhoon intensities estimated from observations of spaceborne microwave sensors are in better agreement with IBTrACS reports with the high correlation of 0.91 and RMSE of 3.8 m/s. Similarly, satellite-estimated RMW is in good agreement with IBTrACS data with the RMSE of 6.12 km. For wind radii, the RMSEs between satellite-estimated and NMC data are 102 km (R7, radius of moderate gale), 43 km (R10, radius of whole wind) and 35 km (R12, radius of hurricane wind), respectively. Moreover, for a TC with a long lifecycle such as Typhoon Koinu (2023), we demonstrate that the high-resolution and multitemporal synergistic observations from SAR and radiometers are valuable for studying fine-scale features of the wind field and the evolution of typhoon intensity and wind structure.