Improving typhoon analysis and forecasting via assimilation of FY-3E WindRAD Ku-band winds

This study presents the assimilation capability of FY-3E Ku-band Ocean Surface Wind Vector (OSWV) products within the Gridpoint Statistical Interpolation (GSI) system using the Hybrid Four-Dimensional Ensemble-Variational (Hybrid-4DEnVar) method. A comprehensive assessment is conducted through a sensitive case study of Typhoon Bebinca (2024) and a one-month cycling assimilation experiment. Results demonstrate that assimilating FY-3E OSWV significantly improves the initial analysis of typhoon structure by correcting the positional bias of the sea level pressure (SLP) center, sharpening the near-surface wind gradients, and enhancing both the warm-core structure and tropospheric moisture distribution. The improved low-level wind fields strengthen air-sea interactions, generating larger enthalpy fluxes that provide a more realistic energy source for typhoon intensification. Consequently, compared to the control run, the 120-h forecast errors of typhoon track, central SLP and maximum wind speed are reduced by approximately 43%, 58%, and 61%, respectively. Furthermore, the one-month cycling experiment confirms the robustness of these improvements, showing sustained error reductions in lower-tropospheric wind analyses and 7-day forecasts. These findings underscore the substantial operational value of FY-3E Ku-band OSWV data for improving tropical cyclone prediction skills.