Ocean Vector Wind Retrievals From TRMM Using a Novel Combined Active/Passive Algorithm

This article presents a novel ocean vector wind (OVW) retrieval algorithm for remote sensing of ocean winds, using the precipitation radar (PR) and tropical rainfall measurement mission (TRMM) microwave imager (TMI) that operated for >17 years on the TRMM observatory. In this study, the wind speed and anisotropic wind direction (WD) characteristics of the ocean backscatter and brightness temperature (Tb) were empirically characterized to produce geophysical model functions for 49 PR beam positions and three TMI frequency channels (10, 19, and 37 GHz). For passive TMI measurements, the modified second stokes parameter (weighted difference of V and H-pol Tb's) was used to cancel the atmosphere contribution, which enhances the WD signal. Thus, combining linearly polarized Tb measurements with the anisotropic backscatter signature of the Ku-band PR, the feasibility of retrieving ocean surface wind vector is demonstrated. The OVW retrieval algorithm is validated by comparing retrievals with collocated numerical weather models wind vectors, and the statistics of OVW retrieval accuracy is presented.