I. Introduction
Microwave sensors on board space-borne satellites can provide extensive observations of the sea surface wind field on a global scale [1]–[3]. Of which, active radars including scatterometer and synthetic aperture radar (SAR) rely on the sea surface roughness to measure the surface winds [4]–[6]. Over the last decades, multiple scatterometer missions have provided high-quality winds products at medium spatial resolution (up to 12.5 km). For example, scatterometers aboard European Remote Sensing (ERS-1/2) at C-band [7], NASA scatterometer (NSCAT) at Ku-band [8], and advanced scatterometer (ASCAT) also at C-band [9], among others. By comparison, SAR can provide wind field at resolution up to hundreds meters [10], [11]. This fine-scale SAR winds can complement scatterometer measurements to better observe spatial variability of local winds.