Surface winds in a midlatitude storm seen by satellites and numerical models

Sea surface winds are observed from polar orbiting satellites by active and passive microwave instruments. The scatterometer on the European Remote Sensing Satellite-1 (ERS-1) has been operating since 1991 providing vector winds at 50 km resolution over a 500 km wide swath, and ERS-2, a twin, was launched in 1995. The Special Sensor Microwave Imager, SSM/I, (on several Defense Meteorological Program satellites since 1987) provides wind speed in non-raining areas over a 1400 km swath. Several altimeters such as those on the ERS satellites and TOPEX-Poseidon (since 1992) sample a 10 km wide path at nadir providing wind speed over the footprint. All these data can be used singly, in conjunction or after assimilation into numerical models to form gridded wind fields that may represent the surface wind over periods ranging from the instantaneous swath view to hours, days, weeks or months. The authors examine how the sampling and the method to form the wind field influences the resulting means of certain wind parameters during the passage of a midlatitude cyclone in the North Pacific Ocean. The main objective is to understand the possible adverse effects of limited sampling of the storm systems moving across the sea