Ocean Wave Effects on Global Altimeter Wind Climate Retrieval

This paper examines the problem of global wind speed retrieval from satellite altimeters and demonstrates the existence of sea state induced biases. A new dataset of collocated Topex/ buoy measurements is used to validate four existing altimeter wind speed models based on formulations of the nadir backscatter used either alone or in combination with altimeter significant wave height. Evidence of sea state induced biases in the retrieved wind speed is presented using a variety of sea state discrimination criteria, including those of open/enclosed seas, fully-developed seas and wave age. We find that all existing models show a residual dependence on wave age, which leads to altimeter underestimating winds by 1 m/s on average in the case of young seas. Sea state effects at nadir are shown to produce both seasonal and regional biases in the altimeter-derived wind speed climatologies.