CoAuthors

Hui Feng (Univ. of New Hampshire, United States); Jean Tournadre (IFREMER, France); Bertrand Chapron (IFREMER, France)

An unanticipated complication for precision ocean altimetry has been the loss of valid ranging data under light wind or smooth water conditions that occur at length scales of 0.1-300 km. Such conditions have been shown to occur over 4-6% of the global ocean, and to persist 20-30% of the time in certain tropical and sub-tropical oceans. Originally termed the AGC or sigma0 blooms in the altimetry context, these quasi-specular conditions lead to greatly increased levels in the radar altimeter return signal and they also frequently lead to erratic estimates of range and platform pointing angle. Altimeter measurements under these conditions have been documented, particularly using TOPEX and Envisat observations. In several respects, the ocean altimeter is better-suited to assess such surface conditions than other available ocean wind observing radar or radiometer systems. This new investigation revisits the phenomena and its altimeter detection from several new directions. Here we first seek to ascertain if long term ocean altimeter datasets can reveal additional information on spatial and temporal variation of smooth water regions from 1992-present. Sigma0 bloom data from the 10 day repeat altimeter missions, TOPEX to Jason-3, are harmonized to develop seasonal time series across ocean warm pools and then to evaluate interannual change. New approaches to delineate between calm wind and biogenic slick control of these smooth surface conditions and their length scales will also be presented.