CoAuthors

Doug Vandemark (Univ. of New Hampshire, United States); Joseph McMichael (JPL, United States); Phillip Callahan (JPL, United States)

New empirical models for the radar altimeter range bias associated with ocean waves have been produced in 2015 as part of ongoing NOAA and NASA projects directed at finalizing the long term data record for the TOPEX ocean altimeter. These sea state bias (SSB) models were developed using the latest timeframe geophysical data record corrections (e.g. orbits, tides, wet path delay) and the SSB models were built for both the MGDR and the new retracked datasets (RGDR) provided by JPL that contain revised range and wave height data derived from an intensive ground system retracking of the altimeter return waveform measurements. The SSB model creation methods applied involve using a multi-year ensemble of yearly SSB correction models produced using direct sea level anomaly data coincident with wind speed and wave height (2D models) or wind speed, wave height, and wave period (3D models). In the latter case the wave period data come from global wave model hindcast data of an NCEP wind forced WAVEWATCH III model produced at IFREMER. SSB models are derived for both Side A and Side B of TOPEX and the model results assessed against currently available SSB models using a series of metrics, the tandem Jason/TOPEX orbit datasets, and ascending vs. descending passes. Recommendations for optimal and sufficient 2D and 3D SSB models for TOPEX application in support of climate record objectives will be provided, both with respect to MGDR and RGDR datasets.