Abstract: A method of forecasting an ocean state via a multi-scale two-step assimilation of Surface Water Ocean Topography (SWOT) observations. The method may include receiving data associated with a prior ocean state forecast associated with SWOT observations, determining a large-scale increment state variable based on a large scale correction associated with the prior ocean state forecast, and determining a small scale initial input value based on (i) a combination of the background state associated with the prior ocean state forecast and (ii) the determined large-scale increment state variable. The method may include generating, based on the determined small scale initial input value, a small scale correction associated with the prior ocean state forecast, determining a small-scale increment state variable based on the small scale correction, and generating a current ocean state forecast based on at least some of this information.

Abstract: A method and apparatus are provided to allow altimeter data sets from multiple altimeter satellites to be used together. The measurable portion of geographically correlated orbit error (GCOE) is removed from the altimeter data sets, thereby allowing the data sets to be combined consistently. The GCOE structure for a reference data set is estimated through crossover difference analysis. The unmeasurable portion of the GCOE is not removed, although the spatial structure of this portion is determined. A reference mean sea level (SL) is corrected for the measurable GCOE and is then used as a reference surface for estimating the GCOE structure for an independent altimeter data set. This is performed by examining crossover differences between the altimeter mean SL and the reference mean SL at the multimission crossover points. The change in sea surface height (SSH) between the input data set and the reference data set is determined.