On generating altimetric sea level time series from crossover differences

Abstract

Abstract The essential features in generating altimetric sea level time series from crossover differences (as originally proposed by Fu and Chelton, and followed by several other adaptations) are reviewed here. New results are also presented in an effort to answer questions raised in the review. All procedures involve explicit or implicit spatial and temporal smoothing, which are necessary for error reduction and for ensuring reasonably dense temporal sampling rates. One crucial step in the procedures involves the designation of a spatial sampling box, where a larger box results in better error reduction and denser temporal sampling, but may cause excessive signal attenuation. These and various other issues are discussed here by comparing the island tide gauge data to GEOSAT (first 17 months, the nonrepeat era) sea level time series in the tropical Pacific. It is found that the optimal box size varies from island to island because of the geographical dependence of the error as well as the signal. Furtherm...