Recent improvements in GEOSAT altimeter data

Abstract

Altimetric sea level measurements made by the U.S. Navy's geodetic satellite (Geosat) during its exact repeat mission (1986–1989) have been successfully applied to the study of a variety of oceanic phenomena [Douglas and Cheney, 1990], and comparisons with in situ measurements have shown that monthly mean altimetric sea level is accurate to approximately 5 cm rms [Miller and Cheney, 1990; Taietai, 1989]. Nevertheless, the original release of geophysical data records (GDRs) produced by the National Oceanic and Atmospheric Administration/National Ocean Service [Cheney et al., 1987] showed significant uncertainties in two important fields: the tropospheric water vapor correction and the satellite orbit. Data from other satellites have been used to derive improved water‐vapor fields specifically for Geosat, while satellite ephemerides that are more precise by an order of magnitude have resulted from the application of advanced gravity models and the incorporation of new tracking data. To make these data readily accessible to the scientific community, new versions of the Geosat GDRs have been produced and are being distributed on compact disc/read only memory, or CD‐ROM [Cheney et al., 1991a]. In this report, we document the increased sea level accuracy attainable in the tropical oceans using these new T2 GDRs.