Oceanic dynamic height anomaly from Geosat: A conceptual model for short collinear orbit segments

Abstract

A method is derived for extracting oceanic dynamic height anomaly from collinear (exact repeat mission) GEOSAT short (∼ 1,000 km long) orbit segments. The procedure requires at least 1 year of simultaneous in situ observations and involves: (1) computing with respect to the ellipsoid, a mean sea surface height (SSH) profile solely from altimetry, (2) linear least‐squares removal of tilt and bias from individual SSH profiles with respect to the mean profile, (3) determining an independent mean dynamic height anomaly profile from hydrographic data along the orbit segment, (4) demeaning the tilt‐and‐bias removed individual SSH profiles and addition of the mean in situ dynamic height anomaly, and (5) correcting for concurrently observed dynamic height anomaly at two or more suborbital points during satellite transit. Analysis of the concept suggests root sum squared errors of ±5 cm, which can be reduced by smoothing and longer term measurements along the same orbit segment. A 1‐year comparison between two orbit segments at an open ocean crossover point shows differences of ±2 cm, and comparison with 6 months of simultaneous in situ data shows corrections of ±3 cm are required. Space‐time plots of demeaned tilt‐and‐bias removed GEOSAT SSH profiles, compared with similarly processed NMC/CAC numerical circulation model calculations, show good agreement with variability in the South Equatorial Current/North Equatorial Counter Current system in the eastern Pacific Ocean, and suggest that further development of the concept is warranted.