Evaluation of TOPEX and basin‐wide Tropical Ocean and Global Atmosphere‐Tropical Atmosphere Ocean sea surface topographies and derived geostrophic currents

Fields of TOPEX‐derived sea level anomalies are validated against and compared with fields of Tropical Ocean and Global Atmosphere‐Tropical Atmosphere Ocean (TOGA‐TAO) dynamic height anomalies for the first 470 days of the TOPEX/POSEIDON mission. At periods longer than 35 days, TOPEX sea level anomalies compare extremely well with TOGA‐TAO dynamic height anomalies throughout the whole basin, with a mean correlation of 0.79 and mean rms differences of 2.6 cm. Zonal geostrophic current anomalies are then derived from both data sets and validated against in situ current meter measurements at the equator. TOPEX‐derived geostrophic current anomalies at the equator are in good agreement with in situ currents at 0°–165°E, 0°–170°W, 0°–140°W, and 0°–110°W. TOGA‐TAO‐derived current anomalies compare well with in situ currents at 0°–110°W, 0°–140°W, and 0°–170°W, but poor comparisons at 0°–165°E are thought to be linked to the absence of instantaneous salinity measurements in the dynamic height calculation. Despite localized discrepancies, basin‐wide TOGA‐TAO geostrophic currents compare reasonably well with TOPEX‐derived geostrophic currents. The discrepancies in the comparison between TOPEX and TAO are shown to be mostly associated with gaps in TOGA‐TAO space‐time sampling and subsequent gridding procedures.