National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2005

Comparisons of scatterometer and TAO winds reveal time-varying surface currents for the tropical Pacific Ocean

Kelly, K.A., S. Dickinson, and G.C. Johnson

J. Atmos. Ocean. Technol., 22(6), 735–745, doi: 10.1175/JTECH1738.1 (2005)

The differences between Tropical Atmosphere Ocean (TAO) anemometer and QuikSCAT scatterometer winds are analyzed over a period of 3 yr. Systematic differences are expected owing to ocean currents because the anemometer measures absolute air motion, whereas a radar measures the motion of the air relative to the ocean. Monthly averaged collocated wind differences (CWDs) are compared with available near-surface current data at 15-m depth from drifters, at 25-m depth from acoustic Doppler current profilers (ADCPs), and at 10-m depth from current meters and with geostrophic currents at the surface from the TOPEX/Poseidon radar altimeter. Because direct current observations are so sparse, comparisons are also made with climatological currents from these same sources. Zonal CWDs are in good agreement with the zonal current observations, particularly from 2°S to 2°N where there are strong currents and a robust seasonal cycle, with the altimeter-derived anomalous currents giving the best match. At higher latitudes there is qualitative agreement at buoys with relatively large currents. The overall variance of the zonal component of the CWDs is reduced by approximately 25% by subtracting an estimate of the zonal currents. The meridional CWDs are nearly as large as the zonal CWDs but are unpredictable. The mean CWDs show a robust divergence pattern about the equator, which is suggestive of Ekman currents, but with unexpectedly large magnitudes.

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