SPATIAL SAMPLING REQUIREMENTS FOR TROPICAL PACIFIC SEA-SURFACE TEMPERATURE VARIABILITY

The Tropical Ocean and Global Atmosphere-Tropical Atmosphere Ocean (TO GA-TAO) array of moored buoys is a real-time ocean-observing system wh ich measures wind and upper ocean temperature and currents in the equa torial Pacific Ocean. The mean square error for TOGA-TAO sea surface t emperature (SST) due to spatial sampling of 1500 km zonally and 200 km meridionally is expressed as the frequency-wavenumber integral of a s ampling design dependent filter multiplied by the space-time spectral density of the SST field. Ten years of NOAA advanced very high resolut ion radiometer SST data, on a 1-degree by 1-degree by 1-day grid, were used to obtain space-time statistics. The zonal correlation length de creases with latitude. The zonal correlation length is 2000 km at the equator and 1500 km at 4-degrees-N. The temporal correlations are 90 d ays at all latitudes from 0-degree-N to 5-degrees-N. The frequency-wav enumber spectrum decreases as the inverse square of the wavenumber in the low-wavenumber domain and as the inverse cube of the frequency in the low-frequency domain. By using the sampling error formalism and th e frequency-wavenumber spectrum obtained from satellite-derived SST, t he sampling errors of the area- and time-averaged SST over the averagi ng box of 15-degrees zonally by 2-degrees meridionally by 1 month were found to be about 12% of the variance of the area-averaged SST for th e TOGA-TAO array spacing.