THE EFFECT OF AVERAGING ON BULK ESTIMATES OF HEAT AND MOMENTUM FLUXESFOR THE TROPICAL WESTERN PACIFIC-OCEAN

The magnitudes of bulk air-sea surface flux estimates calculated using three temporal averaging methods were compared. The reference method is a simple average of fluxes computed from hourly values of bulk mete orological parameters termed the sampling method (SM). In contrast, th e scaler averaging method (SAM) computes the average flux from the ave rage of the bulk data; thus it ignores correlations between variables. The vector averaging method (VAM) is similar to the SAM but uses the magnitude of the average wind vector father than the average magnitude of die hourly wind vectors. The data used in this study were collecte d during the Tropical Ocean and Global Atmospheric pilot cruise of the R/V Wecoma in the equatorial Pacific Ocean near 0-degrees-N, 145-degr ees-E from February 17 to March 10, 1990. The ratios of the SAM and VA M values relative to the SM values were studied as a function of avera ging periods from 2-72 hours. The ratios vary little for times exceedi ng 36 hours. For averaging periods of 72 hours, the SAM estimates of Q (E), Q(H), tau(x), and tau(y) were 102%, 61%, 21%, and 69% of the SM e stimates, respectively; the VAM ratios were even lower. These results suggest that air-sea surface scaler fluxes and stress components compu ted from monthly, weekly, and even daily averaged bulk meteorological parameters can be seriously in error in equatorial, temporally variabl e wind regimes.