Synoptic estimates of air sea fluxes

Abstract : Synoptic and climatological dynamic studies generally rely on bulk aerodynamic flux formulae to describe air sea heat and momentum exchange on synoptic and climatological scales. Barometric pressure maps (which involve an intrinsic temporal averaging of the wind) and wind roses provide two sources of spatial and temporal wind information for flux calculations. Several investigators have shown that, due to the non-linear dependence of the bulk aerodynamic formulae on the winds, time-averaged estimates of the fluxes based on vector averaged winds systematically underestimate the actual time-averaged fluxes. Using 10 to 21 years of three-hourly sampled sea surface meteorological observations from 9 weatherstations in the North Atlantic Ocean and 2 weatherstations in the North Pacific Ocean, the three-hourly stresses, latent heat fluxes and sensible heat fluxes were calculated. The sampled data and the calculated fluxes were then averaged over periods varying up to 28 days. The estimates of the averaged fluxes based on the vector averaged winds were then compared to the directly averaged values.