Evaluation and diagnosis of surface currents in the National Centers for Environmental Prediction's ocean analyses

摘要: Ensemble average currents from the 15 m depth level of National Centers for Environmental Prediction's (NCEP) analyses tropical Pacific Ocean are evaluated against surface mixed layer current observations obtained an extensive set satellite-tracked drifting buoys. These averages display many climatological characteristics region but not intended to serve as a climatology because data trimmed match time-space distribution observations. Substantial discrepancies between and revealed. First, near-equatorial meridional divergence have approximately twice magnitude in This discrepancy is largely independent whether temperature profile assimilated or attributed parameterization vertical viscosity. Second, zonal flow both North Equatorial Countercurrent (NECC) South Current (SEC) much stronger than observations, especially western Pacific. associated with assimilation data. It arises salinity active variable underlying analysis model controlled by boundary fluxes other Under uncontrolled influence advection strong horizontal diffusion becomes nearly homogeneous. Consequently, do account observed temperature-salinity correlations when density computed following leads erroneous pressure gradients that drive excessively geostrophic force large accelerations near boundary. Our results indicate it important consider consequences on structure neglecting during We recommend buoys volunteer observing ships be initiated improve ocean analyses.