EVALUATION OF SATELLITE-DERIVED LATENT-HEAT FLUXES

A method of determining ocean-atmosphere latent heat flux using the Sp ecial Sensor Microwave/Imager (SSM/I) and the Advanced Very High Resol ution Radiometer (AVHRR) is presented and evaluated. While sea surface temperatures are retrieved from AVHRR data with an accuracy of 0.5-1. 0 K, re near-surface wind speed and the surface air humidity are retri eved from measurements of the SSM/I with accuracies of 1.4 m s(-1) and 1.1 g kg(-1), respectively. The latent heat flux is then computed wit h a stability-dependent bulk parameterization model. The derived fluxe s are compared to globally distributed instantaneous shipboard and buo y measurements and to monthly averages of 2 degrees x 2 degrees longit ude and latitude bins. The standard error for instantaneous flux estim ates is approximately 30 W m(-2), and that for monthly averages decrea ses to 15 W m(-2). Additionally, a 1-yr time series of latent hear flu x at the weathership M in the North Atlantic and two shorter time seri es during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmospher e Response Experiment (TOGA COARE) and the Central Equatorial Pacific Experiment (CEPEX) in the tropical Pacific are compared to satellite m easurements. The SSM/I-derived parameters, as well as the latent heat flux. are represented very well on the weathership M. During TOGA COAR E and CEPEX, the near-surface humidity is sometimes systematically ove restimated in the warm pool region, which results in an underestimatio n of the latent heat flux. Nevertheless, the representation of the lat ent heat flux is always in the range of the in situ measurements.