Determination of Monthly Mean Humidity in the Atmospheric Surface Layer over Oceans from Satellite Data

Abstract

A simple statistical technique is described to determine monthly mean marine surface-layer humidity, which is essential in the specification of surface latent heat flux, from total water vapor in the atmospheric column measured by space-borne sensors. Good correlation between the two quantities was found in examining the humidity sounding from radiosonde reports of mid-ocean island stations and weather ships. The relation agrees with that obtained from satellite (Seasat) data and ship reports averaged over 2° areas and a 92-day period in the North Atlantic and in the tropical Pacific. The results demonstrate that, by using a local regression in the tropical Pacific, total water vapor can be used to determine monthly mean surface layer humidity to an accuracy of 0.4 g kg?1. With a global regression, determination to an accuracy of 0.8 g kg?1 is possible. These accuracies correspond to approximately 10 and 20 W m?2 in the determination of latent heat flux with the bulk parameterization method, provided that other required parameters are known.