Based on the precipitable water data provided by Scanning Multichannel Microwave Radiometer (SMMR), and wind data by Geostationary Meteorological Satellite (GMS) and Geostationary Operational Environment Satellite (GOES), the monthly averaged water vapor flux and flux divergence have been estimated over the equatorial Pacific area for July 1980.
The main flow pattern of water vapor transport is essentially the combination of meridional convergence and westward flow. The intertropical convergence zone (ITCZ) in the northern part of the equatorial Pacific around 10°N, is characterized by water vapor convergence, which indicates that precipitation exceeds evaporation. The largest convergence areas of about 500 mm month−1 are seen over the ITCZ.
Evaporation can be estimated from the water vapor convergence if precipitation data, such as island rainfall data, are available. Over the eastern Pacific, where rainfall is nearly zero, evaporation is about 150 mm month−1 averaged over 0°-20S, 170°-90W. While precipitation is obtained if evaporation can be estimated by an independent method. Precipitation of more than 400 mm month−1 is seen around the ITCZ by the use of evaporation by bulk method.