AN EXAMINATION OF THE EAST PACIFIC ITCZ RAINFALL DISTRIBUTION

Very few (if any) in situ measurements of rainfall are available in th e Pacific ITCZ east of the Line Islands (157 degrees W). Hence, climat ological datasets, which are assembled from various in situ sources, a nd satellite-derived analyses of precipitation are frequently relied u pon to provide information on the distribution of rainfall in this imp ortant region. A substantial amount of disagreement exists among these information sources as demonstrated in this paper. In particular, the east-west gradient of estimated rainfall intensity in the eastern Pac ific ITCZ is quite different during the Northern Hemisphere warm seaso n among six different satellite algorithms (one infrared and five micr owave) and two climatologies that are examined. Some of these data sug gest that a local minimum in rainfall intensity is located near 140 de grees W in the Pacific ITCZ during northern summer, with increasing in tensity toward the east and west, while the others depict steadily dec reasing rainfall intensity from west of the Americas to the date line. Conversely, all of the precipitation estimates that are examined depi ct a rainfall maximum in the Pacific ITCZ near 140 degrees W during th e Northern Hemisphere cool season, although the magnitudes vary substa ntially among them. The authors examine estimates of seasonal mean rai nfall over the eastern Pacific ITCZ (east of the date line) from two r ainfall climatologies and six satellite precipitation estimation techn iques during July 1987 through June 1990. Inconsistencies among the pr ecipitation analyses are investigated by examining several independent datasets that include atmospheric circulation data, sea surface tempe rature data, and ship reports of weather type.