A Statistical Analysis of the Relationships among Rainfall, Outgoing Longwave Radiation and the Moisture Budget during January–March 1979

Abstract

An analysis of the statistical relationships among observed daily rainfall, outgoing longwave radiation (OLR) and the moisture budget (precipitation minus evaporation or P ? E), obtained from three independent data sources during January through March, 1979, indicates that on a daily basis P ? E and OLR correlate significantly better with each other than they do with observed rainfall over open-ocean regions where the spatial density of rainfall observing stations is low. A spatial correlation over the Pacific Ocean indicates that P ? E and OLR correlate well in most?but not all?highly convective regions where both variables have moderate to high variances, and are uncorrelated in dry regions. Low correlations are obtained in regions of shallow convection and in areas of weak moisture convergence with cirrus at upper levels. It is demonstrated that OLR, P ? E, or observed rainfall alone cannot properly define the areal extent of large scale convective activity. A technique is developed in which P ? E is used in conjunction with OLR to better establish the intensity and spatial bounds of large-scale convective activity.