Interannual Variations of Outgoing IR Associated with Tropical Circulation Changes During 1974-1978

Brant Liebmann and Dennis L. Hartmann

Department of Atmospheric Sciences AK-40, University of Washington, Seattle 98195

(Manuscript received 25 August 1981, in final form 14 January 1982)

Abstract

Interannual variability of outgoing IR in the tropical Pacific Ocean is studied using measurements derived from the NOAA scanning radiometer. In addition to the usual mean maps, seasonal anomaly maps are constructed from June, July, August 1974-December 1977, January, February 1978. These IR anomalies are closely related to changes in convective cloudiness patterns. Time series representing the equatorial eastern Pacific sea-surface temperature (SST) anomalies and monthly anomalies at various locations are also plotted. During this period a "warming event" occurs, in which SSTs in the eastern Pacific rapidly become anomalously warm. Dramatic changes in outgoing IR occur simultaneously with this SST increase. The region of convergence over Indonesia shifts eastward and connects to a well-developed intertropical convergence zone (ITCZ). The South Pacific convergence zone (SPCA) is also connected to the Indonesian convergence zone, but develops more slowly and does not reach its maximum strength until more than a year after the SST increases occur. By this time the ITCZ has returned to its pre-warming state. Eastward movement of the SPCZ is also apparent.