Behavior of Deep Convective Clouds in the Tropical Pacific Deduced from ISCCP Radiances

Abstract We analyze the properties of deep convection over the equatorial Pacific and its relationship to sea surface temperature (SST) and surface wind divergence using ISCCP radiance data for July 1983 and January 1984. Deep convective clouds (DCC) are diagnosed with both a combined visible-infrared threshold method and an infrared-only threshold method. The visible channel is important in diagnosing deep convection in different regions with different surface and atmospheric properties because of the existence of large-scale variations of DCC top altitudes. The ITCZ and SPCZ exhibit changes in these two months that are characteristic of both the El Nino and seasonal cycles. Deep convection is latitudinally confined to a much smaller spatial scale than that suggested by maps of outgoing longwave radiation. Diurnal variations of DCC cover and associated mesoscale cirrus/anvil cloud (CAC) cover are out of phase, with deep convection peaking in the early morning throughout the equatorial Pacific. The diurna...