Convective Forcing in the Intertropical Convergence Zone of the Eastern Pacific

One of the goals of the East Pacific Investigation of Climate, year 2001 process study (EPIC2001), was to understand the mechanisms controlling the forcing of deep atmospheric convection over the tropical eastern Pacific. An intensive study was made of convection in a 4 4 square centered on 10N, 95W in September and October of 2001. This is called the intertropical convergence zone (ITCZ) study region because it encompasses the eastern Pacific intertropical convergence zone. Starting from an analysis of the theoretical possibilities and a plethora of dropsonde, in situ, radar, and satellite data, it is found that newly developing convection occurs where a deep layer of air (of order 1 km deep or deeper) is conditionally unstable with only weak convective inhibition. Shallower conditionally unstable layers are associated with numerous small clouds, but do not seem to produce deep convection.