The 600–800-mb Minimum in Tropical Cloudiness Observed during TOGA COARE

A minimum in cloud coverage occurring between 800 and 600 mb can be inferred from soundings taken within the tropical western Pacific warm pool. Surface observations of clouds and satellite-derived outgoing longwave radiation values suggest that the cloud minimum in the 600–800-mb layer occurs in all weather conditions. One explanation for the enhanced occurrence of clouds above (in the 400–600-mb layer) and their diminished occurrence within the 600–800-mb layer is a preferential cloud detrainment from convection into the more stable levels existing at pressures below 600 mb and above 800 mb. This mechanism is supported by the results of a buoyancy-sorting model.