Water vapor in the tropical lower stratosphere during the driest phase of the atmospheric "tape recorder"

Data from the Microwave Limb Sounder on the Upper Atmosphere Research Satellite are used to examine sequences of days during the driest phase of the atmospheric “tape recorder” signal in the lower stratosphere. It is found that the Indonesian region is the first place to become dry followed by the western Pacific and Panama. Eventually, dry air is found in a band along the equator with the most northerly extent over Indonesia and Panama. Two-dimensional trajectories show that winds cannot account for the spread of dry air from Indonesia and Panama across the entire tropics. The patterns are difficult to explain but may result from a combination of widespread ascent of air and the effects of deep convection.