The global distribution of ice-supersaturated regions as seen by the Microwave Limb Sounder

Abstract

Cloud-screened microwave limb-sounder data of relative humidity with respect to ice have been used to produce maps of the global distribution of ice-supersaturated regions (ISSRs) at pressure levels 147 and 215 hPa. Geographical regions where ISSRs occur most frequently (in a relative sense) are the tropics at both pressure levels, the midlatitude storm belts at 215 hPa (in the respective hemispheric summer and autumn seasons) and Antarctica in southern winter and spring (at both pressure levels). Additionally, temperatures and absolute humidities were compared in supersaturated and subsaturated air masses. Consistent with earlier results based on data from the Measurement of Ozone by Airbus in-service Aircraft, it is found that ISSRs are generally colder and moister than their subsaturated counterparts. Temperature and humidity contrasts between supersaturated and subsaturated air masses vary considerably, both geographically and between the troposphere and the lowermost stratosphere.