Observations of supercooled liquid water over Tasmania and the Southern Ocean
Limited in-situ observations have reported large concentrations of supercooled liquid water, commonly at or above 0.3 g/kg for 5-minute flight legs at -8° C. However, a complete investigation of any aerosol-cloud-precipitation interaction/evolution involving in-situ and remote observations remains to be undertaken. The physical changes arising from cloud seeding have not been observed and documented, preventing a more complete confidence in the statistical observations.
A-Train observations (CloudSat, Calipso as well as radiometer observations from MODIS) present a new opportunity to explore the phase and temperature of these clouds and potentially shed insight into the structure of more extensive Southern Ocean cloud fields. A MODIS climatology of cloud-top phase finds that extensive fields of supercooled liquid water (SLW) extend over the Southern Ocean and are commonly present in regions of winter-time orographic precipitation across southeast Australia. These satellite observations are consistent with the in-situ observations of high concentrations of SLW relative to glaciogenic cloud seeding programs over the Western United States. The cloud climatology is being extended to A-Train observations. Field observations from the 2010 season will also be presented in which efforts are being made to seed upwind of an A-Train overpass.