P2.57 Regional differences in tropical congestus populations

Wednesday, 30 June 2010
Exhibit Hall (DoubleTree by Hilton Portland)
Sean P. F. Casey, JPL, La Cañada Flintridge, CA; and E. Fetzer and Q. Yue

One years' worth of CloudSat measurements over the tropical oceans are analyzed, with a focus on actively convective clouds. These clouds are separated into two categories: congestus, with cloud-top heights less than 8 km, and deep clouds, with heights above 8 km. The ratio of congestus to deep clouds is on average 2.41 to 1. Large regional discrepancies exist, ranging from 1.85 to 1 over the Maritime Continent to 3.50 to 1 over the North Pacific. Atmospheric Infrared Sounder profiles, collocated to the CloudSat profiles, are then analyzed to identify differences in the environment surrounding the clouds. The mean midtropospheric relative humidity (RH) surrounding congestus clouds in the North Pacific is found to be significantly lower than that found over the Maritime Continent. The authors postulate that lower RH values in the North Pacific may lead to a greater occurrence of cumulus congestus clouds.
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