2.5 Hirdls and Calipso observations of tropical cirrus

Monday, 8 June 2009: 11:40 AM
Pinnacle A (Stoweflake Resort and Confernce Center)
Steve Massie, NCAR, Boulder, CO; and J. Gille, C. Craig, R. Khosravi, J. Barnett, and D. M. Winker

High Resolution Dynamics Limb Sounder (HIRDLS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations of cirrus in the upper tropical troposphere are studied during September 2006 – August 2007. Monthly geospatial averages of cloud frequency of occurrence between 90 and 177 hPa are similar, and correlate well with Microwave Limb Sounder (MLS) relative humidity with respect to ice (RHI) data. Seasonal variations in cloud frequency of occurrence are similar with largest frequencies during winter, and latitudinal variations that are related to monsoon dynamics. Though the CALIPSO and HIRDLS experiments employ nadir and limb viewing observational geometries, CALIPSO horizontal scales of cirrus are frequently larger than 100 km, and therefore similarities are present in the geospatial distributions of cloud occurrence. Cirrus layers have horizontal scales that are largest (on average) during winter. Seasonal and monthly variations of HIRDLS and CALIPSO cloud occurrence frequency, and statistics of horizontal and vertical scales, are summarized in data files that will be useful in climate model validation studies.
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