P1.26 Global and temporal characterization of cirrus clouds using the CALIPSO data

Thursday, 12 November 2009
Hovakim Nazaryan, Hampton University, Hampton, VA; and M. P. McCormick

Using the measurements made by the lidar aboard the Earth-orbiting Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite, we study the global and temporal characteristics of cirrus clouds, which have been identified as one of the most uncertain components in weather and climate studies. Cirrus clouds not only play a significant role in the energy budget of the earth–atmosphere system by means of their effects on the transfer of radiant energy through the atmosphere, but are also important as a vital link in the hydrological cycle. Additionally, cloud parameterizations in climate models need to account properly for the temporal and spatial distributions of high cloud properties. It is difficult to detect cirrus clouds from satellite instruments, and as a result there are few quantitative, global analyses of them. CALIPSO measures clouds with an unprecedented vertical and horizontal resolution, especially high clouds. We investigate the cirrus cloud occurrence frequency and cloud height information obtained by the CALIPSO experiment as a function of time, latitude, longitude, and altitude. We present the time series of the CALIPSO cirrus cloud occurrence frequency at different latitudes. There are some hemispheric differences in cirrus frequency distributions. Cirrus cloud occurrence frequencies have higher maximum values in the Antarctic region than in the Arctic region. Our investigation of the latitude-longitude distribution of the CALIPSO cirrus cloud occurrence frequency shows maximum values of up to 93.5% near the tropics over the 100° - 180° E longitude band. We also study the differences between the occurrence frequencies of cirrus clouds measured by CALIPSO during daytime and nighttime. The zonal mean distributions of the cirrus layer top altitudes and base altitudes for nighttime and daytime are calculated. We obtain that cloud top altitudes from the nighttime data were higher than the daytime top altitudes on average by 0.6 km.

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