Global Distribution of Cirrus and Opaque Clouds Observed by SAGE II

The Stratospheric Aerosol and Gas Experiment (SAGE) II has been collecting global aerosol extinction data from October 1984 to August 2005. Although it was designed mainly to monitor aerosol and trace gases in the stratosphere, it was shown that the profile mesurements would extend well down into the troposphere and thus provide the means for useful studies of cirrus and opaque clouds. Cirrus clouds reported herein are regions of enhanced extinction in the SAGE profile and opaque clouds are regions of "saturated" extinction where measured extinctions are greater than the threshold value. The global distribution of the frequency occurrence of cirrus and opaque clouds are presented. The results of the analysis showed that optically thick clouds form most often in the mid-latitudes and over the tropics, with distinct minima at latitudes bands of 20 - 30 deg in both hemispheres. During northern hemispheric summer, maximum occurrence is near 10 deg N. During southern hemispheric summer, the maximum occurrence has shifted to near 10 deg S. The cirrus occurrence shows a remarkable similar patterns from year to year. The seasonal variation behavior also shows for opaque clouds. The temporal and diurnal variability of clouds is also discussed.