Spatial and Temporal Characteristics of Cirrus Clouds over the Tibetan Plateau Based on CALIPSO and AIRS Observations

The spatial and temporal distribution characteristics of high clouds over the Tibetan Plateau (TP) were studied using the Atmospheric Infrared Sounder (AIRS) and the GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP) monthly mean cloud products from 2007 to 2017. The high clouds over the TP are dominated by cirrus and show seasonal variation characteristics. There were two distinct areas with the high occurrence of cirrus clouds in the area (0 degrees-60 degrees N, 75 degrees-103 degrees E). One was located in the regions from the equator to 25 degrees N, and the other was within the latitude belt from 30 degrees to 40 degrees N. From January to May, cirrus clouds mainly occurred in the central and northern parts of the TP (30 degrees to 40 degrees N), and the cirrus cloud fraction increased from January and reached its maximum (approximate to 0.51) in April. From June to August, cirrus clouds mainly occurred in the southern part of the TP during summer. The cirrus clouds over the southern TP were relatively high (located in 10-17km) and manifested northward and southward movements. The ice clouds in the southern TP are associated with plateau deep convection activities and abundant vapor transmitted by the Asian monsoon. Cirrus clouds over the northern and central TP may be relevant to the atmospheric lift by an approaching cold front and topographic lifting. Moreover, the high clouds below 11km are dominated by opaque clouds, while the nonopaque (or thin) and opaque (or thick) clouds above 11km are comparable.