Vertical cloud structures over the Tibetan Plateau as revealed from cloudsat observations

Based on 3-year (2006.5 – 2008.5) cloudsat observations, the vertical cloud structures over the Tibetan Plateau were examined in terms of occurrence frequencies of 8-type clouds (cirrus, altostratus, altocumulus, stratus, stratocumulus, cumulus, nimbostratus and deep convection) at different height above the surface for four seasons. Over the Tibetan Plateau, predominate cloud types are altostratus (6~10km above the surface) and nimbostratus (4~8km above the surface). Other four types, namely, cirrus, stratus, altocumulus and cumulus have relatively small frequency with a strong seasonal variation, for example, cirrus clouds occurred mostly in summer and spring at 12 km above the surface and very rarely in other two seasons. In addition, more than 90% deep convection was detected in summer with heights up to 12 km above the surface, and there was little stratocumulus found in the Tibetan Plateau. Furthermore, three primary modes were identified in the frequency distribution of radar reflectivity with height, i.e., small reflectivity for low and high clouds, and large reflectivity for middle and deep clouds.