Horizontal and Vertical Distributions of Clouds of Different Types Based on CloudSat-CALIPSO Data

Global mean total amount of clouds is 66.7%. The total cloud fraction of Cirrus (Ci) and Stratocumulus (Sc) clouds is comparable to the sum of clouds of other six types, indicating that Ci and Sc clouds are two most frequently occurring cloud types over the globe. The amount of cumuliform clouds decreases from tropical to subtropical, while the amount of stratiform clouds changes in the opposite direction, indicating different environments for the formation of cumuliform and stratiform clouds. The topography and synoptic systems can affect cloud occurrence too. The cloud height and thickness of eight types of clouds are significantly different in different regions. Ci clouds, with higher cloud base and top, are very thin. Altostratus (As) clouds and Altocumulus (Ac) clouds are mid-level clouds, but As clouds are thicker and located at higher levels than Ac clouds. Stratus (St), Sc, and Cumulus (Cu) clouds are thin clouds occurring in the lower atmosphere. Nimbostratus (Ns) and deep convective (DC) clouds are thick clouds with lower cloud base and higher cloud top. Overall, the height of the cloud base over the ocean is lower than that over the land. The cloud base is higher and the cloud depth is thicker in relatively unstable atmosphere such as over the equator than in stable atmosphere. Clouds over the Plateau are characterized by the features that high-clouds are not high and low-clouds are not low while the cloud depth is usually thin.