A Global Climatology of Single-Layer and Overlapped Clouds and their Optical Properties Developed Using a New Algorithm Applied to Terra/MODIS Data

To date, weather satellites are the only tool to measure cloud and climate variables on a global scale, an objective addressed by the International Satellite Cloud Climatology Project (ISCCP) (Rossow and Schiffer 1991; Rossow and Schiffer 1999). However, there is a dearth of information concerning the global climatology of cloud vertical structure and cirrus cloud properties. This is because the often-used visible and infrared measurements made by weather satellites are overwhelmingly affected by thick water clouds. Thin cirrus clouds have a signal that is so faint that they are difficult to detect. This makes it problematic to retrieve the properties of cloud optical depth and cloud-top height for either of the overlapped cloud layers. Although high-altitude cirrus clouds are often very thin, their presence can bungle the retrieval of lower thick clouds, leading to large errors in the retrieval of cloud height and optical properties, as demonstrated in this paper and in Chang and Li (2004).