Retrieving cloud base heights via the combination of CloudSat and MODIS observations

An algorithm for estimating cloud base height (CBH) based on the combination of cloud products from CloudSat (provides CBH) and Moderate resolution Imaging Spectroradiometer (MODIS) (provides cloud top pressure and cloud optical thickness) is presented. The relationship among cloud geometric parameters and the feasibility of estimating the CBH via combining CloudSat and MODIS observations is analyzed. When the cloud top pressure (CTP) and cloud optical thickness (COT) of a certain point have been obtained by MODIS, its CBH could be estimated by searching the similar point in CloudSat track, which shares the same CTP, COT and CBH with the estimating point. In the process of searching the most matching point, an adjusting factor is introduced to uniform the unit of CTP and COT. The retrieval accuracy of cloud base height heavily on the CBH provided by Cloudsat and the best matching point. Data-exclusion experiments along the CloudSat track also show a nice performance without the Cloudsat cloud classification products. Root mean-square-error is less than 2 km when the exclusion distance is less than 100 km. This method provides a new approach to render a 3D cloud structure in a wide field.