Abstract: A method exploits the spectral signature of cloud bases in microwave moisture sounder data to determine cloud base heights. This signature requires the accurate specification of cloud top height, which in a preferred embodiment, comes from the analysis of data provided by an electro-optical sensor (EO) such as the Advanced Very High Resolution Radiometer (AVHRR) instrument flown on operational NOAA satellites. The method includes a receiving step in which satellite EO (visible through infrared) and microwave radiance data of a view of the earth's atmosphere is received. The view has both location and time information. In a determining step, cloud top height is determined based on the EO and infrared radiance data. Moisture profiles of the view are retrieved in a retrieving step based on the microwave radiance data. Subsequently, in a determining step, cloud base heights of clouds in the view are determined using cloud top heights as a constraint in the retrieval of moisture profiles with tile microwave data.