Although the advanced microwave sounding unit (AMSU)on board the NOAA 15 and NOAA 16 satellites is primarily designed for profilingatmospheric temperature and moisture, the products associated with cloudsand precipitation are also derived using its window channel measurements witha quality similar to those derived from microwave imagers such as the SpecialSensor Microwave Imager. However, the AMSU asymmetry in radiance along thescan was found to be obvious at its window channels and could severely degradethe quality of cloud and precipitation products if not properly corrected.Thus a postlaunch calibration scheme is developed for these channels, andthe causes of the asymmetry are analyzed from the AMSU instrument model. Apreliminary study shows that the asymmetry may be caused by either the AMSUpolarization misalignment or the antenna pointing angle error. A generic radiativetransfer model is developed for a single-layered cloud using a two-streamapproximation and can be utilized for the retrievals of cloud liquid water(L) and total precipitable water (V),cloud ice water path (IWP), and particle effective diameter (De). At the AMSU lower frequencies the scatteringfrom cloud liquid is neglected, and therefore the retrieval of Land V is linearly derived using 23.8 and 31.4 GHz.However, for ice clouds the radiative transfer model is simplified by neglectingthe thermal emission, and therefore the retrieval of IWP and De is analytically derived using the AMSU millimeterwavelength channels at 89 and 150 GHz. These cloud algorithms are tested forthe AMSU on board the NOAA 15 and NOAA 16 satellites, and the results arerather promising. It is also found that the AMSU-derived cloud ice water pathis highly correlated with the surface rain rates and is now directly usedto monitor surface precipitation throughout the world.