Cirrus cloud fields measured by the Atmospheric Infrared Sounder

The Atmospheric Infrared Sounder (AIRS) has made global high-spectral-resolution measurements of clouds on a daily basis beginning in the summer of 2002. We present recent work using the AIRS to detect and characterize cirrus clouds. The fundamental properties of interest include the detection, height, and frequency of cirrus, as well as the effective particle size and optical depth. We use the AIRS operational Level 2 cloud top height, temperature, and effective cloud fraction, along with the vertical temperature and water vapor profiles, to construct a global picture of cirrus occurrence. In turn, the operational products are used to determine the effective particle size and optical depth for thin cirrus clouds using a fast radiative transfer model modified with a thin cirrus parameterization. We use the Atmospheric Radiation Measurement (ARM) program sites in the tropical Western Pacific to understand the accuracy of the operational and offline cirrus quantities.