Radiative Characteristics of Cirrus Clouds as Retrieved from AVHRR

Abstract

An algorithm is developed to retrieve the effective particle radius, cloud optical thickness, and cloud top temperature of cirrus clouds on a global scale using two infrared window channels and a nearinfrared channel of the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) on board NOAA-9 and NOAA-11. In the algorithm, overlapped cloud cases are taken into account. Data from the satellites are reconstructed to segmented data that contain a hundred satellite pixels in each 0.5° × 0.5° latitude and longitude grid. The algorithm is applied to fourmonth segmented AVHRR Global Area Coverage data from 1986 through 1994. The resulted cloud parameters are compared with airborne measurements and the products of International Satellite Cloud Climatology Project (ISCCP). These comparisons show that the effective radius obtained by this algorithm is smaller than that by airborne measurements, and that the cirrus cloud top temperature is about 5∼20 K lower than that of ISCCP. The global distribution, and the time series of these parameters, are shown and discussed.