Determination of cloud properties from bispectral satellite measurements

Abstract

An analysis technique is presented in this paper to determine cloud parameters from geostationary satellite data. The principal data source is visible and infrared radiance measurements from the Geostationary Operational Environmental Satellite (GOES). A brightness critical value to distinguish clouds from underlying non-cloud surfaces is determined as a primary factor to identify the cloud measurement spot. Percentage of cloud cover and number of clouds are analyzed and compared with results derived from photographic images. Through a cloud summary computer program, cloud size, maximum brightness, as well as mean and standard deviation of brightness value for every individual cloud are found, categorized, and compared in time series. Infrared radiance data are used to deteinnine the cloud top temperature, allowing cloud height to be obtained from corresponding rawinsonde data. Cloud movement is estimated by a subjective method based upon computer-generated plots of the satellite data. Comparing simultaneous visible and infrared data sets, cirrus clouds are detected as regions with high infrared radiance value and low visible radiance value. The analysis is done with all of these data sources to study the properties and patterns of clouds for a case study on 22 June 1976 in the Texas High Plains area.