Improved Bi-Spectral Method for Mapping Insolation Using NOAA APT Images

Abstract

An operational low cost system for mapping daily and monthly global solar radiation reaching the ground over a geographical area of 13? latitude by@ longitude using NOAA APT images has been developedfor use in south and southast Asia. An improved statistical bi-spectral model is used with visibleandfarinfraredAPTimagesto calculate the cloudinessoftargetsofsizelllkm bylllkm. One to three measurements in a day by NOAA satellites are combined with variable weights to calculate the effective cloudiness for the whole day. Ground measured radiation data from selected stations within the area covered are then correlated with the calculated cloudiness. Solar radiation can be estimated over the land and over the ocean equally well using the improved model. The standard error of estimation of daily global radiation is in the range 619% of the measured mean.