An operational method of correction for atmospheric and scan angle effects

An operational procedure for correcting the visible and near infrared reflectances of NOAA AVHRR data was developed. Correction for atmospheric effects is based on the estimation of two main parameters: aerosol optical depth (AOD) and the total water vapor content of the atmosphere, that are referenced to ground based surface meteorological data. An error of ±0.02 of NDVI (Normalized Difference Vegetation Index) is expected due to the uncertainty of AOD. Scan angle effects due to the bidirectional reflectance distribution function (BRDF) for a designated area in Iowa is assessed by scanning pixels across a predominantly agricultural area with uniformly growing crops. The research demonstrates the characteristics that are critical to anisotropic reflection. A maximum error of 10% in NDVI is estimated after correcting the data for atmospheric and scan angle effects