Development of a Two-Channel Aerosol Retrieval Algorithm on a Global Scale Using NOAA AVHRR

Abstract

This study proposes a two-channel satellite remote sensing algorithm for retrieving the aerosol optical thickness and the Ångström exponent, which is an index for the aerosol size distribution. An efficient lookup table method is adopted in this algorithm to generate spectral radiances in channels 1 and 2 of National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) over ocean areas. Ten-day composite maps of the aerosol optical thickness and the Ångström exponent have been obtained from AVHRR global area coverage data in January and July of 1988. Aerosol optical thickness maps show that the major aerosol sources are located off the west coast of northern and southern Africa, and the Arabian Peninsula. The most important contributor is soil-derived particles from the Sahara Desert that cross the Atlantic Ocean. The authors’ optical thickness values tend to be larger than values given by the NOAA operational algorithm. A 10-day composite map of Ångström exponent showing man-made air polluted regions, such as the Mediterranean Sea, the Black Sea, and the east coasts of North America and China, has large values, suggesting that small particles are dominant in these regions.