The Ratio of Absorption to Backscatter of Solar Radiation by Aerosols during Khamsin Conditions and Effects on the Radiation Balance

Abstract

Representative average values of the absorption to backscatter ratio of the aerosols in two typical synoptic conditions, namely cloudless khamsinic days and normal cloudless days, have been deduced from four years of data at two sites in Israel, one in the coastal plain and one in the Judean hills. These values (15 for cloudless days and 11 for khamsinic days) have been compared to those, available in, or deducible from, published studies of the aerosol effects in various parts of the world. It was found that the presence in the atmosphere of most of the aerosols induces a net heating effect, as far as the solar radiation balance is affected, over the regions in which they were measured. We have further evaluated the complex part of the refractive index, averaged over the solar spectrum between 0.3 and 2.5 μm (0.03 ± 0.02 for khamsinic days and 0.08 ± 0.02 for normal days). This result is important because of the little data available for this parameter so far.