Observations and Calculations of Aerosol Heating over the Arabian Sea during MONEX

Abstract

Radiation flux observations were obtained during a flight of the NCAR Electra over the Arabian Sea during MONEX when aerosols were present, and these observations have been compared with theoretical calculations based upon simultaneously observed profiles of temperature and water vapor. The results of those comparisons show that the model calculated shortwave heating rates underestimate those observed by as much as 50% in some layers, and the calculated upward and downward longwave flux divergences differ from those observed by as much as 20% in some regions. The shortwave differences are too large to be accounted for by uncertainties in either the observations or calculations and are attributed to aerosols. In the absence of detailed information concerning the radiative properties of the aerosols, the downward shortwave flux observations have been used with the radiative properties of Saharan aerosols to estimate the vertical distribution of the optical depth. When these data are used in the longwave radiation calculations, the observed and calculated flux divergences are found to agree better than when the dust is neglected, although observational errors cloud the results.