Radiative effects and optical properties of aerosol during two dust events in 2013 over Zanjan, Iran

Abstract

Aerosol optical properties like Aerosol Optical Depth (AOD), Angstrom Exponent (AE), ASYmmetry parameter (ASY), Single Scattering Albedo (SSA), and Aerosol Volume Size Distribution (AVSD) have been analyzed for the atmosphere of Zanjan, a city in Northwest Iran. These properties have been studied using the ground-based AErosol RObotic NETwork (AERONET) during the periods from 8 to18 May and 8 to 14 June, 2013. During the study period, 14th May and 10th June are identified as dusty days, and AOD at 500 nm reached a peak value of 0.64 and 0.80, on these days. The high values of AOD and low values of AE during dusty days illustrate that coarse mode particles like dust are dominant. In the visible spectrum ASY usually decreases and then somewhat increases in the near infrared region. Both SSA and AVSD suggest predominance of coarse particles on the dusty days. The Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model is utilized to simulate the solar irradiance values for the above-mentioned periods at the earth’s surface, within the atmosphere, and at the Top of the Atmosphere (TOA). The results show that dominant aerosol types are dust particles which have a cooling effect on the earth’s surface during the study periods, especially on two dusty days, 14 May, and 10 June. The correlation coefficient shows a very good agreement between the ARF values retrieved from AERONET and SBDART simulation results.