Effects of Atmospheric Black Carbon and Aerosols on Solar Flux Reaching the Earth Surface in UV and visible region

Abstract

The atmospheric aerosols are to affect the radiation budget of a region by direct as well newlineindirect interaction with the solar radiation. These interactions can be better understood newlineby having long term measurements of aerosols and solar radiation and studying the newlineoptical properties of aerosols and its distribution in detail. The present study aims to newlineimprove the scientific understanding of aerosols and its interaction with solar radiation newlinebased upon the measurements done in Delhi city. The studies focused on the effects of newlineatmospheric aerosols and the black carbon (BC) aerosols on solar flux reaching the earth newlinesurface in ultraviolet and visible region of the solar spectrum. In the process, the detailed newlinestudy of aerosol optical properties, its variability, along with the study of BC newlineconcentration and its emission over Delhi has also been done for five years (January 2006 newlineto Mach 2011).The measurement of solar radiation flux (total bandwidth, 285-2800 nm) at the surface, newlinewere measured in W m-2. Solar radiation reaching the earth surface gets affected by newlineaerosols. In order to see this effect of AOD on radiation flux we estimated the observed newlineforcing efficiency at different solar zenith angle (SZA). The observed radiative forcing newlineefficiency decreased as the SZA increased. It was about 15 W m-2 at SZA 40o, 12 W m-2at newlineSZA 50o and 9 W m-2 at SZA 60o. The solar global ultraviolet (GUV) and broadband newlineglobal (G) radiation flux obtained on a horizontal plane in Delhi, during April 2010 to newlineMarch 2011 have been used to investigate the temporal variability of these radiations and newlineof UV fraction (UVF).Our findings will contribute to the knowledge of newlineatmospheric aerosols and BC characteristics over Delhi and their interaction with solar newlineradiation.