Surface changes in solar irradiance due to aerosols over central Himalayas

[1] During a comprehensive aerosol field campaign as a part of the ISRO-GBP, extensive measurements of radiative fluxes at the surface were made during December 2004 at Manora Peak, in the Shivalik ranges of the Central Himalayas. The surface radiative fluxes were used to estimate aerosol radiative forcing. Our analysis clearly shows that during the clean atmospheric conditions over Manora Peak, the observed aerosol radiative forcing is in good agreement to those of modeled ones, while for the higher aerosol optical depths (AODs), modeled values are significantly smaller than the observed ones. It was observed that at Manora Peak, the anthropogenic aerosols (from valley below) transported upwards by evolution of boundary layer during the daytime provide an atmosphere conducive for 'mixed' aerosols. Focused efforts are needed to address this issue for which simultaneous observations at high altitude site with those in nearby valley are essential.