The direct observations of large aerosol radiative forcing in the Himalayan region

• Published in: Geophysical research letters Vol. 31; no. 5; pp. L05111 - n/a
• Main Authors: Ramana, M. V., Ramanathan, V., Podgorny, I. A., Pradhan, Bidya B., Shrestha, Basanta
• Format: Journal Article
• Language: English
• Published: American Geophysical Union 16.03.2004; Blackwell Publishing Ltd
• Subjects: Aerosols; Aerosols and particles; Anthropogenic effects; Atmosphere; Atmospheric Composition and Structure; Biological and Chemical; Global Change; Hydrology; Oceanography; Pollution—urban and regional; Transmission and scattering of radiation; Nepal; Asia, Himalaya Mts
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2003GL018824

We show here that absorbing aerosols have led to a large reduction of surface solar radiation during winter over the Himalayan region. Our results are based on radiometric, aerosol and Lidar observations made at three sites in Nepal during winter 2003. The monthly mean aerosol optical depth (AOD) ranged from 0.2 to 0.34 and the TERRA satellite MODIS data reveal that AODs measured over these sites were typical of the entire Himalayan region. The near‐surface aerosol single scattering albedo was in the range from 0.7 to 0.9. The presence of strongly absorbing aerosols resulted in a relatively large diurnal mean aerosol surface radiative forcing efficiency of −73 Wm−2 (per unit optical depth). The seasonal mean reduction in solar flux was as high as 25 Wm−2 and aerosol heating as much as 1 K per day within the first two kilometers.