title: Aerosol optical properties and radiative effects over Manora Peak in the Himalayan foothills: seasonal variability and role of transported aerosols.
abstract: The higher altitude regions of Himalayas and Tibetan Plateau are influenced by the dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. In this study, we present impacts of advection of polluted air masses of natural and anthropogenic emissions, on aerosol optical and radiative properties at Manora Peak (~2000 m amsl) in central Himalaya over a period of more than two years (February 2006-May 2008). We used the most updated and comprehensive data of chemical and optical properties available in one of the most climatically sensitive region, the Himalaya, to estimate atmospheric radiative forcing and heating rate. Aerosol optical depth (AOD) was found to vary from 0.04 to 0.45 with significantly higher values in summer mainly due to an increase in mineral dust and biomass burning aerosols due to transport. In contrast, single scattering albedo (SSA) varied from 0.74 to 0.88 with relatively lower values during summer, suggesting an increase in absorbing BC and mineral dust aerosols. As a result, a large positive atmospheric radiative forcing (about 28 ± 5 Wm(-2)) and high values of corresponding heating rate (0.80 ± 0.14 Kday(-1)) has been found during summer. During the entire observation period, radiative forcing at the top of the atmosphere varied from -2 to +14 Wm(-2) and from -3 to -50 Wm(-2) at the surface whereas atmospheric forcing was in the range of 3 to 65 Wm(-2) resulting in a heating rate of 0.1-1.8 Kday(-1).
authors.affiliation: Indian Institute of Tropical Meteorology (Branch), Prof Ramnath Vij Marg, New Delhi, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Srivastava
authors.affiliation: Institute of Environment & Sustainable Development, Banaras Hindu University, Varanasi, India.
authors.forename: K
authors.initials: K
authors.lastname: Ram
authors.affiliation: Radio & Atmospheric Sciences Division, CSIR-National Physical Laboratory, New Delhi, India. Electronic address: ssingh@nplindia.org.
authors.forename: Sachchidanand
authors.initials: S
authors.lastname: Singh
authors.affiliation: Radio & Atmospheric Sciences Division, CSIR-National Physical Laboratory, New Delhi, India.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Indian Institute of Tropical Meteorology (Branch), Prof Ramnath Vij Marg, New Delhi, India.
authors.forename: S
authors.initials: S
authors.lastname: Tiwari
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data*; D000531:Altitude; D001272:Atmosphere / Q000737:chemistry; D004784:Environmental Monitoring; D007194:India; D012621:Seasons; D014919:Wind
chemical_list: D000336:Aerosols; D000393:Air Pollutants
keywords: Aerosol composition; Aerosol optical properties; Atmospheric heating rate; Himalayan foothills; Indo-Gangetic plain; Radiative forcing