[1] Collocated measurements of the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high-altitude station, Manora Peak in central Himalayas, during a comprehensive aerosol field campaign in December 2004. Despite being a pristine location in the Shivalik Ranges of central Himalayas and having a monthly mean AOD (at 500 nm) of 0.059 ± 0.033 (typical to this site), total suspended particulate (TSP) concentration was in the range 15-40 mg m À3 (mean value 27.1 ± 8.3 mg m À3 ). Interestingly, aerosol BC had a mean concentration of 1.36 ± 0.99 mg m À3 and contributed $5.0 ± 1.3% to the composite aerosol mass. This large abundance of BC is found to have linkages to the human activities in the adjoining valley and to the boundary layer dynamics. Consequently, the inferred single scattering albedo lies in the range of 0.87 to 0.94 (mean value 0.90 ± 0.03), indicating significant aerosol absorption. The estimated aerosol radiative forcing was as low as À4.2 W m À2 at the surface, +0.7 W m À2 at the top of the atmosphere, implying an atmospheric forcing of +4.9 W m À2 . Though absolute value of the atmospheric forcing is quite small, which arises primarily from the very low AOD (or the column abundance of aerosols), the forcing efficiency (forcing per unit optical depth) was $88 W m À2 , which is attributed to the high BC mass fraction.

No abstract

[1] The influences of the springtime northern Indian biomass burning are shown for the first time over the central Himalayas by using three years (2007)(2008)(2009) . These biomass burning induced changes over the central Himalayan atmosphere during spring may also lead to enhanced short-wave absorption above clouds and might have an impact on the monsoonal rainfall.

No abstract

[1] We present, for the first time, spectral behavior of aerosol optical depths (AODs) over Manora Peak, Nainital, located at an altitude of $2 km in the Shivalik ranges of the central Himalayas. The observations were carried out using a multiwavelength solar radiometer during January to December 2002. The main results of the study are extremely low AODs during winter, a remarkable increase to high values in summer, and a distinct change in the spectral dependencies of AODs from relatively steeper spectra during winter to shallower ones in summer. A comparison of the total optical depths of the nighttime measurements taken during the 1970s with the daytime values from the current study underlines the fact that loading of larger size particles during summer also occurred at that time, though less severely than it does today. During transparent days the AOD values usually lie below 0.08, while during dusty (turbid) days they lie between 0.08 and 0.69. The average AOD value during the winter, particularly in January and February, is $0.03 ± 0.01 at 0.5 mm. The mean aerosol extinction law at Manora Peak during 2002 is best represented by 0.10l À0.61 . However, during transparent days, which covers almost 40% of the time, it is represented by 0.02l À0.97 . This value of wavelength exponent, representing reduced coarse concentration and the presence of fine aerosols, indicates that the station measures aerosol in the free troposphere at least during part of the year.