Analyses of black carbon (BC) data from three different environments in India -Delhi megacity, Srinagar metropolitan and Gulmarg hill station, showed that Delhi had the highest annual average BC concentration (12.3 +/- 10.2 mu g m- 3), followed by Srinagar (4.3 +/- 5 mu g m-3) and Gulmarg (2.4 +/- 2 mu g m-3). The inflow of aerosols from the neighboring agricultural regions, notably during Winter, causes Delhi to have the highest seasonal average BC (16.8 mu g m- 3). Srinagar had the highest average seasonal BC during autumn (6.3 mu g m- 3) due to the burning of horticulture residue and hardwood for charcoal making and residential heating. At Gulmarg, on the other hand, the winter season's high BC (2.2 mu g m- 3) is due to the increased emissions from the tourist traffic, snowmobile/ATVs and wood burning for residential heating. BC concentrations in Delhi and Srinagar were roughly in line with their population size. However, compared to sites with the similar population, BC at Gul-marg was roughly twice higher than the other sites. There was a higher contribution to BC from fossil fuels than biomass burning at all three sites, which indicates that cars are the primary source of BC. Overall, values of BC aerosol optical properties in Delhi are much higher than those in Srinagar and Gulmarg. During the cold season, continental air masses transport BC from the neighboring areas to Delhi and westerlies enhance the local BC loading at Srinagar and Gulmarg. The predominant presence of absorbing aerosols, particularly BC, during late autumn and winter at all three sites leads to an increase in aerosol optical depth (AOD), a reduction in single scattering albedo (SSA) and an increase in asymmetry parameter (AP). As a result, there is a significant increase in the radiative forcing of the atmosphere (RFATM), with the highest values observed in January in Delhi (+71.5 W m-2) and Srinagar (+56.05 W m-2), and in November at Gulmarg (+18.5 W m-2). These findings suggest that small rural towns that are affected by seasonal emissions, low planetary boundary layers, and frequent tem-perature inversions, can contribute to a substantial amount of radiative forcing. This study provides a larger perspective on increasing BC in Delhi, and urban-rural fringe areas in the Indian Himalayas, which is crucial for identifying what actions must be taken to control BC emissions to reduce impacts on cryosphere, human health and other sectors.

Black carbon (BC) mass concentration was measured first-time at a high altitude urban site-Srinagar (1600 m asl), in northwestern Himalaya, India using an Aethalometer during 2013 to study temporal variations (monthly, diurnal and seasonal), meteorological influences, source and its radiative forcing. Diurnal variations with two peaks (at 8-10 h and 20-23 h) and two dips (at 13-17 h and 0-3 h) were observed throughout the year with varying magnitude. November and April showed the highest (13.6 mu g/m(3)) and the lowest (3.4 mu g/m(3)) mean monthly BC concentration respectively. Seasonally, autumn displayed the highest (9.2 mu g/m(3)) and spring the lowest (3.5 mu g/m(3)) mean BC concentration. Annual average BC concentration was quite higher (6 mu g/m(3)) than those reported for other high altitude stations. Wind speed, Minimum temperature and total precipitation showed a clear negative correlation with BC (r = -0.63, -0.51 and -0.55 respectively), while as, the evening relative humidity showed positive correlation (r = 0.56). During autumn, spring and winter seasons, the main source of BC at Srinagar is the biomass burning, while during summer season, equal contribution of BC is from fossil fuel and biomass burning. Back trajectory simulations revealed that, except summer, westerly air masses are the dominant winds, transporting BC from central Asia, west Asia, south Asia, Africa and some parts of Europe to Srinagar adding to its local sources. Clear-sky short wave radiative forcing of atmosphere due to BC was highest (58.2 W m(-2)) during autumn which leads to the increase in lower atmospheric heating rate by 1.6 K/d. The high concentration of BC observed over the high-altitude Himalayan Kashmir region has serious implications for the regional climate, hydrology and cryosphere which needs to be investigated. (C) 2017 Elsevier Ltd. All rights reserved.

Regular measurements of spectral Aerosol Optical Depth (AOD) at ten wavelengths, obtained from multi-wavelength radiometer (MWR) under cloudless conditions in the outskirts of the tropical urban region of Hyderabad, India for the period January 2008 to December 2009, are examined. In general, high AOD with a coarse-mode abundance is seen during the pre-monsoon (March to May) and summer monsoon (June to September) with flat AOD spectra and low angstrom ngstrom wavelength exponent (), while in post-monsoon (OctoberNovember) and winter (DecemberFebruary) seasons, fine-mode dominance and steep AOD spectra are the basic features. The aerosol columnar size distribution (CSD) retrieved from the spectral AOD using King's inversion showed bimodal size distributions for all the seasons, except for the monsoon, with an accumulation-mode radius at 0.120.25 mu m and a coarse-mode one at 0.861.30 mu m. On the other hand, the CSD during the monsoon follows the power law for fine mode and the unimodal distribution for coarse mode. The fine-mode aerosols during post-monsoon and winter appear to be associated with air masses from continental India, while the coarse-mode particles during pre-monsoon and monsoon with air masses originating from west Asia and western India. The single-scattering albedo (SSA) calculated using the OPAC model varied from 0.83 +/- 0.05 in winter to 0.91 +/- 0.01 during the monsoon, indicating significant absorption by aerosols due to larger black carbon mixing ratio in winter, whereas a significant contribution of sea-salt in the monsoon season leads to higher SSAs. Aerosol radiative forcing (ARF) calculated using SBDART shows pronounced monthly variability at the surface, top of atmosphere (TOA) and within the atmosphere due to large variations in AOD and SSA. In general, larger negative ARF values at the surface (65 to 80 W m2) and TOA (approximate to 17 W m2) are observed during the pre-monsoon and early monsoon, while the atmospheric heating is higher (approximate to 5070 W m2) during January-April resulting in heating rates of approximate to 1.62.0 K day1. Copyright (c) 2012 Royal Meteorological Society