Black carbon (BC) can be transported over long distances and is an important trigger of climate warming and glacier melting at remote high mountains and polar regions. It is normally assumed that the variation of BC flux in remote regions is dominated by its emissions. However, after a comprehensive investigation of potential influencing factors on temporal variations of BC from ice cores of the Himalayas, this short communication shows that in addition to BC emissions, contributions from dust storms and precipitation are also important (up to 56% together) in regulating the variation of BC deposition flux and concentrations derived from remote Himalayan ice core measurements. Therefore, besides BC emissions, the influence of precipitation and BC transported by dust storms should also be considered to better quantify the lifetime and behavior of BC during its long-range transport from source to sink regions as well as to quantify the climatic effects of BC over remote Himalayan glaciers.

In this study, we report on three important optical parameters, viz. absorption and scattering coefficients (b(abs), b(scat)) and single scattering abledo (SSA) based on one-year chemical-composition data collected from an urban site (Kanpur) in the Indo-Gangetic-Plain (IGP) of northern India. In addition, absorption Angstrom exponent (AAE) was also estimated in order to understand the wavelength dependence of absorption and to decipher emission sources of carbonaceous aerosols, in particular of black carbon. The absorption and scattering coefficients ranged between 8.3 to 95.2 Mm(-1) (1 Mm(-1) = 10(-6) m(-1)) and 58 to 564 Mm(-1), respectively during the study period (for n = 66; from January 2007 to March 2008) and exhibit large seasonal variability with higher values occurring in winter and lower in the summer. Single scattering albedo varied from 0.65 to 0.92 whereas ME ranged from 0.79 to 1.40 during pre-monsoon and winter seasons, respectively. The strong seasonal variability in aerosol optical properties is attributed to varying contribution from different emission sources of carbonaceous aerosols in the IGP. A case study of haze and dust events further provide information on extreme variability in aerosol optical parameters, particularly SSA, a crucial parameter in atmospheric radiative forcing estimates. (C) 2016 Elsevier B.V. All rights reserved.

Dust storm, a natural hazard, has a direct impact on daily life for a short period. Dust storms are periodic events over India, especially in northern regions. This study has been carried out to investigate the dust impacts on the aerosol characteristics over Dehradun (DDN) during pre-monsoon (March-June), 2012 using ground measurements, satellite observations and model simulations. The measurements illustrate the distinct monthly impact on the aerosol properties with maximum dust loading during May (aerosol optical depth at 500 nm (AOD(500)) = 0.72 +/- 0.18) over DDN, which is confirmed with the Terra-MODIS (AOD(550) = 0.70 +/- 0.19) measurements. The major dust loading was recorded in aerosol measurements during May at the station, which permitting to examine the influence of dust transports on the aerosol characteristics. Spectral variation of AOD and Angstrom exponent (alpha) values displayed day to day variation of aerosol during dust episodes. Analysis of aerosol types and seven-day back-trajectories reveal the transportation of desert dust during May over DDN. The Optical Properties of Aerosols and Clouds (OPAC) model was used to compute the aerosol optical properties (e.g., Single scattering albedo (SSA) and asymmetry parameter (g)) and size distribution. The high values of SSA and g are indicating the dust loading in the atmosphere during May. Aerosol volume concentration at the coarse mode (geometric mean radii (R-V) = 2.89 +/- 0.027 mu m) is found to be increased in the May, whereas decrement has been observed in the finer mode (R-V = 0.16 +/- 0.006 mu m). The aerosol direct radiative forcing (ARF) was computed using Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) model in the shortwave (SW) region (0.25-4.00 mu m). The mean top of the atmosphere (TOA) and surface forcing come out to be -14.49 W m(-2) and -53.29 W m(-2) respectively in May. The mean net atmospheric radiative forcing (38.79 W m(-2) maximum during May) corresponds to heating rate of similar to 1.06 degrees K d(-1) in the atmosphere.

Atmospheric aerosols are important aspects of climate research due to their impact on radiative forcing. In the present study, the aerosol optical depth (ADD), the Angstrom exponent (alpha) and the single scattering albedo (SSA) over the urban region of Hyderabad, India, were examined using Sun/Sky radiometer measurements during January-December, 2008. AOD showed higher values on certain Julian days coinciding with the occurrence of wintertime dust storm events in the Gulf Region and biomass burning due to forest fires over Indian Region. The AOD values during wintertime dust event are about similar to 55% higher than those on normal days. The SSAs show positive and negative trends in alpha (R-2 = 0.71) and black carbon (BC) aerosols (R-2 = 0.44), respectively. The aerosol size distribution shows a bimodal pattern with fine (similar to 0.15 mu m) and coarse (similar to>7 mu m) mode during January-December, 2008. The MODIS AOD showed positive correlation with sky radiometer-derived AOD values (R-2 = 0.68). (C) 2011 Elsevier B.V. All rights reserved.