This paper provides an account of observed variations in Black carbon (BC) aerosol concentrations and their induced radiative forcing for the first time over Granada a measurement site in Southeastern Iberian Peninsula. Column-integrated BC concentrations were retrieved for the period 2005-2012. Monthly averages of BC concentrations (one standard deviation) ranged from higher values in January and December with 4.0 +/- 2.5 and 4 +/- 3 mg/m(2), respectively, to lower values in July and August with 1.6 +/- 1.2 and 2.0 +/- 0.5 mg/m(2), respectively. This reduction is not only observed in the average values, but also in the median, third and first quartiles. The average BC concentration in winter (3.8 +/- 0.6 mg/m(2)) was substantially higher than in summer (1.9 +/- 0.3 mg/m(2)), being the eight-year average of 2.9 +/- 0.9 mg/m(2). The reduction in the use of fossil fuels during the economic crisis contributed significantly to reduced atmospheric loadings of BC. According to our analysis this situation persisted until 2010. BC concentration values were analyzed in terms of air mass influence using cluster analysis. BC concentrations for cluster 1 (local and regional areas) showed high correlations with air masses frequency in winter and autumn. In these seasons BC sources were related to the intense road traffic and increased BC emissions from domestic heating. High BC concentrations were found in autumn just when air mass frequencies for cluster 3 (Mediterranean region) were more elevated, suggesting that air masses coming from that area transport biomass burning particles towards Granada. BC aerosol optical properties were retrieved from BC fraction using aerosol AERONET size volume distribution and Mie theory. A radiative transfer model (SBDART) was used to estimate the aerosol radiative forcing separately for composite aerosol (total aerosols) and exclusively for BC aerosols. The mean radiative forcing for composite aerosol was +23 +/- 6 W/m(2) (heating rate of +0.21 +/- 0.06 K/day) and +15 +/- 6 W/m(2) for BC aerosol (heating rate of +0.15 +/- 0.06 K/day). These values of radiative forcing and heating rate for BC aerosol represent-about 70% of their values for composite aerosol, which highlights the crucial role that BC aerosols play in modifying the radiation budget and climate. (C) 2017 Elsevier B.V. All rights reserved.

Optical characterization of aerosol was performed by assessing the columnar aerosol optical depth (AM) and angstrom wavelength exponent (alpha) using data from the Microtops II Sunphotometer. The data were collected on cloud free days over Goa, a coastal site along the west coast of India, from January to December 2008. Along with the composite aerosol, the black carbon (BC) mass concentration from the Aethalometer was also analyzed. The AOD(0.500) (mu m) and angstrom wavelength exponent (alpha) were in the range of 026 to 0.7 and 0.52 to 1.33, respectively, indicative of a significant seasonal shift in aerosol characteristics during the study period. The monthly mean AOD(0.500) (mu m) exhibited a bi-modal distribution, with a primary peak in April (0.7) and a secondary peak in October (0.54), whereas the minimum of 026 was observed in May. The monthly mean BC mass concentration varied between 0.31 mu g/m(3) and 4.5 mu g/m(3), and the single scattering albedo (SSA), estimated using the OPAC model, ranged from 0.87 to 0.97. Modeled aerosol optical properties were used to estimate the direct aerosol shortwave radiative forcing (DASRF) in the wavelength range 0.25 mu m4.0 mu m. The monthly mean forcing at the surface, at the top of the atmosphere (TOA) and in the atmosphere varied between - 14.1 W m(-2) and -35.6 W m(-2), -6.7 W m(-2) and -13.4 W m(-2) and 5.5 W m(-2) to 22.5 W m(-2), respectively. These results indicate that the annual SSA cycle in the atmosphere is regulated by BC (absorbing aerosol), resulting in a positive forcing; however, the surface forcing was governed by the natural aerosol scattering, which yielded a negative forcing. These two conditions neutralized, resulting in a negative forcing at the TOA that remains nearly constant throughout the year. (C) 2013 Elsevier BY. All rights reserved.