Black carbon (BC) is a major pollutant entering the human body through PM2.5 and posing major health effects. India lying in the Asia region is a major contributor to BC emissions from the combustion of biofuels. BC present in the atmosphere is a pollutant deteriorating air quality and is a light-absorbing aerosol (LAA), thus playing a dual role. In India, several studies have been published quantifying BC concentration. The optical measurement of BC has been carried out at multiple locations in India, and its radiative effect has been studied using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. This review is an attempt to collate those studies that have measured BC and estimated its radiative effect. The BC levels, spectral Aerosol Optical Depth (AOD), single scattering albedo (SSA) and direct radiative forcing (DRF) at the top of the atmosphere (TOA), at the surface (SUR) and heat within the atmosphere (ATM) for 20 years (2002 to 2023) have been analysed. It was found that many studies for performing DRF calculations have not used BC measurements and have used AOD analysis to characterise the sources of aerosols as direct BC measurements are not required to estimate the DRF. The selection of AOD wavelength 500 nm or 550 nm is not clear in the literature for BC-RF calculations and needs to be standardised for DRF. IPCC AR6 has estimated Effective Radiative Forcing (ERF) due to BC with temperature and surface feedbacks, and future studies for ERF need to use climate models with tools like WRF-Chem. The source of BC is mostly from fossil fuel or biomass burning during the winter season, while it is dust aerosols during the summer. Biomass burning, use of traditional cook stoves and aerosol episodes contribute to the warming of the ambient environment. Beijing, China, has reduced ATM forcing in the summer when compared to Delhi, India, and has reduced the fraction of heat exerted in the atmosphere. The interactions of BC-UHI are not studied yet in India, and with the ARFINET network, an attempt can be made in this direction. The Urban Pollution Island (UPI)-Urban Heat Island (UHI) review identified PM2.5 contributing to UHI intensity during the summer and winter in metro cities, while BC-UHI interactions are not dealt with in detail.

The aerosol optical depths (AODs) in the wavelength range 380-875 nm and black carbon (BC) mass concentrations were estimated over the tropical Indian Ocean and in the Indian Ocean sector of Southern Ocean, between 14 degrees N and 53 degrees S, during December 2011-February 2012, onboard the Ocean Research Vessel (ORV) Sagar Nidhi. The data were analysed to understand the spectral variability, micro-physical characteristics of aerosols and the associated radiative forcing. Concurrent MODIS-derived chlorophyll a (Chl-a) and sea-surface temperature (SST) provided ancillary data used to understand the variability of biomass in association with fronts and the possible role of phytoplankton as a source of aerosols. AODs and their spectral dependencies were distinctly different north and south of the Inter-Tropical Convergence Zone (ITCZ). North of 11 degrees S (the northern limit of ITCZ), the spectral distribution of AOD followed Angstrom turbidity formule (Junge power law function), while it deviated from such a distribution south of 16 degrees S (southern boundary of ITCZ). At the southern limit of the ITCZ and beyond, the spectral variation of AOD showed a peak around 440 nm, the amplitude of which was highest at similar to 43 degrees S, the axis of the subtropical front (STF) with the highest Chl-a concentration (0.35 mu g l(-1)) in the region. To understand the role of Chl-a in increasing AOD at 440 nm, AOD at this wavelength was estimated using Optical properties of Aerosols and Clouds (OPAC) model. The anomalies between the measured and model-estimated (difference between the measured and estimated AOD values at 440 nm) AOD(440) were correlated with Chl-a concentrations. A very high and significant association with coefficient of determination (R-2=0.80) indicates the contribution of Chl-a as a source of aerosols in this part of the ocean. On the basis of the measured aerosol properties, the study area was divided into three zones; Zone 1 comprising of the area between 10 degrees N and 11 degrees S; Zone 2 from 16 degrees S to 53 degrees S; and Zone 3 from 52 degrees S to 24 degrees S during the return leg. BC mass concentration was in the range 520 ng m(-3) to 2535 ng m(-3) in Zone 1, while it was extremely low in the other zones (ranging from 49.3 to 264.4 ng m(-3) in Zone 2 and from 61.6 ng m(-3) to 303.3 ng m(-3) in Zone 3). The atmospheric direct-short wave radiative forcing (DRSF), estimated using a radiative transfer model (Santa Barbara DISORT Atmospheric Radiative Transfer - SBDART), was in the range 4.72-27.62 wm(-2) north of 16 degrees S, and 4.80-6.25 wm(-2) south of 16 degrees S. (C) 2015 Elsevier Ltd. All rights reserved.

Large spatial extent of biomass burning occurs in northeast region of India during annual dry season for shifting cultivation purposes. Characterization of optical properties of resultant biomass burning aerosols is important for the study of atmospheric radiative process and for remote sensing of both Surface and atmospheric properties in these regions. In the present study, physical and optical properties of biomass burning aerosols in Arunachal Pradesh, North Eastern Region of India have been studied for the first time using ground based measurements using a MICROTOPS-II sunphotometer, an Aethalometer, a quartz crystal microbalance impactor (QCM), SO2 analyser, and an UV meter. Aerosol size distribution suggested dominance of accumulation mode particle loading during burning days compared to normal days. The slope of data points between simultaneous measurements of AOD (500 nm) and UVery suggested that every 0.1 increase in aerosol optical depth (AOD) causes 0.1 minimal erythermal dose (MED h(-1)) reduction during normal day and reduction of 0.36 MED h(-1) in ground reaching UVery during biomass burning periods. Diurnal variations of black carbon aerosol (BC) concentrations increased by a factor of similar to 2 during morning and evening hours compared to afternoon hours during biomass burning period. Daily average black carbon aerosol loading and SO2 concentrations were found to be high during burning day compared to background values. The proportion of BC to total aerosol mass concentration was observed to be similar to 5% during normal days and similar to 14% during burning days. The changes in black carbon mass concentration values have implications for estimating radiative forcing due to aerosols over the region. (C) 2008 Elsevier B.V. All rights reserved.