This study investigates aerosol characteristics using ground-based measurements at two distinct regions, MohalKullu (31.9 degrees N, 77.12 degrees E; 1154 m amsl) and Kosi-Katarmal (29.64 degrees N, 79.62 degrees E; 1225 m amsl), from July 2019 to June 2022. The average Black Carbon (BC) concentrations were 1.5 f 1.0 mu g m- 3 at Mohal and 1.1 f 1.4 mu g m-3 at Katarmal. BC showed strong seasonal variability, with maxima during post-monsoon (2.6 f 1.0 mu g m- 3) and pre-monsoon (1.8 f 0.5 mu g m-3) seasons. The diurnal variation displayed distinct morning and evening peaks in all the seasons. High pre-monsoon AOD500 (0.30 f 0.06 to 0.54 f 0.08) and low values of & Aring;ngstrom exponent (0.67 f 0.10 to 0.95 f 0.30) indicated dominance of large particles, whereas lower AOD500 (0.21 f 0.07 to 0.25 f 0.03) in post-monsoon and winter, along with larger & Aring;ngstrom exponent (1.05 f 0.74 to 1.13 f 0.11), indicated smaller particles. Satellite-derived (OMI and MAIAC) AOD500 showed weak to moderate correlation with ground-based measurements at Mohal (R = 0.4639 for MAIAC, R = 0.1402 for OMI) and Katarmal (R = 0.3976 for MAIAC, R = 0.2980 for OMI). Using optical properties of aerosols and clouds (OPAC) and Santa Barbara discrete ordinate radiative transfer (SBDART) models, the short-wave aerosol radiative forcing (SWARF) was found negative at the surface and top of the atmosphere but positive in the atmosphere, suggesting significant surface cooling and atmospheric warming leading to high heating rates, respectively. Annual mean atmospheric radiative forcing was 27.36 f 6.00 Wm- 2 at Mohal and 21.87 f 7.26 Wm- 2 at Katarmal. These findings may have consequences for planning air pollution strategies and understanding the effects of regional climate change.

Aerosols are an important factor leading to reduced visibility. In order to better comprehend the connection between visibility and aerosols, aerosol optical depth (AOD) and Angstrom exponent (AE) data from the Himawari-8 Advanced Himawari Imager (AHI) are used for validation in comparison with the data from the Aerosol Robotic Network (AERONET) observations in this paper, which amounted to 69,026 sets of data. The results indicate that the AOD of AHI is in good agreement with AERONET observations, but AE performs poorly. The correlation coefficients between the AOD of AHI and AERONET data increase with decreasing visibility and the root mean square error increase. The AE of AHI performs poorly in different visibility conditions. The conclusion drawn from further analysis of the correlation between aerosol products and meteorological factors is that the factor with the highest correlation with visibility. Mixed aerosols dominate at higher visibility and biomass burning/urban-industrial aerosols dominate at lower visibility. The visibility in a typical city (Beijing) has a strong negative correlation with AOD, a weak negative correlation with AE, and a strong correlation with aerosol radiative forcing. The reduction in visibility may be caused by the scattering and adsorption effects of aerosols. The results are important for the improvement and application of AHI aerosol products in regional pollution studies.

We measured black carbon (BC) with a seven-wavelength aethalometer (AE-31) at the Nam Co Lake (NCL), the hinterland of the Tibetan Plateau (TP) from May 2015 to April 2016. The daily average concentration of BC was 145 +/- 85 ng m(-3), increasing by 50% since 2006. The seasonal variation of BC shows higher concentrations in spring and summer and lower concentrations in autumn and winter, dominated by the adjacent sources and meteorological conditions. The diurnal variation of BC showed that its concentrations peaked at 9:00-16:00 (UTC + 8), significantly related to local human activities (e.g., animal-manure burning and nearby traffic due to the tourism industry). The concentration-weighted trajectory (CWT) analysis showed that the long-distance transport of BC from South Asia could also be a potential contributor to BC at the NCL, as well as the biomass burning by the surrounding residents. The analyses of the absorption coefficient and absorption angstrom ngstrom exponent show the consistency of sourcing the BC at the NCL. We suggest here that urgent measures should be taken to protect the atmospheric environment at the NCL, considering the fast-increasing concentrations of BC as an indicator of fuel combustion.

We report measurements of the optical properties of methanol-soluble organic carbon (MSOC) and water-soluble organic carbon (WSOC) in the metropolitan city of Mumbai (19.01(degrees) N, 72.92(degrees) E), India. The MSOC and WSOC extracts were analysed using UV-visible spectroscopy. The study covered a period of nine months from September 2017 to May 2018. On average, MSOC constituted 30% and WSOC constituted 24% of the PM2.5 mass for the sampling period with peak concentration observed in the winter season. The absorption coefficients of MSOC were on average 1.57 times higher than WSOC for the sampling period. The absorption coefficients of MSOC and WSOC were correlated with the brown carbon absorption coefficients. Mass absorption cross- (MAC) was calculated by normalizing the absorption coefficients with its concentration, and the absorption angstrom exponent (AAE) was calculated by exponential fitting of the absorption coefficients. The MAC values for WSOC were estimated to be 1.03 +/- 0.39 m(2) g(-1), while for MSOC, it was 1.41 +/- 0.76 m(2) g(-1). The relative radiative forcing compared to black carbon was estimated at 10.1 +/- 5.2% and 6.3 +/- 3.8% for MSOC and WSOC, respectively.

This study reports black carbon (BC) characteristics and climate effects for a 22-month period during 2018-2020 at a receptor location in the eastern Indo-Gangetic Plains (IGP). The overall averaged BC mass concentration was 7.8 & PLUSMN; 4.7 & mu;g m- 3, and the nighttime average (9.1 & PLUSMN; 6.1 & mu;g m- 3) was nearly double that of the daytime (5.8 & PLUSMN; 3.5 & mu;g m- 3). BC was most enhanced during winter, with mean concentration (14.3 & PLUSMN; 3.8 & mu;g m- 3) higher by 4 times as compared to summer. A two-component mixing model, frequency distribution of the Angstrom exponent, and a simultaneous increase in brown carbon (BrC) absorption coefficient suggested that this enhancement was mostly due to the biomass burning (BB) fraction of BC. CALIPSO-derived products showed that the extinction coefficient was highest at 0.62 & PLUSMN; 0.31 km-1 in winter and lowest at 0.12 & PLUSMN; 0.05 km-1 in summer. Backscatter plots and particle depolarization ratios indicated presence of spherical dust particles during summer and smoke plumes during post-monsoon and winter. Concentration-weighted trajectories (CWTs) helped in quantifying significant contributions of the IGP outflow to BC, BC-BB and BrC absorption. Finally, a large direct radiative forcing of the atmosphere by BC (37 & PLUSMN; 22 W m- 2) was estimated via the radiative transfer model SBDART, with an associated atmospheric heating rate of 1.02 K d-1.

Aerosols play an important role in the earth's environment across the globe through their involvement in various earth system cycles. The change in the aerosol properties may cause short and long-term impacts, the knowledge of such changes is useful in the estimation of the pollution sources of any region. We have carried out the analysis of the aerosols' optical and radiative properties using AERONET station data from 2018 to 2021 in Dibrugarh City. The higher Aerosol Optical Depth (AOD) values during winter and pre-monsoon months indicate high anthropogenic activities, and biomass burning in Dibrugarh. The impact of various sources and daily meteorological parameters help in understanding the diurnal variations of the AOD, Angstrom Exponent (AE), and column water (CW). Fine aerosol fractions dominate the aerosol volume, but sometimes the long-range transport of dust affects aerosol properties during pre-monsoon months (MAM). MODIS-derived AOD and AERONET AOD values show a good correlation, with R-2 = 0.68. The highest volume of the aerosols reaches up to 0.11 mu m(3) mu m(-2) during pre-monsoon months, whereas it lies below 0.05 mu m(3) mu m(-2) in other seasons. SSA values indicate the presence of scattering aerosols but in 2020, a sudden decline in the SSA values shows a strong rise in the absorbing aerosols. Throughout the study period (2018-2021), the positive radiative forcing indicates a rise in atmospheric heating.

This paper presents the results of the study on columnar aerosol optical and physical properties and radiative effects directly observed over Dushanbe, the capital city of Tajikistan, a NASA AERONET site (equipped with a CIMEL sunphotometer) in Central Asia. The average aerosol optical depth (AOD) and Angstrom exponent (AE) during the observation period from July 2010 to April 2018 were found to be 0.28 +/- 0.20 and 0.82 +/- 0.40, respectively. The highest seasonal AOD (0.32 +/- 0.24), accompanied by the lowest average AE (0.61 +/- 0.25) and fine-mode fraction in AOD (0.39), was observed during summer due to the influence of coarse particles like dust from arid regions. Fine particles were found in significant amounts during winter. The 'mixed aerosol' was identified as the dominant aerosol type with presence of 'dust aerosol' during summer and autumn seasons. Aerosol properties like volume size distribution, single scattering albedo, asymmetry parameter and refractive index suggested the influence of coarse particles (during summer and autumn). Most of the air masses reaching this site transported local and regional emissions, including from beyond Central Asia, explaining the presence of various aerosol types in Dushanbe's atmosphere. The seasonal aerosol radiative forcing efficiency (ARFE) in the atmosphere was found high (>100 Wm(-2)) and consistent throughout the year. Consequently, this resulted in similar seasonally coherent high atmospheric solar heating rate (HR) of 1.5 K day(-1) during summer-autumn-winter, and ca. 0.9 K day(-1) during spring season. High ARFE and HR values indicate that atmospheric aerosols could exert significant implications to regional air quality, climate and cryosphere over the central Asian region and downwind Tianshan and Himalaya-Tibetan Plateau mountain regions with sensitive ecosystems. (C) 2020 Elsevier Ltd. All rights reserved.

The role of atmospheric aerosols in earth's radiative balance is crucial. A thorough knowledge about the spectral optical properties of various types of aerosols is necessary to quantify the net radiative forcing produced by aerosol-light interactions. In this study, we exploited an open-source inverse algorithm based on the Python-PyMieScatt survey iteration method, to retrieve the wavelength dependent Mie-equivalent complex refractive indices of ambient aerosols. This method was verified by obtaining the broadband complex refractive indices of monodisperse polystyrene latex spheres and polydisperse common salt aerosols, using laboratory data collected with a supercontinuum broadband cavity enhanced extinction spectrometer operating in the 420-540 nm wavelength range. Field measurements of ambient aerosol were conducted using a similar cavity enhanced extinction spectrometer (IBBCEES) operating in the wavelength range of 400-550 nm, a multi-wavelength aethalometer, and a scanning mobility particle sizer, in Changzhou city, People's Republic of China. The absorption coefficients for the entire wavelength range were retrieved using the absorption Angstrom exponents calculated from a pair of measured absorption coefficients at known wavelengths. The survey iteration method takes scattering and absorption coefficients, wavelength, and size distributions as inputs; and it calculates the Mie-equivalent wavelength dependent complex refractive index (RI = n +/- ik) and estimated errors. The retrieved field RI values ranged from 1.66 <= n <= 1.80 to 1.65 <= n <= 1.86 and from 0.036 <= k <= 0.038 to 0.062 <= k <= 0.067 in the wavelength range (400-550 nm), for low and high aerosol loading conditions, respectively. Additionally, we derived the spectral dependencies of scattering and absorption coefficients along with the n and k Angstrom exponents (AE). The nAE and kAE estimated values suggest a stronger wavelength dependence for aerosol light scattering compared to absorption, and a decreasing trend for the spectrally dependent single scattering albedo during both loading conditions. The extremum of errors in the retrieved n and k values were quantified by considering (a) uncertainties in input parameters in the broad spectral region (400-550 nm), (b) using CAPS extinction values at 530 nm and (c) an estimated size distribution incorporating the coarse particles (at 530 nm).

Atmospheric aerosols are very crucial from air pollution and health perspective as well as for regional and global climate. This paper attempts to summarize the aerosol loading and their properties such as Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA), Angstrom exponent, and Radiative forcing, over India. All the above mentioned parameters have shown significant variability with change in the site and season. From various studies it was observed that AOD is relatively higher over Northern part of India as compared to Southern and Eastern part. Generally, lower values of SSA were observed over all sites during winter and post-monsoon seasons which indicates the dominance of absorbing type aerosol during these seasons. Also the ARF within atmosphere showed comparatively higher values during November-December and lower value during August and September all over the India. The current state of knowledge about aerosol sources, interactions and their effects on environment is limited because of its complexity. Therefore, more focused research in needed to understand the aerosol's role in climatic phenomenon.

Black carbon (BC) is one of the short-lived air pollutants that contributes significantly to aerosol radiative forcing and global climate change. It is emitted by the incomplete combustion of fossil fuels, biofue Is, and biomass. Urban environments are quite complex and thus, the use of mobile jointly with fixed monitoring provides a better understanding of the dynamics of BC distribution in such areas. The present study addresses the measurement of BC concentration using real-time mobile and ambient monitoring in Barranquilla, an industrialized urban area of the Colombian Caribbean. A microaethalometer (MA200) and an aethalometer (AE33) were used for measuring the BC concentration. The absorption Angstrom exponent (AAE) values were determined for the study area, for identifying the BC emission sources. The results of the ambient sampling show that vehicle traffic emissions prevail; however, the influence of biomass burning was also observed. The mean ambient BC concentration was found to be 1.04 +/- 1.03 mu g/m(3) and varied between 0.5 and 4.0 mu g/m(3). From the mobile measurements obtained in real traffic conditions on the road, a much higher average value of 16.1 +/- 16.5 mu g/m(3 )was measured. Many parts of the city showed BC concentrations higher than 20 mu g/m(3). The spatial distribution of BC concentration shows that vehicle emissions and traffic jams, a consequence of road and transport infrastructure, are the factors that most affect the BC concentration. A comparison of results obtained from two aethalometers indicates that the concentrations measured by MA200 are 9% lower than those measured by AE33. The ME obtained was found to vary between 1.1 and 1.6, indicating vehicular emissions as the most crucial source. In addition, it was observed that the BC concentration on working days was 25 times higher than on the weekends in the case of mobile monitoring and 1.5 times higher in the case of ambient monitoring. (C) 2021 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.