Air pollution is a global health issue, and events like forest fires, agricultural burning, dust storms, and fireworks can significantly worsen it. Festivals involving fireworks and wood-log fires, such as Diwali and Holi, are key examples of events that impact local air quality. During Holi, the ritual of Holika involves burning of biomass that releases large amounts of aerosols and other pollutants. To assess the impact of Holika burning, observations were conducted from March 5th to March 18th, 2017. On March 12th, 2017, around 1.8 million kg of wood and biomass were openly burned in about 2250 units of Holika, located in and around the Varanasi city (25.23 N, 82.97 E, similar to 82.20 m amsl). As the Holika burning event began the impact on the Black Carbon (BC), particulate matter 10 & 2.5 (PM10 and PM2.5), sulphur dioxide (SO2), oxides of nitrogen (NOx), ozone (O-3) and carbon monoxide (CO) concentration were observed. Thorough optical investigations have been conducted to better comprehend the radiative effects of aerosols produced due to Holika burning on the environment. The measured AOD at 500 nm values were 0.315 +/- 0.072, 0.392, and 0.329 +/- 0.037, while the BC mass was 7.09 +/- 1.78, 9.95, and 7.18 +/- 0.27 mu g/m(3) for the pre-Holika, Holika, and post-Holika periods. Aerosol radiative forcing at the top of the atmosphere (ARF-TOA), at the surface (ARF-SUR), and in the atmosphere (ARF-ATM) are 2.46 +/- 4.15, -40.22 +/- 2.35, and 42.68 +/- 4.12 W/m(2) for pre-Holika, 6.34, -53.45, and 59.80 W/m(2) for Holika, and 5.50 +/- 0.97, -47.11 +/- 5.20, and 52.61 +/- 6.17 W/m(2) for post-Holika burning. These intense observation and analysis revealed that Holika burning adversely impacts AQI, BC concentration and effects climate in terms of ARF and heating rate.

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.

In South Asia, our understanding of atmospheric aerosols and their optical properties is limited, posing a challenge to comprehending climate change dynamics. This study characterises aerosol optical properties, radiative properties, black carbon (BC) and ozone (O3) at seven South Asian locations, including Nam Co (Tibetan Plateau, TP), Dhaka, Bhola (Bangladesh), and Hanimaadhoo, Kashidhoo, Male' and Gan (Maldives). The study utilises columnar aerosol data from the Aerosol Robotic Network (AERONET) and reanalysis data from Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) from 2001 to 2020. Notably, during the winter, the highest Aerosol optical depth (AOD) levels were observed in Dhaka (1.0 +/- 0.5) and Bhola (0.8 +/- 0.4) among these seven locations. BC concentrations in Dhaka ranged from 2.1 to 2.8 mu g m-3, while Bhola recorded concentrations between 1.4 and 2.1 mu g m-3. O3 levels across Maldives sites remained consistent, with values ranging between 314 and 345 dobson units (DU), surpassing those in Bangladesh and TP. The analysis shows a significant difference in the rate at which the atmosphere heats (HR) up due to aerosols. Higher heating rates were observed over Kashidhoo during the post-monsoon and winter seasons, while lower values were seen during the pre-monsoon and monsoon seasons, compared with Hanimaadhoo and Male'. It is important to note that Bangladesh had higher HR values than the Maldives. This study helps us better understand the impact of atmospheric aerosols on South Asia's climate and the different seasonal patterns.

Refractory black carbon (rBC) is a primary aerosol species, produced through incomplete combustion, that absorbs sunlight and contributes to positive radiative forcing. The overall climate effect of rBC depends on its spatial distribution and atmospheric lifetime, both of which are impacted by the efficiency with which rBC is transported or removed by convective systems. These processes are poorly constrained by observations. It is especially interesting to investigate rBC transport efficiency through the Asian Summer Monsoon (ASM) since this meteorological pattern delivers vast quantities of boundary layer air from Asia, where rBC emissions are high to the upper troposphere/lower stratosphere (UT/LS) where the lifetime of rBC is expected to be long. Here, we present in situ observations of rBC made during the Asian Summer Monsoon Chemistry and Climate Impact Project of summer, 2022. We use observed relationships between rBC and CO in ASM outflow to show that rBC is removed nearly completely (>98%) from uplifted air and that rBC concentrations in ASM outflow are statistically indistinguishable from the UT/LS background. We compare observed rBC and CO concentrations to those expected based on two chemical transport models and find that the models reproduce CO to within a factor of 2 at all altitudes whereas rBC is overpredicted by a factor of 20-100 at altitudes associated with ASM outflow. We find that the rBC particles in recently convected air have thinner coatings than those found in the UTLS background, suggesting transport of a small number of rBC particles that are negligible for concentration.

In this study, we used satellite observations to identify 10 typical dust-loading events over the Indian Himalayas. Next, the aerosol microphysical and optical properties during these identified dust storms are characterized using cotemporal in situ measurements over Mukteshwar, a representative site in Indian Himalayas. Relative to the background values, the mass of coarse particles (size range between 2.5 and 10 mu m) and the extinction coefficient were found to be enhanced by 400% (from 24 +/- 15 to 98 +/- 40 mu g/m3) and 175% (from 89 +/- 57 Mm-1 to 156 +/- 79 Mm-1), respectively, during these premonsoonal dust-loading events. Moreover, based on the air mass trajectory, these dust storms can be categorized into two categories: (a) mineral dust events (MDEs), which involve long-range transported dust plumes traversing through the lower troposphere to reach the Himalayas and (b) polluted dust events (PDEs), which involve short-range transported dust plumes originating from the arid western regions of the Indian subcontinent and traveling within the heavily polluted boundary layer of the Gangetic plains before reaching the Himalayas. Interestingly, compared to the background, the SSA and AAE decrease during PDEs but increase during MDEs. More importantly, we observe a twofold increase in black carbon concentrations and the aerosol absorption coefficient (relative to the background values) during the PDEs with negligible changes during MDEs. Consequently, the aerosol-induced snow albedo reduction (SAR) also doubles during MDEs and PDEs relative to background conditions. Thus, our findings provide robust observational evidence of substantial dust-induced snow and glacier melting over the Himalayas.

Atmospheric particulate matter (PM) as light-absorbing particles (LAPs) deposited to snow cover can result in early onset and rapid snow melting, challenging management of downstream water resources. We identified LAPs in 38 snow samples (water years 2013-2016) from the mountainous Upper Colorado River basin by comparing among laboratory-measured spectral reflectance, chemical, physical, and magnetic properties. Dust sample reflectance, averaged over the wavelength range of 0.35-2.50 mu m, varied by a factor of 1.9 (range, 0.2300-0.4444) and was suppressed mainly by three components: (a) carbonaceous matter measured as total organic carbon (1.6-22.5 wt. %) including inferred black carbon, natural organic matter, and carbon-based synthetic, black road-tire-wear particles, (b) dark rock and mineral particles, indicated by amounts of magnetite (0.11-0.37 wt. %) as their proxy, and (c) ferric oxide minerals identified by reflectance spectroscopy and magnetic properties. Fundamental compositional differences were associated with different iron oxide groups defined by dominant hematite, goethite, or magnetite. These differences in iron oxide mineralogy are attributed to temporally varying source-area contributions implying strong interannual changes in regional source behavior, dust-storm frequency, and (or) transport tracks. Observations of dust-storm activity in the western U.S. and particle-size averages for all samples (median, 25 mu m) indicated that regional dust from deserts dominated mineral-dust masses. Fugitive contaminants, nevertheless, contributed important amounts of LAPs from many types of anthropogenic sources.

Aerosols significantly impact the Earth's climate, affecting the amount of solar radiation that reaches its surface and directly impacting global warming. A large uncertainty regarding the impacts of aerosols on climate is related to Brown Carbon (BrC), an organic constituent emitted due to the incomplete combustion of light-absorbing biomass. This study aimed to define and quantify Black Carbon (BC) and Brown Carbon (BrC) absorptions using in-situ measurements from a campaign carried out in the Pantanal Mato Grosso between 2017 and 2019. The models were adjusted to calculate the Radiative Forcing (RF). By examining the RF perturbations caused by these two components, it was possible to determine the radiative balance perturbations at the upper atmospheric layer (top) and the surface. This study presented innovative findings that may help improve the understanding of the energy balance in the Pantanal region while allowing more accurate estimates of the contribution of aerosols to climate change models.

Rationale. Glaciers in the Tibetan Plateau (TP), especially in the Himalayas, are retreating rapidly due to rising air temperature and increasing anthropogenic emissions from nearby regions. Traditionally, pollutants deposited on the glaciers have been assumed to originate from long-range transport from its outside. Methodology. This study investigated the concentrations of black carbon (BC) and major ions in snowpit samples collected from two glaciers in the south-eastern TP (Demula and Palongzangbu) and one glacier in the west Himalayas (Jiemayangzong). The radiative forcing of BC was calculated based on BC concentration and glacier characteristics. Results. The results revealed that the BC/Ca2+ concentration ratio in snowpit samples from Palongzangbu, located near residential villages, is similar to 2.05 times higher than that of Demula, which is mainly influenced by long-range transported pollutants. Furthermore, on Jiemayangzong glacier, snowpit samples collected with 100-m vertical resolution exhibited that BC-induced radiative forcings at low altitude are similar to 2.37 +/- 0.16 times greater than those at high altitude. Discussion. These findings demonstrated that in addition to long-range transport, emissions from local residents also make substantial contributions to BC and certain major ions (e.g. SO42-). To accurately assess the sources and radiative forcing of BC and other light-absorbing impurities on glaciers of the TP, it is necessary to consider the impact of local populations and altitude-dependent variations.

This work uses a mixture of observations from surface remote sensing (AERONET) and satellite remote sensing (OMI) to uniquely compute the atmospheric column loading of black carbon (BC) mass concentration density (MCD) and number concentration density (NCD) on a grid-by-grid, day-by-day basis at 0.25 degrees x0.25 degrees over rapidly developing and biomass burning (BB) impacted regions in South, Southeast, and East Asia. This mixture of observations is uniformly analyzed based on OMI NO2 retrievals, OMI Near ultraviolet band absorption aerosol optical depth and single scattering albedo (SSA), and AERONET visible and near-infrared band SSA observations, in connection with an inversely applied MIE mixing model approach. This method uniquely solves for the unbiased spatial and temporal domains based on variance maximization of daily NO2. These locations in space and time are then used to quantify the distribution of all possible individual particle core and refractory shell sizes as constrained by all band-by-band observations of SSA from AERONET. Finally, the range of NCD and MCD are computed from the constrained range of per-particle core and refractory shell size on a grid-by-grid and day-byday basis. The maps of MCD and NCD are consistent in space and time with known urban, industrial, and BB sources. The statistical distributions are found to be non-normal, with the region-wide mean, 25th, 50th, and 75th percentile MCD [mg/m2] of 90.3, 56.1, 81.1, and 111 respectively, and NCD [x1012 particles/m2] of 8.76, 4.63, 7.39, and 11.3 respectively. On a grid-by-grid basis, a significant amount of variation is found, particularly over Myanmar, Laos, northern Thailand, and Vietnam, with this subregional mean, 25th, 50th, and 75th MCD [mg/m2] of 90.7, 56.1, 81.3, and 112 respectively and NCD [x1012 particles/m2] of 9.66, 5.49, 8.33, and 12.3 respectively. On a day-to-day basis, events are determined 121 days in 2016, during which the computed statistics of MCD and NCD have mean and uncertainty ranges which scale with each other. However, there are 11 days where the uncertainty ratio of NCD values is larger than 1 while the uncertainty ratio of MCD is small, and 5 days where the reverse is observed, indicating that the particle size is strongly atypical on these days, consistent with mixed aerosol sources, a substantial change in the aerosol aging, or other such factors including a substantial region of overlap between BB and urban sources. The high values observed from March to May lead to an extended BB season as compared to previous work focusing on fire radiative power, NO2, and models, which show a shorter season (usually ending in early April). The results are consistent with BC being able to transport significant distances. The new approach is anticipated to provide support for improving radiative forcing calculations, estimating emissions inventories, and providing a basis by which models can compare against observations.

Black carbon (BC) is one of the major aerosol components with relatively high implications on climatic patterns through its radiative forcing (RF). South Asia has recently experienced an increased concentration of pollution; however, relatively fewer studies have been carried out on long-term assessment of BC and its implications. The present study analyzed the long-term concentration of BC in selected urban locations over South Asia using the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2). The study employed statistical analysis, including linear regression techniques, to assess the long-term concentration of BC. The results show that a rapid increase of BC is observed over most urban locations of South Asia with the predominance in winter and hence requires strict regional control measures to reduce the excess concentration of BC in the atmosphere. High concentration of BC in winter is attributed to anthropogenic activities and changes in meteorological conditions that enhance the accumulation of pollutants in the atmosphere. The relationship of BC with cloud top temperature and cloud effective radius demonstrates the direct and indirect effect of BC on cloud properties in this region. The RF results reveal that aerosol optical depth has positive aerosol RF in the atmosphere and negative RF at the top of the atmosphere (TOA) as well as at the bottom of the atmosphere (BOA). Negative RF at the TOA indicates less forcing efficiency due to fewer BC aerosols. On the other hand, averaging aerosol RF within the atmosphere reveals positive forcing, which suggests the efficiency force exerted by BC aerosols after absorbing solar radiation.