This study investigates the inter-annual variability of carbonaceous aerosols (CA) over Kolkata, a megacity in eastern India, using dual carbon isotopes (C-14 and C-13) alongside measurements of the optical properties of brown carbon (BrC). Sampling was conducted during the post-monsoon, winter, and spring seasons over two consecutive years (2020-21 and 2021-22). The analysis reveals that PM2.5 and CA concentrations were higher in 2020-21 (194 +/- 40 and 54 +/- 15 mu g m(-3), respectively) compared to 2021-22 (141 +/- 31 and 44 +/- 21 mu g m(-3)), likely due to higher precipitation in 2021-22. The contribution of biomass burning and biogenic sources to CA (f(bio_TC)) was slightly higher in 2020-21 (70 +/- 3 %) than in 2021-22 (68 +/- 3 %), with both years exhibiting a consistent decreasing trend from post-monsoon to spring. Observed lower values for oxidised CA proxies, such as the WSOC/OC ratio (0.41 +/- 0.08) and AMS-derived f(44) (0.13 +/- 0.02), throughout the study period suggest that surface CA over Kolkata primarily originates from local sources rather than long-range transport. The relative radiative forcing (RRF) also showed a clear reduction in the subsequent year; however, on average, the RRF of methanol-soluble BrC (16 +/- 6 %) was approximately three times higher than that of the water-soluble fraction (5.5 +/- 2.2 %), highlighting the substantial role of BrC in influencing regional radiative forcing. These findings underscore the substantial impact of local emissions over transported pollutants on Kolkata's ground-level air quality.

This study analyzes the aerosol and precipitable water vapor (PWV) properties at six sites in the Indo-Gangetic Plains (IGP), a densely populated and highly polluted region. The main objective is to explore how the columnar PWV is related to the attenuation of shortwave solar radiation (SWR), as well as the combined role of aerosol properties and PWV on radiative forcing based on AERONET data and model (SBDART) simulations. The analysis revealed high aerosol optical depth (AOD) values (0.4-0.6) throughout the year in all the sites, associated with increased PWV (4-5 cm) during the summer monsoon. Comprehensive investigation shows that changes in PWV levels also affect aerosols' size distribution, optical properties and radiation balance in a similar way - but in different magnitudes - between the examined sites. The water vapor radiative effect (WVRE) is highly dependent on aerosol presence, with its magnitude for both surface (-130 to -140 Wm(-2)) and atmospheric forcing becoming higher under clean atmospheres (without aerosols). Aerosol presence is also considered in the computations of the WVRE. In that case, the WVRE becomes more pronounced at the top of the atmosphere (TOA) (30 to 35 Wm(-2)) but exhibits a lower forcing impact on the surface (about -45 Wm(-2)) and within the atmosphere (70-80 Wm(-2)), suggesting important aerosol-PWV interrelations. The atmospheric heating rate due to PWV is more than double (3.5-4.5 K Day(-1)) that of aerosols (1-1.9 K Day(-1)), highlighting its essential role in radiative effects and climate implications over the IGP region. The radiative impacts of PWV and aerosols are further examined as a function of the single scattering albedo, solar zenith angle, and absorbing AOD at the different sites, revealing dependence on both astronomical and atmospheric variables related to aerosol absorption, thus unravelling the combined role of aerosols and PWV in climate implications.

Altitude profiles of the mass concentrations of aerosol black carbon (BC) have been obtained,up to an altitude of 12 km, from in situ measurements over Hyderabad (17.47 degrees N, 78.57 degrees E, 557 m amsl;a tropical station in the central Indian peninsula), using three successive high altitude balloon ascents during winter and early summer seasons of 2023-2024. The profiles revealed predominant peaks at around 8 and 11 km, where the BC concentrations were reaching as high as nearly three times the surface concentrations (2.82, 2.76, and 2.60 mu g m-3, respectively), persistently in all the three flights. Detailed analyses using official data of air traffic movement, aviation statistics and emission inventory revealed a strong linkage with the emissions from commercial aircraft that touch Hyderabad and overfly the region. These elevated BC layers will have large implications to atmospheric radiative forcing and possible contributions to modification of the cirrus cloud properties.

Pollutant emissions in China have significantly decreased over the past decade and are expected to continue declining in the future. Aerosols, as important pollutants and short-lived climate forcing agents, have significant but currently unclear climate impacts in East Asia as their concentrations decrease until mid-century. Here, we employ a well-developed regional climate model RegCM4 combined with future pollutant emission inventories, which are more representative of China to investigate changes in the concentrations and climate effects of major anthropogenic aerosols in East Asia under six different emission reduction scenarios (1.5 degrees C goals, Neutral-goals, 2 degrees C -goals, NDC-goals, Current-goals, and Baseline). By the 2060s, aerosol surface concentrations under these scenarios are projected to decrease by 89%, 87%, 84%, 73%, 65%, and 21%, respectively, compared with those in 2010-2020. Aerosol climate effect changes are associated with its loadings but not in a linear manner. The average effective radiative forcing at the surface in East Asia induced by aerosol-radiation-cloud interactions will diminish by 24% +/- 13% by the 2030s and 35% +/- 13% by the 2060s. These alternations caused by aerosol reductions lead to increases in near-surface temperatures and precipitations. Specifically, aerosol-induced temperature and precipitation responses in East Asia are estimated to change by -78% to -20% and -69% to 77%, respectively, under goals with different emission scenarios in the 2060s compared to 2010-2020. Therefore, the significant climate effects resulting from substantial reductions in anthropogenic aerosols need to be fully considered in the pathway toward carbon neutrality.

Air quality in Bangladesh has depreciated over the years owing to substantial local and regional aerosol emissions. This study investigates the impact of anthropogenic aerosol emissions, aerosol radiative forcing, and socioeconomic factors on aerosol optical depth (AOD) over Bangladesh. The research focuses on the capital city Dhaka and the coastal island Bhola, using data from the ground-based AERONET, MODIS satellite, and MERRA-2 reanalysis model. AOD exhibited increasing trends over Bangladesh (0.004-0.010/years) and showed significant annual cycles. Northwestern regions of the country experienced extremely high concentrations of anthropogenic black carbon (BC) and organic carbon (OC) aerosols, whereas the central regions exhibited elevated anthropogenic SO2 and SO4 concentrations. The dominance of anthropogenic aerosols (SO4, BC, and OC) over Dhaka (similar to 75%) and natural aerosols (sea salt and dust) over Bhola (similar to 63%) were calculated. SO4 aerosol was the primary driving force over Dhaka contributing 47.60% of the total AOD, while sea salt aerosol was the dominant species (45.78%) over Bhola. High aerosol radiative forcing at the atmosphere (ARF(ATM)) values were calculated for both Dhaka and Bhola. Average heating rate (HR) at Dhaka was 2.05 +/- 0.75 K day(-1), and at Bhola was 1.54 +/- 0.58 K day(-1) indicating the presence of light-absorbing aerosols over Bangladesh. All the socioeconomic factors were positively correlated with AOD except population growth and agriculture land indicating the substantial impact of socioeconomic development on AOD. The findings of this study will have notable influences on long-term air quality management in Bangladesh as well as in Southeast Asia.

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.

This study shows the impact of black carbon (BC) aerosol atmospheric rivers (AAR) on the Antarctic Sea ice retreat. We detect that a higher number of BC AARs arrived in the Antarctic region due to increased anthropogenic wildfire activities in 2019 in the Amazon compared to 2018. Our analyses suggest that the BC AARs led to a reduction in the sea ice albedo, increased the amount of sunlight absorbed at the surface, and a significant reduction of sea ice over the Weddell, Ross Sea (Ross), and Indian Ocean (IO) regions in 2019. The Weddell region experienced the largest amount of sea ice retreat (similar to 33,000 km(2)) during the presence of BC AARs as compared to similar to 13,000 km(2) during non-BC days. We used a suite of data science techniques, including random forest, elastic net regression, matrix profile, canonical correlations, and causal discovery analyses, to discover the effects and validate them. Random forest, elastic net regression, and causal discovery analyses show that the shortwave upward radiative flux or the reflected sunlight, temperature, and longwave upward energy from the earth are the most important features that affect sea ice extent. Canonical correlation analysis confirms that aerosol optical depth is negatively correlated with albedo, positively correlated with shortwave energy absorbed at the surface, and negatively correlated with Sea Ice Extent. The relationship is stronger in 2019 than in 2018. This study also employs the matrix profile and convolution operation of the Convolution Neural Network (CNN) to detect anomalous events in sea ice loss. These methods show that a higher amount of anomalous melting events were detected over the Weddell and Ross regions. Impact Statement Sea ice protects ice sheets, which are melting at a very high rate to raise the sea level. In addition to global warming, this study is indicative that black carbon aerosols transported from anthropogenic wildfire events, such as from the Amazon, darken the snow, reduce their reflectance, increase the absorption of solar energy incident on the surface, and exacerbate the sea ice retreat. Thus, this study points out that anthropogenic wildfire impacts far away from a region can have a severe impact on sea ice and ice sheets over the Antarctic which has a sea level rise potential of 60 m. Our study shows that only over the Weddell region, sea ice retreat was 20,000 km(2) higher during the presence of BC transport events than other days in 2019.

Aerosols can alter atmospheric stability through radiative forcing, thereby changing mean and daily extreme precipitation on regional scales. However, it is unclear how extreme sub-daily precipitation responds to aerosol radiative effects. In this study, we use the regional climate model (RCM) Consortium for Small-scale Modeling (COSMO) to perform convection-permitting climate simulations at a kilometer-scale (0.04 degrees/similar to 4.4 km) resolution for the period 2001-2010. By evaluating against the observed hourly precipitation-gauge data, the COSMO model with explicit deep convection can effectively reproduce sub-daily and daily extreme precipitation events, as well as diurnal cycles of summer mean precipitation and wet hour frequency. Moreover, aerosol sensitivity simulations are conducted with sulfate and black carbon aerosol perturbations to assess the direct and semi-direct aerosol effects on extreme sub-daily precipitation in the COSMO model. The destabilizing effects associated with decreased sulfate aerosols intensify extreme sub-daily precipitation, while increased sulfate aerosols tend to induce an opposite change. In contrast, the response of extreme sub-daily precipitation to black carbon aerosol perturbations exhibits a nonlinear behavior and potentially relies on geographical location. Overall, the scaling rates of extreme precipitation intensities decrease and approach the Clausius-Clapeyron rate from hourly to daily time scales, and the responses to sulfate and black carbon aerosols vary with precipitation durations. This study improves the understanding of aerosol radiative effects on sub-daily extreme precipitation events in RCMs.

Black carbon is a short-lived climate warming agent and serves as a crucial factor influencing the climate. Numerous models, observations, and laboratory studies have been conducted to quantify black carbon's direct or indirect impacts on the climate. Here, we applied bibliometric analysis to identify research trends and key topics on black carbon in the climate field. Based on the Web of Science (WOS) Core Collection database, a total of 4903 documents spanning the period from 2000 to 2023 were retrieved and screened, focusing on the topic of black carbon in the climate field, resulting in the Black-Carbon Climate Local (BCL) dataset. Our study examines the influence and trends of major countries, institutions, and authors in this field. The results show that China and the United States hold leading positions in terms of the number of publications. Based on keyword networks, the BCL dataset is segmented into six distinct research directions, and representative keywords of each direction include biomass burning, radiative forcing, air pollution, aerosol optical depth, optical properties, and biochar. This study helps to identify the current research status and trends of black carbon in the climate, highlighting main research directions and emerging topics.

Aerosol single-scattering albedo (SSA) is the most critical factor for the accurately calculating of aerosol radiative effects, however, the observation of vertical profiles of SSA is difficult to realize. Current assessments of aerosol radiative effects remain uncertain because of the lack of long-term, high-resolution vertical profiles of SSA observations. High-resolution SSA vertical profiles were observed in a semi-arid region of Northwest China during winter using a tethered balloon. The observed SSA vertical profiles were used to calculate the aerosol direct radiative forcing and radiative heating rates. Significant differences in the calculated radiative forcing were found (e.g., a 48.3% relative difference for the heating effect in the atmosphere at 14:00) between the observed SSA profiles and the constant assumption with SSA = 0.90. Diurnal variations in the vertical distribution of SSA decisively influenced direct radiative forcing of aerosols. Furthermore, high-resolution vertical profiles of absorbing aerosols and meteorological parameters provide robust observational evidence of the heating effect of an elevated absorbing aerosol layer. This study provides a more accurate calculation of aerosol radiative forcing using observed aerosol SSA profiles. The scarcity of single-scattering albedo (SSA) observations is the most critical factor limiting the accurate calculations of aerosol radiative effects. A tethered balloon platform was used to obtain long-term, high-resolution observations of the SSA and estimate aerosols' radiative effects. The relative differences in the heating rate and direct radiative forcing calculations using the observed SSA and a constant assumed SSA (i.e., ignoring the vertical distribution of absorbing aerosols) were quantified. The effects of diurnal variations in the vertical distribution of SSA on aerosol direct radiative forcing are summarized. This study has important scientific implications for assessing the radiative effects of aerosols in semi-arid regions, that are highly sensitive to climate change. Tethered balloon observations acquired high-resolution vertical aerosol single-scattering albedo (SSA) profiles The assumed SSA profiles caused a 48.3% relative error in radiative forcing in the atmosphere compared to the observed profiles at 14:00 A robust observational evidence of atmospheric heating by absorbing aerosols above the boundary layer was provided