Since the 1970s, China has continuously improved air pollution treatment and emission standards, but polluted weather still occurs frequently in some areas, especially haze weather. At present, most of the research on haze weather focuses on particulate matter, while ignoring the mechanism of aerosol-radiation-surface ozone interaction under haze weather. Therefore, this paper analyses the relationship between aerosol-radiation-surface ozone with the help of the (SBDART) model for the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), using 2013-2021 as the time line. The results show similar trends in total column ozone and tropospheric ozone, and separate trends in surface ozone. Total column ozone and tropospheric ozone concentrations are at high values in spring and summer and low values in fall and winter; surface ozone is higher in summer and fall and lower in winter and spring. In contrast, Absorbing aerosol index (AAI) had high values in both spring and winter, and low values in summer and autumn. AAI, PM10 and Black carbon (BC) showed negative relations with ozone overall, but AAI and tropospheric ozone reached high values simultaneously in spring, indicating a rapid increase of pollutants caused by meteorological factors and human activities. Ozone concentration decreases from high values when precipitable water increases significantly. The analysis of potential sources of AAI indicated that local sources centered in Guangzhou were the primary source of AAI in the urban agglomeration of GBA, while other potential sources include biomass sources in the south and ozone sources in the northeast. The photolysis rate of fine-grained urban/industrial aerosols did not decrease significantly, leading to an increase in surface ozone concentration. Therefore, low aerosol radiative forcing (ARF) may increase surface ozone concentrations in the fine-particle aerosol mode.

This study assesses the physical and optical properties and estimated the radiative forcing of aerosol at Agra over the Indo-Gangetic Basin (IGB) during July 2016-December 2019 using black carbon (BC) mass concentration (AE-33 aethalometer), data sets from satellite and model simulations. The optical properties of aerosol and radiative forcing have been measured by the Optical and Physical Properties of Aerosols and Clouds (OPAC) and Santa Barbara Discrete Ordinate Radiative Transfer Atmospheric Radiative Transfer (SBDART) model. The high BC mass concentration has been observed in November and lowest in August. An adverse meteorological condition due to a combination of temperature and low wind speed results in poor dispersion in the wintertime is a common factor for high concentration level pollutants over Agra. The diurnal and temporal cycle of BC mass concentration exhibits a high concentration at nighttime due to the lower atmospheric boundary layer. The seasonal variation of absorption coefficient (& beta;abs) and Absorption Angstrom Exponent (AAE) is found to be higher during post-monsoon and lowest in monsoon season. This suggests that black carbon concentration over Agra is mainly generated from crop burning, waste burning, automobile exhaust and long-range transport from Punjab and Haryana as the present site is downwind. OPAC-derived aerosol optical depth (AOD), single-scattering albedo (SSA), Angstrom Exponent (AE) and asymmetry parameter (AsyP) were estimated to be 0.57 & PLUSMN; 0.07, 0.78 & PLUSMN; 0.16, 0.99 & PLUSMN; 0.21 and 0.81 & PLUSMN; 0.15, respectively. AOD and AE from the OPAC and the moderate resolution imaging spectroradiometer (MODIS) have shown the consistent relationship. The mean radiative forcing is 18.3 & PLUSMN; 2.1 W m-2 at the top of the atmosphere while, at the surface, net radiative forcing is -42.4 & PLUSMN; 7.2 and 59.1 & PLUSMN; 6.5 W m-2 at the atmosphere during the study period. Vertical profiles were estimated using the observations from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite and the change in heating rate from the SBDART model over Agra. First-time short-lived climate forcer black carbon mass concentration along with optical properties of aerosols has been reported, and quantification of radiative forcing has been done at the Agra region.The radiative forcing due to black carbon has been found to be high highlighting the heat risk over this region.image

The decadal variability of direct radiative effects of aerosols is investigated at Dibrugarh, a site in northeast India (NEI) at the eastern Himalayan foothills, primarily using multi-wavelength solar radiometer measurements spanning from October 2001 to February 2020. The ground-based aerosol observations are combined with satellite remote sensing, reanalysis data, and model simulations to study the change in atmospheric particle loading over the region. Observations indicate a statistically significant increase (similar to 0.015 yr(-1)) in Aerosol Optical Depth (AOD) during the last two decades in line with an increase in human activity. As compared to 2001-2007 (we call it as Stage I), the aerosol burden has grown rapidly during 2008 until 2020 (Stage II). AOD at 500 nm is found to increase by similar to 40% from Stage I to Stage II, resulting in an increase in the aerosol direct radiative forcing (DRF) at the top of the atmosphere (TOA) by similar to 43% during stage II (similar to-16.0 W m(-2)), from the base value of -11.2 W m(-2) in Stage I. Decreasing biomass burning activities, black carbon aerosol mass concentration, and high sulfate and organic aerosols are the primary factors responsible for the trend in TOA cooling by-0.46 W m(-2) yr(-1). This is further aided by the decrease in rainfall over NEI. MERRA-2 data analysis shows a similar enhancements in aerosol load over the entire NEI and the adjacent highly polluted Indo-Gangetic Plains (IGP). A similar feature is seen over the IGP, primarily driven by anthropogenic emissions, but precedes that in NEI by about a year. A simulation of the regional climate model (RegCM) over the south Asian domain quantifies the contribution of aerosol loading over NEI due to the aerosols carried from the IGP. In the highest aerosol loading period, about 12-30% of the aerosols, equivalent to 15-30% of atmospheric warming, are transported from the IGP to the NEI.

As an important fraction of light-absorbing particles, black carbon (BC) has a significant warming effect, despite accounting for a small proportion of total aerosols. A comprehensive investigation was conducted on the characteristics of atmospheric aerosols and BC particles over Wuhan, China. Mass concentration, optical properties, and radiative forcing of total aerosols and BC were estimated using multi-source observation data. Results showed that the BC concentration monthly mean varied from 2.19 to 5.33 mu g m(-3). The BC aerosol optical depth (AOD) maximum monthly mean (0.026) occurred in winter, whereas the maximum total AOD (1.75) occurred in summer. Under polluted-air conditions, both aerosol radiative forcing (ARF) and BC radiative forcing (BCRF) at the bottom of the atmosphere (BOA) were strongest in summer, with values of -83.01 and -11.22 W m(-2), respectively. In summer, ARF at BOA on polluted-air days was more than two-fold that on clean-air days. In addition, compared with clean-air days, BCRF at BOA on polluted-air days was increased by 76% and 73% in summer and winter, respectively. The results indicate an important influence of particulate air pollution on ARF and BCRF. Furthermore, the average contribution of BCRF to ARF was 13.8%, even though the proportion of BC in PM2.5 was only 5.1%.

The concentrations, optical and radiative effects of carbonaceous aerosols were essential to studies of the climatic, environmental and health effects. The previous studies less combined numerical simulation with in-situ observations, especially for the aerosol vertical profiles. In this study, we off-line measured vertical profiles of submicron black carbon (BC) aerosols and on-line obtained aerosol optical properties over urban Lanzhou during 26 December 2017 to 11 January 2018. The BC optical properties and radiative effects were evaluated using Optical Properties of Aerosols and Clouds (OPAC) and Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) models. The absorption and scattering coefficients and optical depth of BC aerosols ranged from 9 to 83 M m(-1) , 3-24 M m(-1) and 0.02 to 0.2 respectively, which in average accounted for 50%, 3% and 11% of the optical properties of total aerosols during the study period. BC aerosol radiative forcing (ARF) within ATMOS (top-surface) varying from 16.6 to 108.8 W m(-2) accounted for 17.3%-97.4% of total aerosols ARF with an average of 66.6%, and the percentages increased significantly as BC concentrations increased during the period. The mean atmospheric heating rate (AHR) induced by BC aerosols was 1.94 K day(-1) ranging from 0.46 to 3.03 K day(-1) during the study period. This study contributes to understanding the impacts of light-absorbing aerosols on climate and haze pollution in an urban valley.

In the shortwave solar spectrum (0.25-5 mml:mspace width=3.33333ptmml:mspacem), radiation is affected by the change in various aerosol properties and also by water vapour and other gas molecules. The presence of a variety of aerosols over the Bay of Bengal (BoB) during different seasons results in a change in aerosol properties, including the aerosol layer height. The BoB is an integral part of the Indian monsoon, and hence it is essential to understand the radiation budget over the BoB. The sensitivity of the aerosol forcing due to the changes in aerosol properties and other parameters has been studied using the Santa Barbara discrete ordinates radiative transfer model. The aerosol forcing at the top of the atmosphere was found to depend on the aerosol loading (aerosol optical depth), aerosol type (single scattering albedo) and the angular distribution of the scattered radiation (asymmetry parameter). The analysis also shows the presence of a relationship between aerosol layer height and the total amount of water vapour present in the atmosphere. The present study highlights the need for better retrievals of vertical aerosol distribution and water vapour profiles for a better understanding of the role of aerosols in the climate.

In the present study, we estimated the aerosol radiative forcing and heating rates near Yala Glacier, Nepal (28.21 degrees N, 85.61 degrees E; 4900 masl), using in situ black carbon (BC) mass concentration measurements, satellite data sets, and model simulations. The real-time ambient BC mass concentration was continuously measured using an Aethalometer (AE-33) from October 2016 to May 2017. The Optical Properties of Aerosols and Clouds (OPAC) model was used to simulate the aerosol optical properties in conjunction with the in situ measurements and satellite data sets. Outputs from OPAC and the satellite data sets were used as inputs for the Santa Barbara Discrete Ordinate Radiative Transfer Atmospheric Radiative Transfer (SBDART) model to estimate the radiative forcing. The in situ measurements showed that the BC mass concentration peaked during the pre-monsoon season (707.9 +/- 541.8 ng m(-3)), which was corroborated by the higher aerosol optical depth (AOD) values during this season (0.058 +/- 0.002). The diurnal cycle of the BC mass concentration exhibited a night-time low and afternoon high, which were influenced by the boundary layer dynamics and valley wind flow pattern. The Concentration Weighted Trajectory (CWT) analysis indicated diverse source regions, including northern Asia, the Indo-Gangetic Plain (IGP), and parts of Nepal and Bangladesh. The Moderate Resolution Imaging Spectroradiometer (MODIS)-derived AOD and Angstrom exponent (AE), and the OPAC-simulated single-scattering albedo (SSA) and asymmetry parameter (AP) over the study site were estimated to be 0.048 +/- 0.009 and 1.32 +/- 0.01, and 0.938 +/- 0.019 and 0.710 +/- 0.042, respectively, during the study period. The mean radiative forcing during the study period for the top of the atmosphere, surface and atmosphere were 3.4, -0.5 and 3.9 W m(-2), respectively. Higher atmospheric forcing was observed in the pre-monsoon season, leading to changes in the heating rates.

Ground reaching solar radiation flux was simulated using a 1-dimensional radiative transfer (SBDART) and a 3-dimensional regional climate (RegCM 4.4) model and their seasonality against simultaneous surface measurements carried out using a CNR4 net Radiometer over a sub-Himalayan foothill site of south-east Asia was assessed for the period from March 2013-January 2015. The model simulated incoming fluxes showed a very good correlation with the measured values with correlation coefficient R-2 similar to 0.97. The mean bias errors between these two varied from -40 W m(-2) to +7 W m(-2) with an overestimation of 2-3% by SBDART and an underestimation of 2-9% by RegCM. Collocated measurements of the optical parameters of aerosols indicated a reduction in atmospheric transmission path by similar to 20% due to aerosol load in the atmosphere when compared with the aerosol free atmospheric condition. Estimation of aerosol radiative forcing efficiency (ARFE) indicated that the presence of black carbon (BC, 10-15%) led to a surface dimming by -26.14 W m(-2) tau(-1) and a potential atmospheric forcing of + 43.04 W m(-2) tau(-1). BC alone is responsible for > 70% influence with a major role in building up of forcing efficiency of + 55.69 W m(-2) tau(-1) (composite) in the atmosphere. On the other hand, the scattering due to aerosols enhance the outgoing radiation at the top of the atmosphere (ARFE(TOA) similar to -12.60 W m(-2) omega(-1)), the absence of which would have resulted in ARFE(TOA) of similar to+16.91 W m(-2) tau(-1) (due to BC alone). As a result, similar to 3/4 of the radiation absorption in the atmosphere is ascribed to the presence of BC. This translated to an atmospheric heating rate of similar to 1.0 K day(-1), with similar to 0.3 K day(-1) heating over the elevated regions (2-4 km) of the atmosphere, especially during pre-monsoon season. Comparison of the satellite (MODIS) derived and ground based estimates of surface albedo showed seasonal difference in their magnitudes (R-2 similar to 0.98 during retreating monsoon and winter; similar to 0.65 during pre-monsoon and monsoon), indicating that the reliability of the satellite data for aerosol radiative forcing estimation is more during the retreating and winter seasons.

With observations of black carbon (BC) aerosol concentrations, optical and radiative properties were obtained over the urban city of Karachi during the period of March 2006-December 2008. BC concentrations were continuously measured using an Aethalometer, while optical and radiative properties were estimated through the Optical Properties of Aerosols and Clouds (OPAC) and Santa Barbra DISORT Atmospheric Radiative Transfer (SBDART) models, respectively. For the study period, the measured BC concentrations were higher during January, February and November, while lower during May, June, July and August. A maximum peak value was observed during January 2007 while the minimum value was observed during June 2006. The Short Wave (SW) BC Aerosol Radiative Forcing (ARF) both at Top of the Atmosphere (ToA) and within ATMOSphere (ATMOS) were positive during all the months, whereas negative SW BC ARF was found at the SurFaCe (SFC). Overall, SW BC ARF was higher during January, February and November, while relatively lower ARF was found during May, June, July and August. Conversely, the Long Wave (LW) BC ARF at ToA and SFC remained positive, whereas within ATMOS it shifted towards positive values (heating effect) during June-August. Finally, the net (SW+LW) BC ARF were found to be positive at ToA and in ATMOS, while negative at SFC. Moreover, a systematic increase in Atmospheric Heating Rate (AHR) was found during October to January. Additionally, we found highest correlation between Absorption Aerosol Optical Depth (AOD(abs)) and SW BC ARF within ATMOS followed by SFC and ToA. Overall, the contribution of BC to the total ARF was found to greater than 84% for the whole observational period while contributing up to 93% during January 2007. (C) 2017 Elsevier B.V. All rights reserved.

In this paper, we report the results of extensive, and all-season, collocated, measurements of several aerosol parameters [such as spectral aerosol optical depth (AOD) at 10 bands spanning from UV to IR; mass size distribution and mass concentration of composite aerosols; as well as mass concentration and mass mixing ratio of aerosol black carbon (BC)] for over a 4-year period (January 2000 to December 2003), from an unindustrialized coastal location, Trivandrum (8.55 degrees N, 76.9 degrees E), close to the southern tip of Indian peninsula and use these properties to estimate the aerosol short wave radiative forcing. The results show that the top of the atmosphere (TOA) forcing is significantly positive during winter while it changes to negative during monsoon and post monsoon seasons. The surface forcing decreases from winter to summer. Consequently, the net atmospheric absorption decreases from a high value in winter to low values during monsoon.