Estimating Top-of-Atmosphere (TOA) flux and radiance is essential for understanding Earth's radiation budget and climate dynamics. This study utilized polar nephelometer measurements of aerosol scattering coefficients at 17 angles (9-170 degrees), enabling the experimental determination of aerosol phase functions and the calculation of Legendre moments. These moments were then used to estimate TOA flux and radiance. Conducted at a tropical coastal site in India, the study observed significant seasonal and diurnal variations in angular scattering patterns, with the highest scattering during winter and the lowest during the monsoon. Notably, a prominent secondary scattering mode, with varying magnitude across different seasons, was observed in the 20-30 degrees angular range, highlighting the influence of different air masses and aerosol sources. Chemical analysis of size-segregated aerosols revealed that fine-mode aerosols were dominated by anthropogenic species, such as sulfate, nitrate, and ammonium, throughout all seasons. In contrast, coarse-mode aerosols showed a clear presence of sea-salt aerosols during the monsoon and mineral dust during the pre-monsoon periods. The presence of very large coarse-mode non-spherical aerosols caused increased oscillations in the phase function beyond 60 degrees during the pre-monsoon and monsoon seasons. This also led to a weak association between the phase function derived from angular scattering measurements and those predicted by the Henyey-Greenstein approximation. As a result, TOA fluxes and radiances derived using the Henyey-Greenstein approximation (with the asymmetry parameter as input in the radiative transfer model) showed a significant difference- up to 24% in seasons with substantial coarse-mode aerosol presence- compared to those derived using the Legendre moments of the phase function. Therefore, TOA flux and radiance estimates using Legendre moments are generally more accurate in the presence of complex aerosol scattering characteristics, particularly for non-spherical or coarse-mode aerosols, while the Henyey-Greenstein phase function may yield less accurate results due to its simplified representation of scattering behavior.

High uncertainty in optical properties of black carbon (BC) involving heterogeneous chemistry has recently attracted increasing attention in the field of atmospheric climatology. To fill the gap in BC optical knowledge so as to estimate more accurate climate effects and serve the response to global warming, it is beneficial to conduct site-level studies on BC light absorption enhancement (E-abs) characteristics. Real-time surface gas and particulate pollutant observations during the summer and winter over Wuhan were utilized for the analysis of E-abs simulated by minimum R squared (MRS), considering two distinct atmospheric conditions (2015 and 2017). In general, differences in aerosol emissions led to E-abs differential behaviors. The summer average of E-abs (1.92 +/- 0.55) in 2015 was higher than the winter average (1.27 +/- 0.42), while the average (1.11 +/- 0.20) in 2017 summer was lower than that (1.67 +/- 0.69) in winter. E-abs and R-BC (representing the mass ratio of non-refractory constituents to elemental carbon) constraints suggest that E-abs increased with the increase in R-BC under the ambient condition enriched by secondary inorganic aerosol (SIA), with a maximum growth rate of 70.6% in 2015 summer. However, E-abs demonstrated a negative trend against R-BC in 2017 winter due to the more complicated mixing state. The result arose from the opposite impact of hygroscopic SIA and absorbing OC/irregular distributed coatings on amplifying the light absorbency of BC. Furthermore, sensitivity analysis revealed a robust positive correlation (R > 0.9) between aerosol chemical compositions (including sulfate, nitrate, ammonium and secondary organic carbon), which could be significantly perturbed by only a small fraction of absorbing materials or restructuring BC through gaps filling. The above findings not only deepen the understanding of BC, but also provide useful information for the scientific decision-making in government to mitigate particulate pollution and obtain more precise BC radiative forcing.

Aerosol behavior over the Himalayas plays an important role in the regional climate of South Asia. Previous studies at highaltitude observatories have provided evidence of the impact of long-range transport of pollutants from the Indo-Gangetic Plain (IGP). However, little information exists for the valley areas in the high Himalayas where significant local anthropogenic emissions can act as additional sources of short-living climate forcers and pollutants. The valley areas host most economic activities based on agriculture, forestry, and pilgrimage during every summer season. We report here first measurements at a valley site at similar to 2600 m a.s.l. on the trek to the Gangotri glacier (Gaumukh), in the Western Himalayas, where local infrastructures for atmospheric measurements are absent. The study comprised short-term measurement of aerosols, chemical characterization, and estimation of aerosol radiative forcing (ARF) during the winter and summer periods (2015-2016). The particulate matter mass concentrations were observed to be higher than the permissible limit during the summer campaigns. We obtained clear evidence of the impact of local anthropogenic sources: particulate nitrate is associated with coarse aerosol particles, the black carbon (BC) mass fraction appears undiluted with respect tomeasurements performed in the lower Himalayas, and inwinter, both BC and sulfate concentrations in the valley site are well above the background levels reported from literature studies for mountain peaks. Finally, high concentrations of trace metals such as copper point to anthropogenic activities, including combustion and agriculture. While most studies in the Himalayas have addressed pollution in the high Himalayas in terms of transport from IGP, our study provides clear evidence that local sources cannot be overlooked over the high-altitude Himalayas. The estimated direct clear-sky ARF was estimated to be in the range of -0.1 to +1.6Wm(-2), with significant heating in the atmosphere over the highaltitude Himalayan study site. These results indicate the need to establish systematic aerosol monitoring activities in the high Himalayan valleys.

Continuous long-term monitoring of black carbon (BC) mass concentration and aerosol light scattering coefficient (sigma(SCA)), supplemented by number size distribution and chemical composition, are utilized in this study to understand the temporal changes in aerosol properties, associated source processes and radiative effects at Ny-angstrom lesund (79 degrees N) in the Svalbard Archipelago. A statistically significant decreasing trend in BC (- 24.7 ng m(-3) decade(-1)) is observed during spring of 2010-2019. In contrast, sigma SCA depicted a general increasing trend (5.2 Mm(-1) decade(-1)) during 2011-2016. BC and sigma(SCA) were higher during winter and spring. Aerosol single scattering albedo was highest in May similar to 0.95 (during spring) and lowest in September similar to 0.87 (during summer). Fractional share of BC to total aerosol mass was higher in winter and summer. Anthropogenic SO42- and NO3- (after ssNa(+)) species dominated the summer, when total number and mass concentrations of aerosols were at their minimum. Elemental Carbon (EC) and Organic Carbon (OC) showed higher concentrations in spring with EC-to-OC ratio similar to 0.08 - 0.22. The columnar AOD varied between 0.01 and 0.20 (annual mean similar to 0.09), resulting in aerosol radiative forcing (in the top of the atmosphere) similar to 0.15 - 2.69 Wm(-2) in the month of April (during spring). Potential source contribution function (PSCF) revealed the dominant source areas to be over Europe and Russia in terms of contributing to the seasonal high BC mass concentrations at Ny-angstrom lesund. Our study has also revealed an unusual impact of biomass burning aerosols (advected from the Alaska wildfire) during July 2015.

Industrial pollution has a significant effect on aerosol properties in Changsha City, a typical city of central China. Therefore, year-round measurements of aerosol optical, radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed. During the observation period, the energy structure was continuously optimized, which was characterized by the reduction of coal combustion. The aerosol properties have obvious seasonal variations. The seasonal average aerosol optical depth (AOD) at 500 nm ranged from 0.49 to 1.00, single scattering albedo (SSA) ranged from 0.93 to 0.97, and aerosol radiative forcing at the top of the atmosphere (TOA) ranged from -24.0 to 3.8 W m(-2). The chemical components also showed seasonal variations. Meanwhile, the scattering aerosol, such as organic carbon, SO42-, NO3-, and NH4+ showed a decrease, and elemental carbon increased. Compared with observation in winter 2012, AOD and TOA decreased by 0.14 and -1.49 W m(-2) in winter 2014. The scattering components, SO42-, NO3- and NH4+, decreased by 12.8 mu g m(-3) (56.8%), 9.2 mu g m(-3) (48.8%) and 6.4 mu g m(-3) (45.2%), respectively. The atmospheric visibility and pollution diffusion conditions improved. The extinction and radiative forcing of aerosol were significantly controlled by the scattering aerosol. The results indicate that Changsha is an industrial city with strong scattering aerosol. The energy structure optimization had a marked effect on controlling pollution, especially in winter (strong scattering aerosol).

Total suspended particulates were collected from the marine boundary layer of Bay of Bengal (BOB) as part of the Integrated Campaign for Aerosols gases & Radiation Budget (ICARB) conducted under the Geosphere Biosphere Programme of Indian Space Research Organisation during pre-monsoon period. These samples were analyzed to quantify various chemical species and to bring out a comprehensive and quantitative picture of the chemical composition of aerosols in the marine environment of Bay of Bengal. Almost all the species showed highest mass concentration over north/head BoB. On the other hand, their mass fractions were high over mid/south BoB which has implications on the radiative forcing in this region. The source characteristics of various species were identified using specific chemical components as tracers. Presence of significant amount of non-sea-salt aerosols (similar to 7-8 times of sea-salt) and several trace species like Ni, Pb, Zn, etc were observed in this marine environment indicating significant continental/anthropogenic influence. An approximate estimate of the contributions of anthropogenic and natural aerosols to the total aerosol mass loading showed prominence of anthropogenic component over mid and south BoB also. Based on this study first-cut aerosol chemical models were evolved for BoB region. (C) 2014 Elsevier Ltd. All rights reserved.

Palsa peatlands, permafrost-affected peatlands characteristic of the outer margin of the discontinuous permafrost zone, form unique ecosystems in northern-boreal and arctic regions, but are now degrading throughout their distributional range due to climate warming. Permafrost thaw and the degradation of palsa mounds are likely to affect the biogeochemical stability of soil organic matter (that is, SOM resistance to microbial decomposition), which may change the net C source/sink character of palsa peatland ecosystems. In this study, we have assessed both biological and chemical proxies for SOM stability, and we have investigated SOM bulk chemistry with mid-infrared spectroscopy, in surface peat of three distinct peatland features in a palsa peatland in northern Norway. Our results show that the stability of SOM in surface peat as determined by both biological and chemical proxies is consistently higher in the permafrost-associated palsa mounds than in the surrounding internal lawns and bog hummocks. Our results also suggest that differences in SOM bulk chemistry is a main factor explaining the present SOM stability in surface peat of palsa peatlands, with selective preservation of recalcitrant and highly oxidized SOM components in the active layer of palsa mounds during intense aerobic decomposition over time, whereas SOM in the wetter areas of the peatland remains stabilized mainly by anaerobic conditions. The continued degradation of palsa mounds and the expansion of wetter peat areas are likely to modify the bulk SOM chemistry of palsa peatlands, but the effect on the future net C source/sink character of palsa peatlands will largely depend on moisture conditions and oxygen availability in peat.

Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased by about 1.4 times during intense foggy/hazy days. Concentrations of SO4 (2-), NO3 (-), NH4 (+) and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH4 aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (< 1 A mu m). AOD value at 0.5 A mu m wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63). OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing during intense foggy/hazy days (+75.8 W/m(2)) than that during clear sky or less foggy/hazy days (+38 W/m(2)), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from -40 W/m(2) during clear sky or less foggy/hazy days to -76 W/m(2) during intense foggy/hazy days, mainly due to the scattering aerosols like SO4 (2-).