Atmospheric Radiation Balance Research Articles

Spatiotemporal variations and source on black carbon over Chongqing, China: Long-term changes and observational experiments

Black carbon (BC), as a critical light-absorbing constituent within aerosols, exerts profound effects on atmospheric radiation balance, climate, air quality and human health, etc. And it is also a long-standing focus in rapidly developing megacities. So, this study primarily focuses on investigating the variation characteristics and underlying causes of BC in Chongqing (31,914,300 population), which is one of the municipalities directly under the central government of China, serving as a pivotal economic hub in southwest China. Utilizing MERRA-2 reanalysis data, we examined the long-term changes of atmospheric BC over Chongqing 20 years (from 2002 to 2021). Moreover, BC mass concentration observations were conducted using an Aethalometer (AE-33) from March 15 to June 14, 2021 in Liangping District, Chongqing. The statistical analysis over the last 20 years reveals an annual mean BC concentration in Chongqing of 3.42 ± 0.20 μg/m3, exhibiting growth from 2002 to 2008, followed by a decline from 2008 to 2021. Monthly concentration displays a “U-shaped” trend, with the lowest values occurring in summer and the highest in winter. Due to topographical and meteorological influences, local emissions primarily contribute to BC pollution, characterized by a spatial distribution pattern of high in the west and low in the east. Ground observation indicates a distinct dual-peaked pattern in the diurnal variation of BC, with peak concentrations aligning with periods of high traffic emissions. The variation in BC is significantly influenced by meteorological conditions (wind, temperature, atmospheric boundary layer) and local pollution sources (predominantly traffic). Furthermore, extreme events analysis suggests that local emissions and regional transport (with higher contributions from Chongqing and the Sichuan Basin) predominantly contributed to BC pollution. This study effectively makes up for the deficiency in analyzing the distribution and sources of BC pollution in Chongqing, providing valuable scientific insights for the atmospheric environment of megacities.

Impact of atmospheric O3 and NO2 on the secondary sulfates in real atmosphere

As an important component of secondary aerosols, sulfate plays a crucial role in regulating atmospheric radiative balance and influencing the secondary formation of ozone (O3). In real atmosphere, atmospheric oxidants NO2 and O3 can promote the oxidation of SO2 to form sulfate (SO42−) through multiphase chemistry that occur at different time scales. Due to the combined impact of meteorology, pollution sources, atmospheric chemistry, etc., time-scale dependence of SO2-SO42− conversion makes the impact of NO2/O3 on it more complex. In this study, based on long-term time series (2013-2020) of air pollution variables from seven stations in Hong Kong, the Multifractal Detrended Cross-Correlation Analysis (MFDCCA) method has been employed to quantify the cross-correlations between SO2 and SO42− in real atmosphere at different time scales, for examining the time-scale dependence of SO2-SO42− conversion efficiency. Furthermore, the Pearson correlation analysis has been used to study the influence of NO2/O3 on SO2-SO42− conversion, and the regional and seasonal differences have been analyzed by considering factors such as meteorology, pollution sources, and regional transport. Changes in the main components of secondary aerosols are closely linked with the co-control of regional PM2.5 and O3. Therefore, the exploration of the impact of co-existing NO2/O3 gases on the secondary formation of sulfates in real atmosphere is significant.

Measurement report: Atmospheric ice nuclei in the Changbai Mountains (2623 m a.s.l.) in northeastern Asia

Abstract. Atmospheric ice nucleation plays an important role in modulating the global hydrological cycle and atmospheric radiation balance. To date, few comprehensive field observations of ice nuclei have been carried out at high-altitude sites, which are close to the height of mixed-phase cloud formation. In this study, we measured the concentration of ice-nucleating particles (INPs) in the immersion freezing mode at the summit of the Changbai Mountains (2623 m above sea level), northeast Asia, in summer 2021. The cumulative number concentration of INPs varied from 1.6 × 10−3 to 78.3 L−1 over the temperature range of −5.5 to −29.0 °C. Proteinaceous-based biological materials accounted for the majority of INPs, with the proportion of biological INPs (bio-INPs) exceeding 67 % across the entire freezing-temperature range, with this proportion even exceeding 90 % above −13.0 °C. At freezing temperatures ranging from −11.0 to −8.0 °C, bio-INPs were found to significantly correlate with wind speed (r = 0.5–0.8, p < 0.05) and Ca2+ (r = 0.6–0.9), and good but not significant correlation was found with isoprene (r = 0.6–0.7) and its oxidation products (isoprene × O3) (r = 0.7), suggesting that biological aerosols may attach to or mix with soil dust and contribute to INPs. During the daytime, bio-INPs showed a positive correlation with the planetary boundary layer (PBL) height at freezing temperatures ranging from −22.0 to −19.5 °C (r > 0.7, p < 0.05), with the valley breezes from southern mountainous regions also influencing the concentration of INPs. Moreover, the long-distance transport of air mass from the Japan Sea and South Korea significantly contributed to the high concentrations of bio-INPs. Our study emphasizes the important role of biological sources of INPs in the high-altitude atmosphere of northeastern Asia and the significant contribution of long-range transport to the INP concentrations in this region.

Airborne Measurements of Scale‐Dependent Latent Heat Flux Impacted by Water Vapor and Vertical Velocity Over Heterogeneous Land Surfaces During the CHEESEHEAD19 Campaign

AbstractThe water vapor transport associated with latent heat flux (LE) in the planetary boundary layer (PBL) is critical for the atmospheric hydrological cycle, radiation balance, and cloud formation. The spatiotemporal variability of LE and water vapor mixing ratio (rv) are poorly understood due to the scale‐dependent and nonlinear atmospheric transport responses to land surface heterogeneity. Here, airborne in situ measurements with the wavelet technique are utilized to investigate scale‐dependent relationships among LE, vertical velocity (w) variance (), and rv variance () over a heterogeneous surface during the Chequamegon Heterogeneous Ecosystem Energy‐balance Study Enabled by a High‐density Extensive Array of Detectors 2019 (CHEESEHEAD19) field campaign. Our findings reveal distinct scale distributions of LE, , and at 100 m height, with a majority scale range of 120 m–4 km in LE, 32 m–2 km in , and 200 m–8 km in . The scales are classified into three scale ranges, the turbulent scale (8–200 m), large‐eddy scale (200 m–2 km), and mesoscale (2–8 km) to evaluate scale‐resolved LE contributed by and . The large‐eddy scale in PBL contributes over 70% of the monthly mean total LE with equal parts (50%) of contributions from and . The monthly temporal variations mainly come from the first two major contributing classified scales in LE, , and . These results confirm the dominant role of the large‐eddy scale in the PBL in the vertical moisture transport from the surface to the PBL, while the mesoscale is shown to contribute an additional ∼20%. This analysis complements published scale‐dependent LE variations, which lack detailed scale‐dependent vertical velocity and moisture information.

Sink, Source or Something In‐Between? Net Effects of Precipitation on Aerosol Particle Populations

AbstractInteractions between atmospheric aerosols, clouds, and precipitation impact Earth's radiative balance and air quality, yet remain poorly constrained. Precipitating clouds serve as major sinks for particulate matter, but recent studies suggest that precipitation may also act as a particle source. The magnitude of the sources versus sinks, particularly for cloud condensation nuclei (CCN) numbers, remain unquantified. This study analyzes multi‐year in situ observations from tropical and boreal forests, as well as Arctic marine environment, showing links between recent precipitation and enhanced particle concentrations, including CCN‐sized particles. In some cases, the magnitude of precipitation‐related source equals or surpasses corresponding removal effect. Our findings highlight the importance of cloud‐processed material in determining near‐surface particle concentrations and the value of long‐term in situ observations for understanding aerosol particle life cycle. Robust patterns emerge from sufficiently long data series, allowing for quantitative assessment of the large‐scale significance of new phenomena observed in case studies.

Stratospheric aerosol lidar with a 300 µm diameter superconducting nanowire single-photon detector at 1064 nm.

Stratospheric aerosols play an important role in the atmospheric chemical and radiative balance. To detect the stratospheric aerosol layer, a 1064 nm lidar with high resolution and large dynamic range is developed using a superconducting nanowire single-photon detector (SNSPD). Measurements are typically performed at 1064 nm for its sensitivity to aerosol, whereas detectors are limited by low efficiency and high dark count rate (DCR). SNSPDs are characterized by high efficiency in the infrared wavelength domain, as well as low noise and dead time, which can significantly enhance the signal quality. However, it is still challenging to build an SNSPD with both large active area and high count rate. To improve the maximal count rate (MCR) so as to avoid saturation in the near range, a 16-pixel interleaved SNSPD array and a multichannel data acquisition system are developed. As a reference, a synchronous system working at 532 nm is applied. In a continuous comparison experiment, backscatter ratio profiles are retrieved with resolutions of 90 m/3 min, and the 1064 nm system shows better performance, which is sensitive to aerosols and immune to the contamination of the ozone absorption and density of molecule change in the lower stratosphere.

Unexpected self-lofting and dynamical confinement of volcanic plumes: the Raikoke 2019 case

Recent research has provided evidence of the self-lofting capacity of smoke aerosols in the stratosphere and their self-confinement by persistent anticyclones, which prolongs their atmospheric residence time and radiative effects. By contrast, the volcanic aerosols—composed mostly of non-absorptive sulphuric acid droplets—were never reported to be subject of dynamical confinement. Here we use high-resolution satellite observations to show that the eruption of Raikoke volcano in June 2019 produced a long-lived stratospheric anticyclone containing 24% of the total erupted mass of sulphur dioxide. The anticyclone persisted for more than 3 months, circumnavigated the globe three times, and ascended diabatically to 27 km altitude through radiative heating of volcanic ash contained by the plume. The mechanism of dynamical confinement has important implications for the planetary-scale transport of volcanic emissions, their stratospheric residence time, and atmospheric radiation balance. It also provides a challenge or “out of sample test” for weather and climate models that should be capable of reproducing similar structures.

Aerosols on the Tropical Island of La Réunion (21°S, 55°E): Assessment of Climatology, Origin of Variability and Trend

Aerosols are essential climate variables that need to be observed at a global scale to monitor the evolution of the atmospheric composition and potential climate impacts. We used the measurements performed over the May 2007–December 2019 period by a ground-based sun photometer installed at the island of La Réunion (21°S, 55°E), together with a linear regression fitting model, to assess the climatology and types of aerosols reaching this observation site located in a sparsely documented pristine area, and the forcings responsible for the variability of the observed aerosol optical depth (AOD) and related trend. The climatology of the aerosol optical depth (AOD) at 440 nm (AOD440) and Ångström exponent between 500 and 870 nm (α) revealed that sea salts could be considered as the La Réunion AOD440 and α baselines (0.06 ± 0.03 and 0.61 ± 0.40, respectively, from December to August), which were mainly modulated by biomass burning (BB) plumes passing over La Réunion (causing a doubling of AOD440 and α up to 0.13 ± 0.07 and 1.06 ± 0.34, respectively, in October). This was confirmed by the retrieved aerosol volume size distributions showing that the coarse-mode (fine-mode) dominated the total volume concentration for AOD440 lower (higher) than 0.2 with a mean radius equal to 3 μm (0.15 μm). The main contribution to the AOD440 variability over La Réunion was evaluated to be the BB activity (67.4 ± 28.1%), followed by marine aerosols (16.3 ± 4.2%) and large-scale atmospheric structures (5.5 ± 1.7%). The calculated trend for AOD440 equaled 0.02 ± 0.01 per decade (2.6 ± 1.3% per year). These results provide a scientific reference base for upcoming studies dedicated to the quantification of the impact of wildfire emissions on the southwestern Indian Ocean’s atmospheric composition and radiative balance.

Cloud processing and weeklong ageing affect biomass burning aerosol properties over the south-eastern Atlantic

Southern Africa produces a third of global biomass burning emissions, which have a long atmospheric lifetime and influence regional radiation balance and climate. Here, we use airmass trajectories to link different aircraft observations to investigate the evolution of biomass-burning aerosols during their westward transport from Southern Africa over the south-eastern Atlantic, where a semi-permanent stratocumulus cloud deck is located. Our results show secondary organic aerosol formation during the initial 3 days of transport, followed by decreases in organic aerosol via photolysis before reaching equilibrium. Aerosol absorption wavelength dependency decreases with ageing, due to an increase in particle size and photochemical bleaching of brown carbon. Cloud processing, including aqueous-phase reaction and scavenging, contributes to the oxidation of organic aerosols, while it strongly reduces large diameter particles and single-scattering albedo of biomass burning aerosols. Together, these processes resulted in a marine boundary layer with fewer yet more oxidized and absorbing aerosols.

Contrasting mineral dust abundances from X-ray diffraction and reflectance spectroscopy

Abstract. Mineral dust particles dominate aerosol mass in the atmosphere and directly modify Earth's radiative balance through absorption and scattering. This radiative forcing varies strongly with mineral composition, yet there is still limited knowledge on the mineralogy of atmospheric dust. In this study, we performed X-ray diffraction (XRD) and reflectance spectroscopy measurements on 37 different dust deposition samples collected as airfall in an urban setting to determine mineralogy and the relative proportions of minerals in the dust mixture. Most commonly, XRD has been used to characterize dust mineralogy; however, without prior special sample preparation, this technique is less effective for identifying poorly crystalline or amorphous phases. In addition to XRD measurements, we performed visible and short-wave infrared (VSWIR) reflectance spectroscopy for these natural dust samples as a complementary technique to determine mineralogy and mineral abundances. Reflectance spectra of dust particles are a function of a nonlinear combination of mineral abundances in the mixture. Therefore, we used a Hapke radiative transfer model along with a linear spectral mixing approach to derive relative mineral abundances from reflectance spectroscopy. We compared spectrally derived abundances with those determined semi-quantitatively from XRD. Our results demonstrate that total clay mineral abundances from XRD are correlated with those from reflectance spectroscopy and follow similar trends; however, XRD underpredicts the total amount of clay for many of the samples. On the other hand, calcite abundances are significantly underpredicted by SWIR compared to XRD. This is caused by the weakening of absorption features associated with the fine particle size of the samples, as well as the presence of dark non-mineral materials (e.g., asphalt) in these samples. Another possible explanation for abundance discrepancies between XRD and SWIR is related to the differing sensitivity of the two techniques (crystal structure vs. chemical bonds). Our results indicate that it is beneficial to use both XRD and reflectance spectroscopy to characterize airfall dust because the former technique is good at identifying and quantifying the SWIR-transparent minerals (e.g., quartz, albite, and microcline), while the latter technique is superior for determining abundances for clays and non-mineral components.

Aloft Transport of Haze Aerosols to Xuzhou, Eastern China: Optical Properties, Sources, Type, and Components

Rapid industrialization and urbanization have caused frequent haze pollution episodes during winter in eastern China. Considering that the vertical profile of the aerosol properties changes significantly with altitude, investigating aerosol aloft information via satellite remote sensing is essential for studying regional transport, climate radiative effects, and air quality. Through a synergic approach between lidar, the AErosol RObotic NETwork sunphotometer observations, and WRF-Chem simulations, several transboundary aloft transport events of haze aerosols to Xuzhou, eastern China, are investigated in terms of source, type, and composition and the impact on optical properties. Upper-air aerosol layers are short-lived tiny particles that increase the total aerosol optical depth (AOD). The aloft aerosols not only play a critical role during the haze event, enhancing the scattering of aerosol particles significantly but also cause a rise in the AOD and the Ångström exponent (AE), which increases the proportion of fine particles, exacerbating the pollution level near the surface. Based on the model simulation results, our study highlights that the transported aloft aerosols lead to the rapid formation of secondary inorganic substances, such as secondary sulfates, nitrates, and ammonium salts, which strongly contribute to haze event formation. Moreover, the results provide evidence that the haze frequency events associated with polluted dust outbreaks were higher for 2014–2015 winter. A closer analysis shows that the advected dust layers over Xuzhou originated from Inner Mongolia and the Xinjiang Uygur Autonomous Region. The study of the occurrence frequency, height, thickness, and optical properties of aloft anthropogenic haze in China will further deepen our understanding and provide a strong basis to assess aerosol impact on transport and the Earth–atmosphere radiative balance.

Insights into the day-night sources and optical properties of coastal organic aerosols in southern China

Organic aerosols (OAs) in particulate matter with an aerodynamic diameter of smaller than 2.5 μm (PM2.5) can affect the atmospheric radiation balance through varying molecular structure and light absorption of the aerosols. In this study, daytime and nighttime PM2.5 mass, and contents of OA including nitrated aromatic compounds (NACs), polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and hopanes were measured from April 11th to May 15th, 2017, at the coastal Sanya, China. The average concentration of 18 total quantified PAHs (∑PAHs) was 2.08 ± 1.13 ng·m−3, which was 2.8 and 12 times higher than that of ∑NACs and hopanes, while was 7.5 times lower that of n-alkanes. Combustion-derived PAHs contributed 74% to the ∑PAHs. This finding, in addition to a high benzo[a]pyrene/(benzo[a]pyrene+benzo[e]pyrene) ratio, indicates that the PAHs mainly derived from fresh fuel combustion during the sampling periods. Furthermore, dramatic day-night differences were observed in the loadings of total NACs, PAHs, and n-alkanes, which had a high coefficient of divergence values of 0.67, 0.47, and 0.32, respectively. Moreover, hopanes exhibited similar variation as well. The proportion of dimethyl-nitrophenol (DM-NP), dinitrophenol (DNP), and nitrosalicylic acid (NSA) in PM2.5 were higher in the daytime than at nighttime, suggesting the co-influence of primary emissions and secondary formation related to biomass combustion. The positive matrix factorization (PMF) model revealed that motor vehicle and biomass burning emissions were the two main pollution sources in the daytime, contributing 51.7% and 24.6%, respectively, of the total quantified OAs. The proportion of industrial coal combustion emissions was higher at nighttime (20.6%) than in daytime (10%). Both the PAHs and NACs displayed light absorbing capacities among OAs compounds over Sanya City, and thus their influence on solar radiation must be considered in the future control policies.

Carbonaceous aerosol source apportionment and assessment of transport-related pollution

Diesel vehicles are one of many sources of black carbon (BC) emissions in Europe; nevertheless, due to recent changes in fuel composition towards renewable fuel such as biodiesel, advances in engine design and pollution control technology, BC and organic carbon (OC) emissions may worsen air quality and encourage global warming. As there are no regulatory terms on BC mass concentration levels, assessment of pollution sources is crucial for air quality improvement policies and mitigation of climate change. BC mass concentration and aerosol optical absorption were derived using 7-wavelenght Aethalometer during 3 measurement campaigns in 2014, 2017, and 2020. BC source apportionment analysis was performed using 18 combinations of absorption Ångström exponent (AAE) values for assessing BC to fossil fuel combustion and biomass burning. The choice of the most suitable AAE combination (0.9 and 2.2, respectively) was supported by organic aerosol (OA) source apportionment results. AAE value for transport exhaust emission (0.95) from locally available diesel fuel was established using (CI) 1.9 TDI engine with different engine torque regimes and 7-wavelenght Aethalometer. Statistically and experimentally obtained values were compared and showed great agreement. Subsequently, a statistically obtained AAEtr value was used for BC source apportionment and long-term analysis. A significant increase in the contribution of transport-related BC contribution was observed between years 2014 and 2020 (from 51% to 65%) which was associated with a boost in the use of diesel vehicles (by 83.9% of diesel passenger cars comparing 2014 and 2020) and growing diesel fuel consumption. These findings underline the diesel transport-induced problem for local air quality together with its impact on atmospheric radiative balance and raise concerns for public health.

Hourly snow energy and mass balance at Atwater Study Plot, Alta, Utah

AbstractAtwater Study Plot (ASP), located in the town of Alta, UT in the Wasatch Mountains, which was established in 1939 by Monty Atwater and Ed LaChapelle, is one of the longest running snow observation sites in the Western United States. The historical observations have been primarily snow safety and avalanche forecasting focused. Beginning in 2017 the Snow Hydrology Research to Operations Laboratory (Snow HydRO Lab) at the University of Utah began regular hydrology focused snow pit observations within study plot boundaries. In 2019 the Snow HydRO Lab and the Utah Department of Transportation further supplemented ASP with an instrumentation suite for continuous snow energy and mass balance observations, including incoming and outgoing solar and terrestrial radiation. The goal of the new observations is to support process based hydrologic modelling and better understand controls on snowmelt timing and magnitude. The instrumentation installation and observations make ASP the first snow energy balance study plot in the Wasatch Mountains, and the site has since been used as a validation site for NASA's SnowEx project and is part of the NSF Critical Zone Collaborative Network. Here, we describe the study plot and present (1) the hourly instrumented dataset, which includes standard atmospheric variables (air temperature, relative humidity, and wind speed/direction), radiation balance, precipitation, and snow depth, (2) snow energy balance modelling used to calculate hourly energy exchanges and phase changes, and (3) provide directions to access the publicly available ASP datasets.

Equal abundance of summertime natural and wintertime anthropogenic Arctic organic aerosols

Aerosols play an important yet uncertain role in modulating the radiation balance of the sensitive Arctic atmosphere. Organic aerosol is one of the most abundant, yet least understood, fractions of the Arctic aerosol mass. Here we use data from eight observatories that represent the entire Arctic to reveal the annual cycles in anthropogenic and biogenic sources of organic aerosol. We show that during winter, the organic aerosol in the Arctic is dominated by anthropogenic emissions, mainly from Eurasia, which consist of both direct combustion emissions and long-range transported, aged pollution. In summer, the decreasing anthropogenic pollution is replaced by natural emissions. These include marine secondary, biogenic secondary and primary biological emissions, which have the potential to be important to Arctic climate by modifying the cloud condensation nuclei properties and acting as ice-nucleating particles. Their source strength or atmospheric processing is sensitive to nutrient availability, solar radiation, temperature and snow cover. Our results provide a comprehensive understanding of the current pan-Arctic organic aerosol, which can be used to support modelling efforts that aim to quantify the climate impacts of emissions in this sensitive region.

Preliminary results of water cloud and aerosol properties in the Yinchuan area using a Multi-wavelength lidar based on dual field of view

Aerosol-cloud interaction has an extremely important impact on regional and even global climate and environmental change. It is undoubtedly of great scientific significance and research value to study its impact and mechanism on atmospheric radiation balance and climate change. As a active remote sensing, lidar can be employed to study aerosol-cloud interaction. In this paper, A novel multi-wavelength lidar system equipped with a dual field of view device is developed to measure the optical and microphysical parameters of water clouds. The scattered light is detected by the inner and outer field of view, respectively. For verifying the feasibility of the novel lidar system, some preliminary experiments were carried out at North Minzu University (106°06′E, 38°29′N) in the Yinchuan, China. The experiments shows that the novel lidar system can effective detect the optical and microphysical property parameters of water clouds, including extinction coefficient, effective particle radius and liquid water content, with a cloud base height of less than 5 km. Compared with traditional lidar systems that detect optical properties alone, it can use return signals from different fields of view to detect the microphysical properties of warm clouds and thin layered clouds, therefore, it is of great practical significance to develop the cloud water resources efficiently and improve the accuracy of artificial rainfall operations.

Seasonality in Saharan Dust Across the Atlantic Ocean: From Atmospheric Transport to Seafloor Deposition

AbstractSaharan dust is transported in great quantities from the North African continent every year, most of which is deposited across the North Atlantic Ocean. This dust impacts regional and global climate by affecting the atmospheric radiation balance and altering ocean carbon budgets. However, little research has been carried out on time series of Saharan dust collected in situ across the open Atlantic. Here, we present a unique three‐year time series of Saharan dust along a trans‐Atlantic transect, sampled by moored surface buoys and subsurface sediment traps. Results show a good correlation between the particle‐size distributions of atmospheric dust and the lithogenic particles settling to the deep ocean floor, confirming the aeolian origin of the lithogenic particles intercepted by the subsurface sediment traps, even in the distal western part of the Atlantic Ocean. Dust from both dry and wet deposition as collected by the sediment traps, shows increased deposition fluxes and coarser grain size in summer and/or autumn that coincides with increased precipitation at the sampling sites as derived from satellite data. In contrast, both buoys that sampled dust during transport at sea level show little seasonal variation in both concentration and particle size, as the large amounts of dust transported in summer and early autumn at high altitudes are far above their sampling range. This implies that wet deposition in summer and autumn defines the typical seasonal trends of both the dust deposition flux and its particle‐size distribution observed in the sediment traps.

Spatial and seasonal variations of black carbon over the Arctic in a regional climate model

Black Carbon (BC) absorbs the radiation and alters snow/ice albedo, which influences the Earth–Atmosphere radiation balance over the Arctic region. BC masses are estimated using Weather Research and Forecasting with Chemistry (WRF-CHEM) model over the Arctic region during the boreal winter and summer seasons of 2018. The meteorological parameters such as near surface temperature and relative humidity in WRF-CHEM are found to agree well with the observations. BC masses are found between 5–20 ng m−3 during boreal winter over most parts of the Arctic, while BC values are double in summer. Siberian and Canadian regions exhibit higher BC concentrations (>30 ng m−3) owing to the fire activities. BC produced by fires in the Alaska and Canadian regions of Arctic have lesser spread than BC form Siberian fires as the winds are mostly from east to west in winter. The model simulated BC is lower and higher than the observed BC during winter and summer respectively over Ny-Ålesund. However, the day to day variations can be captured by the model. The vertical profile of BC shows two peaks in winter, one at 1 km and the other strong peak at higher altitude of 12.5 km associated with long-range transport from mid-latitude and tropical regions, while in summer one peak at lower altitude is found. BC has large spatial variations in the Arctic which can significantly impact the Arctic as well as global climate.

Important Oxidants and Their Impact on the Environmental Effects of Aerosols.

Oxidants are central species in the atmosphere, where they not only determine secondary particle formation but also impact human health and climate change. In general, they are unstable, highly reactive, and recyclable and have been studied in field observations, laboratory studies, and model simulations. The most widely investigated oxidants, such as OH radicals, O3, and Cl atom, HONO, NO3, N2O5, and Criegee Intermediates (CIs) have attracted more attention recently. Furthermore, secondary particles formed in the oxidations processes impact the particle physicochemical properties, such as hygroscopicity and optical properties and therefore impact the atmospheric radiation balance. Therefore, the newest investigation results of important oxidants (HONO, NO3, N2O5, and CIs) are reviewed in this manuscript, and the environmental effects of secondary particles formed through corresponding oxidation processes are also stated. Furthermore, some perspectives are further discussed in the article.

Investigation of Black Carbon characteristics over southern ocean: Contribution of fossil fuel and biomass burning

Black Carbon (BC) is an absorbing aerosol which has significant impact on the Earth - Atmosphere radiation balance and hence on climate. The variation of BC mass concentration and contribution of fossil fuel and biomass burning have been investigated over the Indian ocean sector of the Southern Ocean during austral summer. BC mass was in the range of 300-500ngm-3 between 23.3oS to 24.5oS followed by decrease in BC to 150ngm-3 as moving to higher southern latitudes till 41oS latitude. An increase in BC mass from 250 to 450ngm-3 was found between 41 and 50oS due to trap of air masses by cyclonic wind and transport of aerosols from the southern part of African and eastern Madagascar regions. Higher BC concentration (250-350ngm-3) was observed in the latitude range of 57-60oS which can be attributed to convergence of north-westerly and south-easterly winds. The dominant contributor to BC was fossil fuel, which was > 80% during half of the total observations, while > 20% biomass burning contributed to one fifth of observations. The coastal Antarctic region showed higher BC mass concentration with mixed type of contributions of biomass and fossil fuel. Such accumulation of BC near the Antarctic coast can have a crucial impact on the sea-ice albedo which significantly affect the Antarctic climate system locally and global climate in general.