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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. [ABSTRACT FROM AUTHOR]

Absorbing aerosols uniquely impact radiation, aerosol transport, and meteorology. This paper quantifies black carbon core and sulphate shell size and mass using decadal measurements of multi‐spectral aerosol optical depth, single scattering albedo, and angstrom exponent from Aerosol Robotic Network stations located throughout East, Southeast, and South Asia, in connection with a MIE model. All sites are uniquely characterized into four types: urban, biomass burning, long‐range transport, and clean. Unique size and mass probability distributions of both the core and shell are calculated within each classification. Well known urban, biomass burning, and clean sites are all properly identified. Furthermore, two unique sites previously thought to not have multiple characteristics are identified, with urban and biomass burning significant in Beijing and long‐range transport significant in the otherwise clean South China Sea at Taiping Island. It is hoped that these results will allow for advances in attribution and radiative forcing studies. Plain Language Summary: Black Carbon strongly absorbs visible radiation, leading to unique impacts on atmospheric radiation, climate, the water cycle, and PM2.5. This work attributes different aerosol source characteristics, and further specifies the size distribution and concentration of aerosol black carbon cores and refractive shells. This work uses measurements of aerosol optical depth, single scatter albedo, and angstrom exponent, across multiple different wavelengths of light, in combination with statistics and a MIE model (physical model of aerosol/radiation interaction) using a Core‐Shell approximation. The results show that aerosols observed in East, Southeast, and South Asia can be uniquely classified into four types: urban, biomass burning, long‐range transport, and clean. These results are consistent in terms of aerosol size and mass at each site within each type of characterization. Furthermore, two unique sites are identified in which a second characteristic occurs some significant fraction of every year, which otherwise was not known or previously identified in the literature. These results are expected to help enhance the understanding of attribution of aerosols, as well as provide specific size and mass details of the aerosols useful to improve radiative forcing models and aerosol impacts on climate change. Key Points: Aerosols are categorized into biomass burning, urban, and long‐range types over Asia using decadal long multi‐spectral measurementsBased on multiple Aerosol Robotic Network Single Scatter Albedo measurements and a MIE model, physical characteristics of different aerosol types are deducedMost aerosols are found to be mixed, with two sites having different characteristics during different times of the year [ABSTRACT FROM AUTHOR]

The contribution of biomass burning to the total aerosol loading over Monsoon Asia is both significant and continuing to increase. To better match the spatio‐temporal distribution of aerosols and trace gasses observed in the free troposphere, this work applied a 3‐D constrained emission inventory based on top‐down remotely sensed NO2 measurement to investigate the most extreme of the annually occurring biomass burning seasons in Monsoon Asia. In 2016, this constituted an extreme event observed over a 6‐day period covering millions of square kilometers, including over regions that are typically in the rainy phase of the Asian Monsoon. The results are shown to be consistent with respect to Tropical Rainfall Measuring Mission precipitation, AERONET measurements, MODIS AOD, MOPITT CO, and reanalysis meteorology, over both the biomass burning source as well as the millions of square kilometers downwind both to the East and to the Southwest. Reproducing the observed long‐range transport pattern requires the time of biomass burning to be increased, regions not previously identified as burning to be actual source regions, and the emissions of Black Carbon (BC) to be 6.6 to 11.9 times larger than current inventories. The underlying mechanism for this long‐range transport involves a new 3‐D pathway that can occur during the transition from the North phase to the South phase of the Asian Monsoon. The results are also consistent with the new idea that large loadings of BC in the lower free troposphere may significantly affect the meteorological field and the overall vertical distribution of aerosols in the tropical troposphere. Plain Language Summary: A new top‐down 3‐D emission inventory based on NO2 measurements is used to investigate the spatial‐temporal distribution of extreme aerosol events spread over millions of square kilometers observed in March 2016, as confirmed by independent observations of aerosols, trace gasses, and precipitation. The results show a 6.6–11.9 times increase in Black Carbon emissions from known but underestimated and previously unidentified sources in Eastern India and Northern Southeast Asia. These new sources are required for models to successfully match extreme events measured over a 6‐day period as far away as in Singapore, Malaysia, Sumatra, Taiwan, and the Western Pacific. The transport pathway involves a complicated 3‐D pathway of lofting to the free troposphere and interaction with the change in the East Asian Monsoon. This work helps to understand how aerosols from new or misunderstood sources in South and Southeast Asia may ultimately impact the environment both locally and thousands of kilometers away, and provide a pathway to analyze such previously untraceable events. Key Points: New constrained emissions provide the best daily to weekly scale model fit with independent measurements in space, time, and magnitudeIncreases in Black Carbon emissions from 6.6 to 11.9 times are required to match the observed aerosol loadings in free tropospheric Monsoon AsiaA new spatiotemporal pathway is observed to transport aerosols far both to the southwest and to the east to match extreme aerosol events [ABSTRACT FROM AUTHOR]

Proper quantification of the aerosol vertical height is essential to constrain the atmospheric distribution and lifetime of aerosols, as well as their impact on the environment. We use globally distributed, daily averaged measurements of aerosol stereo heights of fire aerosols from the Multi-angle Imaging SpectroRadiometer (MISR) to understand the aerosol distribution. We also connect these results with a simple plume rise model and a new multi-linear regression model approach based on daily measurements of NO2 from OMI and CO from MOPITT to understand and model the global aerosol vertical height profile over biomass burning regions. First, plumes associated with the local dry-burning season at midlatitudes to high latitudes frequently have a substantial fraction lofted into the free troposphere and in some cases even the stratosphere. Second, plumes mainly associated with less-polluted regions in developing countries and heavily forested areas tend to stay closer to the ground, although they are not always uniformly distributed throughout the boundary layer. Third, plumes associated with more serious loadings of pollution (such as in Africa, Southeast Asia and northeast China) tend to have a substantial amount of smoke transported uniformly through the planetary boundary layer and up to around 3 km. Fourth, the regression model approach yields a better ability to reproduce the measured heights compared to the plume rise model approach. This improvement is based on a removal of the negative bias observed from the plume model approach, as well as a better ability to work under more heavily polluted conditions. However, over many regions, both approaches fail, requiring deeper work to understand the physical, chemical and dynamical reasons underlying the failure over these regions. [ABSTRACT FROM AUTHOR]

An analytical solution for the steady-state aerosol size distribution achieved in a steady-state, continuous flow chamber is derived, where particle growth is occurring by gas-to-particle conversion and particle loss is occurring by deposition to the walls of the chamber. The solution is presented in the case of two condensing species. By fitting the predicted steady-state aerosol size distribution to that measured, one may infer information about the nature of the condensing species from the calculated values of the species's molecular weights. The analytical solution is applied to three sets of experiments on secondary organic aerosol formation carried out in the U.S. Environmental Protection Agency irradiated continuous flow reactor, with parent hydrocarbons: toluene, α-pinene, and a mixture of toluene and α-pinene. Fits to the observed size distributions are illustrated by assuming two condensing products for each parent hydrocarbon; this is a highly simplified picture of secondary organic aerosol formation, which is known to involve considerably more than two condensing products. While not based on a molecular-level model of the gas-to-particle conversion process, the model does allow one to evaluate the extent to which the observed size distribution agrees with that based on a simple, two-component picture of condensation, and to study the sensitivity of those size distributions to variation of the essential properties of the condensing compounds, such as molecular weight. An inherent limitation of the steady-state experiment is that it is not possible to calculate the vapor pressures of the condensing species. [ABSTRACT FROM AUTHOR]

Due to changes in economics, technology, population, agriculture, and climate, there have been significant changes in terms of fires around the, and their impacts on air pollution, climate, and society. In specific, we are interested to know more about how these effects play out, from source to sink, on the atmospheric loadings and associated impacts of aerosols and some specific co-emitted trace gasses. Fires produce plumes of aerosols which are first lofted to a significant height, and then advected near and far to impact the larger atmosphere. We know from measurements that the absolute magnitude of smoke from fires is currently vastly underestimated. In this paper, we demonstrate a new database of emissions, formed in a uniform way, using 4 different remotely sensed measurements, coupled with three types of models. We then work to demonstrate what has worked well and why, as well as outline what still needs to be improved. We combine existing measurements of NO2 columns, AOD, CO, vertical distribution, with models at Global Scale, Mesoscale, and plume scale, into a single product. This product yields a spatially and temporally variable distribution of the emissions from global fires of aerosols and some trace gasses. Furthermore, we draw a set of relationships based on the physics and chemistry: making a connection from the emissions amounts and the heat tsources to the ultimate vertical structure and magnitude. The point is not only to be able to force a model to match the measurements, but to build a system through which we can mode deeply understand and constrain these relationships. This will slowly allow us to understand to the point where we can improve the model predictions analytically, as well as to perform massive uncertainty calculations. Given the changes occurring over the past decade, this is essential. We draw three conclusions. First, that the total underestimate of BC emissions is more than 40 percent to 70 percent of the present total global emissions, a more than doublig in magnitude. Second, that there are significant missing sources with a time scale from 3 to 6 weeks in duration, annually occurring in mountainous regions of Africa and Asia which are not present in existing databases. Thirdly, we demonstrate that a larger fraction of total emissions is lofted high up, and hence the impact on the atmosphere is larger than presently assumed. We make some initial conclusions in terms of these relationships over Africa, Southeast Asia, and the High Arctic, and show that they are different in each of these critical areas. We then try to explain a bit as to why this is the case, and build towards a more comprehensive and physically based relationship for future work. [ABSTRACT FROM AUTHOR]