The emission of black carbon (BC) particles, which cause atmospheric warming by affecting radiation budget in the atmosphere, is the result of an incomplete combustion process of organic materials. The recent wildfire event during the summer 2019-2020 in south-eastern Australia was unprecedented in scale. The wildfires lasted for nearly 3 months over large areas of the two most populated states of New South Wales and Victoria. This study on the emission and dispersion of BC emitted from the biomass burnings of the wildfires using the Weather Research Forecast-Chemistry (WRF-Chem) model aims to determine the extent of BC spatial dispersion and ground concentration distribution and the effect of BC on air quality and radiative transfer at the top of the atmosphere, the atmosphere and on the ground. The predicted aerosol concentration and AOD are compared with the observed data using the New South Wales Department of Planning and Environment (DPE) aethalometer and air quality network and remote sensing data. The BC concentration as predicted from the WRF-Chem model, is in general, less than the observed data as measured using the aethalometer monitoring network, but the spatial pattern corresponds well, and the correlation is relatively high. The total BC emission into the atmosphere during the event and the effect on radiation budget were also estimated. This study shows that the summer 2019-2020 wildfires affect not only the air quality and health impact on the east coast of Australia but also short-term weather in the region via aerosol interactions with radiation and clouds.

The radiative forcing caused by aerosol-cloud interaction (ACI) is one of the most critical factors that lead to climate research uncertainty. In East China and the adjacent sea areas, the severe air pollution makes the ACI effect stronger than in other regions, but few observational studies focus on the effect of different aerosol components. This study estimated the shortwave radiation effect at the top of the atmosphere (TOA) caused by the interaction between the increased aerosol and the warm liquid cloud in East China and the East China Sea by applying the multiple linear regression into two ACI effect calculating methods proposed by Quaas et al. (2008; Method 1) and Chen et al. (2014; Method 2). Four aerosol components, black carbon (BC), dust (DU), organic carbon (OC), and sulfate (SU), are included in this research. The total ACI radiation effect of the four aerosol components is -12.08 +/- 4.63 W m(-2) in Method 1 and - 9.25 +/- 10.44 W m(-2) in Method 2, respectively, indicating a cooling effect to the planet. The divergence in the two methods is probably because the higher aerosol loading increases the cloud property retrieval deviation, and the cloud droplet spectral dispersion is neglected in Method 1. The effect of different aerosol components has significant diversity, with OC and SU have a cooling effect, DU has a heating effect, and BC shows an obvious geographical distinction. Further analysis suggests that under a similar aerosol optical depth (AOD), the areas with high relative humidity (RH) and low-tropospheric stability (LTS) have a more significant cooling effect due to the suppression of droplet evaporation and entrainment. Regions with higher average cloud top height also have a stronger cooling effect, especially for BC and SU. The possible reason is that high cloud altitude reduces the aerosol concentration within the cloud, further alleviates the heating effect of absorbing aerosols, and reduces the cloud droplet evaporation caused by the over much cloud condensation nuclei. This research contributes to a better understanding of the aerosolcloud radiative effect and its mechanism in East China and the East China Sea.

Historically, cargo ships have been powered by low-grade fossil fuels, which emit particles and particle-precursor vapors that impact human health and climate. We used a global chemical-transport model with online aerosol microphysics (GEOS-Chem-TOMAS) to estimate the aerosol health and climate impacts of four emission-control policies: (1) 85% reduction in sulfur oxide (SOx) emissions (Sulf); (2) 85% reduction in SOx and black carbon (BC) emissions (Sulf-BC); (3) 85% reduction in SOx, BC, and organic aerosol (OA) emissions (Sulf-BC-OA); and (4) 85% reduction in SOx, BC, OA, and nitrogen oxide (NOx) emissions (Sulf-BC-OA-NOx). The SOx reductions reflect the 0.5% fuel-sulfur cap implemented by the International Maritime Organization (IMO) on 1 January 2020. The other reductions represent realistic estimates of future emission-control policies. We estimate that these policies could reduce fine particulate matter (PM2.5)-attributable mortalities by 13 300 (Sulf) to 38 600 (Sulf-BC-OA-NOx) mortalities per year. These changes represent 0.3% and 0.8%, respectively, of annual PM2.5-attributable mortalities from anthropogenic sources. Comparing simulations, we estimate that adding the NOx cap has the greatest health benefit. In contrast to the health benefits, all scenarios lead to a simulated climate warming tendency. The combined aerosol direct radiative effect and cloud-albedo indirect effects (AIE) are between 27 mW m(-2) (Sulf) and 41 mW m(-2) (Sulf-BC-OA-NOx). These changes are about 2.1% (Sulf) to 3.2% (Sulf-BC-OA-NOx) of the total anthropogenic aerosol radiative forcing. The emission control policies examined here yield larger relative changes in the aerosol radiative forcing (2.1%-3.2%) than in health effects (0.3%-0.8%), because most shipping emissions are distant from populated regions. Valuation of the impacts suggests that these emissions reductions could produce much larger marginal health benefits ($129-$374 billion annually) than the marginal climate costs ($12-$17 billion annually).

A version of the Community Earth System Model modified at the North Carolina State University (CESM-NCSU) is used to simulate the current and future atmosphere following the representative concentration partway scenarios for stabilization of radiative forcing at 4.5 W m(-2) (RCP4.5) and radiative forcing of 8.5 W m(-2) (RCP8.5). Part I describes the results from a comprehensive evaluation of current decadal simulations. Radiation and most meteorological variables are well simulated in CESM-NCSU. Cloud parameters are not as well simulated due in part to the tuning of model radiation and general biases in cloud variables common to all global chemistry-climate models. The concentrations of most inorganic aerosol species (i.e., SO42-, NH4+, and NO3-) are well simulated with normalized mean biases (NMBs) typically less than 20%. However, some notable exceptions are European NH4+, which is overpredicted by 33.0-42.2% due to high NH3 emissions and irreversible coarse mode condensation, and Cl-, that is negatively impacted by errors in emissions driven by wind speed and overpredicted HNO3. Carbonaceous aerosols are largely underpredicted following the RCP scenarios due to low emissions of black carbon, organic carbon, and anthropogenic volatile compounds in the RCP inventory and efficient wet removal. This results in underpredictions of PM2.5 and PM10 by 6.4-55.7%. The column mass abundances are reasonably well simulated. Larger biases occur in surface mixing ratios of trace gases in CESM-NCSU, likely due to numerical diffusion from the coarse grid spacing of the CESM-NCSU simulations or errors in the magnitudes and vertical structure of emissions. This is especially true for SO2 and NO2. The mixing ratio of O-3 is overpredicted by 38.9-76.0% due to the limitations in the O-3 deposition scheme used in CESM and insufficient titration resulted from large underpredictions in NO2. Despite these limitations, CESM-NCSU reproduces reasonably well the current atmosphere in terms of radiation, clouds, meteorology, trace gases, aerosols, and aerosol-cloud interactions, making it suitable for future climate simulations. (C) 2016 Elsevier Ltd. All rights reserved.

It is known that aerosol and precursor gas emissions over East Asia may be underestimated by 50% due to the absence of data on regional rural and township industries. As the most important element of anthropogenic emissions, sulphur dioxide (SO2) can form sulfate aerosols through several chemical processes, thus affecting the regional and global climate. In this study, we use the Community Atmospheric Model 5.1 (CAM5.1) to investigate the effects of anthropogenic aerosols on radiative forcing and the climate over East Asia, taking into consideration various SO2 emission levels, including double the amount of SO2 emissions over East Asia. Numerical experiments are performed using high-resolution CAM5.1 with pre-industrial (PI) and present day (PD) aerosol emission levels, and with PD aerosol emission levels with double SO2 emissions over East Asia (PD2SO2). The simulated aerosol optical depth and surface sulfate concentrations over East Asia are significantly increased in PD2SO2, which is in better agreement with the observational results. The simulation results show extensive aerosol direct and indirect radiative forcing for PD PI (the difference between PI and PD), which significantly weakens the large-scale intensity of the East Asian summer monsoon (EASM) and reduces the summer precipitation. Compared to PD, the aerosol direct radiative forcing is significantly increased in PD2SO2, whereas the aerosol indirect radiative forcing is markedly decreased due to the inhibition of cloud formation, especially over North China. The increase in aerosol direct radiative forcing and decrease in aerosol indirect radiative forcing result in insignificant changes in the total amount of aerosol radiative forcing. These results also show that the large-scale intensity of the EASM and the associated summer precipitation are insensitive to the doubling of current SO2 emissions.

Mineral dust aerosols, the tiny soil particles suspended in the atmosphere, have a key role in the atmospheric radiation budget and hydrological cycle through their radiative and cloud condensation nucleus effects. Current understanding of spatial and temporal variations of mineral dust, as well as its impacts on the climate system and cloud properties is outlined. Mineral dust aerosols are blown into the atmosphere mainly from arid and semi-arid regions where annual rainfall is extremely low and substantial amounts of alluvial sediment have been accumulated over long periods. They are subject to long-range transport of an intercontinental scale, including North African dust plumes over the Atlantic Ocean, summer dust plumes from the Arabian Peninsula over the Arabian Sea and Indian Ocean and spring dust plumes from East Asia over the Pacific Ocean. Mineral dust aerosols influence the climate system and cloud microphysics in multiple ways. They disturb the climate system directly by scattering and partly absorbing shortwave and longwave radiation, semi-directly by changing the atmospheric cloud cover through evaporation of cloud droplets (i.e. the cloud burning effect), and indirectly by acting as cloud and ice condensation nuclei, which changes the optical properties of clouds (i.e. the first indirect effect), and may decrease or increase precipitation formation (i.e. the second indirect effect). Radiative forcing by mineral dust is associated with changes in atmospheric dynamics that may change the vertical profile of temperature and wind speed, through which a feedback effect on dust emission can be established. (C) 2013 Elsevier B.V. All rights reserved.

[1] The indirect effect of anthropogenic aerosols is investigated using the global climate model National Center for Atmospheric Research Community Climate Model Version 3 (NCAR CCM3). Two types of anthropogenic aerosols are considered, i.e., sulfate and black carbon aerosols. The concentrations and horizontal distributions of these aerosols were obtained from simulations with a life-cycle model incorporated into the global climate model. They are then combined with size-segregated background aerosols. The aerosol size distributions are subjected to condensation, coagulation, and humidity swelling. By making assumptions on supersaturation, we determine cloud droplet number concentrations in water clouds. Cloud droplet sizes and top of atmosphere (TOA) radiative fluxes are in good agreement with satellite observations. Both components of the indirect effect, i.e., the radius and lifetime effects, are computed as pure forcing terms. Using aerosol data for 2000 from the Intergovernmental Panel on Climate Change (IPCC), we find, globally averaged, a 5% decrease in cloud droplet radius and a 5% increase in cloud water path due to anthropogenic aerosols. The largest changes are found over SE Asia, followed by the North Atlantic, Europe, and the eastern United States. This is also the case for the radiative forcing (indirect effect), which has a global average of -1.8 W m(-2). When the experiment is repeated using data for 2100 from the IPCC A2 scenario, an unchanged globally averaged radiative forcing is found, but the horizontal distribution has been shifted toward the tropics. Sensitivity experiments show that the radius effect is similar to3 times as important as the lifetime effect and that black carbon only contributes marginally to the overall indirect effect.