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.

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.