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.

This study examines the mass distributions and direct and semi-direct effects of different Anthropogenic Aerosols (AAs) [i.e. sulphate, Black Carbon (BC), Organic Carbon (OC) and all together (SBO)] over South Africa using the 12 year runs of the Regional Climate Model (RegCM4). The maximum burden and Surface Radiative Forcing (SRF) values are found over AA source regions: up to 9mg m(-2) [-12W m(-2)] for sulphate and 12.1mg m(-2) [-14W m(-2)] for SBO during austral summer, as well as, up to 0.85mg m(-2) [-2W m(-2)] for BC and 2.2mg m(-2) [-0.68W m(-2)] for OC during austral winter. Contrary to sulphate, both BC and OC aerosols reduce incoming solar radiation reaching the ground via enhancing shortwave radiative heating in the atmosphere. The climatic feedback caused by AAs resulted in changes in background aerosol concentrations. As a result of this and other processes of the climate system, the climatic effects of AAs were also found in remote areas away from the main AA loading zones. However, in terms of statistical significance, the climatic influences of AAs are more prominent in the vicinity of their source regions. The overall feedback of the climate system to the radiative effects of AAs resulted in both positive and negative changes to the Net Atmospheric radiative Heating Rate (NAHR). Areas that experience a reduction in NAHR exhibited an increase in Cloud Cover (CC). During the NAHR enhancement, CC over arid areas decreased; while CC over the wet/semi-wet regions increased. The changes in Surface Temperature (ST) and sensible heat flux are more closely correlated with the CC change than SRF of AAs. Furthermore, decreases or increases in ST, respectively, lead to reductions or enhancements in boundary layer height and the vice versa in surface pressure. Overall, the results suggest that the feedback of cloud fields has a far-reaching role in moderating other climatic anomalies.

An online coupled regional climate and chemistry model was used to investigate the direct effects of anthropogenic aerosols (sulfate, nitrate, black carbon BC and organic carbon OC) with different mixing states over China. Three mixing assumptions were considered, including external (EM), internal (IM, BC-core surrounded by well mixed scattering-shells) and partially internal (PIM, 32.2% of sulfate and nitrate, 35.5% of BC and 48.5% of OC were internally mixed) mixtures. Results indicated that high levels of anthropogenic aerosols were found in Southwest and Central to East China. Regional mean surface loadings of sulfate, nitrate, BC, primary OC over China were 9.56, 3.64, 2.30, and 2.99 mu g m(-3), respectively. PIM-aerosol optical depth and single scattering albedo, which were consistent with AERONET and satellite observations, were 0.51 +/- 0.37 and 0.95 +/- 0.02 in Central to East China, implying that proportions of internally mixed aerosols in PIM were reasonable to some degrees. Both aerosol direct radiative forcing (DRF) and corresponding climate responses were sensitive to aerosol mixing states and BC/OC hygroscopicities. The more BC was internally mixed or hydrophilic, the more solar radiation was absorbed, thus leading to more decreases in cloud amount (CA) and subsequently less surface cooling. Combining with the uncertainties of BC/OC hygroscopicities, regional mean PIM-aerosol DRF at the top of atmosphere ranged from -0.78 to -0.61 W m(-2) in all-sky and from -5.24 to -4.95 W m(-2) in clear-sky. Additionally, responses of cloud amount and water path, total column absorbed solar radiation (TCASR), surface air temperature and precipitation (TP) to PIM-aerosol DRFs over China were about -0.45 similar to -0.37%, -0.44 similar to -0.32 g m(-2), +0.69 similar to +0.72 W m(-2), -0.13 similar to -0.11 K and -4.56 similar to -4.29%, respectively. These responses were also sensitive to the lateral boundary condition perturbations especially for CA, TCASR and TP, while DRFs themselves were not. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

Carbonaceous aerosol is one of the main ingredients of the atmospheric aerosol, which includes black carbon and organic carbon. The numerical simulations from 1960 to 2000 are aimed at the direct radiative effects on climate induced by carbonaceous aerosol in East Asia using NCAR Community Atmospheric Model version 3.1 (CAM). The mean radiative forcing(RF) under all sky in Chinese mainland at TOA and surface are 0.38 and -5.31W/m(2) respectively. This distinct RF leads to -0.1K surface temperature decrease in Chinese mainland, which includes -0.26K drop of daily maximum and 0.07K rise of minimum temperature. Air column temperature has also been increased 0.11K in Chinese mainland. Significant vapor and precipitation increase can be resulted from RF of carbonaceous aerosol in north China and the Yellow and Huai River basin, accompanied by the decrease in northeast China, far-east region, and Tibet Plateau. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organization Committee.

Numerical simulations were conducted for 1960-2000 to estimate the direct effects of aerosols on temperature and precipitation in East Asia. Radiative forcing and regional climatic effects of total combined aerosol-including sulfate, dust, black carbon, and organic carbon-over the East Asian region were investigated using the NCAR Community Atmospheric Model, Version 3.1. Surface dimming is revealed by the simulated negative radiative forcing at the surface, and the most distinct dimming can exceed 30 and 25 W m(-2) under clear and all sky conditions, respectively; dimming cools the surface by 1.5 K in most regions in the study domain. Air column temperatures increase in northern India and northwestern and northern China, and decrease in other areas. The profiles of air temperature show similar trends in different areas, with a decrease below 850 hPa and an increase in the middle of the troposphere. The finding of increases in vapor content and precipitation in northern and northwestern China contradicts recent trends of flooding in the south and drought in the north of China, which have been attributed to the effects of aerosol absorption in some simulation studies. In our study, significant precipitation increases by a maximum of 9 % in northern and northwestern China, while it decreases by up to 12 % in the southern part of the Tibetan Plateau, the Sichuan Basin, and most of southern, southeastern, and northeastern China.