We estimated the current (base years) and future (2021-2100) direct radiative forcing ( DRF) of four aerosol components (water-soluble, insoluble, black carbon (BC), and sea-salt) at urban (Yeonsan (Busan) and Gwangjin (Seoul)) and background sites (Aewol and Gosan (Jeju Island)), based on a modeling approach. The analysis for base years was conducted using PM2.5 samples measured at two urban and two background sites (Yeonsan and Gwangjin: 2016, Aewol and Gosan: 2014). The future DRFs were estimated according to changes in relative humidity (RH) of RCP8.5 climate change scenario at the same sites during four different periods (PI: 2021 similar to 2040, PII: 2041 similar to 2060, PIII: 2061 similar to 2080, and PIV: 2081 similar to 2100). In addition, we compared the differences between the DRFs of future (PI similar to PIV) and base years (2016 and 2014). Overall, the water-soluble component was predominant over all other components in terms of the concentrations, optical parameters (e.g., AOD), and DRFs, regardless of sites. For the base years, the monthly patterns of total DRFs for all components and the DRFs for the water-soluble component varied with sites, and months of their highest and lowest DRFs were different depending on sites. This might be due to the combined effect of the monthly patterns of the concentrations and RHs for each site. For the differences between the DRFs of future and base years, the highest future DRFs at Yeonsan and Aewol ranged from -59 to -63 W/m(2) increasing -20 (July in PII) to -28 W/m(2) (August in PIII) compared to the base years and from -73 to -74 W/m(2) increasing -31 (July in PII) to -41 W/m(2) (September in PIV), respectively. These DRFs at Gwangjin and Gosan ranged from -79 to -84 W/m(2) increasing -29 (June in PII and PIII) to -34 W/m(2) (June in PI) and from -58 to -92 W/m(2) increasing -14 (July in PII) to -26 W/m(2) (May in PI), respectively. The high heating rates at Yeonsan (up to 4.4 K/day in November) and Aewol (up to 3.7 K/day in February) of BC component might be caused by its strong radiative absorption.

The temporal variations (diurnal and seasonal) of the optical properties and direct aerosol radiative forcing (DARF) of different aerosol components (water-soluble, insoluble, black carbon (BC), and sea-salt) were analyzed using the hourly resolution data (PM2.5\) measured at an urban site in Seoul, Korea during 2010, based on a modeling approach. In general, the water-soluble component was predominant over all other components (with a higher concentration) in terms of its impact on the optical properties (except for absorbing BC) and DARF. The annual mean aerosol optical depth (AOD, tau) at 500 nm for the water-soluble component was 0.38 +/- 0.07 (0.06 +/- 0.01 for BC). The forcing at the surface (DARF(SFC)) and top of the atmosphere (DARF(TOA)), and in the atmosphere (DARF(ATM)) for most aerosol components (except for BC) during the daytime were highest in spring and lowest in late fall or early winter. The maximum DARF(SFC) occurred in the morning during most seasons (except for the water-soluble components showing peaks in the afternoon or noon in summer, fall, or winter), while the maximum DARF(TOA) occurred in the morning during spring and/or winter and in the afternoon during summer and/or fall. The estimated DARF(SFC) and DARF(ATM) of the water-soluble component were in the range of -49 to -84 W m(-2) and +10 to +22 W m(-2), respectively. The DARF(SFC) and DARF(ATM) of BC were -26 to -39 W m(-2) and +32 to +51 W m(-2), respectively, showing highest in summer and lowest in spring, with morning peaks regardless of the season. This positive DARF(ATM) of BC in this study area accounted for approximately 64% of the total atmospheric aerosol forcing due to strong radiative absorption, thus increasing atmospheric heating by 2.9 +/- 12 K day(-1) (heating rate efficiency of 39 K day(-1) tau(-1)) and then causing further atmospheric warming. (C) 2017 Elsevier B.V. All rights reserved.

The optical properties and direct aerosol radiative forcing (DARF) of different aerosol components in PM2.5 (water-soluble, insoluble, black carbon (BC), and sea-salt) were estimated using the hourly resolution data measured at Aewol intensive air monitoring site on Jeju Island during 2013, based on a modeling approach. In general, the water-soluble component was predominant over all other components with respect to its impact on the optical properties (except for absorbing BC) and DARF. The annual mean aerosol optical depth (AOD) at 500 nm for the water-soluble component was 0.14 +/- 0.14 (0.04 +/- 0.01 for BC). The total DARF at the surface (DARF(SFC)) and top of the atmosphere (DARF(TOA)), and in the atmosphere (DARF(ATM)) for most aerosol components (except for sea-salt) during the daytime were highest in spring and lowest in fall and/or summer. The maximum DARF(SFC) of most aerosol components occurred around noon (12:00 similar to 14:00 LST) during all seasons, while the maximum DARF(TOA) occurred in the afternoon (13:00 similar to 16:00 LST) during most seasons (except for spring). In addition, the estimated DARF(SFC) and DARF(ATM) of the water-soluble component were -20 to -59 W/m(2) and +3.5 to +14 W/m(2), respectively, while those of BC were -18 to -29 W/m(2) and +23 to +37 W/m(2), respectively.

Temporal variations of optical properties of urban aerosol in Seoul were estimated by the Optical Properties of Aerosols and Clouds (OPAC) model, based on hourly aerosol sampling data in Seoul during the year of 2010. These optical properties were then used to calculate direct radiative forcing during the study period. The optical properties and direct radiative forcing of aerosol were calculated separately for four chemical components such as water-soluble, insoluble, black carbon (BC), and sea-salt aerosols. Overall, the coefficients of absorption, scattering, and extinction, as well as aerosol optical depth (AOD) for water-soluble component predominated over three other aerosol components, except for the absorption coefficient of BC. In the urban environment (Seoul), the contribution of AOD (0.10 similar to 0.12) for the sum of OC and BC to total AODs ranged from 23% (spring) to 31% (winter). The diurnal variation of AOD for each component was high in the morning and low in the late afternoon during the most of seasons, but the high AODs at 14: 00 and 15: 00 LST in summer and fall, respectively. The direct negative radiative forcing of most chemical components (especially, NO3 -of water-soluble) was highest in January and lowest in September. Conversely, the positive radiative forcing of BC was highest in November and lowest in August due to the distribution pattern of BC concentration.

Estimation of Particulate Matter (PM) concentration and aerosol absorption is very important in air quality and climate studies. To date, smoke, mineral dust and anthropogenic pollutants are the most uncertain aerosol components in their optical and microphysical properties. In this study, we retrieve the PM2.5 and Absorbing Aerosol Optical Depth (AAOD) from the Total Ozone Mapping Spectrometer (TOMS), the Moderate Resolution Imaging SpectroRadiometer (MODIS) and the Multiangle Imaging SpectroRadiameter (MISR) measurements. A global chemical transport model (GEOS-CHEM) is used to simulate the vertical profiles of PM2.5 and AAOD. We find that the 2003 heat wave has strong impact on PM2.5 across Europe and increased the average PM2.5 concentration by 18%. The aerosol species with the largest concentration increase are ammonium nitrate, black carbon and mineral dust. The Aerosol Robotic Network (AERONET) measurements have been used to validate our retrieval of AAOD. We find that there is a significant agreement between AERONET measurements and our retrievals with the correlation coefficient, slope and intercept of 0.91, 0.99 and 0.001, respectively. The absorbing aerosols can exert negative health effect, increase positive aerosol radiative forcing and contribute positive aerosol-climate feedbacks. (C) 2009 Elsevier Ltd. All rights reserved.

[1] New aerosol modules of global ( circulation and chemical transport) models are evaluated. These new modules distinguish among at least five aerosol components: sulfate, organic carbon, black carbon, sea salt, and dust. Monthly and regionally averaged predictions for aerosol mass and aerosol optical depth are compared. Differences among models are significant for all aerosol types. The largest differences were found near expected source regions of biomass burning ( carbon) and dust. Assumptions for the permitted water uptake also contribute to optical depth differences ( of sulfate, organic carbon, and sea salt) at higher latitudes. The decline of mass or optical depth away from recognized sources reveals strong differences in aerosol transport or removal among models. These differences are also a function of altitude, as transport biases of dust do not always extend to other aerosol types. Ratios of optical depth and mass demonstrate large differences in the mass extinction efficiency, even for hydrophobic aerosol. This suggests that efforts of good mass simulations could be wasted or that conversions are misused to cover for poor mass simulations. In an attempt to provide an absolute measure for model skill, simulated total optical depths ( when adding contributions from all five aerosol types) are compared to measurements from ground and space. Comparisons to the Aerosol Robotic Network (AERONET) suggest a source strength underestimate in many models, most frequently for ( subtropical) tropical biomass or dust. Comparisons to the combined best of Moderate-Resolution Imaging Spectroradiometer ( MODIS) and Total Ozone Mapping Spectrometer ( TOMS) indicate that away from sources, model simulations are usually smaller. Particularly large are discrepancies over tropical oceans and oceans of the Southern Hemisphere, raising issues on the treatment of sea salt in models. Totals for mass or optical depth in many models are defined by the absence or dominance of only one aerosol component. With appropriate corrections to that component ( e. g., to removal, to source strength, or to seasonality) a much better model performance can be expected. Still, many important modeling issues remain inconclusive as the combined result of poor coordination ( different emissions and meteorology), insufficient model output ( vertical distributions, water uptake by aerosol type), and unresolved measurement issues ( retrieval assumptions and temporal or spatial sampling biases).