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- Author or Editor: K. Isaksen x
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Abstract
Radiative transfer calculations based on a new sulfate distribution from a chemistry-transport model simulation have been performed. A wide range of sensitivity experiments have been performed to illustrate the large uncertainty in the radiative forcing due to sulfate aerosols. The most important factors seem to be processes involved in the mixing of sulfate aerosols with other particles and uncertainties in the relative humidities. These factors can explain much of the large range in previous estimates of the radiative forcing due to sulfate aerosols reflected, for example, in the Intergovernmental Panel on Climate Change estimate. Included in this study is a simple subgrid-scale parameterization of relative humidity to investigate a potentially large uncertainty in the radiative forcing due to sulfate aerosol.
Abstract
Radiative transfer calculations based on a new sulfate distribution from a chemistry-transport model simulation have been performed. A wide range of sensitivity experiments have been performed to illustrate the large uncertainty in the radiative forcing due to sulfate aerosols. The most important factors seem to be processes involved in the mixing of sulfate aerosols with other particles and uncertainties in the relative humidities. These factors can explain much of the large range in previous estimates of the radiative forcing due to sulfate aerosols reflected, for example, in the Intergovernmental Panel on Climate Change estimate. Included in this study is a simple subgrid-scale parameterization of relative humidity to investigate a potentially large uncertainty in the radiative forcing due to sulfate aerosol.
Abstract
A global three-dimensional chemical transport model (CTM) is used to model the yearly cycle of sea salt. Sea salt particles are produced by wind acting on the sea surface, and they are removed by wet and dry deposition. In this study, forecast meteorological data are taken from the ECMWF. The modeled concentrations are compared to measured concentrations at sea level, and both absolute values and monthly variations compare well with measurements. Radiation calculations have been performed using the same meteorological input data as the CTM calculations. The global, yearly average burden of sea salt is found to be 12 mg m−2. This is within the range of earlier estimates that vary between 11 and 22 mg m−2. The radiative impact of sea salt is calculated to be −1.1 W m−2. The total, yearly flux of sea salt is estimated to be 6500 Tg yr−1.
Abstract
A global three-dimensional chemical transport model (CTM) is used to model the yearly cycle of sea salt. Sea salt particles are produced by wind acting on the sea surface, and they are removed by wet and dry deposition. In this study, forecast meteorological data are taken from the ECMWF. The modeled concentrations are compared to measured concentrations at sea level, and both absolute values and monthly variations compare well with measurements. Radiation calculations have been performed using the same meteorological input data as the CTM calculations. The global, yearly average burden of sea salt is found to be 12 mg m−2. This is within the range of earlier estimates that vary between 11 and 22 mg m−2. The radiative impact of sea salt is calculated to be −1.1 W m−2. The total, yearly flux of sea salt is estimated to be 6500 Tg yr−1.
