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End date: 2020 × Start date: 2020 × Start date: 1990 × DDC: 550 × Subject: aerosol × Subject: radiative forcing ×

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Now showing 1 - 3 of 3
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    Aerosol hygroscopicity parameter derived from the light scattering enhancement factor measurements in the North China Plain
    (Göttingen : Copernicus, 2014) Chen, J.; Zhao, C.S.; Ma, N.; Yan, P.
    The relative humidity (RH) dependence of aerosol light scattering is an essential parameter for accurate estimation of the direct radiative forcing induced by aerosol particles. Because of insufficient information on aerosol hygroscopicity in climate models, a more detailed parameterization of hygroscopic growth factors and resulting optical properties with respect to location, time, sources, aerosol chemistry and meteorology are urgently required. In this paper, a retrieval method to calculate the aerosol hygroscopicity parameter, κ, is proposed based on the in situ measured aerosol light scattering enhancement factor, namely f(RH), and particle number size distribution (PNSD) obtained from the HaChi (Haze in China) campaign. Measurements show that f(RH) increases sharply with increasing RH, and that the time variance of f(RH) is much greater at higher RH. A sensitivity analysis reveals that the f(RH) is more sensitive to the aerosol hygroscopicity than PNSD. f(RH) for polluted cases is distinctly higher than that for clean periods at a specific RH. The derived equivalent κ, combined with the PNSD measurements, is applied in the prediction of the cloud condensation nuclei (CCN) number concentration. The predicted CCN number concentration with the derived equivalent κ agrees well with the measured ones, especially at high supersaturations. The proposed calculation algorithm of κ with the f(RH) measurements is demonstrated to be reasonable and can be widely applied.
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    Spectral surface albedo over Morocco and its impact on radiative forcing of Saharan dust
    (Abingdon : Taylor & Francis, 2009) Bierwirth, E.; Wendisch, M.; Ehrlich, A.; Heese, B.; Tesche, M.; Althausen, D.; Schladitz, A.; Müller, D.; Otto, S.; Trautmann, T.; Dinter, T.; Von Hoyningen-Huene, W.; Kahn, R.
    In May-June 2006, airborne and ground-based solar (0.3-2.2 μm) and thermal infrared (4-42 μm) radiation measurements have been performed in Morocco within the Saharan Mineral Dust Experiment (SAMUM). Upwelling and downwelling solar irradiances have been measured using the Spectral Modular Airborne Radiation Measurement System (SMART)-Albedometer. With these data, the areal spectral surface albedo for typical surface types in southeastern Morocco was derived from airborne measurements for the first time. The results are compared to the surface albedo retrieved from collocated satellite measurements, and partly considerable deviations are observed. Using measured surface and atmospheric properties, the spectral and broad-band dust radiative forcing at top-of-atmosphere (TOA) and at the surface has been estimated. The impact of the surface albedo on the solar radiative forcing of Saharan dust is quantified. In the SAMUM case of 19 May 2006, TOA solar radiative forcing varies by 12 W m-2 per 0.1 surface-albedo change. For the thermal infrared component, values of up to +22 W m-2 were derived. The net (solar plus thermal infrared) TOA radiative forcing varies between -19 and +24 W m-2 for a broad-band solar surface albedo of 0.0 and 0.32, respectively. Over the bright surface of southeastern Morocco, the Saharan dust always has a net warming effect. © 2008 The Author Journal compilation © 2008 Blackwell Munksgaard.
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    Climatic response to anthropogenic sulphate aerosols versus well-mixed greenhouse gases from 1850 to 2000 AD in CLIMBER-2
    (Abingdon : Taylor and Francis Ltd., 2008) Bauer, E.; Petoukhov, V.; Ganopolski, A.; Eliseev, A.V.
    The Earth system model CLIMBER-2 is extended by a scheme for calculating the climatic response to anthropogenic sulphur dioxide emissions. The scheme calculates the direct radiative forcing, the first indirect cloud albedo effect, and the second indirect cloud lifetime effect induced by geographically resolved sulphate aerosol burden. The simulated anthropogenic sulphate aerosol burden in the year 2000 amounts to 0.47 TgS. The best guesses for the radiative forcing due to the direct effect are -0.4 W m-2 and for the decrease in short-wave radiation due to all aerosol effects -0.8 W m-2. The simulated global warming by 1 K from 1850 to 2000 caused by anthropogenic greenhouse gases reduces to 0.6 K when the sulphate aerosol effects are included. The model's hydrological sensitivity of 4%/K is decreased by the second indirect effect to 0.8%/K. The quality of the geographically distributed climatic response to the historic emissions of sulphur dioxide and greenhouse gases makes the extended model relevant to computational efficient investigations of future climate change scenarios.