The Study On The Direct Radiation Effect Of Dust Aerosol From Satellite Observations

The dust aerosols affect the radiation balance of the earth-atmosphere system by scattering and absorbing solar radiation called the Direct Radiative Effect due to dust aerosols(DRE_dust),and the Direct Radiative Forcing Efficiency of the dust aerosol(DRFE_dust)were defined as the DRE_dust caused by per unit dust aerosol optical depth.As the major component of tropospheric aerosols,the radiartive energy in the earth-atmosphere system could be redistributed by dust aerosols through DRE_dust.Therefore,the estimation of DRE_dust and DRFE_dust is important for the research of global climate change.Satellite directly observing the radiation budget of the earth atmosphere system at the top of the atmosphere,and satellite remote sensing can provide the distribution of aerosol optical depth in high spatial-temporal resolution.Thus,DRE_dust and DRFE_dust can be estimated based on satellite observations directly with smaller uncertainties.It is important but difficult to measure the shortwave radiative forcing of the dust aerosols over land from satellite observed radiance.The method for estimating DRE_dust and DRFE_dust over land based on satellite observations is developed in this study,based on the research and sensitivity analysis of DRE_dust and DRFE_dust.The method is used to estimate DRE_dust and DRFE_dust in dust storms for case study.The main uncertainty of this method mainly caused by satellite observation and inversion error.Therefore,the satellite-based method provides a direct way to validate the DRE_dust and DRFE_dust derived from forward model.The DRFE_dust in the main dust source regions of the world is estimated based on the method developed in this study,through comparing the DRFE_dust in the main dust source regions of the world,the microphysical and optical properties of dust aerosols are analized and their effects on radiation are evaluated.Meanwhile,DRFE_dust is simulated by radiative transfer model to test and verify the satellite estimation results.The results show good agreement between the DRFE_dust derived from satellite estimations and radiative transfer model simulations.The satellite estimation and model simulation results both shows dust arosols in the Taklimakan desert scattering more shortwave radiation,DRFE_dust in the Taklimakan desert is highest among these dust source regions(Wm^-2?^-1 by the satellite;-41.51?-47.36Wm^-2?^-1 by the radiative transfer model),DRFE_dust in the Dehna desert(Wm^-2?^-1 by the satellite;-38.51?-43.91 Wm^-2?^-1 by the radiative transfer model),the Sahara desert(Wm^-2?^-1 by the satellite;--34.91?-44.27Wm^-2?^-1 by the radiative transfer model),the Sonoran desert(Wm^-2?^-1 by the satellite;-14.82?-34.31 Wm^-2?^-1 by the radiative transfer model)and the Simpson desert(Wm^-2?^-1 by the satellite;-7.44?-23.58Wm^-2?^-1 by the radiative transfer model)are decrease in turns.Moreover,through comparing the results with model simulations previous studies,the rationality and reliability of this research are proved.The results can be used as a reference for designing the dust aerosol parameterization schemes in different dust source regions.