东亚沙尘光学特性及其对辐射强迫和温度的影响

The Optical Properties of East Asian Dust Aerosol and Its Impact on Radiative Forcing and Temperature

利用塔克拉玛干沙漠沙尘复折射指数数据对RegCM4-Dust耦合模式中的沙尘光学特性进行了更新,研究了东亚沙尘气溶胶光学特性对辐射强迫和温度的影响。结果表明:东亚沙尘气溶胶光学特性与模式默认值(OPAC模型)存在明显的差别,主要表现在:消光能力较弱;吸收性较弱,散射性较强;前向散射较弱,后向散射较强。2006年春季沙尘气溶胶光学厚度高值区主要位于塔克拉玛干沙漠、古尔班通古特沙漠、巴丹吉林沙漠、鄂尔多斯高原及黄土高原等地区,最大值出现在巴丹吉林沙漠。采用东亚沙尘光学模型模拟2006年春季东亚地区大气顶净强迫为-4.86 W·m-2,其中短波强迫为-5.34 W·m-2,长波强迫为0.48 W·m-2;地面净强迫为-11.23 W·m-2,其中短波强迫为-13.70 W·m-2,长波强迫为2.47 W·m-2。2006年春季沙尘气溶胶导致东亚地区整体地面降温约0.21℃,陆地上降温明显,而海洋上温度变化不明显,甚至出现升温,这样将导致海陆间热力差异的改变,从而对东亚季风环流产生影响。

The complex refractive index observed from the China-Japan joint project（Aeolian Dust Experiment on Climate Impact,ADEC）in Southern Xinjiang,China and more realistic dust source distribution data are used to update the model default values of optical properties of dust aerosol and land cover types in RegCM4-Dust coupling model.The impacts of optical properties of East Asian dust aerosol on radiative forcing and temperature are studied by a comparison model run.The results show that there are evident differences between the optical properties of East Asian dust aerosol derived from the observed complex refractive index and the default values in the RegCM4-Dust model.The East Asian dust aerosol show weaker extinction,absorption and forward scattering.The region of high dust optical depth is mainly concentrated in Taklimakan Desert,Gurbantunggut Desert,Badian Jaran Desert,Ordos Plateau and Loess Plateau with the maximum located in Badian Jaran Desert.Using the updated optical properties of East Asian dust,the simulated net radiative forcing at the top of atmosphere（TOA）in spring of 2006 is-4.86 W爛m-2,the short wave（SW）forcing is-5.34 W爛m-2,and the long wave（LW）is＋0.48 W爛m-2.The net radiative forcing on the surface is-11.23 W爛m-2,SW and LW forcing are-13.70 W爛m-2 and＋2.47 W爛m-2,respectively.The surface temperature is reduced 0.21 ℃ on average due to dust aerosol over East Asia.As compared with the sea surface air temperature,the surface temperature in the continent is reduced obviously,this will change the temperature gradient between land and sea and affect East Asian monsoon circulations.