青藏高原地区气溶胶直接辐射强迫的数值模拟研究

Numerical Simulation of Aerosol Direct Radiation Forcing over the Tibetan Plateau

通过比较EMAC模式模拟结果和卫星观测结果证实了模式的可信性,进而利用模拟结果分析研究了2010~2012年青藏高原上空气溶胶光学厚度及其直接辐射强迫的时空分布规律。结果表明:所有气溶胶组分中,沙尘、水溶性气溶胶和气溶胶中液态水是高原的主要消光物质,三者年平均消光占比分别为0.27、0.20和0.49。2011年夏季纳布罗火山爆发,高空气溶胶消光在海拔14 km以上显著增强。青藏高原气溶胶在大气顶和地表的直接辐射强迫分布总体上由北向南递减,沙尘气溶胶在高原北部边缘大气顶产生正辐射强迫,气溶胶大气层直接辐射强迫对大气有增温效应,主要出现在沙尘含量高的地区。此外,受纳布罗火山爆发的影响,平流层气溶胶在2011年秋、冬季产生了明显较强的负辐射强迫,相比于无火山爆发的2010年和2012年,青藏高原上空平流层气溶胶负辐射强迫在2011年秋季和冬季分别增加了55.50%和52.38%。

The EMAC(ECHAM/MESSy Atmospheric Chemistry)general circulation model had been used to compare with satellites observation,EMAC was proven to be reliable from 2010 to 2012.Therefore,the results of EMAC simulation for the years 2010–2012 were used to analyze the seasonal changes in the optical properties of different aerosols and quantitatively evaluate aerosol direct radiative forcing.The results showed that mineral dust,water-soluble species,and aerosol liquid water were the main extinction substances in the aerosols over the Tibetan Plateau.Their annual extinction ratios are 0.27,0.49,and 0.20,respectively.In June 2011,the eruption of Nabro Volcano considerably enhanced the upper aerosol extinction over 14 km.The distribution of direct radiative forcing of aerosols at the top of the atmosphere and surface decreased from the north to south of the Tibetan Plateau.Mineral dust caused positive radiative forcing at the top of the atmosphere over the Tibetan Plateau’s northern edge from March to September.Aerosols over the Tibetan Plateau caused positive radiative forcing to the atmosphere,mainly in areas with high mineral dust concentrations.In addition,the stratospheric aerosol generated considerably stronger negative radiation forcing in the second half of 2011 due to the impact of the eruption of Nabro Volcano.Compared with the year without volcanic eruption,the negative radiation forcing of aerosols in the stratospheric atmosphere in 2011 increased by 55.50% and 52.38%,in autumn and winter,respectively,over the Tibetan Plateau.