北京夏季一次深对流过程对不同溶解度气体垂直输送的模拟

Modeling of Vertical Transport of Gases with Different Solubilities by a Deep Convective Process during Summer in Beijing

利用中尺度大气化学模式WRF-Chem,对2012年7月21日北京及其周边地区一次深对流过程中大气成分垂直输送过程进行了模拟,量化深对流系统对大气中不同溶解度气体成分再分布的贡献。将本次模拟个例与微波临边观测仪(Microwave Limb Sounder,MLS)卫星数据的对比发现,数值模拟可以较好地再现深对流天气过程中大气成分CO和O_(3)的分布特征。在本次模拟个例中,从CO、O_(3)、SO_(2)和NH_(3)等不同溶解度气体体积浓度随时间和高度的变化特征发现:深对流可以将不同溶解度的气体输送到对流层上层,甚至进入到平流层下层;在对流层上层,不易溶的CO(O_(3)),其体体积浓度由对流发生前期的70 ppb(1 ppb=10^(-9))(220 ppb)增加(降低)到对流最强盛期的111 ppb(102 ppb),增加(降低)的百分比为58.6%(53.6%);而易溶的SO_(2)和NH_(3),在对流层上层,其体积浓度分别由对流前期的0.036 ppb和0.011 ppb增加到对流最强盛期的0.4 ppb和0.15 ppb,增加的百分比为1011.1%和1263.6%。

The WRF-Chem model was used to simulate the vertical transport of atmospheric composition during deep convection over Beijing and its surrounding areas on 21 Jul 2012.The study quantified the contribution of the deep convective system to the redistribution of atmospheric composition with different solubilities.Comparison with Microwave Limb Sounder(MLS)measurements showed that the model simulation accurately reproduced the distribution of CO and O_(3) during deep convection.The time and altitude cross-section of CO,O_(3),SO_(2),and NH_(3) demonstrated that deep convection could transport gases with different solubilities to the upper troposphere and even into the lower stratosphere.In the upper troposphere,the volume concentration of low-solubility gas CO increased from 70 ppb(1 ppb=10-9)to 111 ppb during the convection,representing a 58.6%increase.Conversely,O_(3) decreased from 220 ppb to 102 ppb,showing a 53.6%decrease.For high-solubility gases,SO_(2) and NH_(3) concentrations increased from 0.036 ppb and 0.011 ppb in the preconvection to 0.4 ppb and 0.15 ppb by volume during the convection,with percentage increases of 1011.1%and 1263.6%,respectively.