中国北方一次强沙尘暴爆发的数值模拟研究

Numerical simulation of a severe dust-storm outbreak in northern China

利用意大利国际理论物理研究中心发展的耦合了沙尘模块的区域气候模式(RegCM3)对发生在中国北方2006年4月9～11日期间的一次强沙尘暴的爆发进行了数值模拟研究。与实际观测相比,RegCM3成功地模拟出了本次沙尘暴爆发区域、天气形势及相应的沙尘气溶胶光学厚度(AOD)分布。4月9日6时,沙尘暴首先爆发于塔里木和吐鲁番盆地。受蒙古气旋的影响,24 h后甘肃中部及内蒙古西部地区也开始爆发沙尘暴。源区地面起沙率大于3 mg.m-2.s-1,单位面积上的沙尘载荷量高于3 000 mg/m2。对流层中低层沙尘主要向东输送,可影响我国华北绝大部分地区,本次沙尘暴过程造成中国北方主要城市空气质量的下降。模拟的AOD分布特征与地面起沙率和载荷量分布特征相对应,并与TOMS卫星观测的气溶胶指数(AI)的区域和中心值具有较好的一致性。AOD分布由西向东呈递减的趋势,且有两个大于2的高值中心,一个位于新疆塔里木、吐鲁番盆地和古尔班通古特沙漠地区;另一个位于河西走廊和内蒙古交界地区。对比他人研究结果,RegCM3对沙尘的起沙、传输等过程以及AOD的时空分布模拟合理。

Northern China is a region where dust storms occur frequently.Millions of tons of dust can be injected into atmosphere accompanying with the explosion of dust storms every year,especially in spring.Dust storms not only can cause huge damage to human lives and production activities,but also can influence the climate and environment due to physical and chemical effects of dust aerosols.However,available observations of the dust cycle are too limited to satisfy need of scientific research for in-depth understanding dust activities in northern China.So climate models incorporating with dust schemes including the emission,transport and deposition are often used to explore processes of dust activities.Meanwhile,it is important to improve or develop a model which can be used to forecast a dust storm.Although some scientists used different models to investigate dust storms in northern China,previous results were discrepant based on different model kernels.The regional climate model version 3（RegCM3）,developed by the Abdus Salam International Centre for Theoretical Physics（ICTP）,has been coupled with a desert dust module to investigate dust cycles and variations of dust aerosol optical depth（AOD）.Although the RegCM3 has been widely used worldwide,there are few studies about its application in modeling dust storm events over northern China.Here the paper simulate a case of the severe dust storm of 9-11 April 2006 to evaluate the performance of this model.The paper mainly focus on two dust source regions of northern China.One is in the Taklimakan desert,the other is in the Gansu corridor.The simulated results show that the outbreak sites,synoptic situation and pattern of the corresponding AOD of this dust storm are successfully simulated,comparing with observation.This severe dust storm extensively exploded in the Tarim Basin and Turpan Basin at 6：00 a.m.on April 9 in 2006.24 hours later,the sandstorm began to outbreak in central Gansu and the western Inner Mongolia under the effect of Mongolia Cyclone.The dust emission rate and column burden of those places were greater than 3 mg·m-2·s-1 and 3 000 mg·m-2,respectively.The transportation of dust in lower and middle troposphere was eastward and its effect can reach the most provinces of east China.This dust storm caused the air quality decline of the cities in north China.In addition,distribution characteristics of AOD,which were well consistent with the distribution and values of TOMS AI,corresponded with those of dust emission rate and column burden.The AOD showed a decline trend from west to east with two maximums which was great than 2.One was located in the desert area of the Tarim Basin,Turpan Basin and Gurbantonggut.The other was close to the border between the Gansu corridor and western Inner Mongolia.Comparing with results from other models,the dust emission rate,transport and spatial-temporal distribution of AOD were reasonably simulated.The results show the validity of RegCM3 in simulating this severe dust storm event in northern China.However,more case studies and integrated analyses are needed before the model is practically used to forecast dust weather and air quality.