中国东部秋冬季极端干旱事件的数值模拟研究

Modeling Analysis of a Severe Autumn/Winter Drought in Eastern China by using Regional Atmospheric Modeling System(RAMS)

利用区域大气模式RAMS(Regional Atmospheric Modeling System)对2008/2009年秋、冬季节中国东部地区的一次极端干旱事件进行了数值模拟,并与欧洲中期天气预报中心ECMWF(European Centre for Medium-Range Weather Forecasts)再分析资料(ERA-Interim)和全球观测数据GSOD(Global Summary Of Day)进行了对比。结果表明,我国东部地区处于稳定的槽后西北气流控制,冷空气活动频繁,但是从南海来的水汽通量北向输送较弱,呈现为不利于降水的环流特征。模式很好地再现了上述干旱形成的环流特征,较好地模拟出了我国及干旱发生区的降水和温度时空分布状况,干旱区的温度和降水模拟值与观测值相关系数的平方达到了0.8以上。尽管RAMS模式对此次极端干旱事件的模拟能力较好,但模拟的精度还需要提高,仍需更多实例对比来进行研究总结。

To testify RAMS＇ performance on drought events, the simulation of 2008/2009 severe autumn/winter drought event over eastern China was conducted in this study. The RAMS outputs were compared with Europe- an Centre for Medium-Range Weather Forecasts （ERA-interim） Reanalysis data and Global Summary of Day （GSOD） observation data respectively. The ERA-interim reanalysis data showed that most parts of the north China were controlled by northwest wind which was accompanied by cold air, the warm and moist air from South Sea is so weak to meet with cold air from the northern region, therefore forming a circulation which is un- favorable for precipitation over Eastern China, and the downward motion and low relative humidity prevailed over the drought area which intensified the drought. RAMS has proven to be capable of reproducing the afore- mentioned general atmospheric circulation, and RAMS captured the distribution features of the rainfall and air temperature over China authentically. Meanwhile, compared with GSOD observations, RAMS showed good per- formance on the simulation of precipitation and air temperature time variations over the drought area, both the square of correlation coefficient between simulations and observations of precipitation and that of air temperature reached above 0. 8. Although the performance of RAMS on this drought simulation is fairly accurate, the spatial resolution of RAMS simulation needs enhancement and large amount of drought simulations should be complet- ed and contrasted to draw a conclusive evaluation of RAMS capability.