月和季节尺度区域气候模拟的对比分析

Comparison between the Monthly-Scale and Seasonal-Scale Regional Climate Simulation

利用区域气候模式RegCM3分别进行了东亚夏季月尺度和季节尺度区域气候模拟试验,并将两种时间尺度试验的逐月模拟结果进行了对比分析。结果表明,不同初始场和不同时间尺度模拟降水量存在一定的不确定性,但模拟的降水分布格局和模拟时间尺度关系不大,其模拟结果主要取决于模式对区域内大气降水过程的描述能力。两种时间尺度模拟的月平均环流形势几乎一致,随着模拟时间延长,两种时间尺度模拟的月平均环流、温度和湿度之间的差别在模式内部区域有所增加。但两者没有出现本质差别,且两者之间的偏差不会随模拟时间尺度的延长而无限制增长,只在一定范围内波动。两种时间尺度模拟对7月份淮河流域降水集中期暴雨和高低空急流刻画差别不大,但两者对8月份东北降水集中期模拟差别稍明显一些,其差别主要表现在对低空急流的模拟上。

The Regional Climate Model （RegCM3） has been used to conduct the monthly-scale and the seasonal-scale simulation for the abnormal climate event of China in the summer of 1998, and the comparative study has been performed between the two time-scale simulations. The results show that, different initial conditions and time scales can cause some uncertainties to the simulated precipitation amount, but precipitation scenario is independent with the simulation time scale. Instead, it lies on the ability of the model to represent the weather and climate system associated with precipitation processes in the atmosphere. Due to the effect of large scale boundary force, the simulated circulation patterns of two time scale experiments are almost the same. As the simulation time scale extends longer, the difference of simulated month-average circulation pattern, temperature and humidity between two time scale simulations is not significant, only increases a little in the inner region. However, there are no essential distinctions be- tween monthly-scale and seasonal-scale simulations. And the bias between them will not increase unlimitedly with the time scale extends, instead, it only fluctuates in a range. The difference between two time scale simulations for the precipitation over the Huaihe river valley in July is not so obvious, whereas it becomes a little more significant for the precipitation over Northeast China in August, especially for the low level jet.