中国东部夏季降水与东亚垂直环流结构及其预测试验

The Influence of Vertical Atmospheric Circulation Pattern over East Asia on Summer Precipitation in the East of China and Its Forecasting Test

本文在分析中国东部夏季降水的时空分布特征基础上,从东亚高、中、低层大尺度环流异常着手,选取对中国东部夏季降水异常有显著影响的大气环流预报因子,分别应用逐步回归和最优子集回归法两种统计降尺度方法,以动力气候模式CAM3.1预报输出的大气环流预报因子为基础,以中国东部夏季降水的典型空间分布型为预报对象,建立动力与统计相结合的中国东部夏季降水预测模型,并对1981～2000年的中国东部夏季降水进行回报试验。结果表明:中国东部夏季降水具有4类典型的空间分布型式,且具有显著的准2年和年代际尺度振荡周期;东亚高、中、低层大气环流异常的特定配置,对东部夏季降水的空间分布型有显著影响;使用两种降尺度方案建立的动力与统计相结合的预测模型对中国东部夏季降水异常具有一定的预报技巧,可以在一定程度上提高动力模式对中国东部夏季降水的预报效果。

The model error exists for the reason that a certain difference is present between the weather state described by the model and the true weather state though more and more physical processes and complicated boundary conditions are considered in numerical weather prediction models.Filter divergence was found in the ensemble Kalman filter system when the model errors were neglected in previous studies.In this paper,it is shown that the model errors increase linearly with the decrease of resolution and the increase of the model error is obvious with the increase of model forecasting length through estimating the discriminations among the forecasting fields at different resolutions.