利用高原积雪信号改进我国南方夏季降水预测的新方法及其在2014年降水预测中的应用试验

2014年夏季我国南方出现严重洪涝、北方大部干旱，国内绝大多数预测模型在三月起报的汛期预测中均未能抓住位于南方地区的异常雨带，导致预测准确率明显偏低。基于模式对东亚地区夏季海平面气压场的高预报技巧和青藏高原冬季积雪与南方地区夏季降水的高相关性，本文提出一个针对我国夏季降水异常的组合统计降尺度预测新方法（Hybrid Statistical Downscaling Prediction，简称HSDP），该方法综合利用了气候模式输出的高可预报性环流信息和前期观测的高原积雪异常信号，从而实现对我国南方夏季降水进行动力-统计相结合的改进预报。据此方法建立了一个基于国家气候中心气候预测模式的统计降尺度模型。对我国南方夏季降水进行跨季节预测的交叉检验结果显示，HSDP方法对于南方地区多年平均空间距平相关系数从模式原始预报的-0.006提高到0.24，且在大多数年份均有改进。基于HSDP方法于三月份制作的2014年夏季降水预测，能够很好地抓住南涝北旱的基本形势和我国南方的降水大值区，空间距平相关系数达到0.43。这表明，该方法对于我国夏季降水预测具有较好业务应用前景。

Improve the Prediction of Summer Precipitation in South China by a New Approach with the Tibetan Plateau Snow and the Applicable Experiment in 2014

Sever floods occurred in southern China and droughts were prevalent in northern China in the summer of 2014. Most predicted models in China missed the southern rain band in their flood season predictions conducted in March 2014, which led to relatively low prediction accuracy. Based on the higher prediction skill for summer sea level pressure of climate models and the significant relationship between the preceding winter Tibetan Plateau Snow and summer precipitation in the south, a new Hybrid Statistical Downscaling Prediction (abbreviated as HSDP) method for summer precipitation anomaly prediction in China was proposed in this paper. The method can integrate the information of the highly predictable circulation from climate models and the influential signal of Tibet Plateau Snow in the preceding winter to improve the dynamical-statistical combination prediction for summer precipitation in the south. Using this method, a statistical downscaling model was established based on the climate prediction model of National Climate Center of China. The cross validation of seasonal prediction for the summer precipitation in the south was performed and the results showed that the HSDP improved the multi-year average of anomaly correlation coefficient from -0.006 to 0.24, and it had a higher predicting skill than the original climate model in most years. Using HSDP, the precipitation prediction for the summer of 2014 could well capture the basic situations, i.e. floods in southern China and droughts in northern China, and the positive precipitation anomaly in the south. The anomaly correlation coefficient could reach 0.43. This result indicated that the HSDP has a great operational application prospect with regard to summer precipitation prediction in China.