陕西汛期降水年际增量预测新技术研究

Study on Interannual Increment Forecasting Approach for Rainy Season Precipitation in Shaanxi

应用年际增量预测方法,通过分析影响陕西汛期降水的物理机制,建立了具有较高预测效能的陕西汛期降水年际增量预测模型。研究表明,赤道太平洋中东部海温年际增量、500 hPa高度年际增量与陕西汛期降水具有很好的相关性。当前一年秋、冬季赤道太平洋中东部海温增量在南北方向上表现为"—+—"分布型时,陕西当年汛期降水偏多,反之,陕西当年汛期降水偏少。当前一年秋、冬季500 hPa高度年际增量在赤道附近呈带状正值分布时,陕西当年汛期降水偏多;呈带状负值分布时,陕西当年汛期降水偏少。国家气候中心提供的74项环流特征量、陕西省0 cm地温增量因子与陕西汛期降水也有很好的相关关系。在对预测因子物理意义分析的基础上,用逐步回归方法引入因子,建立陕西10个气候区域的汛期(6~8月)降水总量和各分月(6、7、8月)的降水年际增量预测模型(共40个),汛期降水总量预测模型交叉检验距平同号率达78.4%。对2010—2013年汛期降水总量和各分月降水量进行试报,其准确率PS评分分别达到75.8和66分。增量预测方法具有较强的预测能力,能够在一定程度上提高陕西汛期降水预测水平,可作为有效方法投入实际业务应用。

An interannual precipitation increment forecasting model with high-predictive capability for forecasting the summer rainfall in Shaanxi Province is presented by analyzing the physical mechanisms of precipitation during flood season based on the interannual increment forecasting approach.The research results show that the interannual SST increment in middle and eastern equatorial Pacific,the 500 hPa height interannual increment and rainfall during flood season in Shaanxi have very good correlations.When the distribution pattern is north-south ' — + — ' in interannual increment of SST in middle and eastern equatorial Pacific from the previous autumn to winter,there would be more rains in the summer.Conversely it would rain less.When the distribution pattern of the interannual increment at 500 hPa height is positive,showing zonal,near the equator from the previous autumn to winter,there would be more rains in the summer.Otherwise,it would be dry.In this research,we find a good correlation between the interannual increment of 74 circulation features from National Climate Centre,soil temperature at 0 cm depth and precipitation during flood season in Shaanxi.Based on the analysis of the physical meanings of predictors,predictors are introduced via the optimal subset regression,and 40 prediction models for rainy season precipitation and each month(June,July and August) of 10 climatic regions of Shaanxi are established by using the interannual increment approach.Cross-validation testing of rainy season precipitation shows that the anomaly consistency rate reaches 78.4%.It is shown by the hindcasting results during 2010 — 2013 that the PS score of flood season precipitation is 75.8 and 66,separately.Thus,this work demonstrates that the interannual increment approach has good predictive skill.It can improve the level of predicting rainfalls in Shaanxi flood season and can be used as an effective way in forecasting operations.