我国南方夏季降水异常和旱涝特征分析

Analysis on Summer Precipitation Anomalies and Drought-Flood in Southern China

利用我国南方225个测站降水资料和NCEP/NCAR再分析资料,采用线性趋势分析、EOF、合成分析等方法,分析了1961—2010年南方夏季降水异常变化的规律。结果表明:1)南方夏季降水的稳定性从西向东递增。各月中以7月稳定性最差,其次是8月,6月最好;2)南方夏季降水呈东部增多西部减少的分布特征,西部以-5—-20 mm/(10 a)的速率不显著减少,东部大多数区域以5—30 mm/(10 a)的速率不显著增多,其中浙江东部—江苏东南部显著增加;3)南方夏季降水异常主要有全区一致型、南北差异型和东西相反型3种分布模态;西太平洋副热带高压和南支槽是影响南方降水异常的主要系统,两系统的空间配置及其强度变化决定了南方降水异常的不同分布型;4)南方夏季旱涝分布具有相似之处,干旱发生频率高的区域也是洪涝的高频区,但各月分布有差异,夏季及各月的洪涝发生频率高于干旱频率。

Based on the precipitation data of 225 stations in southern China and the NCEP/NCAR reanalysis data over the past50 years,the characteristics of the summer precipitation anomalies in the South were discussed by the methods of linear trend analysis,EOF and synthetic analysis.The results showed that：1）The stability of summer precipitation enhanced gradually from west to east,with the lowest and highest stabilities in July and June,respectively.2）The summer precipitation increased in the east while decreased in the west.The precipitation reduced insignificantly at the rate of-5 to-20 mm/（10 a）in the west,and increased insignificantly at the rate of 5to 30 mm/（10 a）in most regions of the east,but increased significantly from the eastern Zhejiang province to the southeastern Jiangsu.3）There were 3 distribution modes of summer precipitation anomalies in southern China,including same anomalies in whole area,different anomalies between south and north and opposite anomalies between east and west.The subtropical high pressure over the western Pacific and southern branch trough had great influence on the summer precipitation anomalies in southern China,and the spatial allocation and intensity of the two systems determined the distribution patterns of the precipitation anomaly.4）The distribution of summer drought and flood showed similarities,and the regions with high frequency of drought also presented high frequency of flood,however,the frequency of flood in summer and in each month was higher than that of drought.