黄河流域夏季旱涝变化及气候物理因素的影响

利用1951—2008年NCAR/NCEP再分析资料及中国气象局整编的160站降水资料,探讨了黄河流域夏季降水气候分布范围,在此基础上研究了黄河流域夏季降水旱涝的年代际变化特点。结果表明：20世纪90年代以前,黄河流域夏季旱涝变化为9—11 a和2—3 a周期,20世纪90年代后周期变化不明显。对导致黄河流域夏季旱涝的气候物理因素分析表明,东亚高度场负距平异常直接造成中国黄河流域的夏季偏旱,而亚洲高度距平场东高西低的配置造成中国黄河流域偏涝;夏季南亚季风、东亚季风在中国黄河流域的辐合是流域降水偏多的关键。在同期OLR距平场,涝年黄河流域处在大的负距平中,对流强盛有利于水汽的辐合。影响大气的主要下垫面要素海温场,赤道东太平洋海温指数与夏季中国黄河流域降水同期呈负相关关系。中国黄河流域旱年赤道东太平洋海温多为正位相,对应中国黄河流域涝年赤道东太平洋海温多为负位相。提出了一个寻找旱涝成因方法并为预测旱涝变化提供参考。

Characteristics of changes of summer drought and flood and impact of climatic physical factors on these changes in the Yellow River valley,China

Based on the NCAR/NCEP reanalysis data and precipitation data in 160 weather stations from the National Meteorological Center from 1951 to 2008,the distributions of summer precipitation in the Yellow River valley were analyzed.The interdecadal variations of the summer drought and flood were discussed.The results indicate that there are 9-11 years and 2-3 years cycles for the summer drought and flood in the Yellow River valley before 1990s,while those are not obvious after 1990s.The climatic physical factors leading to the summer drought and flood are analyzed in the Yellow River valley.It shows that the negative anomaly abnormality of geopotential height field over East-Asia results in summer drought directly,while the height anomaly field with the east high and west low over Asia leads to summer flood in the Yellow River valley.The convergence of South Asia monsoon and East Asia monsoon in summer is the key factor causing increasing precipitation in the Yellow River valley.For the OLR anomaly field in the same period,the area of the Yellow River valley shows the large negative anomaly in flood year,and the strong convection facilitates vapor convergence.Surface sea temperature（SST） field is the main influencing factor.SST index of equatorial eastern pacific has a negative correlation with summer precipitation in the Yellow River valley in the same period.Equatorial eastern pacific SST is often a positive phase in drought year,while it is often a negative phase in flood year.An analysis method of drought and flood is proposed,and it can provide scientific references for drought and flood prediction.