近五十年来华北地区旱涝特征与全球变化的研究及对未来趋势的探讨

A STUDY ON THE FEATURES OF DROUGHT AND FLOOD IN NORTH CHINA IN RECENT 50 YEARS AND RELATIONS BETWEEN THEM AND GLOBAL CHANGES

对近五十年华北地区的降水资料进行了时空分析， 研究了水资源枯、丰的变迁及它们的地域特征。并对大气环流及海温异常进行了对比分析。结果表明：华北降水距平有明显的二十年左右的年代际变化。从总体上说，从５０ 年代初至７０ 年代为丰水期，７０ 年代至９０年代则为枯水期，而从１９９２ 年以后又开始变为正距平。这种年代际变化有很强的地域性。个别地区表现出与平均趋势截然不同的变化。对比丰水期和枯水期的环流状态发现：华北地区二十年左右旱、涝的交替是大气环流异常的结果，这种异常不仅表现在对华北降水有直接关联的天气系统上，而且有明显的全球性。在平均距平图上从低纬至中高纬出现正、负距平中心相间的波列，它自西南向东北延伸。对于丰水期和枯水期，波列的距平中心符号正好相反。说明华北地区降水异常的年代际变化是大气环流气候性变化和调整的结果。对比华北地区旱、涝期２０ 年平均的海温距平分布发现，对旱、涝期而言，全球热带海温的距平中心位置几乎完全一致，而它们的符号则相反。这种相反的海温距平场配置不仅表现在降水期的夏季，在其前春和前冬都十分清晰。海温作为外源强迫对大气环流及天气气候，特别是华北地区降水的年代际变化有不可忽视的作用。综合以上研究，我们对华?

The rainfall data in North China in recent 50 years are analyzed. It indicates that an inter decade variation is existed. From 1950's to 1970's, the precipitation in North China was obviously above normal, called high flow period. From 1970's to 1990's, it was a dry period. This kind of 20 years alternation between dry and wet climate resulted from the variation and adjustment of general circulations. On the mean departure map of H at 500 hPa, it appears a wave train from southwest of Asia to the North America. Comparing SST anomalies between two periods, it shows that the pattern of SSTA is similar, but their signs are just opposite. The opposite distributions of SSTA in those two periods not only appears in the raining season, but also in their preceding winter and spring. The SST forcing played an indispensable role in the inter decade variation. According to the results above, a preliminary forecasting of precipitation trend in North China has been made for the following 20 years.