华北地区的降水特征及趋势估计

华北地区位于干旱和半干旱地区。气候降水是该区水资源的主要来源之一，也是影响该区水资源周期性变化的主要因素之一。华北及其北、中、南三个分区的年降水距平曲线变化趋势３具有相似性，而且此四个地区连续出现正距平的年数不超过４年，华北及其北、中部连续出现负距平的年数不超过５年，南部不超过６年，华北、黄淮和东北地区东部与印度次大陆大地区夏季降水距平之间存在正相关关系，同时又与澳洲大部分地区冬季降水距平有负相关

THE CHARACTERISTICS OF RAINFALL AND ITS TENDENCY ESTIMATE OVER NORTH CHINA

North China is situated in arid and semiarid regions. Climate rainfall is not only one of main sources of water resources,but also one of major factors affecting periodic change of water resources over this region. Change trend of annual rainfall anomalies is similar in North China, and northern, southern and middle part of North China. Years of positive and negative anomalies occurr continualy that are not more than 4 years and 6 years respectively in four regions mentioned above. The positive correlation between summer rainfall anomalies over North China and most of India,and negative correlation between summer rainfall anomalies of two regions mentioned above and winter rainfall anomalies of most of Australia are observed. Occurring frequency of this teleconnection mentioned above is 63% over North China,most of India and Australia. The frequency of same sign of summer rainfall anomalies is 80% between North China and its adjacent regions and most of India. The frequency of opposite sign of rainfall anomalies is 73% between North China and its adjacent regions and most of Australia during June to August. Rainfall anomaly series with quasi 3,5,6,7 years oscillation period are composed over North China,percentage of same sign between composed and original rainfall anomaly series is 76%. Rainfall anomaly series with quasi-3,4,8 years oscillation period are also composed over northern part of North China, The percentage of same sign between composed and original rainfall anomaly series is 92%. Finally , the sign of annual rainfall anomalies is estimated by wave-composite method over North China during 1995 to 2004 years. The results indicate that annual rainfall anomalies of 1995 1996, 1999, 2002 and 2003 years are positive,annual rainfall anomalies of 1997, 1998, 2000, 2001 and 2004 years are negative.