北京地区季节旱涝长期变化分析

本文对北京地区各季旱涝状态进行了识别比较。结果表明,用Gamma分布划分旱涝级别更能反映该地区的气候状态。发现近30年来四季出现干旱气候状态较以前增多,但各季变化略有不同.夏季干旱增加表现较为明显。从长期变化来看,冬春季有变涝趋势,夏秋季则有变旱趋势。 对北京旱涝状况成因初步分析表明,它与太平洋地区海温冷暖有关。对它们出现的周期性分析表明,未来10～30年期间,夏季干旱程度可能有所缓解。

Long-Term Variations of Seasonal Dryness/Wetness in Beijing

The seasonal dryness/wetness in Beijing is identified and compared. The results show that the dry/wet grades derived from the Gamma probability distribution are more effective to be representative of climate states in. that area than from other distributions. It is found that the dry climate state in the four seasons during recent 30 years occurred more frequently than ever before, and the occurrence frequency varies slightly with different season. Moreover, the dry climate state in summer occurred more frequently Than in other seasons. It follows that from the long-term variations, the dryness is prone to changing into the wetness in winter and spring; the wetness is prone to changing into the dryness in summer and autumn. From a causal analysis, it is known that, the dryness in Beijing is related to the warm/cold state of the see surface temperature in the Pacific. Also, the periodic analysis of the dry/wet grade series shows that the severity of dry state in summer would be mitigated in the next 10-30 years.