中国极端强降水事件年内非均匀性特征分析

基于中国314个台站逐日降水资料,根据百分位值法定义了极端强降水阈值,引入了表征时间分配特征的新参数--极端强降水事件集中度和集中期,对中国极端强降水事件年内非均匀性进行了分析,结果表明:中国年极端强降水事件集中度与集中期自西北向东南均呈“低-高-低”的分布特点,其异常空间分布也存在很大的区域差异;从区域平均来看,西北西部是中国年极端强降水事件最分散的区域,东北是最集中的区域。东北、西北东部、华北以及青藏高原年极端强降水事件集中期相当,明显迟于其它区域,而长江中下游是最早的区域;另外各区域年极端强降水事件的集中度与集中期的长期趋势并不一致,而它们均存在着较一致的周期振荡。

Analyses on Intra-annual Inhomogeneity Characteristic of Extreme Strong Precipitation Events in China

The climate research was focused mainly on change of average temperature and precipitation.Extensive researches showed that extreme climate events caused tremendous economic loss,so they were concerned by public.Based on daily precipitation datasets from 314 stations in China from 1955 to 2004,the extreme strong precipitation threshold of different stations were defined by centesimal value method.Firstly,year after year extreme strong precipitation events were counted up at different stations,then extreme strong precipitation event concentration degree (ECD) and concentration period (ECP) which reflect time distribution fea-tures were introduced,finally,intra-annual inhomogeneity characteristics of extreme strong precipitation event were analyzed by the new parameter in China.The result shows that average spatial distribution of ECD and ECP displays a “low-high-low” characteristic from Northwest China to the Southeast China,Xinjiang is the weakest region of ECD,Xizang (Tibetan) Plateau is the strongest region of ECD;and Southeast China is the earliest region of ECP,while Southwest China,central North China and centrel Northeast China are the latest region of ECP.It is proved that relative greater regional difference exists in the anomalous spatial distribution of ECD and ECP.In terms of regional average,western Northwest China the most scattered region of ECD,and Northeast China is the most concentrated region of ECD.It is also found that ECP is equivalent in Northeast China,eastern Northwest China,North China and the Qinghai-Tibet Plateau,which is apparently later than that of the other regions.The middle and lower Yangtze River is the earliest region,in addition the long-term tendencies of ECD and ECP are inconsistent in various regions,but their period of vibration characteristic is basically consistent.In recent 50 years the change of ECP showed a 2-4yr,7-9yr and 13-15yr period of vibration and the change of reflected a 2-4yr,6-8yr and 11-13yr period of vibration in various regions.