华北地区作物生长期暴雨的时空特征

Temporal and Spatial Character of Rainstorm during Crop Growing Season in North China Region

利用华北地区1961～2005年逐日降水数据资料,统计分析了华北地区作物生长期暴雨强度和暴雨过程发生的时空分布特征。结果表明,华北地区作物生长期暴雨强度和暴雨过程具有明显的年际波动和年代变化特征;华北地区虽然年年都发生暴雨和大暴雨,但年际变化较大,变异系数分别高达36.9%和53.1%;特大暴雨每4～5年发生1次,暴雨过程则平均11年一遇,特大暴雨和暴雨过程虽然只发生在较少的年份,但年际间波动更加明显;20世纪60年代是暴雨强度较大和暴雨过程多发期的峰值区,而1999年以后暴雨强度和暴雨过程则处于1961～2005年历史阶段的低值区;70～90年代则处于两者之间,期间不同强度暴雨发生并不同步。此外,华北地区年均暴雨日数空间分布呈现从西北向东南明显增加的趋势,暴雨日数变异系数则呈现自东南向西北逐渐增大的趋势。一般地,年均暴雨日数越多,变异系数越小,反之亦然。统计还表明,华北地区降水量与暴雨日数之间存在明显的正相关关系。

The temporal and spatial distribution features of intensities and processes of rainstorms during crop growing season in North China Region were studied by using 1961-2005 daily precipitation dataset.The results showed that the intensities and occurrences of rainstorm during crop growing season in North China had an obvious yearly variation.Although rainstorm occurred every year in North China,the yearly variation was significant,with a coefficient of variation up to 36.9% for rainstorm and 53.1% for heavy rainstorm.Rainstorm occurred once in every 4-5 years,and rainstorm process occurred once in approximately every 11 years.The peaks of intensities and rainstorm process occurred in sixties in the 20th century,and a low value range started after 1999.Moreover,there was an increasing trend of yearly average of rainstorm days from northwest to southeast in Northern China,while the coefficient of variation of rainstorm days increased from southeast to northwest.Generally,the more the rainstorm days were,the less the coefficient of variation,and vice versa was.The results also showed that rainfall in North China was obviously positively correlated with rainstorm days.