1961—2012年京津冀地区不同等级降水日数时空演变特征

Temporal-spatial characteristics of precipitation days in different levels in Beijing-Tianjin-Hebei from 1961 to 2012

利用1961—2012年京津冀地区78个气象站逐日降水资料,采用趋势分析、Morlet小波和经验正交函数(EOF)等方法,分析京津冀地区不同等级降水日数的时空演变特征。结果表明:近52 a来,京津冀地区各等级降水日数的变化趋势不明显。空间分布上,降雨日总数和小雨日数呈自西北向东南递减的特征;中雨日数和大雨日数分别存在两个大值中心,二者大值中心的位置相似,一个位于京津冀地区东北部,另一个位于西部太行山区;暴雨日数的空间分布特征不明显,具有随机性。降雨日总数和小雨日数存在准13 a和准6 a两个尺度的振荡周期;中雨日数、大雨日数及暴雨日数存在15—18 a和8—11 a两个尺度的振荡周期。EOF第一模态分析表明,降京津冀地区各等级降水日数在全区具有较好的一致性;第二模态分析表明,降雨日总数、小雨日数、中雨日数和大雨日数具有南北反位相的特征,暴雨日数具有西北部和东部多(少)、中部和西部少(多)的分布特征。

Based on daily precipitation data at 78 weather stations of Beijing-Tianjin-Hebei region during 1961-2012,spatial and temporal evolution of precipitation days at different levels were analyzed using methods of a trend analysia,a Morlet wavelet and an empirical orthogonal function（EOF）.The results show that it has not a significant trend for precipitation day at different levels in the recent 52 years in the study area.Spatial distribution of the total rain and light rain days is in a decreasing trend from northwest to southeast.The moderate and heavy rain days have two similar centers of high values,and both are located in the northeast of Beijing-Tianjin-Hebei region and in the west of Taihangshan mountain region,respectively.However,the spatial distribution of torrential rain day has no significant feature and it is random.Both total and light rain days have two time-scale oscillation periods i.e.13 years and 6 years,so are moderate,heavy and torrential rain days i.e.15-18 years and 8-11 years.The first mode of EOF analysis suggests that the number of precipitation days in all levels has a better consistency in the region.The second mode of EOF analysis suggests that total rain days,light,moderate and heavy rain days have an opposite phase in the north and south,and torrential rain days is more（less） in the northeast and east of study area Jess（more） in middle and west of study area.