甘肃省黄土高原区夏季极端降水的时空特征

借助ArcGIS和Matlab数据软件平台,运用复值Morlet小波分析和数理统计方法对甘肃省黄土高原区夏季极端降水的频数和强度在时空上的变化特征进行分析。结果表明:①近半个世纪以来,该区极端降水事件发生的频数和强度在6、7月周期较长,8月周期较短:即6、7月极端降水事件发生的主周期是11~12 a,8月是4~5 a的周期。②从空间尺度来看,该区夏季极端降水带移动由西向东表现为:大致以庄浪、秦安、天水一线为界,6月频数和强度大值区在这一线以西海拔相对高的山区,而7—8月在这一线以东地区,尤其是陇东地区的东南部。③总体趋势是6月极端降水频数和强度明显呈上升趋势;7月极端降水频数和强度呈下降趋势;8月极端降水频数呈下降趋势,强度呈微弱上升趋势。

Spatial and Temporal Characteristics of Summer Extreme Precipitation in Loess Plateau of Gansu Province,China

Based on ArcGIS and Matlab software platform, the spatial and temporal characters of frequency and intensity of summer extreme precipitation in 1961—2009 in Loess Plateau of Gansu Province, China are investigated by use of complex Morlet wavelet analysis and mathematical statistics. Following conclusions are concluded. (1)Variation of frequency and intensity of summer extreme precipitation has a longer fluctuation period in June and July than in August, and the main period in June and July is 11—12 a, but the main period in August is 4—5 a.（2）Summer extreme precipitation zone in Loess Plateau of Gansu Province transfers from west to east. The line from Zhuanglang-Qinan-Tianshui is its eastern boundary. The extreme precipitation zone in June is in the western high mountainous area, and the zone in July and August is in the eastern area, particularly in the south-eastern part of Longdong region.（3）The overall trend of the frequency and intensity of extreme precipitation in June is a upward trend, and the trend in July is downward. In August, the trend of extreme precipitation frequency is downward, but the intensity shows a slight upward trend.