西北地区45a来降水异常的时空变化及其标度特征

利用西北地区(73°~113°E,30°~50°N)157个气象站的1960—2004年日降水观测资料,通过非参数趋势检测和旋转主成分分析方法对年降水异常的时空特征进行研究.根据降水特征的差异,西北地区可以划分为西北东北部、东南部、西北部、西南部、中北部及中南部等6大区域.结果表明:西北地区降水自东南向西北逐步递减,降水变化趋势则是东南为负、西北为正,变化幅度东南大于西北.根据每个分区的降水序列标度特征,采用消除波动趋势分析方法,对6个分区45 a来降水时间序列所纪录的大气动力过程影响的时空差异进行分析,定量区分区域气候系统和局地要素对不同区域降水贡献的差异及其年代际变化.

Spatial and Temporal Variations and Scaling of Precipitation over Northwest China during 1960-2004

Based on precipitation data from 157 meteorological observation stations from 1960 to 2004 in Northwest China(73°~113°E,30°~50°N),Sen’s Slope and Mann-Kendall non-parametric methods are applied to detect the long term trend,and Rotated Empirical Orthogonal Functions analysis is used to get six main spatial modes of normalized precipitation over Northwest China.They are the northeast region,southeast region,northwest region,southwest region,central north region and central south region.Annual precipitation decreased generally from the southeast region to the northwest region.In the last 45 years,decreasing precipitation trend was detected in the southeast region,but a significant increasing precipitation trend was detected in the northwest region.Of note,the decreasing amount was greater than the increasing amount.According to the scaling features obtained by Detrended Fluctuation Analysis,spatial and temporal variations of dynamic mechanism which affect the precipitation process of sub-dividing areas in the last 45 years were analysed.The contributions of regional climatic system and local factors to the precipitation change were quantified.