1960~2011年中国日降水集中程度的时空变化特征

利用1960~2011 年的日降水资料，计算降水集中指数（Concentration Index，CI），分析中国区域降水集中程度的空间分布及时间变化特征，得到以下主要结论：CI 指数可有效描述我国日降水集中程度；我国CI 指数介于0.575 与0.750 之间，平均为0.652，总体呈现出东部大、西部小，夏季大、冬季小的特征；44.17%站点的CI 指数表现出增加趋势，55.83%的站点表现出减少趋势，其中10.36%站点的变化趋势通过95%信度水平的显著性检验，CI 指数显著增大的站点主要分布在西北、华中和西南地区，显著减小的站点主要分布在东北、华北、东南沿海及青藏高原东部等地区；3~5 年是各子区域CI 指数变化的主要周期，与对应区域降水量的变化周期较一致；1970 年左右和2000 年左右是显著周期性变化出现较集中的时间段。

Spatial and Temporal Variability of Daily Precipitation Concentration in China during 1960-2011

Based on daily precipitation data during 1960 and 2011, the precipitation concentration index (CI) is calculated for the purpose to study the spatial and temporal variability of daily precipitation concentration in China. The results are as follows. CI can well reflect the degree of precipitation concentration over China. The value of CI is between 0.575 and 0.750, and its mean value is 0.652. The CI values are large in eastern China and in the summer, and small in western China and in the winter. 44.17% of the stations show an upward trend of CI change and 55.83% show a trend of CI decrease, but the trends of CI change at only 10.36% of these stations are significant at the 95% confidence level. Those stations with significant CI increases are mainly distributed over northwestern China, central China, and southwestern China, while those stations with significant CI decreases are mainly distributed over northeastern China, northern China, southeastern coastal areas of China and the eastern Tibetan Plateau. The dominant period of CI change is 3 to 5 years, which is the same as that of precipitation. Significant periodic changes in CI are concentrated within the period from 1970 to 2000.