半干旱草原型流域不同时间尺度降水特征分析

基于锡林浩特气象站1960-2015年逐日降水数据，运用M-K法、R/S 法和Morlet 小波法，分析了半干旱草原型流域--锡林河流域近56a不同时间尺度下降水趋势及突变特征、未来变化趋势、降水周期规律的变化情况。结果表明：近56a来锡林河流域年降水量呈下降的趋势，在1974、1980、1989年和1998年发生过4次突变，存在28a的主周期变化。夏季降水特征和年降水特征基本一致，冬季降水量呈显著上升的趋势。汛期8月份降水量呈显著下降的趋势，并在1998年左右发生突变，降水第一主周期在12a处，非汛期11和12月份降水量都呈显著上升的趋势，其中，12月份降水在2000 年左右发生显著突变，这两个月份降水的第一主周期分别是30a和9a。不同时间尺度下降水序列的Hurst指数均>0.5，说明流域降水趋势具有持续性，未来降水趋势与过去保持一致。

Precipitation characteristics at different time scales for a semi-arid steppe watershed

Analysis of the precipitation characteristics has been paid wide attention in recent years because it is an important hydrologic factor that is intimately connected with the distribution of water resources and the human life. However, previous researches about the precipitation characteristics were most carried out in arid and semi-arid regions of northwest China, it cannot reflect the steppe watershed. Therefore, an analysis of the precipitation characteristics for a steppe watershed is necessary. By using the daily precipitation data obtained from Xilinhot meteorological station from 1960 to 2015, M-K, R/S and Morlet's wavelet methods were used to analyze the precipitation trend and abrupt change characteristic, the future trend, and the precipitation cycles at different time scales in a semi-arid steppe watershed-the Xilin River Basin, Inner Mongolia, China. The results show that the annual precipitation presented a nonsignificant decreasing trend and four abrupt changes took place in 1974, 1980, 1989 and 1998 during recent 56 a. There were a major cycle of 28 a, and two minor cycles of 4 a and 6a which occurred in the period from middle 1970s to the late 1990s and after the late 1990s, respectively. At the seasonal scale, the characteristic of summer precipitation was basically consistent with that of the annual precipitation, the rainfall of autumn had a large fluctuation, and the precipitation of the other two seasons both increased, especially in winter, the precipitation presented a significantly increasing trend. The precipitation in August of the flood season presented a significant decreasing trend and changed in 1998, and the first major cycle was 12 a. The precipitation in November and December of the non-flood season demonstrated a significantly increasing trend, therein, precipitation in December in 2000 showed a significant abrupt change. The first major precipitation cycles during the two months were 30 a and 9 a, respectively. The Hurst indices of the precipitation series at different time scales were all greater than 0.5, indicating that the precipitation had a persistent trend, the change of future precipitation will be consistent with that of the past. This conclusion can provide a reference for the management of water resources and ecological protection in Xilin River Basin in the future. However, the precipitation data selected in this study has some limitations. Besides, in recent years, with the process of urbanization, the transformation of basin underlying surface caused by human activity is also increasing, which also has an effect on the precipitation in this region. Therefore, the influence of human activities on the precipitation will be taken into consideration in further research.