泾河流域降雨量变化特征分析

Characters of Precipitation Variation in Jinghe Watershed

利用1961年～2004年泾河流域及周边地区的气象站点的月降水资料，以降水倾向率、Mann．Kendall非参数检验等方法分析了降雨变化趋势及时空分布特征。分析结果显示：泾河流域降雨量年际问波动较大，每相隔10年降雨正负距平发生转化，上世纪90年代至今降雨处于新的减少期；40年间流域降雨量下降趋势不显著，减少幅度约为4．7mm／10年；但流域上中下游季节性降雨趋势变化明显，主要表现为秋季降雨减少而冬季降雨增多，秋季降雨减少可能是年降雨量减少的主要原因。流域降雨时空分布特征变化与全球气候变暖导致东亚季风加强北移，以及区域地形差异，地表差异等因素联系密切。分析结果还表明：1981年～2004年及1961年～1980年前后20多年里流域大部分地区降雨增减变化不大，降雨减少区位于流域西北和西南角固原、华亭、千阳一带，降雨增加区位于流域中下游农业高产区，以长武、咸阳为中心，有助于粮食增产。

In the last 100 years, global climate is on the tendency of warming that will influence the water circulation and lead to variation including precipitation, run-off, and frequencies of flood or drought. Jinghe watershed lies in the northwest of China which belongs to arid and semi-arid area. And water resource in that region is the main limiting factor of both social economic and ecosystem, which has significantly positive inter-relationship with precipitation. Therefore, it is important to make it clear what the precipitation will change in concerned area under the impact of global warming. This paper attempts to detect the trends and spatiotemporal characters of precipitation in the Jinghe watershed. The monthly precipitation data from 1961 to 2004 was collected from meteorological stations in Jinghe watershed and the surrounding areas. By using the analysis methods of linear regression and Mann-Kendall test, the results show that the precipitation in Jinghe watershed fluctuates greatly. The positive and negative distance to the mean value of precipitation alternates every ten years. Furthermore, it appears that from 1990s till now precipitation is prominent in the decreasing period. In the last more than 40 years the negative trend of precipitation has no significant effect through Mann-Kendall test and the declining rate is about 4.7mm every ten years. However, the negative trend of precipitation in autumn and positive trend of precipitation in winter can be observed among the upper, middle and lower Jinghe watershed. And the decline of precipitation in autumn may be the main cause leading to annual precipitation decline. The spatiotemporal variation of precipitation in Jinghe watershed is closely related to global warming, which may intensify the east asian monsoon to move northward, regional different topography and surface. The results also indicate that in the majority part of the watershed, precipitation changes little comparing the average contour of precipitation between two stages, which is in turn from 1981 to 2004 and from 1961 to 1980. The negative areas are mainly situated at the northwest and southwest part of Jinghe watershed such as Guyuan, Huating and Qianyan. The positive areas are located in the middle-lower watershed which is agriculture high yield region. Changwu and Xianyan seem to be the two central places of precipitation enrichment regions. And it will help to increase these areas agriculture production.