长江上游川江段气温、降水及径流变化趋势分析

本文运用Mann-Kendall统计检验、线性倾向估计和小波分析等方法对长江上游川江段气象水文要素的长期变化趋势及周期性进行了分析。研究表明：①川江段气温、径流呈不同程度的减少趋势，而降水则呈小幅度增加趋势，年变化率分别为气温-0.0017℃、降水0.3023mm、宜昌径流-6.6668m³/s、寸滩径流-9.5840m³/s，其中寸滩径流量减少趋势十分显著，通过了5%显著水平的信度检验；②川江段气温、降水、径流序列具有不同的周期成分，如年平均气温具有4年、8年和23年主周期，年降水具有3年、6年和16年主周期，寸滩站径流具有3年、8年和16年主周期，宜昌站径流具有3年、16年和45年主周期，且在时域分布上也是不均匀的；③另一方面，在气温略有降低、降水略有增加的气候组合下，川江段径流却呈现减小的变化趋势，同时川江段寸滩站和宜昌站的年径流量从20世纪90年代后期至今在变化特征上也表现出相反的趋势，这是因为人类活动所致还是气候变化影响所致，还有待深入研究。

Changing Pattern of the Temperature, Precipitation and Runoff in Chuanjiang Section of the Yangtze River

The temperature, precipitation and runoff are the three key factors of climate and hydrology. It is of great importance to the development of agriculture and economy to analyze the changing pattern of temperature, precipitation and runoff. On the basis of average temperature and precipitation database from 1954 to 2004 collected from five meteorological stations and the runoff database in Yichang (1890-2000) and Cuntan (1893-2003) hydrological stations in Chuanjiang Section of the Yangtze River, the long-term and periodic variation of temperature, precipitation and runoff are analyzed by using both parametric and nonparametric methods. The Mann-Kendall statistic test is a ranking-based and nonparametric approach, which has been widely used to estimate the significance of changing pattern in hydro-meteorological time series, such as water quality, streamflow, temperature, precipitation and others. The changing pattern of temperature, precipitation and runoff in Chuanjiang Section of the Yangtze River is analyzed in this paper and the Mann-Kendall test is applied to annual temperature, precipitation and runoff time series. Also, the linear regression is compared with the results obtained by Mann-Kendall test. The periodicity of temperature, precipitation and runoff in the study area is analyzed by using Morlet wavelet translation method. The result shows that: 1) the average temperature exhibits a decreasing trend and the slope is-0.00017℃/year. The general changing pattern of average temperature in Chuanjiang area is basically the same with that in Sichuan basin. The annual runoff also demonstrates a falling trend and the slope is -6.6668m3/s/year in Yichang hydrological station. The annual runoff in Cuntan hydrological station witnesses a significant and continuous decrease with the 5% level of significance during the past 111 years and the decreasing rate is -9.5840m3/s/year. There is a minor increase in annual precipitation in the study area over the last 51 years with the slope of 0.3023mm/year. Having compared the results estimated by the two methods, the Mann-Kendall test and linear regression, we find that the changing patterns of temperature, precipitation and runoff are consistent; 2) there are multi-periodicity for the same time series including temperature, precipitation and runoff, the periodicities of which are not equally distributed in time. The main periods of temperature are 4-year, 8-year and 23-year; while those of precipitation series are 3-year, 6-year and 16-year. The main periods of annual runoff series in Cuntan hydrological station are 3-year, 8-year and 16-year, while those of the annual runoff series in Yichang hydrological station are 3-year, 16-year and 45-year.