西北干旱区内陆河年径流过程的非线性特征——塔里木盆地三源河的实证分析

以塔里木盆地三源河为例,基于1957-2002年的时间序列,运用小波分析方法从不同的时间尺度上分析了年径流过程的非线性变化趋势,并运用关联维数和R/S分析方法揭示了其分形与混沌特征.主要结论如下:(1) 西北干旱区内陆河年径流过程,是复杂的非线性系统,它们具有波动性以及分形和混沌特征.(2) 从大的时间尺度,即16(24)年的时间尺度上来看,阿克苏河、叶尔羌河的年径流量,在整体上基本呈上升趋势,而和田河在整体上却基本呈轻微的下降趋势.如果把时间尺度缩小到8 (23)或4 (22)年,则各河流的年径流量就不再是上升或下降趋势,而是呈明显的波动变化,而且4(22)年尺度上的波动比8(23)年尺度上的波动更加明显.(3)和田河、叶尔羌河与阿克苏河的关联维数分别为3.222 7、3.211 8与 3.209 2,均为非整数,是分形,这说明三源河的年径流过程具有混沌特征.由于每一个关联维数都大于3,这就意味着,要从动力学角度描述三源河的径流过程,至少需要4个独立变量.(4) 从1989-2002年期间的Hurst指数可以判断,在2002年以后的14年里,阿克苏河与叶尔羌河的年径流量基本上将呈增加趋势,而和田河基本上将呈轻微的减少趋势.

Checking the nonlinear characteristics of annual runoff processes of inland rivers in arid area of northwest China: A demonstration from the three headwaters of the Tarim River

As a demonstration from the three headwaters of the Tarim River, the paper checked the nonlinear characteristics of annual runoff processes of inland rivers in arid area of northwest China by using the wavelet analysis method and the fractal theory. The main conclusions are as follows: (1) The annual runoff processes of inland river in northwest China are complex nonlinear systems, which have nonlinear trends, as well as fractal and chaotic characteristics. (2) At the time scale of 16 (24) years, the annual runoff in the Aksu and Yarkand River basically present an increasing trend as a whole from 1957 to 2002, but that in the Hotan River basically present a slightly decreasing trend in the period. If the time scale is reduced to 8 (23) or 4 (22) years, the annual runoff in each river does not present an increasing or decreasing trend, it has fluctuated more obviously during the period. (3) The correlation dimension for the annual runoff process in the Hotan, Yarkand and Aksu River is respectively 3.2227, 3.2118 and 3.2092, all are non-integral, which indicate that the annual runoff processes in the three headwaters of the Tarim River have both fractal and chaotic characteristics. All the correlation dimensions are above 3, which mean that at least four independent variables are needed to describe the dynamics of annual runoff process of each river. (4) The time series of annual runoff in the three headwaters of the Tarim River present a long-term correlation characteristic. The Hurst exponent in the period from 1989 to 2002 indicates that the annual runoff in the Aksu and Yarkand River will show an increasing trend, and that in the Hotan River will show a decreasing trend in the coming 14 years after 2002.