Runoff Change on the South Slopes of Mount Tomur and Its Response to Climatic Variation
XIE Chang-wei, DING Yong-jian, LIU Shi-yin, SHEN Yong-ping, HAN Hai-dong, WANG Jian (Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou Gansu 730000, China)
Runoff of the rivers on the south slopes of the Mount Tomur has increased since the mid 1980s, because temperature and precipitation in this area has increased rapidly. As supply rate of meltwater from glaciers is important to these rivers, fluctuation of temperature and its impact on the ablation of glaciers and snow influence the runoff directly. The respondency of runoff to temperature and precipitation is analyzed by means of cross-spectral analysis. In addition, some new functions, such as coherence function, gain function and phase spectrum function, are calculated from the cross-amplitude function and the simple-density spectrum. It is revealed that the runoff's fluctuation with periods of 5~6 a and 11 a is controlled principally by temperature, and the change of runoff lags the fluctuation of temperature for 21 and 23 mouths. However, precipitation influences the runoff's fluctuation a little when the frequency is low. When the frequency is high, both precipitation and temperature influence the runoff. In all the frequency, temperature has a predominate effect on the runoff. Finally, it is considered that temperature is the first factor and precipitation is the second factor to impact the change of the runoff at the south slopes of the Mount Tomur.