Interdecadal variations of pan-evaporation at the southern and northern slopes of the Tianshan Mountains, China

Evaporation controlled by meteorological parameters plays a crucial role in hydrology, meteorology and water resources management. An insight view of long-term variation in evaporation will help understanding the effects of climate change and provide useful information for rational utilization of water resources, especially in the arid land where the shortage of water resources exists. However, the lack of data on evaporation led to difficulties in assessing the impacts of climate change on evaporation, especially in arid mountainous area. This study investigated the long-term variation of the pan-evaporation (Ep) measured by E601 type evaporation pan and its influencing climatic factors at both northern and southern slopes of the Tianshan Mountains in Xinjiang of China using the ensemble empirical mode decomposition method and Path analysis. The results revealed that Eps at both northern and southern slopes had obvious interdecadal variation within cycles of 3-4 and 7-8 years. Eps at both slopes sharply decreased in early 1980s, but increased after late 1990s. Path analysis showed that the 3-4 years cycle of Ep at the northern and southern slopes was mainly dependent upon actual water vapor pressure with a negative direct path coefficient of -0.515 and sunshine duration with a positive direct path coefficient of 0.370, respectively. The variation of Ep with cycle of 7-8 years at the northern slope was attributed to the wind speed with a direct path coefficient of 0.774. Average temperature had a direct path coefficient of 0.813 in 7-8 years cycle at the southern slope. The assessment of Ep variation and its causes provides information essential for a good understanding of hydrologic cycle and regional climate of arid mountainous regions in Xinjiang of China and offers a theoretical reference for distribution and utilization of water resources.