Spatio-temporal Pattern and Changes of Evapotranspiration in Arid Central Asia and Xinjiang of China

Arid areas are among the regions which are most sensitive to global change. Central Asia, which accounts for one third of the world’s arid areas, has become a hotspot for global change research. Issues concerning water resources remain to be the focus of environment and ecological studies in these regions. As the ultimate way to water consumption in arid inland water cycle, evapotranspiration (ET) is the most influential factor in maintaining a balance in regional water and energy levels. Accurately estimating the spatial and temporal variation of land surface ET is beneficial to adequately understanding the hydrological cycle and energy balance, as well as evaluating the functions of regional water cycle and water balance.

In order to probe into the inversion of actual ET process and discuss the impact of spatio-temporal pattern and changes, Prof. CHEN Xi and some other researchers developed an appropriate approach for ET inversion in arid lands based on model validation analysis at varied scales in five Central Asian countries and China’s Xinjiang. The actual ET during growing seasons of the study area was defined, and the changes in water participating in evaporation in regional water cycle were then educed.

The results show the simulation error of SEBS (Surface Energy Balance System) model under cloud amount consideration was 1.34% at 30-m spatial scale, 2.75% at 1-km spatial scale and 6.37% at 4-km spatial scale. ET inversion for 1980–2007 applying SEBS model in the study area indicates: (1) the evaporation depth (May–September) by land types descends in the order of waters (660.24 mm) > cultivated land (464.66 mm) > woodland (388.44 mm) > urbanized land (168.16 mm) > grassland (160.48 mm) > unused land (83.08 mm); and (2) ET during the 2005 growing season in Xinjiang and Central Asia was 2,168.68×10⁸ m³ (with an evaporation/precipitation ratio of 1.05) and 9,741.03×10⁸ m³ (with an evaporation/precipitation ratio of 1.4), respectively. The results unveiled the spatio-temporal variation rules of ET process in arid areas, providing a reference for further research on the water cycle and water balance in similar arid regions.

This research was supported by the National Natural Science Foundation of China (40730633 and 40571030). The findings have been published on Journal of Arid Land, 2012, 4(1): 105-112. The paper is also archived at http://jal.xjegi.com/EN/abstract/abstract130.shtml.