Temporal and Spatial Distribution of Evapotranspiration and Its Influencing Factors on Qinghai-Tibet Plateau from 1982 to 2014

doi:10.5814/j.issn.1674-764X.2019.02.012

Abstract

Abstract:

Evapotranspiration is the key driving factor of the earth’s water cycle, and an important component of surface water and energy balances. Therefore, it also reflects the geothermal regulation function of ecohydrological process. The Qinghai-Tibet Plateau is the birthplace of important rivers such as the Yangtze River and the Yellow River. The regional water balance is of great significance to regional ecological security. In this study, ARTS, a dual- source remote sensing evapotranspiration model developed on a global scale, is used to evaluate the actual evapotranspiration (ET) in the Qinghai-Tibet Plateau from 1982 to 2014, using meteorological data interpolated from observations, as well as FPAR and LAI data obtained by satellite remote sensing. The characteristics of seasonal. interannual and dynamic changes of evapotranspiration were analyzed. The rates at which meteorological factors contribute to evapotranspiration are calculated by sensitivity analysis and multiple linear regression analysis, and the dominant factors affecting the change of evapotranspiration in the Qinghai-Tibet Plateau are discussed. The results show that: (1) The estimated values can explain more than 80% of the seasonal variation of the observed values (R² = 0.80, P < 0.001), which indicates that the model has a high accuracy. (2) The evapotranspiration in the whole year, spring, summer and autumn show significant increasing trends in the past 30 years, but have significant regional differences. Whether in the whole year or in summer, the southern Tibetan Valley shows a significant decreasing trend (more than 20 mm per 10 years), while the Ali, Lhasa Valley and Haibei areas show increasing trends (more than 10 mm per 10 years). (3) Sensitivity analysis and multiple linear regression analysis show that the main factor driving the interannual change trend is climate warming, followed by the non-significant increase of precipitation. However, vegetation change also has a considerable impact, and together with climate factors, it can explain 56% of the interannual variation of evapotranspiration (multiple linear regression equation R² = 0.56, P < 0.001). The mean annual evapotranspiration of low-cover grassland was 26.9% of high-cover grassland and 21.1% of medium-cover grassland, respectively. Considering significant warming and insignificant wetting in the Qinghai-Tibet Plateau, the increase of surface evapotranspiration will threaten the regional ecological security at the cost of glacial melting water. Effectively protecting the ecological security and maintaining the sustainable development of regional society are difficult and huge challenges.

Key words: evapotranspiration, Qinghai-Tibet Plateau, climatic factors, spatial and temporal distribution

CUI Mingyue,WANG Junbang,WANG Shaoqiang,YAN Hao,LI Yingnian. Temporal and Spatial Distribution of Evapotranspiration and Its Influencing Factors on Qinghai-Tibet Plateau from 1982 to 2014[J]. Journal of Resources and Ecology, 2019, 10(2): 213-224.

Figures/Tables 8

Fig. 1 The estimated ET was assessed through the observed ET on eddy covariance towers at Haibei, Qinghai and Hohhot, Inner Mongolia.

Fig. 2 Interannual variations of precipitation (a), temperature (b), radiation (c), LAI (d), and ET (e), and percentage of interannual anomaly (f) over the Qinghai-Tibet Plateau from 1982 to 2014.

Fig. 3 Spatial distribution of ET multi-year mean and ET change rate in Qinghai-Tibet Plateau from 1982 to 2014

Fig. 4 Average seasonal evapotranspiration and its trend in the Qinghai-Tibet Plateau from 1982 to 2014

Fig. 5 Contributions of the dominant factors to interannual and seasonal evapotranspiration in the study area

Fig. 6 Spatial map of contribution rate of various influencing factors to ET change in Qinghai-Tibet Plateau from 1982 to 2014

Fig. 7 Spatial trend of meteorological factors and leaf area index over the Qinghai-Tibet Plateau from 1982 to 2014

Fig. 8 Interannual and seasonal variations of actual evapotranspiration of grasslands with different coverage in the Qinghai-Tibet Plateau from 1982 to 2014

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