Relationships between Evapotranspiration and Environmental Temperature and Humidity in an Alpine Meadow at Three Elevations in the Northern Tibet Plateau
The relationships between actual and potential evapotranspiration and environmental temperature and moisture factors (soil and temperatures, soil moisture, air relative humidity and vapor pressure deficit) during the period from June~September in 2010~2013 in an alpine meadow at three elevations (4300m, 4500m and 4700m) was analyzed based on correlation analyses and multiple stepwise regression analyses. Soil and air temperatures and vapor pressure deficit decreased with increasing elevation, whereas soil moisture increased with increasing elevation. In addition, elevation had non-significant effects on relative humidity, actual and potential evapotranspiration. The correlation analyses showed that: (1) actual evapotranspiration generally decreased with increasing soil and air temperatures and vapor pressure deficit, but increased with increasing soil moisture and relative humidity; (2) potential evapotranspiration generally increased with increasing soil and air temperatures and vapor pressure deficit, but decreased with increasing soil moisture and relative humidity. The multiple stepwise regression analyses indicated that relative humidity and vapor pressure deficit pre-dominated the variation of actual and potential evapotranspiration, respectively. Specifically, the air humidity condition pre-dominated the variations of actual and potential evapotranspiration in the alpine meadow of the Northern Tibet. Moreover, actual and potential evapotranspiration may show quite the contrary response direction to climatic change.