Elevation‐dependent changes in the trend of reference evapotranspiration in the Tibetan Plateau during 1960–2017

Abstract

Elevation plays a crucial role in modulating the spatiotemporal distributions of climatic variables in mountainous regions, which affects water and energy balances, among which reference evapotranspiration (ET0) is a key hydrological indicator. However, the response of ET0 to climate change with elevation continues to be poorly understood, especially in the Tibetan Plateau (TP) which has elevation variations of more than 4,000 m. The spatiotemporal variations of ET0 with elevation were investigated using long‐term (1960–2017) meteorological observations from 82 stations on the TP. The results suggest that the average annual ET0 showed an insignificant increasing trend. A significant negative correlation between ET0 and elevation was found (p < .01). The positive trends of ET0 decreased with elevation, whereas the negative trends of ET0 increased significantly with elevation (p < .05). The magnitude of trends of ET0 becomes smaller at higher‐elevation stations. Sensitivity analysis indicated that ET0 was most sensitive to shortwave radiation (Rs). Moreover, the sensitivities of temperature (T) and wind speed (U) significantly decreased with elevation, whereas those of Rs and vapour pressure deficit (VPD) increased slightly with elevation. The contribution and path analyse indicated that increasing VPD was the dominant contributor to the increase in ET0. The effect of elevation on ET0 variation mainly depended on the tradeoff between the contributions of U and VPD. U was the largest contributing factor for the change in ET0 below 2,500 m, whereas VPD was the primary contributor to the increase in ET0 above 2,500 m. This study provides insights into the response of ET0 to climate change with elevation on the TP, which is of great significance to hydrometeorological processes in high‐altitude regions.

Spatiotemporal Variation of Evapotranspiration and Its Driving Factors in the Urumqi River Basin

“…Traditional methods such as pan evaporation, lysimeters, and flux points can obtain single-point high-precision ET information [9,10], but they are also limited by the heterogeneity of the number of observatories and their spatial distribution [11]. As remote sensing continues to evolve, estimates of ET at different regional scales and over long periods have provided a robust database for research [12,13]. Among these data sources, MOD16 products have been proven to have an accuracy of 80-90% in ET estimation and are widely used in ET studies at different scales [14][15][16].…”

Reference evapotranspiration estimation using reanalysis and WaPOR products in dryland Croplands

“…In greater detail, ET o is influenced by elevation-related factors that can lead to notable variations in ET o values, especially in mountainous regions. Higher elevations typically yield lower ET o values due to the combined impact of lower temperatures, reduced atmospheric pressure, and potential alterations in solar radiation and relative humidity [ 70 , 71 ]. Therefore, if the elevation of a weather station differs substantially from the average elevation of the corresponding grid cell, the gridded data may not accurately reflect the weather conditions measured at that station [ 72 ].…”