Spatio-Temporal Variation of Reference Evapotranspiration and Its Climatic Drivers over the Tibetan Plateau during 1970–2018

Abstract

Reference evapotranspiration (ET0) is a key component of hydrologic cycle and it is important for water resources management. Analysis of ET0 changes is particularly critical for understanding the impacts of climatic change on hydrology in ecologically fragile regions. In this study, using the Penman–Monteith method and the Mann–Kendall test, the variation characteristics of ET0 on the Tibetan Plateau (TP) from 1970 to 2018 was analyzed, and the dominant climatic factors controlling the change of ET0 was also explored. The result shows that in TP region: (1) there was an abrupt change in the trend of ET0 around 1997, and the ET0 declined at a rate of −25.9 mm/decade during 1970–1996 but increased by 31.1 mm/decade during 1997–2018; (2) ET0 is most sensitive to solar radiation, then relative humidity, wind speed and mean temperature; (3) the decrease of ET0 before 1997 was mainly due to the decline of wind speed and the increase of relative humidity, while the increase of ET0 after 1997 was mainly due to the decrease of relative humidity. The results of this study can provide data reference for the research of water balance on the TP.

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

“…ET 0 experienced an increasing trend with the rate of 0.33 mmÁyear −1 during 1960-2017, although it showed an upward-downward-upward trend with changing points of 1973 and 1993. This is similar to a previous study (Wang et al, 2013) but different from other studies (Zhang et al, 2009;Xie and Zhu, 2013;Hu et al, 2021;Liu et al, 2021). Wang et al (2013) found that ET 0 presented a zigzag (increasingdecreasing-increasing) pattern with two joint points (1973 and 1993), while no significant trend was observed during the entire period of 1961-2010.…”

“…Xie and Zhu (2013) indicated that ET 0 on the TP showed an obvious decreasing trend from 1970 to 2009. Zhang et al (2009) indicated that ET 0 decreased in most regions of the TP on annual and seasonal scales during 1970-2004. Hu et al (2021 reported that annual ET 0 showed an insignificant decreasing trend with the abrupt change in 1997 during 1970-2018.…”

“…The sensitivity coefficient (SC) of ET 0 to a climatic variable was calculated using the differential equation method (McCuen, 1974;Yin et al, 2010;Hu et al, 2021),…”

“…Zhang et al (2009) demonstrated that the integrated effect of decreasing U and sunshine duration predominated the changes in ET 0 across the TP during 1971-2004. Yin et al (2010 pointed out that U was the primary factor for decreasing ET 0 on the TP during 1961-2008. Hu et al (2021 reported that the decreasing ET 0 was attributable to the decreasing U and increasing relative humidity during 1970-1996, whereas the dominant factor changed to the decreasing relative humidity for the increasing ET 0 during 1997-2018 over the TP.…”

“…Previous studies have investigated the variation of evapotranspiration in the TP (e.g., Peng et al, 2016;Wang et al, 2020). Furthermore, extensive research has been conducted on the variation of ET 0 and the impacts of climatic variables on ET 0 in the TP (e.g., Zhang et al, 2009;Wang et al, 2013;Xie and Zhu, 2013;Hu et al, 2021). For example, Chen et al (2006) calculated ET 0 for 101 stations in the TP and surrounding areas during 1961-2000 and reported that the decreasing trend in ET 0 was attributable to the changes in U.…”