Climate‐related trends of actual evapotranspiration over the Tibetan Plateau (1961–2010)

Abstract

Actual evapotranspiration (ETa) is an important component of the hydrologic cycle. In this study, ETa on the Tibetan Plateau (TP) is calculated using the advection‐aridity model (AA model) with data from 86 meteorological stations during the period from 1961 to 2010. Results show that the mean annual ETa over the TP was 543 mm and range from 147 to 687 mm, with higher values in the southern part and lower values in the northern part of the TP. During 1961–2010, annual and seasonal mean ETa show statistically increasing trend at most all stations. Annual ETa in area‐averaged over the TP changed +1.01 mm year−1. Among the four seasons, the changes were most pronounced in March, April, May (MAM) and June, July, August (JJA). ETa variation is significantly and positively correlated with a drought index, defined as the difference between precipitation (P) and potential evapotranspiration (ETp), i.e. P − ETp, showing that the ETa increases over the TP tend to be affected by an increasing soil water supply associated with global warming, such as the retreat of permafrost, increase in P, and decline of ETp.

Improving Actual Evapotranspiration Estimation Integrating Energy Consumption for Ice Phase Change Across the Tibetan Plateau

“…The annual mean ET of the whole TP from our result (294.21 mm) was lower than the results from Zhang et al () and Wang et al (). The mean annual ET was 543 mm during 1961–2010 in Zhang et al () estimated by the advection‐aridity model and was 378.1 mm during 1982–2012 in Wang et al (), which was retrieved by a modified Penman‐Monteith‐Leuning model. In contrast, the annual mean ET of our result was higher than the results from Peng et al () who made a comparison of satellite‐based ET and Zhang et al () who estimated the ET based on the complementary hypothesis from Bouchet ().…”

“…The annual mean ET of the whole TP from our result (294.21 mm) was lower than the results from Zhang et al () and Wang et al (). The mean annual ET was 543 mm during 1961–2010 in Zhang et al () estimated by the advection‐aridity model and was 378.1 mm during 1982–2012 in Wang et al (), which was retrieved by a modified Penman‐Monteith‐Leuning model.…”

“…The comparison results showed that the values of input parameters were consistent to the observed data in most cases, which can ensure the accuracy of the ET estimation in present study. Third, the different choice of method to estimate the ET would also lead to the discrepancies (Song et al, ; Wang et al, ; Xie & Zhu, ; Yu, ; Zhang et al, ). In fact, all the methods used to estimate the ET have their limitations, but we could not deny their contributions to the ET estimation over the TP.…”

“…Many studies on the ET estimation were at the site scale, in which the input variables were obtained from meteorological stations or hydrologic stations. For example, Zhang et al (2018) used data from 86 meteorological stations to estimate the ET over the TP. Most of the selected observation stations were located in the eastern part of the TP, in which present higher P re and T air than the western part.…”

“…Although potential ET, pan ET, or reference ET can indicate the long‐term patterns of ET because contrast changing trends can be found between ET p /ET pan and ET in certain cases over the TP (Wang et al, ; Wang & Alimohammadi, ; Zhang et al, ), they could not exactly depict the changing patterns of ET. Recently, several studies adopted different methods, including satellite retrieval data (Wang et al, ) and advection‐aridity models (Zhang et al, ), to study the spatial and temporal variations in ET over the whole TP but showed a large discrepancy in the annual mean ET (Song et al, ; Wang et al, ; Xie & Zhu, ; Yu, ; Zhang et al, ). Therefore, it is necessary to find an effective method to improve the ET estimations from different time scales.…”