Past and future spatiotemporal changes in evapotranspiration and effective moisture on the Tibetan Plateau

Abstract

[1] Observed evaporative demand has decreased worldwide during the past several decades. This trend is also noted on the Tibetan Plateau, a region that is particularly sensitive to climate change. However, patterns and trends of evapotranspiration and their relationship to drought stress on the Tibetan Plateau are complex and poorly understood. Here, we analyze spatiotemporal changes in evapotranspiration and effective moisture (defined as the ratio of actual evapotranspiration (ET a ) to reference crop evapotranspiration (ET o )) based on the modified Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ). Climate data from 80 meteorological stations on the Tibetan Plateau were compiled for the period 1981-2010 and future climate projections were generated by a regional climate model through the 21 st century. The results show regional trends towards decreasing ET o and statistically significant increases in ET a (p < 0.05) and effective moisture during the period 1981-2010 (p < 0.001). A transition from significant negative to positive ET o occurred in 1997. Additionally, a pronounced increase in effective moisture occurred during the period 1981-1997 because of significant decreased ET o before 1997. In the future, regional ET o and ET a are projected to increase, thus reducing drought stress, because of generally increased effective moisture. Future regional differences are most pronounced in terms of effective moisture, which shows notable increases in the northwestern plateau and decreases in the southeastern plateau. Moreover, the reduced magnitude of effective moisture is likely to intensify in the long term, due mainly to increased evaporative demand.

Detecting hydrological consistency between soil moisture and precipitation and changes of soil moisture in summer over the Tibetan Plateau

“…So, it is partly considered that in the west of the TP, the response of soil moisture to precipitation is relatively weaker because the rainfall amount is relatively smaller and the soil is drier than that in other regions of the TP. Furthermore, with the climate warming, evapotranspiration increases over the most part of the TP (Yang et al 2011;Yin et al 2013), which may be another factor that results in the soil moisture reduce over the west of the TP. Figure 5 shows annual changes of soil moisture anomaly and precipitation anomaly averaged on the TP.…”

“…Studies suggested that global warming have accelerated the hydrological cycle, especially on the TP (Held and Soden 2006;Yang et al 2011;Yin et al 2013Yin et al , 2016You et al 2016b). An analysis of seasonal variation in the water budget components demonstrated that the dominant water cycling arises from the processes of precipitation and evaporation that are typical in the eastern TP (Zhang et al 2003).…”

“…An analysis of seasonal variation in the water budget components demonstrated that the dominant water cycling arises from the processes of precipitation and evaporation that are typical in the eastern TP (Zhang et al 2003). Observed and simulated evaporation show overall increasing trends, leading to decreased discharge on major TP water resource areas (semi-humid and humid zones in the eastern and southern TP) (Yin et al 2013(Yin et al , 2016. Figure 7 shows partial correlations between trended and detrended soil moisture, precipitation and air temperature.…”

Trends and Changes in Recent and Future Penman-Monteith Potential Evapotranspiration in Benin (West Africa)

“…A global study finds large basins with positive (e.g., Niger), negative (e.g., Amazon) and non-significant (e.g., Congo) PET trends over 1958-2001 [57]. Both increasing and decreasing trends have been found in China [58,59]. Figure 3 shows annual PET estimated from the observed meteorology variables and those estimated from simulated variables by RCMs.…”

The spatiotemporal variation of reference evapotranspiration and the contribution of its climatic factors in the Loess Plateau, China

“…Furthermore, we also recommend that more attention should be paid to actual evapotranspiration (ET a ) (Vetter et al 2012), especially in response to climate change and human activities. For example, we can acquire the spatiotemporal ET a for a particular region or basin with ET a products (Cai et al 2014;Li et al 2014b;Xue et al 2013), or construct better ET a model for our own study area with more precise forcing datasets (Minderlein and Menzel 2015;Yin et al 2013;Zhang et al 2008b). Clearer knowledge of ET a will provide a better vehicle for a full understanding of reference evapotranspiration.…”