Spatiotemporal Variations of Reference Evapotranspiration and Its Determining Climatic Factors in the Taihang Mountains, China

Tingting Kang,Zeng Li,Yanchun Gao

doi:10.3390/w13213145

Abstract

Reference evapotranspiration (ETo) is an effective measure of atmospheric water demand of the land surface. In-depth investigations of the relationship between ETo and primary climatic factors can facilitate the adaptable agriculture and optimize water management, especially in the ecologically fragile Taihang Mountains (THM). This work assessed the spatiotemporal dynamics of ETo and its driving climatic factors from 1973 to 2016 in THM. Results showed: (1) Annual ETo slightly increased during 1973–2016; relative humidity (RH) decreased more slowly, the temperature increased more rapidly, and wind speed (WS) decreased more rapidly at higher elevation than those at lower elevations; (2) two breakpoints occurred in ETo series at 1990 and 1997, and an “evaporation paradox” existed in 1973–1990; (3) ETo at higher elevations had greater sensitivity to changes in RH and lower sensitivity to changes in Tmax and WS. Sensitivity of ETo to minimum air temperature (Tmin) at middle elevations was lowest among three elevation bands; (4) RH and sunshine duration (SD) were the dominant climatic factors of ETo for most periods and stations. This study helps us understand the impact of climate change on ETo in mountainous areas and confirms reference evapotranspiration in high-elevation areas is particularly sensitive to climate change.

Highlights

Against a backdrop of global change, climate change has become an indisputable fact, affecting the components of the eco-hydrological process to a great extent, especially evapotranspiration (ET) [1,2,3,4,5]
The mean annual ETo gradually increased from the western highland to the eastern plain across the whole Taihang Mountains (THM), ranging from 617.9 to 1081.1 mm
The lowest value was observed at Wutaishan station (715.1 mm), and the highest ETo occurred at Yuncheng station (1135.1 mm) (Table 1)

Summary

Introduction

Against a backdrop of global change, climate change has become an indisputable fact, affecting the components of the eco-hydrological process to a great extent, especially evapotranspiration (ET) [1,2,3,4,5]. Evapotranspiration links the water cycle (evaporation), energy cycle (latent heat flux), and carbon cycle (transpiration-photosynthesis trade-off) [6,7]. It is the predominant variable needed for agricultural water management (irrigation so that the amount of water applied is approximately equal to the atmospheric demand for evapotranspiration) [8,9]. Reference evapotranspiration (ETo) is a type of potential ET, expressed as “the rate of evapotranspiration from a hypothetical grass reference crop with an assumed crop height of 0.12 m, a fixed surface resistance of 70 s·m−1 and an albedo of 0.23” [8] It can reflect the evaporative power of the atmosphere and indicate the drywet conditions of a specific region differing from actual ET and potential ET.

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Discussion

Conclusion