Optimal Selection of Empirical Reference Evapotranspiration Method in 36 Different Agricultural Zones of China

Yong Yang,Chuntan Han,Zhangwen Liu,Rensheng Chen,Xiqiang Wang

doi:10.3390/agronomy12010031

Abstract

The Food and Agriculture Organization has proposed the current version of the Penman–Monteith method (FAO56-PM) as the standard for calculating reference evapotranspiration (ET0); however, high meteorological data requirements limit its application in many areas. There is thus an urgent need to identify the best alternative empirical method to accurately calculate ET0 in regions that lack sufficient meteorological data. In this study, three temperature-based methods and five radiation-based methods were evaluated using ET0 values generated using the FAO56-PM method in 36 agricultural zones in China based on meteorological data from 823 stations, measured between 2011 and 2020. The results showed that the optimal temperature-based method and radiation-based method differed for different agricultural zones, and no one temperature method or radiation method could be suitable for all agricultural zones. The eight empirical methods were regionally calibrated to improve the ET0 calculation accuracy in the different zones. The relationship between the optimal methods and climatic conditions showed that the most reliable empirical method could be selected according to the local annual mean temperature and aridity index. The results provide useful guidance for the selection of reliable empirical ET0 methods in agricultural zones outside China.

Highlights

Evapotranspiration (ET) is one of the most important components of the hydrological cycle, directing approximately 60% of the precipitated water on land back to the atmosphere [1]
The results obtained using the FAO56-PM method indicated that the area-averaged annual mean ET0 in China between 2011 and 2020 was approximately 893.0 mm
The zones with the highest ET0 values calculated using the FAO56-PM method were located on Hainan Island and its nearby areas (NT-HU-2 and MP-HU-1), whereas the lowest ET0 values were obtained from two zones in Northeast China (CT-HU-1 and MTHU-2) and one zone in Northern Xinjiang (MT-SA-3) (Figure 3a)

Summary

Introduction

Evapotranspiration (ET) is one of the most important components of the hydrological cycle, directing approximately 60% of the precipitated water on land back to the atmosphere [1]. Accurate estimations of actual evapotranspiration (ETa) are highly significant for many fields, such as agronomy, hydrology, climatology, meteorology, ecology, and environmental science [2]. Direct observations of ETa remain unavailable in many locations worldwide [3,4], and several methods have been proposed to estimate ETa in these areas [5]. The product of the reference crop evapotranspiration (ET0) and crop coefficient is a widely used method worldwide for estimating ETa [3,6,7,8], and it has been recommended by the Food and Agriculture Organization (FAO) [9] for computing crop water requirements. The temporal and spatial variations of ET0 have attracted extensive research attention with regard to climate change [12,13]

Objectives

Methods

Results

Discussion

Conclusion