The effect of different evapotranspiration methods on portraying soil water dynamics and ET partitioning in a semi-arid environment in Northwest China

Abstract

Abstract. Different methods for assessing evapotranspiration (ET) can significantly affect the performance of land surface models in portraying soil water dynamics and ET partitioning. An accurate understanding of the impact a method has is crucial to determining the effectiveness of an irrigation scheme. Two ET methods are discussed: one is based on reference crop evapotranspiration (ET 0 ) theory, uses leaf area index (LAI) for partitioning into soil evaporation and transpiration, and is denoted as the ET ind method; the other is a one-step calculation of actual soil evaporation and potential transpiration by incorporating canopy minimum resistance and actual soil resistance into the Penman-Monteith model, and is denoted as the ET dir method. In this study, a soil water model, considering the coupled transfer of water, vapor, and heat in the soil, was used to investigate how different ET methods could affect the calculation of the soil water dynamics and ET partitioning in a crop field. Results indicate that for two different ET methods this model varied concerning the simulation of soil water content and crop evapotranspiration components, but the simulation of soil temperature agreed well with lysimeter observations, considering aerodynamic and surface resistance terms improved the ET dir method regarding simulating soil evaporation, especially after irrigation. Furthermore, the results of different crop growth scenarios indicate that the uncertainty in LAI played an important role in estimating the relative transpiration and evaporation fraction. The impact of maximum rooting depth and root growth rate on calculating ET components might increase in drying soil. The influence of maximum rooting depth was larger late in the growing season, while the influence of root growth rate dominated early in the growing season.

Modelling root water uptake under deficit irrigation and rewetting in Northwest China

“…(), who found that winter wheat had a similar root density at this stage for different treatments. According to the change of critical SWC in different soil layers, we suggest that SWC of a winter wheat field should not be lower than 60% of field capacity (Yu et al., ; Yu, Cai, Zheng, Li, & Wang, ). Otherwise, the water stress will have adverse effects on RWU and hinder the healthy growth of crops.…”

“…The actual ET was automatically measured by two large weighing lysimeters (New Huize measurement and control technology Co., Ltd, Xi'an, China), which are the same size as the plots. The range of the device was 0 to 6 t, and the measurement accuracy was less than 150 g (Yu et al., ). We randomly selected 10 plants every 7 to 10 d to measure crop height using a tapeline with accuracy of 1 mm.…”

“…Complex crop responses to water stress have continually been a research focus of deficit irrigation (Andarzian et al., ; Iqbal et al., ; Mkhabela & Bullock, ; Steduto, Hsiao, Raes, & Fereres, ; Toumi et al., ). Many studies have analyzed the relationships between crop growth, ET, and RWU (Goosheh, Pazira, Gholami, Andarzian, & Panahpour, ; Han et al., ; Jha et al., ), while others have studied crop growth and ET under deficit irrigation (Salemi et al., ; Yu, Zeng, Su, Cai, & Zheng, ). Andarzian et al.…”

Liquid‐Vapor‐Air Flow in the Frozen Soil

“…The water vapor flow, which has been proved to be of great importance in water and heat transfer of dry soils (Bittelli et al, ; Yu et al, ; Zeng, Su, et al, ; Zeng, Wan, et al, ), recently have been taken into account by land surface models (LSMs; Garcia Gonzalez et al, ). Similar to the drying soils, vapor flow also plays an important role in frozen soils.…”

Preface: Land Surface Processes and Interactions—From HCMM to Sentinel Missions and Beyond

“…Similar conclusions were also derived by the GEWEX radiative flux assessment, which attributes the patterns of disagreement among the flux products to ancillary data differences (e.g., atmospheric temperature-humidity, surface temperature, aerosols, etc.). The aforementioned discrepancy issues can be further exaggerated at the regional scale, where the appropriate land surface parameterization may differ dramatically over different biomes and climates [12][13][14]. The following papers in this special issue discussed some of these challenges.…”