Incorporation of Net Radiation Model Considering Complex Terrain in Evapotranspiration Determination with Sentinel-2 Data

Linjiang Wang,Abdelrazek Elnashar,Zonghan Ma,Bingfang Wu,Xiaodong Niu,Nana Yan,Shirong Liu,Weiwei Zhu

doi:10.3390/rs14051191

Abstract

Evapotranspiration (ET) is the primary mechanism of water transformation between the land surface and atmosphere. Accurate ET estimation given complex terrain conditions is essential to guide water resource management in mountainous areas. This study is based on the ETWatch model driven by Sentinel-2 remote sensing data at a spatial resolution of 10 m incorporating a net radiation model considering the impact of a complex terrain. We tested our model with two years of data in two regions with a high relief near the Huairou (2020) and Baotianman (2019) weather stations. Regarding the validation results of the ET model, the coefficient of determination (R2) reached 0.84 in Huairou and 0.86 in Baotianman, while the root mean square error (RMSE) value reached 0.59 mm in Baotianman and 0.82 mm in Huairou. The validation results indicated that the model is applicable in regions with a complex terrain, and the ET results can capture topographic textures. In terms of the slope aspect, the ET value on south-facing slopes is higher than that on north-facing slopes in both study areas. Accurate ET monitoring in mountainous regions with a high relief yields a profound meaning in obtaining a better understanding of the characteristics of heat and water fluxes at different vegetation growth stages and underlying surface types, which can provide constructive suggestions for water management in mountainous areas.

Highlights

Introduction iationsEvapotranspiration (ET), mainly comprising plant transpiration and soil evaporation, is the essential pathway of water transformation between the land surface and atmosphere, linking changes in surface water, carbon cycling, and surface energy [1–3]
In the net radiation calculation process, this study focused on the influence of terrain factors on solar radiation and divided solar radiation into three parts: direct solar radiation, sky diffuse radiation, and reflected radiation in adjacent regions
The sky view factor is an important indicator reflecting the characteristics of the terrain, and the value spatial distribution of the slope and sky view factor in the two study areas

Summary

Introduction

Evapotranspiration (ET), mainly comprising plant transpiration and soil evaporation, is the essential pathway of water transformation between the land surface and atmosphere, linking changes in surface water, carbon cycling, and surface energy [1–3]. Factors such as meteorological, vegetation, and radiation conditions and soil moisture influence the ET process [4,5]. Air pressure and temperature and water vapor pressure tend to decrease with increasing elevation, wind speed, and precipitation [8–10]. Radiation conditions can vary considerably from slope to slope [11,12]. Sunny slopes tend to receive more solar

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Conclusion