Estimates of Daily Evapotranspiration in the Source Region of the Yellow River Combining Visible/Near-Infrared and Microwave Remote Sensing

Rong Liu,Zuoliang Wang,Xin Wang,Yu Liu,Ming Zhang,Jun Wen

doi:10.3390/rs13010053

Abstract

The spatial variation of surface net radiation, soil heat flux, sensible heat flux, and latent heat flux at different times of the day over the northern Tibetan Plateau were estimated using the Surface Energy Balance System algorithm, data from the FY-2G geostationary meteorological satellite, and microwave data from the FY-3C polar-orbiting meteorological satellite. In addition, the evaporative fraction was analyzed, and the total evapotranspiration (ET) was obtained by the effective evaporative fraction to avoid the error from accumulation. The hourly change of latent heat flux presented a sound unimodal diurnal variation. The results showed the regional ET ranged between 2.0 and 4.0 mm over the Source Region of the Yellow River. The conditional expectations of surface energy components during the experimental period of the study area were statistically analyzed, and the correspondence between different surface temperatures and the effective energy distribution was examined. The effective energy distribution of the surface changed significantly with the increase in temperature; in particular, when the surface temperature exceeded 290 K, the effective energy was mainly used for surface ET. The aim of this study was to avoid the use of surface meteorological observations that are not readily available over large areas, and the findings lay a foundation for the commercialization of land surface evapotranspiration.

Highlights

The variation of regional evapotranspiration is of significance for the land surface process and the energy exchanges in the hydrosphere, atmosphere, and biosphere [1,2,3].Due to the development of observation methods and understanding of the turbulence process in the atmospheric boundary layer, the method of calculating land surface evapotranspiration has gradually developed from the traditional spot-measurements-based method to regional evapotranspiration estimation based on the technology of large-scale satellite remote sensing [4].Since the mid-1970s, numerous scholars have undertaken a large amount of research on the accuracy of evapotranspiration retrieved by remote sensing [5,6]
3 showsresults, the daily of the near-surface ellite remote algorithm and the estimated thevariation field observations were comenergy the Source Region of the Yellow River (SRYR) retrieved by satellite remote on 18 August
3 shows the sensing daily variation of the near-surface figure shows thethe hourly radiation, soil heatremote flux, sensible flux, and latent heat energy flux in SRYRnet retrieved by satellite sensingheat on August

Summary

Introduction

The variation of regional evapotranspiration is of significance for the land surface process and the energy exchanges in the hydrosphere, atmosphere, and biosphere [1,2,3].Due to the development of observation methods and understanding of the turbulence process in the atmospheric boundary layer, the method of calculating land surface evapotranspiration has gradually developed from the traditional spot-measurements-based method to regional evapotranspiration estimation based on the technology of large-scale satellite remote sensing [4].Since the mid-1970s, numerous scholars have undertaken a large amount of research on the accuracy of evapotranspiration retrieved by remote sensing [5,6]. The variation of regional evapotranspiration is of significance for the land surface process and the energy exchanges in the hydrosphere, atmosphere, and biosphere [1,2,3]. Due to the development of observation methods and understanding of the turbulence process in the atmospheric boundary layer, the method of calculating land surface evapotranspiration has gradually developed from the traditional spot-measurements-based method to regional evapotranspiration estimation based on the technology of large-scale satellite remote sensing [4]. Remote sensing evapotranspiration models can be roughly divided into three categories. First category is based on the Penman-Monteith algorithm with an improvement of its parameters, using remote sensing data and ground observation data to estimate the actual evapotranspiration [7]. The second type is a statistical empirical model, which attempts to establish a correlation between evapotranspiration and vegetation index (VI) or surface-air temperature difference [8,9], or derives the two-dimensional

Objectives

Results

Conclusion