Assessment and Inter-Comparison of Multi-Source High Spatial Resolution Evapotranspiration Products over Lancang–Mekong River Basin, Southeast Asia

Houbing Chen,Palingamoorthy Gnanamoorthy,Qinghai Song,Ganlin Feng,Chenna Sun,Lamin R Mansaray,Kuo Liao,Yaoliang Chen,Aoni Shi

doi:10.3390/rs14030479

Abstract

Evapotranspiration (ET) plays a crucial role in water balance within the global hydrological cycle. Timely assessment of ET products can provide the scientific basis for quantitative analysis of hydrological cycle processes and water resources assessment. In this paper, four high spatial resolution remote sensing ET products—the Moderate-resolution Imaging Spectroradiometer global terrestrial evapotranspiration product (MOD16), the ET product based on Penman–Monteith–Leuning equation version 2 (PML-V2), the ET product based on the Breathing Earth System Simulator (BESS) and the ET product of the Global LAnd Surface Satellite (GLASS)—were firstly assessed using the eddy covariance (EC) of different vegetation types in the Lancang–Mekong River Basin (LMRB). To fully assess the performances of these four products, spatiotemporal inter-comparisons and literature comparisons were also conducted across different climatic zones. The results are summarized as follows: (1) MOD16 does not perform well as compared to the other three products, with its Root Mean Square Error (RMSE) being higher than GLASS, PML-V2 and BESS, which are approximately 0.47 mm/8-day, 0.66 mm/8-day, and 0.90 mm/8-day, respectively; (2) the performance of each product varies across different vegetation types, and even within the same climate zone. PML-V2 performs best in evergreen broadleaf forests, BESS performs best in deciduous broadleaf forests and croplands, and GLASS performs best in shrubs, grasslands and mixed vegetation; (3) each product can well reflect the spatial difference brought by topography, climate and vegetation over the entire basin but all four ET products do not show either a consistent temporal trend or a uniform spatial distribution; (4) ET ranges of these four products over LMRB are consistent with previous literature in evergreen broadleaf forests, deciduous broadleaf forests, needleleaf forests and mixed forests in other regions with the same climate zones, but they show great differences in croplands, grasslands and shrubs. This study will contribute to improving our understanding of these four ET products in the different climatic zones and vegetation types over LMRB.

Highlights

Terrestrial evapotranspiration (ET) is an important biophysical process in the land–atmosphere system
The Root Mean Square Error (RMSE) of all four products are less than 8 mm and 31 mm at 8-day and monthly scales, respectively (Figure 2), implying that the RMSE of each product is approximately less than 1 mm per day
The main source of the differences between MOD16 and the other three products comes from regions with low observed ET (i.e.,

Summary

Introduction

Terrestrial evapotranspiration (ET) is an important biophysical process in the land–atmosphere system. As the second largest component of the global hydrological circle, it returns around 60–70% of precipitation to the atmosphere [1]. It is one of the most uncertain components in the global water cycle [2,3,4]. ET, though the two algorithms have been proposed for more than four decades [5,6,7,8,9,10]. Extensive studies have been conducted to improve the PM algorithm from different aspects, such as stomatal conductance [7], soil moisture [10], temperature difference between day and night [7,10,11], etc. To date, accurate estimation of actual ET at regional scales is still challenging [12]

Objectives

Methods

Results

Conclusion