Satellite-Derived Spatiotemporal Variations in Evapotranspiration over Northeast China during 1982–2010

Lilin Zhang,Xuanyu Wang,Zhiqiang Wang,Xiaotong Zhang,Yunjun Yao,Jia Xu,Kun Jia,Xiaowei Chen,Yuhu Zhang

doi:10.3390/rs9111140

Abstract

Evapotranspiration (ET) is a critical process for the climate system and water cycles. However, the spatiotemporal variations in terrestrial ET over Northeast China over the past three decades calculated from sparse meteorological point-based data remain large uncertain. In this paper, a recently proposed modified satellite-based Priestley–Taylor (MS–PT) algorithm was applied to estimate ET of Northeast China during 1982–2010. Validation results show that the square of the correlation coefficients (R2) for the six flux tower sites varies from 0.55 to 0.88 (p < 0.01), and the mean root mean square error (RMSE) is 0.92 mm/d. The ET estimated by MS–PT has an annual mean of 441.14 ± 18 mm/year in Northeast China, with a decreasing trend from southeast coast to northwest inland. The ET also shows in both annual and seasonal linear trends over Northeast China during 1982–2010, although this trend seems to have ceased after 1998, which increased on average by 12.3 mm per decade pre-1998 (p < 0.1) and decreased with large interannual fluctuations post-1998. Importantly, our analysis on ET trends highlights a large difference from previous studies that the change of potential evapotranspiration (PET) plays a key role for the change of ET over Northeast China. Only in the western part of Northeast China does precipitation appear to be a major controlling influence on ET.

Highlights

Over the past three decades, global warming has influenced the climate condition and the hydrological cycle of Northeast China [1,2]
To evaluate the ability of the modified satellite-based Priestley–Taylor (MS–PT) algorithm to estimate ET over Northeast China, we have validated the MS–PT algorithm at daily timescales based on the eddy correlation (EC) observations
The results demonstrated that MS–PT algorithm has a good performance in estimating regional ET over Northeast China

Summary

Introduction

Over the past three decades, global warming has influenced the climate condition and the hydrological cycle of Northeast China [1,2]. Numerous studies have reported that significant changes in ET are influencing ecosystem processes, surface drought conditions, and the consequent local climate feedback over Northeast China [6,7,8,9,10,11]. Based on the meteorological measurements, the annual reference ET (ET0) of Northeast China has increased at a rate of 3.89 mm/decade during 1961–2007, with large interannual fluctuations [12]. Due to a lack of direct measurements, there are still large biases in estimating the actual ET for the detection of variations in water budget and surface drought in Northeast China. It is urgent to improve ET estimation and evaluate the long-term variation of ET for understanding the hydrologic changes and solving problems in water resource management

Objectives

Methods

Results

Discussion

Conclusion