Trends in evapotranspiration and their responses to climate change and vegetation greening over the upper reaches of the Yellow River Basin

Shiqin Xu, Zhongbo Yu*, Chuanguo Yang, Xibin Ji, Ke Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

122 Scopus citations

Abstract

This study comprehensively analyzed long-term (1960–2014) variations of potential and actual evapotranspiration (ET) and quantified their inter-annual and seasonal sensitivity and attribution to climate and vegetation growth changes in the upper reaches of the Yellow River Basin (UYRB). Satellite-derived vegetation greenness and in situ measured hydrometeorological datasets were used. Average annual reference evapotranspiration (ET0) showed significant decreasing trend (p < 0.05) by 0.32 mm year−1 over the past 55 years. Results obtained from recovered stationary series and sensitivity analyses showed that reduction of wind speed was the major driving force for decreasing trends in annual and seasonal ET0. Water budget-derived actual evapotranspiration (ETa) increased dramatically during the study period, whereas potential evapotranspiration (ETp) calculated from Penman equation and pan evaporation (ETpan) decreased significantly, suggesting the existence of evaporation paradox over the UYRB. ETa and ETp or ETpan exhibited complementary behavior, while the complementary relationship was asymmetric. During the period 1982–2014, vegetation greening occurred in most areas (65.6%) of the UYRB and was mediated by elevation. Interestingly, non-uniform climate warming imposed opposite impacts on vegetation growth, namely inter-annual and seasonal NDVI was stimulated by daytime temperature but suppressed by nighttime temperature. Furthermore, the positive impacts imposed by daytime temperature on NDVI was much larger in spring than in autumn and summer. Large-scale coherent vegetation greening would be the primary factor affecting inter-annual ETa in comparison with climate factors. These results help in deep understanding the hydrological response to climate change in cold mountain regions.

Original languageEnglish (US)
Pages (from-to)118-129
Number of pages12
JournalAgricultural and Forest Meteorology
Volume263
DOIs
StatePublished - Dec 15 2018

Bibliographical note

Funding Information:
We thank the editor, the associate editor, and two anonymous reviewers for their helpful and constructive comments for improving the manuscript. This work was funded by the National Key R&D Program of China (Grant No. 2016YFC0402706 , 2016YFC0402710 ); National Natural Science Foundation of China (Grant No. 41271036 , 41323001 , 51539003 , 41471016 ); National Science Funds for Creative Research Groups of China (No. 51421006 ); the program of Dual Innovative Research Team in Jiangsu Province and the Special Fund of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering (Grant No. 20145027312 ); the Fundamental Research Funds for the Central Universities (Grant No. 2014B17014 ).

Publisher Copyright:
© 2018

Keywords

  • Asymmetric climate warming
  • Cold mountain region
  • Complimentary relationship
  • Evapotranspiration
  • Vegetation greening

ASJC Scopus subject areas

  • Forestry
  • Global and Planetary Change
  • Agronomy and Crop Science
  • Atmospheric Science

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