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Spatiotemporal variations of pan evaporation in China during 1960–2005: changing patterns and causes

Authors

  • Qiang Zhang,

    Corresponding author
    1. Department of Water Resources and Environment, Sun Yat-sen University, Guangzhou, China
    2. School of Earth Sciences and Engineering, Suzhou University, Anhui, China
    3. Key Laboratory of Water Cycle and Water Security in South China of Guangdong High Education Institute, Sun Yat-sen University, Guangzhou, China
    • Correspondence to: Q. Zhang, Department of Water Resources and Environment, Sun Yat-sen University, Guangzhou 510275, China. E-mail: zhangq68@mail.sysu.edu.cn

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  • Tianyao Qi,

    1. Department of Water Resources and Environment, Sun Yat-sen University, Guangzhou, China
    2. Key Laboratory of Water Cycle and Water Security in South China of Guangdong High Education Institute, Sun Yat-sen University, Guangzhou, China
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  • Jianfeng Li,

    1. Department of Geography and Resource Management, The Chinese University of Hong Kong, China
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  • Vijay P. Singh,

    1. Department of Biological & Agricultural Engineering, Texas A & M University, College Station, TX, USA
    2. Department of Civil and Environmental Engineering, Texas A & M University, College Station, TX, USA
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  • Zongzhi Wang

    1. Nanjing Hydraulic Research Institute, Nanjing, China
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ABSTRACT

Observed pan evaporation data from 588 stations covering the entire territory of China are analysed using the modified Mann–Kendall trend test method. Fuzzy C-Means clustering is conducted for regionalization. Sensitivity analysis is performed to identify the principal influencing factors. Results indicate that: (1) the entire country can be categorized into three parts, i.e. A: southern, central and southwestern China; B: northwestern China and C: strip zone extending from northeastern to southwestern China; (2) significant decreasing pan evaporation can be identified in southern, central, southwestern, eastern and northwestern China. Stations with significant increasing pan evaporation seem to be scattered sporadically across China. Besides, the strip zone extending in the NE-SW direction is dominated by significant and also nonsignificant increasing trends of pan evaporation and (3) sensitivity analysis indicates that relative humidity is the principal influencing factor for pan evaporation, especially in northwestern, northern and northeastern China. Generally, in northwestern, northern and northeastern China, relative humidity has an adverse relation with pan evaporation, implying pan evaporation paradox and also intensifying hydrological cycle in these regions. In southeastern China, particularly the middle and lower Yangtze River basin and the Pearl River basin, relations between pan evaporation and relative humidity are relatively complex, showing that other factors in addition to relative humidity can have impacts on pan evaporation changes, such as cloud coverage, temperature and aerosol concentration. Local features of aerodynamic and radiative drivers of the hydrological cycle and their regional responses to climate changes, and also different features of ground surface may play considerable roles in pan evaporation changes.

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