Trends in reference evapotranspiration in the humid region of northeast India

Authors

  • Deepak Jhajharia,

    Corresponding author
    1. Department of Agricultural Engineering, North Eastern Regional Institute of Science and Technology, Nirjuli, Itanagar-791109, Arunachal Pradesh, India
    • Department of Agricultural Engineering, North Eastern Regional Institute of Science and Technology, Nirjuli, Itanagar-791109, Arunachal Pradesh, India.
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  • Yagob Dinpashoh,

    1. Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Iran
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  • Ercan Kahya,

    1. Civil Engineering Department, Istanbul Technical University, Istanbul, Turkey
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  • Vijay P. Singh,

    1. Department of Biological and Agricultural Engineering, Texas A & M University, 2117 TAMU, Scoates Hall, College Station, TX 77843-2117, USA
    2. Department of Civil and Environmental Engineering, Texas A & M University, 2117 TAMU, Scoates Hall, College Station, TX 77843-2117, USA
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  • Ahmad Fakheri-Fard

    1. Department of Water Engineering, Faculty of Agriculture, University of Tabriz, Iran
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Abstract

In the present study, the trends in the reference evapotranspiration (ETO) estimated through the Penman-Monteith method were investigated over the humid region of northeast (NE) India by using the Mann-Kendall (MK) test after removing the effect of significant lag-1 serial correlation from the time series of ETO by pre-whitening. During the last 22 years, ETO has been found to decrease significantly at annual and seasonal time scales for 6 sites in NE India and NE India as a whole. The seasonal decreases in ETO have, however, been more significant in the pre-monsoon season, indicating the presence of an element of a seasonal cycle. The decreases in ETO are mainly attributed to the net radiation and wind speed, which are also corroborated by the observed trends in these two parameters at almost all the times scales over most of the sites in NE India. The steady decrease in wind speed and decline in net radiation not only balanced the impact of the temperature increases on ETO, but may have actually caused the decreases in ETO over the humid region of northeast India. Copyright © 2011 John Wiley & Sons, Ltd.

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