Nonparametric trend analysis of reference evapotranspiration for Khyber Pakhtunkhwa, Pakistan Online publication date: Wed, 14-Mar-2018
by Sajid Gul; Ijaz Hussain; Muhammad Yousaf Shad; Muhammad Faisal; Alaa Mohamd Shoukry; Shahzada Adnan
International Journal of Global Warming (IJGW), Vol. 14, No. 3, 2018
Abstract: Reference evapotranspiration (ETo) is a key element of the hydrological cycle that integrates atmosphere demand and surface environment conditions. In this study, we aimed to determine the trend of ETo using nonparametric methods - Mann-Kendall and Sen's slope estimator, whereas ETo is estimated using globally accepted Food and Agriculture Organization (FAO) Penman-Montieth FAO-56 (PM) method. We used ten years data (2000-2009) of 11 weather stations located in Khyber Pakhtunkhwa Province, Pakistan. We identified a decreasing trend in ETo rate has been recorded mostly in winter, pre-monsoon and spring with an upward trend during autumn and red-summer. Further, the statistical analysis shows a significant decreasing trend in ETo during winter. In summary, we provide a systematic approach that may be used in agro meteorological modelling and irrigation development.
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