Evaluation and calibration of temperature, radiation, and mass transfer based equations for estimating evapotranspiration in sub-humid climatic conditions based on standardized Penman Monteith model
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Date
2016-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present study was conducted to evaluate and calibrate various temperature-, radiation-, and mass transfer- based equations on daily, weekly and monthly basis in sub-humid climatic conditions of Udham Singh Nagar, Tehri-Garhwal and Hazaribagh district based on standardized Penman Monteith (FAO56-PM) model with specific objectives as, to evaluate performance of various temperature, radiation, and mass transfer based ET0 equations in comparison to FAO56-PM model; to calibrate all considered ET0 equations in comparison to FAO56-PM model; to evaluate performance of all calibrated equations in terms of statistical indices; and to compare performance of original and calibrated equations graphically. In this study, individual years were classified into 52 Standard Meteorological Weeks (SMWs) in tune with CWS-1format suggested by the Indian Meteorological Department, Pune which were later grouped to get 12 months (January-December), whereas, all 52 SMWs were clubbed to get complete year. The Microsoft TM Excel (R) was used as computing tool for conducting analysis and draw fruitful inferences from them. Prior to analysis, quality control of daily weather dataset was ensured by detecting missing data and outliers.
The results revealed that on daily, weekly and monthly basis, almost all calibrated ET0 equations performed better at study area and extended better results in comparison to their original versions. Further, it was found that, all calibrated ET0 equations performed well at Udham Singh Nagar, Tehri-Garhwal and Hazaribagh districts on daily, weekly and monthly basis; calibrated Hargreaves M1 ET0 equation was found best at all three districts on daily, weekly and monthly basis, whereas, among radiation-based ET0 equations, calibrated Valiantzas equation performed best at all three districts at all timescales. The calibrated Trabert equation was found best at on daily and weekly basis at all districts, and it performed best at Udham Singh Nagar and Hazaribagh district on monthly basis, whereas, calibrated Rohwer equation performed well at Tehri-Garhwal district on monthly basis. Among calibrated temperature-based ET0 equations, calibrated Romanenko equation was found worst at Udham Singh Nagar and Hazaribagh districts on daily basis, whereas, calibrated Schendel equation was found worst at Tehri-Garhwal district on daily basis; calibrated Romanenko equation was found worst at all sub-humid districts on weekly and monthly basis. Among calibrated radiation-based ET0 equations, performance of calibrated Caprio equation was found worst at all three districts, whereas, calibrated BrockampWenner equation performed worst at all three districts at all timescales.
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