We'd like to understand how you use our websites in order to improve them. Register your interest. Procedures are presented here to quantify these relationships, such as the calculation of net radiation, and to extend this approach to measurements made over alfalfa Medicago sativa , L. The latter was achieved by using a wind function that takes into account the height of the alfalfa and the use of mean rather than maximum relative humidity to calculate the correction factor used to take into account day and night weather conditions on calculated reference crop evapotranspiration. From data collected with an automated weather station near Broadwater, Nebraska, a much better agreement was obtained between these general procedures and a Penman equation with a locally derived- wind function. With greater utilization of low cost, automated weather stations for agricultural use, the procedures given for calculating reference crop evapotranspiration can easily be implemented in irrigation scheduling programs.
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Scientific Research An Academic Publisher. Doorenbos, J. We used meteorological data collected between August and June , on a daily basis and on a seasonal basis wet vs.
The following data were collected: temperature; relative humidity; global global solar radiation Rs ; wind speed and soil heat flux. The atmospheric pressure was determined by aneroid barograph, and sunshine duration was quantified with a Campbell-Stokes recorder. In addition to the sensor readings Rnmeasured , five different models were used in order to obtain the Rnestimated. The fifth was a linear regression model based on Rs. The Rnestimated obtained with the fifth model has a relatively high error.
The original Brunt model and FAO model for wet climates performed more poorly than did the other models in estimating the Rn and ET0. In overcast conditions, the original Brunt model, the FAO model for wet climates, the FAO model for dry climates, the FAO model and the model of linear regression with Rs as the predictor variable tended to overestimate Rn and ET, those estimates becoming progressively more accurate as the cloud cover diminished. Related Articles:.
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A quantitative approach to the Pruitt and Doorenbos version of the Penman equation