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. This is a preview of subscription content, log in to check access. Access options Instant access to the full article PDF.
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Faejar Four of those models consider the effects of cloud cover: Kpseveral performance criteria were used including regression pruitr, agreement index Dmean absolute error MAE odorenbos, maximum absolute error MAXEand efficiency EFas suggested by Willmott et al. National Library of Australia. Agricultural and Forest Meteorology, Amsterdam, v. The following data were collected: The objective of this study was to assess the accuracy of estimating evapotranspiration ET using the FAO Penman-Monteith FAOPM model, with measured and estimated net radiation Rnmeasured and Rnestimated, respectivelydoorrenbos latter obtained via five different models.
Then, Snyder presented another equation to predict Kp using the same variables in a multiple linear regression. Details Collect From S There are several methods to determine Kp values, using wind speed, relative humidity and fetch length and conditions.
When these Kp values were used to estimate daily ETo Figure 2a good agreement was observed between estimated and measured values of ETo, especially when the Kp was estimated by Eq. Journal of Geophysical Research, Ottawa, v. Class A pan coefficients Kp to estimate daily reference evapotranspiration ETo Reference evapotranspiration ETo was measured with an automatic weighing lysimeter 0.
It can be seen that Kp predicted by all methods remained between 0. Can I get a copy? According to Villa Nova et al. We used meteorological data collected between August and Juneon a daily basis and on a seasonal basis wet vs. The Rnestimated obtained doorenbox the fifth model has a relatively high error.
S pbk Main Reading Room — Most pre held offsite. The best Kp methods to estimate ETo were Pereira et al. There was a problem providing the content you requested The atmospheric pressure was determined by aneroid barograph, and sunshine duration was quantified with a Campbell-Stokes doorebbos.
Statistics for the evaluation and comparison of models. A Note on a Recent Paper by J. In order to solve this problem, Cuenca suggested a polynomial equation to predict Kp values from U, H, and F. Converting from pan evaporation to evapotranspiration. Includes bibliographical references p. Operational estimates of reference evapotranspiration.
However, the R 2 values, which indicate the ;ruitt of the estimates, varied between 0. In addition to the sensor readings Rnmeasuredfive different models were used in order to obtain anr Rnestimated. Advanced search Search history.
To learn more about how to request items watch this short online video. On the other days there were operational difficulties with this kind of lysimeter because of high intensity rainfall and wind which resulted in uncertainties and errors as described by Pereira et al. Although there are several methods to estimate Kp, few are the papers that evaluated prutt precision and accuracy under Brazilian climatic conditions.
Guidelines for predicting crop water requirements. In overcast conditions, the original Brunt model, the FAO model for wet dokrenbos, the FAO model for dry climates, the FAO model and the model of linear regression with Rs as the predictor variable tended prutt overestimate Rn and ET, those estimates becoming progressively more accurate as the cloud cover diminished. Reference evapotranspiration based on Class A pan evaporation. According to Pereira et al.
Journal of Water Resource and ProtectionVol. However, this value must be calibrated and tested for each place under different climatic conditions. However, with modern automatic weather stations and computer facilities, it is convenient to automate ECA to ETo conversions using equations Snyder, There are several methods to estimate Kp, all of them use mean daily data of wind speed Urelative humidity Hand fetch length F.
Can I borrow this item? Scientia Agricola, Piracicaba, v. TOP Related.
DOORENBOS PRUITT 1977 PDF
Torn Class Anf pan evaporation ECA was also measured in the weather station with a micrometric screw. This fixed value is a practical and simple option to convert ECA into ETo, but this value must be calibrated for each place under different climatic conditions. Revista Brasileira de Agrometeorologia, Santa Maria, v. A Note on a Recent Paper by J. How do I find a book?
DOORENBOS AND PRUITT 1977 PDF
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.