Analytical Estimation of Modified Penman Equation Parameters
Publication: Journal of Irrigation and Drainage Engineering
Volume 123, Issue 4
Abstract
The mathematical expression of the modified Penman equation requires values for the adjustment factor C, the saturation vapor pressure and its slope with respect to air temperature, the extraterrestrial radiation, and the maximum sunshine duration, among others. The values of these parameters are measured, taken from tables, or estimated from analytical expressions. Using tables is cumbersome and introduces uncertainties in estimating the parameters. Various research works found in the literature refer to the analytical evaluation of these parameters, but the need to more accurately calculate them is essential since errors introduced in evapotranspiration estimates are sometimes quite significant. In this paper, mathematical expressions that describe the parameters used for the calculation of the Penman reference crop evapotranspiration are derived through a nonlinear regression procedure. Comparisons of these expressions to those found in the literature show that they undoubtedly give more reliable results.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
Allen, R. G., and Pruitt, W. O.(1991). “FAO-24 reference evapotranspiration factors.”J. Irrig. and Drain. Engrg., ASCE, 117(5), 758–773.
2.
Bosen, J. F.(1960). “A formula for approximation of saturation vapor pressure over water.”Monthly Weather Rev., 88(8), 275–276.
3.
Doorenbos, J., and Pruitt, W. O. (1977). “Crop water requirements.”FAO irrig. and drain. paper No. 24, 2nd Ed., Food and Agricultural Org. of UN, Rome, Italy.
4.
Draper, N. R., and Smith, H. (1981). Applied regression analysis. John Wiley & Sons Inc., New York, N.Y.
5.
Duffie, J. A., and Beckman, W. A. (1980). Solar engineering of thermal processes. John Wiley & Sons Inc., New York, N.Y.
6.
Evapotranspiration and Irrigation Water Requirements. (1990). M. E. Jensen, R. D. Burman, and R. G. Allen, eds., ASCE Manuals and Rep. on Engrg. Pract. No. 70, ASCE, New York, N.Y.
7.
Frevert, D. K., Hill, R. W., and Braaten, B. C.(1983). “Estimation of FAO evapotranspiration coefficients.”J. Irrig. and Drain. Engrg., ASCE, 109(2), 265–270.
8.
Goff, J. A., and Gratch, S.(1946). “Low pressure properties of water from −160 to 212°F.”Trans. Amer. Soc. Heating and Ventilation Engrg., 52, 95–129.
9.
Harrison, L. P. (1963). “Fundamental concepts and definitions relating to humidity.”Humidity and Moisture, Vol. 3, Wexler, ed., Reinhold Publishing Corp., New York, N.Y.
10.
List, R. J. (1984). Smithsonian meteorological tables, 6th Revised Ed., Smithsonian Institution, Washington, D.C.
11.
Murray, F. W.(1967). “On the computation of saturation vapor pressure.”J. Appl. Meteorology, 6, 203–204.
12.
Pruitt, W. O. (1973). “Factors affecting potential evapotranspiration.”Biological effects in the hydrological cycle. Proc., 3rd Int. Seminar for Hydrol. Professors, 82–102.
13.
Svehlik, Z. J. (1987). “Estimation of irrigation water requirements.”Irrigation development planning, J. R. Rydzewski, ed., John Wiley & Sons Ltd., Chichester, U.K.
14.
Wright, J. L.(1982). “New evapotranspiration crop coefficients.”J. Irrig. and Drain. Engrg., ASCE, 108(1), 57–74.
Information & Authors
Information
Published In
Journal of Irrigation and Drainage Engineering
Volume 123 • Issue 4 • July 1997
Pages: 253 - 256
Copyright
Copyright © 1997 American Society of Civil Engineers.
History
Published online: Jul 1, 1997
Published in print: Jul 1997
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.