Simplified versions for the Penman evaporation equation using routine weather data

dc.contributor.author	Valiantzas, JD	en
dc.date.accessioned	2014-06-06T06:47:14Z
dc.date.available	2014-06-06T06:47:14Z
dc.date.issued	2006	en
dc.identifier.issn	00221694	en
dc.identifier.uri	http://dx.doi.org/10.1016/j.jhydrol.2006.06.012	en
dc.identifier.uri	http://62.217.125.90/xmlui/handle/123456789/3469
dc.subject	Evapotranspiration	en
dc.subject	Hydrologic models	en
dc.subject	Open water evaporation	en
dc.subject	Penman equation	en
dc.subject	Penman-Monteith	en
dc.subject	Water resources management	en
dc.subject.other	Atmospheric humidity	en
dc.subject.other	Evapotranspiration	en
dc.subject.other	Hydrology	en
dc.subject.other	Regression analysis	en
dc.subject.other	Solar radiation	en
dc.subject.other	Hydrologic models	en
dc.subject.other	Open water evaporation	en
dc.subject.other	Penman equation	en
dc.subject.other	Penman-Monteith equation	en
dc.subject.other	Water resources management	en
dc.subject.other	Evaporation	en
dc.subject.other	Atmospheric humidity	en
dc.subject.other	Evaporation	en
dc.subject.other	Evapotranspiration	en
dc.subject.other	Hydrology	en
dc.subject.other	Regression analysis	en
dc.subject.other	Solar radiation	en
dc.subject.other	air temperature	en
dc.subject.other	climate conditions	en
dc.subject.other	data set	en
dc.subject.other	evaporation	en
dc.subject.other	global climate	en
dc.subject.other	Penman-Monteith equation	en
dc.subject.other	relative humidity	en
dc.subject.other	solar radiation	en
dc.subject.other	weather station	en
dc.subject.other	wind velocity	en
dc.subject.other	Pereira	en
dc.title	Simplified versions for the Penman evaporation equation using routine weather data	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.jhydrol.2006.06.012	en
heal.publicationDate	2006	en
heal.abstract	At standard weather stations the routine weather records usually available are air temperature, T (°C), solar radiation RS (MJ/m2/d), relative humidity, RH (%), and wind velocity, u (m/s). A simple algebraic formula, equivalent in accuracy to the Penman equation is derived for computing evaporation from readily available measured data. The derivation of the formula is based on simplifications made to the ""standardized"" form of the Penman equation. The two components of the standard Penman equation (radiation and aerodynamic) were computed indirectly from the available routine weather data using the standardized calculation procedure recommended by Shuttleworth [Shuttleworth, W.J., 1993. In: Maidment, D.R. (Ed.), Evaporation, McGraw-Hill, New York, pp. 4.1-4.53 (Chapter 4)] and Allen et al. [Allen, R.G., Pereira, L.S., Raes, D., Smith, M., 1998. Crop evapotranspiration: guidelines for computing crop water requirements. FAO Irrigation and Drainage Paper, 56, Rome, 300 pp]. In addition, another, more simplified formula, easy to use for routine hydrologic applications, is also developed. On the other hand, at many places reliable wind speed data are rarely available. For such cases, an expression, which does not require wind speed data, is proposed. The simplified formula for the Penman equation proposed to estimate potential evaporation from open-water without recourse to wind data is EPEN ≈ 0.047 RS sqrt(T + 9.5) - 2.4 (RS / RA)2 + 0.09 (T + 20) (1 - RH / 100) where RA (MJ/m2/d) is the extraterrestrial radiation. A simplified expression for the calculation of RA is also given. The simplicity of the formulas is demonstrated in a computational example applied for monthly climatic data. The performance of the new derived formulas was tested under various climatic conditions using a global climatic data set including monthly data as well as daily data obtained from a weather station. The new open water evaporation formulas were also adapted for calculating reference crop evapotranspiration. © 2006 Elsevier B.V. All rights reserved.	en
heal.journalName	Journal of Hydrology	en
dc.identifier.issue	3-4	en
dc.identifier.volume	331	en
dc.identifier.doi	10.1016/j.jhydrol.2006.06.012	en
dc.identifier.spage	690	en
dc.identifier.epage	702	en