Comparison of evaporation from barley with Penman estimates

Grant, D.R.

doi:10.1016/0002-1571(75)90017-5

Cited by 32 publications

(13 citation statements)

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“…Grindley [1970] also recommended that under certain conditions of incomplete canopy cover the Penman estimates should be reduced by one third. This was applied only for barley for the initial 40-60 days of the season when incomplete cover was evident [Grant, 1975]. In the absence of any recommended reduction for senescence, the PG estimates were not corrected during the end of the season.…”

Section: Comparison Wlti-i the Pg Modelmentioning

confidence: 99%

“…This could in part explain the overestimation of the evapotranspiration illustrated so clearly in Figure 3; but there is also evidence to suggest that Penman's [1948] equation overestimates the potential evapotranspiration during the spring and summer months [Thom and Oliver, 1977;Morel and Wright, 1978]. Further, the largest overestimates tend to occur during the ripening or senescent stage when in the absence of a wet crop the transpiration efficiency of the crop is }, ....... v•ratlon during the flowering stage all come from the 1970 data were Grant [1975] has reported about 30% of incident radiation reaching the ground, which implies full cover did not occur in that year. The estimates for the tillering stage seem to give a much better fit, probably because they have been reduced by one third according to Grindley's [1970] growing season, the senescent stage and the stage of incomplete cover are parts of the growth process of every crop, and the lack of provisions for these conditions in the model is a deficiency which in part results in the poor performance.…”

Section: Comparison Wlti-i the Pg Modelmentioning

confidence: 99%

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Estimating Nonpotential Evapotranspiration by Means of the Equilibrium Evaporation Concept

Mawdsley¹,

Ali²

1985

Water Resources Research

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Equilibrium evaporation was first described by Slatyer and McIlroy (1961). Priestley and Taylor (1972) later developed an equation which used the concept to estimate potential evapotranspiration. Subsequently, their equation has been widely tested with some success. Both Priestley and Taylor and soon after Davies and Allen (1973) extended the concept still further to estimate nonpotential evapotranspiration. We have further modified and developed these ideas so that the model can be applied using only regularly recorded data. We fitted the model and then tested it using three data sets from the United Kingdom: one planted with barley, one with turf, and one with rye grass. The results demonstrate, as one might expect, that the model does not provide a full description of nonpotential evapotranspiration, but this does not mean that the model may not be useful in applied hydrology. To assess the model's potential in this respect we compared the results with those obtained from the Penman-Grindley model, a model widely applied in the United Kingdom at least. This comparison suggests that despite the model's deficiencies it should still prove useful in climates similar to the United Kingdom, and with further testing, in all climates. slope of the saturated vapor pressure versus temperature curve; 7 is the psychrometric constant; R, is the net radiation, G is the ground heat flux; e• is the vapor pressure in the air, normally at 2 m; %* is the saturated vapor pressure of the air at the temperature T• measured at the same point as the vapor pressure; r•v is the aerodynamic resistance for latent heat transfer; and cp is the specific heat at constant pressure of the air. This equation combines the energy budget with a mass transfer equation to eliminate the need for humidity and temperature data at two levels, but at some cost: the resulting estimate is only applicable when the evapotranspiration rate is independent of the moisture content of the soil, that is, when the soil is quite wet. Under conditions when a lack of soil moisture does cause a reduction in the evapotranspiration rate, the application of Penman's equation with measured net radiation estimates the potential evapotranspiration: an upper bound to the actual rate of evaporation. [Brutsaert, 1982] to be applicable under all soil moisture con-Ultll, Jl13, l lib ß blllllO•ll'l¾11,Jll[•,•l[11 •lUO•[l•Jll [{1,3 1[ 13 11•J•'lt 8•,•11•,•lally known) still assumes a one-dimensional flux of vapor, but otherwise it is applicable under all conditions. The modification introduced a new term, the stomatal resistance, a resistance which results from the movement of water vapor from the substomatal cavities to the surface of the leaf. The

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Section: Comparison Wlti-i the Pg Modelmentioning

confidence: 99%

Section: Comparison Wlti-i the Pg Modelmentioning

confidence: 99%

Estimating Nonpotential Evapotranspiration by Means of the Equilibrium Evaporation Concept

Mawdsley¹,

Ali²

1985

Water Resources Research

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“…Generally, soil moisture evaporation can be determined for most hydrologic studies by varying surface resistance with cumulative evaporation. Grant (1975) proposes calculating an integrated surface resistance, r s , for uniform vegetation cover which considers vegetative surface resistance and soil resistance in parallel. His equation is of the form:…”

Section: Soil Evaporation and R Smentioning

confidence: 99%

Evaporation and Transpiration

Rigon¹,

Bottazzi²,

Tubini³

et al. 1996

Hydrology Handbook

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“…A estimativa da resistência da cobertura vegetal pode ser feita a partir de medidas diretas da resistência estomática média, pelo uso de porâmetros de difusão, e do índice de área foliar da planta, estimado por amostragem. No entanto, esta é uma tarefa árdua e trabalhosa e, por esta razão, dentro dos limites dos erros experimentais, a resistência da cobertura vegetal pode ser determinada como resíduo da aplicação do modelo de Penman-Monteith, desde que se conheça a evapotranspiração, obtida pelo uso de lisímetros, ou pela razão de Bowen, e as variáveis climáticas envolvidas no processo (Monteith, 1980;Sharma, 1983;Monteith, 1985;Luchiari Jr. & Riha, 1991;Oke, 1992 Também com cevada, Grant (1975) Analisando a variação da rc em relação à radiação solar, Hatfield (1985) observou que a resistência da cobertura vegetal para trigo respondeu rapidamente a variações na incidência de radiação solar, diminuindo exponencialmente com o aumento da radiação solar global incidente. Para valores de radiação global entre 250 e 300 kJ m-2 h-1 , rc variou de 25 a 230 s m-1 .…”

Section: Definiçõesunclassified

“…Uma função relacionando a resistência da cobertura vegetal ao índice de área foliar e ao déficit de umidade no solo foi derivada por Grant (1975).…”

Section: Definiçõesunclassified

Estimativa da evapotranspiração de referencia pelo uso da termometria ao infravermelho

Maggiotto¹

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Comparison of evaporation from barley with Penman estimates

Cited by 32 publications

References 3 publications

Estimating Nonpotential Evapotranspiration by Means of the Equilibrium Evaporation Concept

Estimating Nonpotential Evapotranspiration by Means of the Equilibrium Evaporation Concept

Evaporation and Transpiration

Estimativa da evapotranspiração de referencia pelo uso da termometria ao infravermelho

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