Estimating potential evapotranspiration: the effect of random and systematic errors

Meyer, Steven J.; Hubbard, Kenneth G.; Wilhite, Donald A.

doi:10.1016/0168-1923(89)90032-4

Cited by 45 publications

(17 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Error ratios, defined as the magnitude of error divided by the standard deviation [42], were introduced so as to evaluate the model sensitivity to the errors in a and b. Systematic error ratios ranging from −1 to 1 with an increment of 0.1 were used to simulate both positive and negative bias in a and b, while random error ratios ranging from 0.1 to 1 with an increment of 0.1 were used to simulate only positive random errors because of symmetry in distribution.…”

Section: Sensitivity Testmentioning

confidence: 99%

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Zhao

Lüers

2017

Atmosphere

View full text Add to dashboard Cite

Estimation of evapotranspiration plays an important role in understanding the water cycle on the earth, especially the water budget in agricultural ecosystems. The parameterization approach of the Penman-Monteith-Katerji-Perrier (PM-KP) model, accounting for the influence of meteorological variables and aerodynamic resistance on surface resistance, was proposed in the literature, but it has not been applied to Asian croplands, and its error and sensitivity have not been reported yet. In this study, the estimation of evapotranspiration on half-hourly scale was carried out for two typical East Asian cropland research sites, and evaluated by using eddy-covariance measurements corrected with the energy-balance-closure concept. Sensitivity coefficients as well as systematic bias and random errors of the PM-KP approach were used to evaluate the model performance. Different distributions of the calibration coefficients between different crops were reported for the first time, indicating that the calibration of this model was more stable for the rice field than for the potato field. The commonly-used parameterization approach suggested by the Food and Agriculture Organization (FAO) was used as reference and was site-specifically optimized. The results suggest that the PM-KP approach would be a better alternative than the PM-FAO approach for estimating evapotranspiration for the flooded rice field, and an acceptable alternative for rain-fed croplands when the soil is well watered and the air is humid during the summer monsoon.

show abstract

Section: Sensitivity Testmentioning

confidence: 99%

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Zhao

Lüers

2017

Atmosphere

View full text Add to dashboard Cite

show abstract

“…We assumed that systematic errors in original climate observations at stations had been removed already. Uncertainties in variables PR, ET 0 and K c were assumed random, independent and close to a normal (Gaussian) distribution (Ahn, 1996;Xu et al, 2006a;Droogers and Allen, 2002;Meyer et al, 1989;Troutman, 1985).…”

Section: Sensitivity and Uncertainty Analysismentioning

confidence: 99%

Sensitivity and uncertainty in crop water footprint accounting: a case study for the Yellow River basin

Zhuo

Mekonnen²,

Hoekstra³

2014

Hydrol. Earth Syst. Sci.

139

View full text Add to dashboard Cite

Abstract. Water Footprint Assessment is a fast-growing field of research, but as yet little attention has been paid to the uncertainties involved. This study investigates the sensitivity of and uncertainty in crop water footprint (in m 3 t −1 ) estimates related to uncertainties in important input variables. The study focuses on the green (from rainfall) and blue (from irrigation) water footprint of producing maize, soybean, rice, and wheat at the scale of the Yellow River basin in the period 1996-2005. A grid-based daily water balance model at a 5 by 5 arcmin resolution was applied to compute green and blue water footprints of the four crops in the Yellow River basin in the period considered. The one-at-a-time method was carried out to analyse the sensitivity of the crop water footprint to fractional changes of seven individual input variables and parameters: precipitation (PR), reference evapotranspiration (ET 0 ), crop coefficient (K c ), crop calendar (planting date with constant growing degree days), soil water content at field capacity (S max ), yield response factor (K y ) and maximum yield (Y m ). Uncertainties in crop water footprint estimates related to uncertainties in four key input variables: PR, ET 0 , K c , and crop calendar were quantified through Monte Carlo simulations.The results show that the sensitivities and uncertainties differ across crop types. In general, the water footprint of crops is most sensitive to ET 0 and K c , followed by the crop calendar. Blue water footprints were more sensitive to input variability than green water footprints. The smaller the annual blue water footprint is, the higher its sensitivity to changes in PR, ET 0 , and K c . The uncertainties in the total water footprint of a crop due to combined uncertainties in climatic inputs (PR and ET 0 ) were about ±20 % (at 95 % confidence interval). The effect of uncertainties in ET 0 was dominant compared to that of PR. The uncertainties in the total water footprint of a crop as a result of combined key input uncertainties were on average ±30 % (at 95 % confidence level).

show abstract

“…Equation 3 is based on an empirical approach where the radiative term is increased by two quantities capable of taking into account both advective phenomena (through the air humidity expressed as a function of temperature) and vegetation described by the LAI (Davies and Allen 1973;Brutsaert 1982;Meyer et al 1989;Stannard 1993;Shuttleworth 1993;Hatfield and Allen 1996). LAI data was determined through satellite images according to the equation suggested by Nel and Wessman (1993):…”

Section: Conceptual Definition Of Droughtmentioning

confidence: 99%

Integrated Drought Watch System: A Case Study in Southern Italy

Mendicino

Versace

2006

Water Resour Manage

View full text Add to dashboard Cite

Drought is a natural hazard with varying patterns in space, time, and intensity. Because of the spatial and temporal variability and multiple impacts of drought, it is necessary to improve tools and data available for mapping and monitoring this phenomenon on all scales. Starting from some initiatives promoted by the European Community, an integrated drought watch system aimed at analysing and forecasting the effects produced by prolonged water deficit periods has been developed in southern Italy. Using GIS technologies integrated with tele-metering network, hydrological databases and distributed water balance models, it allows the analysis of different aspects of the wider drought phenomenon. Specifically, meteorological, agricultural and hydrological aspects have been together considered in a common framework according to the features required by Web-GIS applications with the aim of using Internet as a diffusion tool of the spatially distributed information managed by the system. In this paper, after a brief description of the drought watch system functionalities, the capability of detecting severe and prolonged water deficit periods have been verified in two regions in southern Italy during the last decade, considering meteorological and satellite indices together with the principal water balance components. The analysis carried out on the study area pointed out an extremely intense drought phenomenon during the period 1996-2002, characterised by a reduction in precipitation together with higher evapotranspiration values and, as a consequence, by a broad decrease in surface and groundwater runoff.

show abstract

Estimating potential evapotranspiration: the effect of random and systematic errors

Cited by 45 publications

References 10 publications

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Parameterization of Evapotranspiration Estimation for Two Typical East Asian Crops

Sensitivity and uncertainty in crop water footprint accounting: a case study for the Yellow River basin

Integrated Drought Watch System: A Case Study in Southern Italy

Contact Info

Product

Resources

About