Evaluation of the evaporative fraction for parameterization of the surface energy balance

Nichols, William; Cuenca, Richard H.

doi:10.1029/93wr01958

Cited by 113 publications

(70 citation statements)

References 20 publications

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“…Once the three components above are estimated, the latent heat flux is estimated as the remaining term using Equation 1. To extrapolate the instantaneous ET into daily values, the evaporative fraction Λ (defined as the ratio of latent heat flux to the net available energy at the surface) was used; experimental evidence indicates that the Λ has a constant value during cloud-free days (Nichols and Cuenca, 1993). The calculation of the ET a includes the transformation of the 24 h integrated net radiation (Rn 24 h ) from W·m -2 to mm per day using the surface temperature-dependent latent heat of vaporization as follows:…”

Section: Data and Image Processingmentioning

confidence: 99%

Remote Sensing Derived Crop Coefficient for Estimating Crop Water Requirements for Irrigated Sorghum in the Gezira Scheme, Sudan

Bashir

Hata²,

Tanakamaru³

et al. 2007

J ENV INFORM

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ABSTRACT. Improved management of crop water requires accurate scheduling of irrigation which, in turn, requires accurate calculation of actual daily evapotranspiration (ETa). This study was carried out to examine seasonal changes in crop coefficients and evapotranspiration values for sorghum irrigated in the Gezira scheme, with the use of remote sensing data and field measurements. Three methods, namely remote sensing-derived kc, Farbrother kc (experimental) and FAO kc, revealed that the crop coefficient for sorghum reached growing season peaks of approximately 1.15, 1.21, and 1.17, respectively, at the beginning of October. The crop coefficient, derived from remote sensing data, varied over the growing season from 0.62 in the initial growth stage, 1.15 in the mid-season stage to 0.58 at harvest. The total ETc over the growing season of irrigated sorghum estimated by remote sensing-derived kc, experimental kc and FAO kc was 674, 704, and 642 mm, respectively. The ETc by the three methods, combined with the Penman-Monteith reference ET0, was also compared with the actual ET measured by the water balance approach. Statistical analysis showed that the remote sensing-derived kc was superior to the others in all regression parameters. This study demonstrates that remote sensing data are a very useful tool for estimating water requirements for field crops, hence providing irrigation decision makers with information not available before.

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Section: Data and Image Processingmentioning

confidence: 99%

Remote Sensing Derived Crop Coefficient for Estimating Crop Water Requirements for Irrigated Sorghum in the Gezira Scheme, Sudan

Bashir

Hata²,

Tanakamaru³

et al. 2007

J ENV INFORM

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“…For the periods between data retrievals, f is estimated via interpolation. As a result, this approach is predicated on the assumption that f is self-preserving, i.e., that it is constant or nearly constant, and thus varies only slowly over time (Brutsaert and Sugita, 1992;Nichols and Cuenca, 1993;Crago, 1996). In order to conform to this assumption, the components of the radiation or energy budget are often selected as χ such that f is an analog of evaporative fraction.…”

Section: Introductionmentioning

confidence: 99%

Effect of the revisit interval and temporal upscaling methods on the accuracy of remotely sensed evapotranspiration estimates

Alfieri

Anderson

Kustas

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. Accurate spatially distributed estimates of actual evapotranspiration (ET) derived from remotely sensed data are critical to a broad range of practical and operational applications. However, due to lengthy return intervals and cloud cover, data acquisition is not continuous over time, particularly for satellite sensors operating at medium ( ∼ 100 m) or finer resolutions. To fill the data gaps between clear-sky data acquisitions, interpolation methods that take advantage of the relationship between ET and other environmental properties that can be continuously monitored are often used. This study sought to evaluate the accuracy of this approach, which is commonly referred to as temporal upscaling, as a function of satellite revisit interval. Using data collected at 20 Ameriflux sites distributed throughout the contiguous United States and representing four distinct land cover types (cropland, grassland, forest, and open-canopy) as a proxy for perfect retrievals on satellite overpass dates, this study assesses daily ET estimates derived using five different reference quantities (incident solar radiation, net radiation, available energy, reference ET, and equilibrium latent heat flux) and three different interpolation methods (linear, cubic spline, and Hermite spline). Not only did the analyses find that the temporal autocorrelation, i.e., persistence, of all of the reference quantities was short, it also found that those land cover types with the greatest ET exhibited the least persistence. This carries over to the error associated with both the various scaled quantities and flux estimates. In terms of both the root mean square error (RMSE) and mean absolute error (MAE), the errors increased rapidly with increasing return interval following a logarithmic relationship. Again, those land cover types with the greatest ET showed the largest errors. Moreover, using a threshold of 20 % relative error, this study indicates that a return interval of no more than 5 days is necessary for accurate daily ET estimates. It also found that the spline interpolation methods performed erratically for long return intervals and should be avoided.

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“…Because EF is a ratio of latent heat flux to the sum of latent heat flux and sensible heat flux, it is used to characterize the energy partition over land surfaces and has potential for inferring daily energy balance information based on midday measurement (Nichols and Cuenca, 1993). One of the perceived advantages of using EF is its apparent stability during daylight hours (Shuttleworth et al, 1989).…”

Section: Brebmentioning

confidence: 99%

“…Zhang and Lemeur (1995) found no correlation between the two parameters during the HAPEX-MOBILHY experiment in southwestern France. Nichols and Cuenca (1993) studied the relationships between EF and surface soil moisture, and between ET and soil moisture of the entire root zone, but identified no correlation. In our experiments, although a correlation was also difficult to identify, we were able to determine that EF increased with soil moisture.…”

Section: Effect Of Irrigation On Efmentioning

confidence: 99%

Measurement of evapotranspiration in a winter wheat field

Zhang

Liu

Shen

et al. 2002

Hydrological Processes

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Abstract:Daily evapotranspiration from a winter wheat field on the North China Plain measured by large-scale weighing lysimeter was linearly related to that measured by the Bowen ratio energy balance (BREB) technique. Soil evaporation averaged about 23Ð6% of evapotranspiration from the post-winter dormancy revival stage to the grain ripening stage in 1999. On clear days during winter dormancy, about half of the net radiation flux R n was used to warm soil. During the revival stage, conductive heat flux G also used most of the incoming R n , but the ratio of latent heat flux E to R n increased. During the stem-extension stage, E was about 50% of R n ; thereafter, E/R n increased continually, but G remained less than 10% of R n . During the ripening stage, E was almost 90% of R n . Evaporative fraction (EF) can be expressed as a function of plant status and atmospheric boundary layer conditions. The relationship between EF and available energy under moderate air temperature and vapour pressure deficit conditions was examined for five combinations of aerodynamic and canopy conductance. Although the theoretical relationship indicates that EF should be highly correlated to soil water content, the correlation has been difficult to identify under field conditions. However, we observed that there exists a threshold value of R n G, above which EF is less than 1Ð0, and that the threshold value is lower under soil-water deficit conditions than under abundant soil-water conditions.

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Evaluation of the evaporative fraction for parameterization of the surface energy balance

Cited by 113 publications

References 20 publications

Remote Sensing Derived Crop Coefficient for Estimating Crop Water Requirements for Irrigated Sorghum in the Gezira Scheme, Sudan

Remote Sensing Derived Crop Coefficient for Estimating Crop Water Requirements for Irrigated Sorghum in the Gezira Scheme, Sudan

Effect of the revisit interval and temporal upscaling methods on the accuracy of remotely sensed evapotranspiration estimates

Measurement of evapotranspiration in a winter wheat field

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