Abstract
A two-layer model of soil hydrology is developed for applications where only limited computer time and complexity are allowed. Volumetric soil water is computed in a thin upper layer for use in calculation of surface evaporation. Storage of water is computed for an underlying deeper layer.
In an effort to identify the influence of significant asymmetric truncation errors in the two-layer model, this model is compared with the 100-level model of Boersma et al. (1983). Comparisons are made for modelled soils with clay, loam and sand properties for various time dependencies of potential evaporation and precipitation. Truncation errors in the resulting two-layer model appear to be modest, at least compared to errors associated with difficulty in estimation of the hydraulic diffusivity and its strong dependence on soil water content.
Minimization of the influence of truncation errors requires: (1) choosing the upper layer to be sufficiently thin, (2) allowing the soil water gradient to control surface evaporation directly and (3) using suitable numerical implementation of the evaluation of internal soil water flux.
Résumé
On propose un modèle d'hydrologie du sol à deux couches, spécialement élaboré pour des applications où le temps de calcul et la complexité doivent être aussi réduits que possible. Le contenu en eau du sol dans la mince couche de surface est utilisé pour évaluer l'évaporation, tandis que la réserve en eau est calculée pour la couche profonde, beaucoup plus épaisse.
Afin d'estimer les erreurs de troncature et leurs effets dans le modèle à deux couches, des comparaisons sont faites avec le modèle à 100 niveaux de Boersma et al. (1983). Ces comparaisons portent sur des sols de natures variées (argile, terres végétales et sable) et incluent divers taux d'évaporation potentielle et de précipitation. Les effets des erreurs de troncature dans le modèle à 2 couches semblent peu importants par rapport à ceux associés à la mauvaise connaissance de la diffusivité hydraulique et de sa dépendance à l'égard du contenu en eau du sol.
La réduction de l'influence de ces erreurs de troncature nécessite: (1) le choix d'une couche supérieure suffisamment fine; (2) le contrôle direct de l'évaporation vers l'atmosphère à partir de la répartition verticale du contenu en eau du sol; (3) l'utilisation d'une procédure particulière pour évaluer le flux d'eau entre les deux couches du sol.
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References
Bailey, W. G. and Davies, J. A.: 1981, ‘The Effect of Uncertainty in Aerodynamic Resistance on Evaporation Estimates from the Combination Model’, Boundary-Layer Meteorol. 20, 187–199.
Barton, I. J.: 1979, ‘A Parameterization of the Evaporation from Non-saturated Surfaces’, J. Appl. Meteorol. 18, 43–47.
Black, T. A., Tanner, C. B., and Gardner, W. R.: 1970, ‘Evapotranspiration from a Snap Bean Crop’, Agron. J. 62, 66–69.
Boersma, L., Ungs, M. J., and McCoy, E. L.: 1983, Transfer Problems in Soils, Ag. Exp. St., Oregon State University, Corvallis, 97331, U.S.A.; see also: W. F. Ames (ed.), Proceedings IMACS World Congress on Systems Simulation and Scientific Computation. 8–13 August, 1982. Montreal, Canada. International Association for Mathematics and Computers in Simulation.
Budyko, M. I.: 1956, Teplovoi Balans Zemnoi Poverkhnosti, Gidrometeoizdat, Leningrad; Heat Balance of the Earth's Surface, translated by N. A. Stepanova, U.S. Weather Bureau, Washington, D.C., 1958.
Camillo, P., Guerney, R., and Schmugge, T. J.: 1983, ‘Soil and Atmosphere Boundary Layer Model for Evapotranspiration and Soil Moisture Studies’, Water Resources Res. 19, 371–380.
Campbell, G. S.: 1974, ‘A Simple Method for Determining Unsaturated Conductivity from Moisture Retention Data’, Soil Science 117, 311–314.
Clapp, R. B. and Hornberger, G. M.: 1978, ‘Empirical Equations for some Soil Hydraulic Properties’, Water Resources Res. 14, 601–604.
Davies, J. A. and Allen, C. D.: 1973, ‘Equilibrium, Potential and Actual Evaporation from Cropped Surfaces in Southern Ontario’, J. Appl. Meteorol. 12, 649–657.
Day, P. R. and Luthin, J. N.: 1956, ‘A Numerical Solution of the Differential Equation of Flow for a Vertical Drainage Problem’, Soil Sci. Soc. Am. Proc. 20, 443–447.
Deardorff, J. W.: 1977, ‘A Parameterization of Ground-Surface Moisture Content for Use in Atmospheric Prediction Models’, J. Appl. Meteorol. 16, 1182–1185.
Eagleson, P. S.: 1982, ‘Dynamic Hydro-Thermal Balances at Marcroscale’, 289–360. Proceedings of World Meteorological Organization, Presented at JSC Study Conference on Land Surface Processes in Atmospheric General Circulation Models. January 5–10, 1981.
Feddes, R. A., Bresler, E., and Neuman, S. P.: 1974, ‘Field Test of a Modified Numerical Model for Water Uptake by Root Systems’, Water Resources Res. 10, 1199–1206.
Gardner, W. R.: 1960, ‘Dynamic Aspects of Water Availability to Plants’, Soil Sci. 89, 63–73.
Gardner, W. R., Hillel, D., and Benyamini, Y.: 1970, ‘Post-Irrigation Movement of Soil Water, 2. Simultaneous Redistribution and Evaporation’, Water Resources Res. 6(4), 1148–1153.
Hanks, R. J. and Bowers, S. A.: 1962, ‘Numerical Solution of the Moisture flow Equation for Infiltration into Layered Soils’, Soil Sci. Soc. Am. Proc. 26, 530–534.
Hanks, R. J., Klute, A., and Bresler, E.: 1969, ‘A Numeric Method for Estimating Infiltration Redistribution, Drainage, and Evaporation of Water from Soil’, Water Resources Res. 5, 1064–1069.
Hillel, D.: 1980, Fundamentals of Soil Physics, Academic Press, 413 pp.
Jackson, R. D.: 1973, ‘Diurnal Changes in Soil Water Content during Drying’, Field Soil Water Regime 33, 37–55.
Jersey, Gilbert R.: 1982, ‘Incorporation of a Simple Evapotranspiration Parameterization in an Efficient Model of the Atmospheric Boundary Layer’, Masters thesis, Dept. of Meteorology, The Pennsylvania State University. University Park, PA.
Marsh, P., Rouse, W. R., and Woo, M.-K.: 1981, ‘Evaporation at a high Arctic Site’, J. Appl. Meteorol. 20, 713–716.
Marshall, T. J. and Holmes, J. W.: 1979, Soil Physics, Cambridge University Press, Cambridge, 345 pp.
McCumber, M. C. and Pielke, R. A.: 1981,‘Simulation at the Effects of Surface Fluxes of Heat and Moisture in a Mesoscale Numerical Model’, J. Geophys. Res. 86, 9929–9938.
Mukammal, E. I. and Neumann, H. H.: 1977, ‘Application of the Priestly-Taylor Evaporation Model to Assess the Influence of Soil Moisture on the Evaporation from a large Weighing Lysimeter and Class A Pan’, Boundary-Layer Meteorol. 12, 243–256.
Nimah, M. N. and Hanks, R. J.: 1973, ‘Model for Estimating Soil Water, Plant, and Atmospheric Interrelations: I. Description and Sensitivity’, Soil Sci. Soc. Amer. Proc. 37, 522–527.
Passioura, J. B. and Cowan, I. R.: 1968, ‘On Solving the Non-linear Diffusion Equation for the Radial Flow of Water to Roots’, Agric. Meteorol. 5, 129–134.
Rouse, W. R., Mills, P. F., and Stewart, R. B.: 1977, ‘Evaporation in High Latitudes’, Water Resources Res. 13(6), 909–914.
Seaton, K. A., Landsberg, J. J., and Segley, R. H.: 1977, ‘Transpiration and Leaf Water Potentials of Wheat in Relation to Changing Soil Water Potential’, Aust. J. Agric. Res. 28, 355–367.
Thornthwaite, C. W. and Mather, J. R.: 1955, ‘The Water Balance’, Publications in Climatology 8, 1, Laboratory of Climatology, Centerton, NJ, 86 pp.
Williams, R. J., Boersma, K., and van Ryswyk, A. L.: 1978, ‘Equilibrium and actual Evapotranspiration from a Very Dry Vegetated Surface’, J. Appl. Meteorol. 17, 1827–1832.
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Mahrt, L., Pan, H. A two-layer model of soil hydrology. Boundary-Layer Meteorol 29, 1–20 (1984). https://doi.org/10.1007/BF00119116
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DOI: https://doi.org/10.1007/BF00119116