A regional-scale land surface parameterization based on areally-averaged hydrological conservation equations

Abstract

In order to account for subgrid-scale spatial variability (heterogeneity) of land surface characteristics in regional-scale hydrological-atmospheric models, a land surface parameterization of areally-averaged sensible heat and évapotrans-piration fluxes which is based upon areally-averaged hydrological soil water flow and soil heat flow equations, was developed. This land surface parameterization is fully coupled in a two-way interaction with the atmospheric boundary layer and the regional atmospheric model's first layer. The Monin-Obukhov similarity theory which is utilized in modelling the atmospheric boundary layer, and the areallyaveraged hydrological conservation equations are strictly valid only over stationaryheterogeneous areas where the fluctuations of the hydrological and boundary layer state variable values, parameter values, and of boundary conditions have spatially invariant means, spatially invariant higher moments and spatially invariant probability distributions. Therefore, the coupled two-way interactive model was run first for the computation of land surface fluxes over stationary-heterogeneous land patches, each corresponding to a single soil texture-vegetation class. Then, utilizing a mosaic scheme, the land surface fluxes over a regional model grid cell were obtained by numerical probabilistic averaging. The application of the regional model with this land surface parameterization to California during April 1989 has produced promising results. Paramétrisation du territoire à l'échelle régionale basée sur les équations de conservation hydrologique Résumé Pour tenir compte de la variabilité des caractéristiques de surface d'un territoire à une échelle inférieure à celle du maillage du modèle régional couplant phénomènes hydrologiques et atmosphériques, nous avons développé une paramétrisation des moyennes surfaciques des flux de chaleur sensible et d'évapo-transpiration basée sur les équations des flux d'eau et de chaleur dans le sol. Cette paramétrisation de la surface du sol repose sur l'interaction avec la couche limite atmosphérique et la première couche du modèle atmosphérique régional. La théorie de Monin-Obukhov qui a été utilisée pour modéliser la couche limite atmosphérique et les équations de conservation hydrologiques moyennées spatialement ne sont strictement applicables que sur des aires hétérogènes stationnaires où les fluctuations des variables d'état hydrologiques et de celles de la couche limite, les paramètres et les conditions aux limites possèdent des moyennes, des moments et des distributions de probabilité spatialement invariants. Par conséquent, le modèle couplé a d'abord Open for discussion until 1 February 1999 Downloaded by [University of Utah] at 07:20 06 October 2014 612 M. L, Kavvas et al.été utilisé pour le calcul des flux sur des parcelles de terrain hétérogènes mais stationnaires correspondant à différentes classes de texture de la végétation. Les flux selon le maillage du modèle régional ont été obtenus en effectuant numériquement une moyenne probabiliste à part...

Model structure and uncertainty for stochastic non-point source modelling applications

“…This up-scaling also plays an important role in dealing with those parameters which also vary spatially (e.g. Chen et al 1994, Kavvas et al 1998. Model parameters are usually based on spatial variation of point-scale data (or parameters mapped to such data) obtained using GIS, remote sensing and other tools.…”

Spatiotemporal Patterns of Crop Irrigation Water Requirements in the Heihe River Basin, China

“…A range of climate and hydrological models, including the Soil and Water Assessment Tool (SWAT), the Global Hydrologic Evaluation Model (GHEM), the Regional Hydro-climate Model (Reg-HCM), the Rainfall-Runoff Modeling System (PRMS), and the Water Balance/Transport Model (WBM/WTM), have all been used to quantitatively estimate rainfall and runoff at different scales, including globally, nationally, and at the level of individual basins [24][25][26][27]. In contrast, research on water demand has mainly focuses on the usage of different sectors such as agricultural, urban domestic and ecological.…”

Application of WEHY-HCM for Modeling Interactive Atmospheric-Hydrologic Processes at Watershed Scale to a Sparsely Gauged Watershed

“…), but also atmospheric conditions (e.g., radiation, air temperature, humidity, wind speed, precipitation, etc.). Vegetation, soil characteristics, and atmospheric data are plugged into WEHY-HCM and the estimation of ET values is from the concept of atmospheric conditions and moisture availability in WEHY-HCM, as described in detail in previous works [48][49][50]. Although most precipitation occurs during the wet period (October-March), the main parameter values for the ET estimation are quite small during the wet period.…”