摘要:

Catchments with a small elevation range and relatively long dry periods in high radiation conditions may be described as an array of vertical one-dimensional pathways for water and energy. Such a representation makes it possible for Soil-Vegetation-Atmosphere Transfer (SVAT) models to simulate mass exchange across the catchment. This note reports on a comparison of a Soil-Vegetation-Atmosphere Transfer model and a stochastic hydrological model. We have used a stochastically distributed one-dimensional SVAT model (SiSPAT), which transfers any runoff generated at a particular location instantaneously to the catchment outlet. The hydrological model used here is the quasi-distributed Variable Infiltration Capacity model of Woodet al.(1992). Our results indicate that the uncalibrated SiSPAT model does not yield better results than the uncalibrated VIC model. However, even the uncalibrated VIC model requires knowledge of the maximum and minimum observed storage capacity to derive soil water status. The results also show that a calibrated VIC model performs better than the uncalibrated SiSPAT, but that minimum storage calibrated against the observed runoff does not retain its physical significance, since it is larger than the mean storage capacity.

ISSN:0262-6667    

DOI:10.1080/02626669809492156

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

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 evapotranspiration 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 stationary-heterogeneous 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.

ISSN:0262-6667    

DOI:10.1080/02626669809492157

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The dynamics of soil moisture and temperature states are forced by land surface fluxes that form the coupling between the soil and the atmosphere. This two-way interaction between the soil and the atmosphere results in feedback mechanisms that affect the temporal patterns of variability of the system. To understand these characteristics of soil moisture and temperature variability, a one-dimensional coupled mixed-layer model of the land surface and the planetary boundary layer energy and humidity budgets is constructed. To allow integrations on the order of days, the model includes both the growth phase and the collapse phase of mixed layer evolution. The model includes the radiative effects due to the presence of clouds. Given the incoming shortwave radiation, lapse rates of temperature and humidity above the mixed layer and lateral windspeed, the model predicts all longwave radiative and turbulent surface heat fluxes. The model is shown to capture accurately observations taken during the FIFE field experiment. With this model, the impact of soil heterogeneity on the evolution of the surface and mixed-layer energy and humidity budgets is examined, using hydraulic properties from sand, loam and clay soils. It is assumed that the small correlation length scale of soil hydraulic properties and surface inhomogeneities are averaged out in the mixed layer. Relative to a uniform soil, heterogeneity increases the spatial mean latent heat flux for conductive soils and decreases it for unconductive soils, due to decreased and increased percolation respectively. Locally decreasing latent heat fluxes cause a warmer and drier mixed layer and through that an increase of the latent heat flux over other areas. This mixed-layer feedback reduces the impact of heterogeneous surface fluxes.

ISSN:0262-6667    

DOI:10.1080/02626669809492158

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492159

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492161

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492162

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492163

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492145

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor