From a set of initial parameters representative of the site conditions on which the model is implemented, a number of prognostic variables (32 in total) are calculated from the SVAT model including the surface energy fluxes (H, LE and ground heat flux) at the soil surface, and in, around and above the vegetation canopy, the flux of carbon dioxide between the atmosphere and the plants, the grid-cell scale integrated surface temperature (Ts) of the vegetation and soil mixture. SimSphere requires a number of parameters for its initialization (53 in total), divided into seven groups: time and location, vegetation, surface, hydrological, meteorological, soil and atmospheric. The model performs simulations over a 24-hour cycle, starting from a set of initial conditions given in the early morning (at 05:30 hours local time) and simulates the continuous evolving interaction between soil, plant and atmospheric layers. SimSphere has been developed to simulate the various physical processes that take place as a function of time in a column that extends from the root zone below the soil surface up to a level higher than the surface vegetation canopy. Simsphere applies to a point or, at least, a limited region as long as the atmospheric, surface slope and incident radiation are uniformly distributed over the domain. input parameters) are representative of the horizontal area to be simulated. Thus, it is conceivable that the horizontal scale of the model is defined by the degree to which the model's initial conditions (i.e. In the horizontal domain, the scale of the model implicitly represents a horizontal area of the Earth's surface of undefined size that can be considered to be composed of a mixture of bare soil and vegetation, in proportions (Fr) and (1-Fr) varying from 0 to 1.0, where Fr being the fractional vegetation cover per unit area. The SimSphere SVAT model is essentially a one-dimensional boundary layer model with a plant component ( Figure 1). The most recent version of the SVAT model is freely available from the Department of Meteorology of Pennsylvania State University, USA ( or ). An extensive mathematical account of the basis of the model has been provided previously by, whilst the model's bare soil component is described by, its vegetation component by, and its representation of plant hydraulics by. Further systematic description of this architecture and the model initialisation procedure can be found in as well as in the online e-learning site where the model is currently hosted ( ). The aim here is to provide a non-mathematical description, free of technical jargon, which allows the reader to understand the basic principles of the model architecture. This section provides a descriptive account of the SVAT model architecture, based on the most recent implementation by, termed “SimSphere”. "An overview of the use of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) Model for the study of land-atmosphere interactions." Sensors 9, no. Quoted from: Petropoulos, George, Toby N.
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