Description of the LSPM-SVAT scheme

The Land Surface Process Model (LSPM) has been developed by our groups (Turin University, Italy, and Institute of Atmospheric Physics of Beijing, China) in the frame of the World Laboratory Project Land 2 (Cassardo et al., 1995), and tested in Ruti et al., (1997) and in Cassardo et al., (1998). LSPM is a typical SVAT scheme developed to be used both as a “stand alone” model (in this case, a set of specific routines for the calculation of the input data is provided) and as the surface boundary subroutine of an atmospheric circulation model (in this case, all input data are taken by the atmospheric model itself).
In this work LSPM is used in its stand-alone version, so the input data required are: air temperature, atmospheric pressure, specific or relative humidity, solar incoming radiation or cloudiness, horizontal wind speed components, rate of precipitation.
The schematic spatial structure of LSPM includes three main zones: the atmospheric layer above the vegetation (extending from a reference height to the vegetation canopy level), the vegetation layer (extending downward to the soil), and the soil layer. The hierarchy of the model allows a separation among soil, canopy and atmospheric layers. In the atmospheric layer, all output variables are calculated as weighted averages between atmospheric and canopy components. The canopy is considered as an uniform layer (big-leaf) characterised by the following parameters: vegetation cover, height, leaf area index (LAI), albedo, minimum stomatal resistance, leaf dimension, emissivity and root depth. Soil temperature and moisture are calculated using multi-layer schemes whose main parameters are: thermal conductivity, hydraulic conductivity, soil porosity, permanent wilting point, dry volumetric heat capacity, soil surface albedo and emissivity. The user can select a variable number of soil layers. Each flux is partitioned according to the vegetation and snow fractional covers. The model includes two subroutines for the long-wave and short-wave incoming radiation calculation (if not any observed radiation is available, the cloud coverage data is needed). The turbulent heat, water vapour and momentum fluxes are calculated by using the “analogue electric” scheme, in which the flux is expressed as a ratio between a generalised gradient (of temperature or moisture) and “resistances”. LSPM can provide the values of each component of thermal and hydrological budgets in the soil, of the water balance in the planetary boundary layer and atmospheric turbulent fluxes.
The reader can refer to the previously quoted papers and to Loglisci et al., (2001) for a full description of the model and parameterisations used.