3D vector approach to local thermally driven slope winds modeling

A vector model has been setup to evaluate wind velocity and direction for thermally driven slope winds. This model is based on an extension of the Prandtl model and uses the new GRASS 3D vector implementation as well as its connection to external DBMS. This model follows a previous raster approach for the implementation of a local metereological model based on the 3D raster GRASS capability. The new vector implementation allows the evaluation of temperature, wind velocity and direction on a set of irregular placed points, while the raster approach is constrained to use points on a regular grid. Moreover, all the attributes that are used as parameters in the model are managed through SQL statements, providing a standard approach to attributes' management and use in the model. A new algorithm has been developed to evaluate the normal direction through a point in the 3D space, since all the model parameters depend on the distance from the surface along the normal direction. this algorithm has been implemented in a GRASS module. A comparison between the vector and the raster approach, in terms of implementation and use, is presented. Finally a synthetic and a real simulation and a comparison with the raster model results are reported.