SPRAY is a three dimensional model designed to simulate the airborne pollutant dispersion, able to take into account the spatial and temporal inhomogeneities of both the mean flow and turbulence. Concentration fields generated by point, areal or volume sources can be simulated by the model. The trajectory of the airborne pollutant is simulated through virtual particles: the mean motion is defined by the local wind and the dispersion is determined solving the Langevin stochastic differential equations for the velocity fluctuations, reproducing the statistical characteristics of the turbulent flow. Different portions of the emitted plumes can therefore experience different atmospheric conditions, allowing realistic reproductions of complex phenomena, such as low wind-speed conditions, strong temperature inversions, flow over topography, landuse and terrain variability. ISAC-Torino has a long-term collaboration with Arianet srl in Spray development: Spray is now a commercial model licensed by Arianet. Spray can be driven by a diagnostic mass-consistent model (SWIFT, developed at Aria Technologies, Paris) and by the atmospheric model RAMS (in the modelling suite RMS developed at ISAC-Torino).

Simulation of the dispersion of airborne pollutants through the stochastic motion of virtual particles in the turbulent atmospheric flow in complex topography, from the local scale (1 to 5 km) to the mesoscale (100 km).

Silvia Trini Castelli
bibliographic references: 

Tinarelli G., Anfossi D., Bider M., Ferrero E. and Trini Castelli S., 2000. A new high performance version of the Lagrangian particle dispersion model SPRAY, some case studies. Air Pollution Modelling and its Application XIII, Gryning S.E.and Batchvarova E. Eds., Plenum Press, New York, 23, 499-506. ISBN: 0-306-46188-9

Tinarelli G., Anfossi D., Brusasca G., Ferrero E., Giostra U., Morselli M.G., Moussafir J., Tampieri F., Trombetti F., 1994. Lagrangian particle simulation of tracer dispersion in the lee of a schematic two-dimensional hill. Journal of Applied Meteorology, 33, N. 6, 744-756.

Anfossi D., Ferrero E., Brusasca G., Marzorati A., Tinarelli G., 1993. A simple way of computing buoyant plume rise in Lagrangian stocastic dispersion models. Atmospheric Environment 27A, 1443-1451.

Tinarelli G., Giostra U., Ferrero E., Tampieri F., Anfossi D., Brusasca G., Trombetti F., 1992. SPRAY, a 3-D particle model for complex terrain dispersion. Proc. of 10th Symposium on Turbulence and Diffusion, American Meteorological Society, Portland, Oregon (USA), 29-Sept. - 2 Oct, P2.9, 147-150.

Brusasca G., Tinarelli G., Anfossi D. 1992. Particle model simulation of diffusion in low windspeed stable conditions. Atmospheric Environment 26, 707-723.