On the wind-induced transport of scent in the snow: a numerical study to improve the rescue of avalanche victims.

The aim of this work is that of improve the understanding of main processes influencing the detection of avalanche victims by rescue dogs. Currently, there is no available physical description of the phenomenon of scent emission, transport and detection by the dog in literature. This study aims at filling this gap using a numerical model that is able to represent the problem of scent transport in the snowpack. A work of bibliographic research has been carried out in order to provide a complete physical description of the problem. The phenomenon that could affect more the scent transport is found out to be that of \textit{wind-pumping}, that is the wind-induced enhancement of the chemical species transport in the snowpack. Wind-pumping effects have been taken into account using the Darcy's law for air flow in porous media and the advection-dispersion equation for chemical species transport in porous media. A numerical model has been implemented using the \textit{COMSOL Multiphysics} software, which allows for numerical implementation and resolution with finite element methods. The snowpack has been treated as a porous medium, so that the Darcy's law and the advection-dispersion equation have been numerically solved inside the snowpack. Then, the model has been used to analyse how the scent transport is influenced by the modification of some environmental parameters like the snowpack density, wind speed, and the stability of the atmospheric surface layer. The mean wind speed and surface layer stability are found out to be the most important parameters and their variation can increase the time required to detect the victim up to one hour. On the other hand the variation in the values of the snow density are found to cause a delay in the scent transport up to 10 minutes. Our work and the obtained results are expected to be useful in order to optimize the rescue operations using dogs and to provide to rescuers a more detailed understanding of this phenomenon.