Romain Herren: Caractérisation et tracking en continu des précipitations : analyse des pluies de 2006 sur l’Ouest de la Suisse.

Romain Herren
Supervisor: Prof. Michel Jaboyedoff
Experts: Dr. Richard Metzger, Pascal Horton

The purpose of this work is to develop a continuous rainfall tracking and characterisation method on the basis of radar reflectivity images. The aim is to detect rain from all intensities and origins (frontal, convective or orographic) that occur within one year in West Switzerland, captured by the radar of La Dôle, from the MeteoSwiss network. This original method is divided into three main stages, namely the detection of rain cells, their statistical analysis, which helps determine the characteristics of cells such as intensity, size, orientation or form, and tracking which allows analysis of the development paths and intensities. An analysis resulting from this method shows that the distribution of lengths of the major and minor axes is close to a lognormal distribution. The ellipticity factor is represented by a normal distribution, which tends to show that the cells, regardless of their origins or chosen threshold, are twice longer than wide. These results reinforces an ellipsoidal shape approach of the cell. The cells have an uniform orientation. The tracking, in addition to providing the path orientation and direction, can follow the evolution of the intensity and size of cells. These statistics can be used to power precipitation prediction tool or a synthetic rain generator. The method gives satisfaction, offers many opportunities for improvement and promises great potential for development.