GNSS contribution to monitor severe rainfalls: an innovative procedure for wide and orographically complex area with existing infrastructures

The paper presents an innovative methodology for monitoring the content of Precipitable Water Vapour (PWV) in atmosphere for wide and orographically complex area. The water vapour content is strictly related to the occurrence of rains, hence the knowledge of PWV can be useful to interpret and monitor severe meteorological events. An automatic procedure has been conceived for producing 2D PWV maps with high spatial and temporal resolution starting from Zenith Tropospheric Delay (ZTD) estimations, obtained from GNSS Permanent Stations (PSs) network compensation, and from Pressure (P) and Temperature (T) observations, all collected by existing infrastructures. In the present work both a 1D approach to analyse ZTD and PWV time series and a 2D approach to localize severe meteorological events in time and space are presented. The procedure is then applied to a wide and orographically complex area, to study two severe meteorological events occurred in Genoa with reliable results. The introduction of the Heterogeneity Index (HI), accounting the spatial variability of PWV, allows to individuate the correct timing and location of severe meteorological events.