Validation of precipitable water vapour products using CyMETEO GNSS network in Cyprus

The Eastern Mediterranean region is one of the most prominent hot spots of climate change in the world and extreme weather and climatic phenomena in this region such as extreme precipitation events are expected to become more frequent and intense. Water Vapour is the most abundant of greenhouse gases and is a direct indicator of severe weather events such as heavy precipitation and floods as it can change rapidly. To improve nowcasting of local heavy rainfall and flash storm events we need Precipitable Water Vapour (PWV) data. PWV is the amount of water potentially available in the atmosphere for precipitation, vertically integrated. In Cyprus and globally PWV data are sparse and inhomogeneous. One technique to estimate PWV is by exploiting the propagation delay of the GNSS (Global Navigation Satellite System) signals. CyMETEO GNSS network installed in the frames of strategic infrastructure project “Cyprus GNSS Meteorology Enhancement” (CYGMEN) aims at developing a GNSS-based PWV monitoring system, that will be used to investigate extreme precipitation events, with the ultimate goal to improve short-range weather forecasting in Cyprus. To perform the GNSS-based PWV product evaluation of CyMETEO, we created a complete dataset of heavy precipitation events over Cyprus for the 12 CyMETEO stations from 2020 to 2024. The GNSS-PWV data were validated by utilizing existing independent datasets, such as the ERA5 Reanalysis, during selected extreme precipitation events. Additionally, the relationship between GNSS-PWV and precipitation during the selected heavy precipitation events over Cyprus were also investigated.