Atmospheric Precipitable Water in Somma-Vesuvius Area During Extreme Weather Events from Ground-Based GPS Measurements
In this paper, we analyze the tropospheric delay observed on some ground-based CGPS stations in a dense small regional network and its time evolution during extreme weather conditions. In particular, we studied two severe weather events occurring in the Campanian Region (Italy) on October 12, 2012 and December 2, 2014, reaching 42 and 28 mm rainfall during about 1 h at Naples (MAFE) and Gragnano (GRAG) stations respectively. The main concern of this study is the retrieval of the precipitable water (PW) from co-located GPS and meteorological stations. We investigate the correlation between PW and rain amount at ground level. We analyse phase residuals for each visible GPS satellite using sky plots of the phase residuals along the GPS satellites tracks, showing that the two phenomena are shown in the phase residual plots. Moreover, we compare PWdata retrieved from observed meteorological data and from models (GPT2 and ECMWF), evidencing that there is a need for co-located CGPS and weather stations to improve the assessment of water content in the troposphere.
Non-geodetic” approaches in the analysis of terrestrial CDGPS data for the retrieval of the atmospheric precipitable water at local scale during severe weather phenomena
Precipitable water (PW) derived from the CDGPS (Continuous Differential Global Positioning System) zenith tropospheric delay (ZTD) is evaluated through comparison of three procedures: using GPT (Global Pressure and Temperature) and GPT2 global models as well as observed data. The results show that the difference between PW retrieved from models (GPT and GPT2) and PW obtained by observed meteorological data, at least for sites and period observed in this paper, is also a function of the position of the station. The short period considered does not allow for any consideration of possible intra-annual or annual periodicity. The analysis of the residuals between observed PW and modeled PW shows a peak before the rain event.
Evaluation of the atmospheric precipitable water at local scale during extreme weather using groundbased CGPS measurements
Global Positioning System (GPS) has demonstrated its ability to monitor the atmospheric water vapor content with an accuracy comparable to other techniques and means of measurements (e.g. radio soundings, microwave radiometers), even with good time resolution and under all meteorological conditions. The nowadays extensive use of permanent GPS stations, operating for geodetic purposes, offers a tool for a dense and reliable remote sensing of atmospheric water vapor. Here the tropospheric delay observed on some continuous GPS (CGPS) stations of the Italian GPS network (RING) is analyzed and its time evolution is discussed. We focus mainly on the study of the wet component of the atmospheric delay of the GPS signals and the computation of the precipitable water by using co-located GPS and meteorological stations. The results are described and discussed in comparison with different meteorological observations collected during extreme weather conditions impacting the Campania region.