Tropospheric Delay in the Neapolitan and Vesuvius Areas (Italy) by Means of a Dense GPS Array: A Contribution for Weather Forecasting and Climate Monitoring

Abstract

Studying the spatiotemporal distribution and motion of water vapour (WV), the most variable greenhouse gas in the troposphere, is pivotal, not only for meteorology and climatology, but for geodesy, too. In fact, WV variability degrades, in an unpredictable way, almost all geodetic observation based on the propagation of electromagnetic signal through the atmosphere. We use data collected on a dense GPS network, designed for the purposes of monitoring the active Neapolitan (Italy) volcanoes, to retrieve the tropospheric delay parameters and precipitable water vapour (PWV). This study has two main targets: (a) the analysis of long datasets (11 years) to extract trends of climatological meaning for the region; (b) studying the main features of the time evolution of the PWV during heavy raining events to gain knowledge on the preparatory stages of highly impacting thunderstorms. For the latter target, both differential and precise point positioning (PPP) techniques are used, and the results are compared and critically discussed. An increasing trend, amounting to about 2 mm/decades, has been recognized in the PWV time series, which is in agreement with the results achieved in previous studies for the Mediterranean area. A clear topographic effect is detected for the Vesuvius volcano sector of the network and a linear relationship between PWV and altitude is quantitatively assessed. This signature must be taken into account in any modelling for the atmospheric correction of geodetic and remote-sensing data (e.g., InSAR). Characteristic temporal evolutions were recognized in the PWV in the targeted thunderstorms (which occurred in 2019 and 2020), i.e., a sharp increase a few hours before the main rain event, followed by a rapid decrease when the thunderstorm vanished. Accounting for such a peculiar trend in the PWV could be useful for setting up possible early warning systems for those areas prone to flash flooding, thus potentially providing a tool for disaster risk reduction.

A 1D Bayesian inversion of microwave radiances using several radiative properties of solid hydrometeors

“…The distributions of weights of the cloud and/or precipitation profiles are displayed using violin plot diagrams (Barton et al, 2021; Riccardi et al, 2021; Thrun et al, 2020) as shown in Figure 4. Thanks to their representation of the probability density for each value of the distribution, these diagrams have the advantage of being able to represent multimodal distributions, unlike box plot diagrams.…”

Comprehensive Study on the Tropospheric Wet Delay and Horizontal Gradients during a Severe Weather Event

“…Extreme weather phenomena, such as heavy precipitation, typhoons, or storms [11], have been thoroughly assessed before using the horizontal tropospheric gradients, and it was generally found that the tropospheric parameters can represent the patterns followed by extreme weather phenomena. The effect of topography on water vapor distribution has been recently studied [12]. Water vapor variation was found to be associated with convective rainfall through an index derived from the tropospheric gradients [13], suggesting that the GPS-derived indices of water vapor inhomogeneity reflect local variation in water vapor associated with atmospheric convection.…”