Meteorological OSSEs for New Zenith Total Delay Observations: Impact Assessment for the Hydroterra Geosynchronous Satellite on the October 2019 Genoa Event

Abstract

Along the Mediterranean coastlines, intense and localized rainfall events are responsible for numerous casualties and several million euros of damage every year. Numerical forecasts of such events are rarely skillful, because they lack information in their initial and boundary conditions at the relevant spatio-temporal scales, namely O(km) and O(h). In this context, the tropospheric delay observations (strongly related to the vertically integrated water vapor content) of the future geosynchronous Hydroterra satellite could provide valuable information at a high spatio-temporal resolution. In this work, Observing System Simulation Experiments (OSSEs) are performed to assess the impact of assimilating this new observation in a cloud-resolving meteorological model, at different grid spacing and temporal frequencies, and with respect to other existent observations. It is found that assimilating the Hydroterra observations at 2.5 km spacing every 3 or 6 h has the largest positive impact on the forecast of the event under study. In particular, a better spatial localization and extent of the heavy rainfall area is achieved and a realistic surface wind structure, which is a crucial element in the forecast of such heavy rainfall events, is modeled.

Using InSAR Data to Improve the Water Vapor Distribution Downstream of the Core of the South American Low‐Level Jet

“…Lagasio et al. (2020) evaluated the potential benefit of assimilating geosynchronous InSAR synthetic data to forecast a heavy rainfall event, concluding that observations at 2.5 km spacing every 3 or 6 hr had a larger positive impact on the forecast.…”

SWING, The Score-Weighted Improved NowcastinG Algorithm: Description and Application

“…These kinds of events are not rare in this part of Italy, which is very prone to flood and flash floods of such magnitude due to the peculiar geographical configuration. The particular morphology leads to the formation of meteorological patterns specific to the region, which are capable of producing rainfall of relatively short duration and extremely high intensity (up to an average of 200 mm in one hour and 500-600 mm in 12 h, [23]). In fact, heavy precipitation is triggered by the very steep topography of the coast: it occurs frequently that the monthly average rainfall falls in just a few hours and/or a significant fraction (up to 30-40%) of the yearly average falls in 1 day [24,25].…”

The predictive capacity of the high resolution weather research and forecasting model: a year-long verification over Italy

“…CIMA is also actively involved in research activities about the impacts that the assimilation of high resolution water vapor maps has on the forecast of heavy rains (Meroni et al 2020). These activities also contribute to the development of a future geosynchronous SAR (Synthetic Aperture Radar) satellite mission (Ruiz Rodon et al 2013;Monti Guarnieri and Rocca 2017;Monti Guarnieri et al 2018;Lagasio et al 2020), which would provide unprecedented observations of the water cycle on Earth. Starting from 2018 CIMA has provided the outputs of two WRF modelling setups to ARPA Liguria (the Regional Agency for Environmental Protection of Liguria) and to the Italian Civil Protection Department for operational purposes, in particular an open loop setup covering the entire country (see next section for the details), and a setup with DA covering the northern part of Italy (not shown).…”