Probabilistic Dressing of a Storm Surge Prediction in the Adriatic Sea

R Mel,P Lionello

doi:10.1155/2016/3764519

Abstract

Providing a reliable, accurate, and fully informative storm surge forecast is of paramount importance for managing the hazards threatening coastal environments. Specifically, a reliable probabilistic forecast is crucial for the management of the movable barriers that are planned to become operational in 2018 for the protection of Venice and its lagoon. However, a probabilistic forecast requires multiple simulations and a considerable computational time, which makes it expensive in real-time applications. This paper describes the ensemble dressing method, a cheap operational flood prediction system that includes information about the uncertainty of the ensemble members by computing it directly from the meteorological input and the local spread distribution, without requiring multiple forecasts. Here, a sophisticated error distribution form is developed, which includes the superposition of the uncertainty caused by inaccuracies of the ensemble prediction system, which depends on surge level and lead time, and the uncertainty of the meteorological forcing, which is described using a combination of cross-basin pressure gradients. The ensemble dressing is validated over a 3-month-long period in the year 2010, during which an exceptional sequence of storm surges occurred. Results demonstrate that this computationally cheap method can provide an acceptably realistic estimate of the uncertainty.

Highlights

Increasing population, tourism pressure, sea level (SL) rise, and increased storminess [1] pose a significant hazard for many coastal areas of the world
If we look at the most important storm surges, there are little differences between the ensemble members and observed sea residual (SR), in particular for small lead times, where the majority of the ensembles capture the peaks and the majority of the observations lay inside the ensemble forecast distribution; this suggests that the ensemble prediction system (EPS) probabilistic forecast is reliable
A fully informative and accurate storm surge forecast is of paramount importance for an effective warning of the population in Venice and in the other islands of the lagoon, reducing damage produced by sea hazards

Summary

Introduction

Increasing population, tourism pressure, sea level (SL) rise, and increased storminess [1] pose a significant hazard for many coastal areas of the world. The generation of extreme coastal SLs and wind-waves produces overtopping of flood defenses and constitutes a significant threat to life and property, becoming a hazardous threat for coastal communities. Providing a fully informative forecast of storm surge and of associated flooding is of paramount importance for a wide range of problems related to coastal environments protection, receiving increasing attention from both the research and the operational communities. Venice Lagoon, Italy, which is the subject of the current study, is located at the shore of the Northern Adriatic Sea. Floods, which are locally called “acqua alta” (meaning “high water”), are a recurrent threat for this unique city, damaging monuments and buildings, frequently disrupting everyday life and affecting the local economy

Methods

Results

Conclusion