Time clustering of wave storms in the Mediterranean Sea

Giovanni Besio,Alessandro Romano,Lorenzo Mentaschi,Riccardo Briganti,Paolo De Girolamo

doi:10.5194/nhess-17-505-2017

Abstract

Abstract. In this contribution we identify storm time clustering in the Mediterranean Sea through a comprehensive analysis of the Allan factor. This parameter is evaluated from a long time series of wave height provided by oceanographic buoy measurements and hindcast reanalysis of the whole basin, spanning the period 1979–2014 and characterized by a horizontal resolution of about 0.1° in longitude and latitude and a temporal sampling of 1 h Mentaschi et al. (2015). The nature of the processes highlighted by the AF and the spatial distribution of the parameter are both investigated. Results reveal that the Allan factor follows different curves at two distinct timescales. The range of timescales between 12 h to 50 days is characterized by a departure from the Poisson distribution. For timescales above 50 days, a cyclic Poisson process is identified. The spatial distribution of the Allan factor reveals that the clustering at smaller timescales is present to the north-west of the Mediterranean, while seasonality is observed across the whole basin. This analysis is believed to be important for assessing the local increased flood and coastal erosion risks due to storm clustering.

Highlights

In recent years the occurrence of different coastal storms in a short time has been studied in the context of storm-driven erosion of beaches and dunes
It has been shown by different authors (Vousdoukas et al, 2012; Coco et al, 2014; Splinter et al, 2014; Karunarathna et al, 2014; Dissanayake et al, 2015) that storms occurring in quick succession may result in greater beach erosion than the cumulated erosion induced by single storms of far higher return periods
In micro-tidal environments, such as the Mediterranean Sea, wave storms are the principal driver of short term coastal erosion and flooding; it is important to understand the occurrence of clustering

Summary

Introduction

In recent years the occurrence of different coastal storms in a short time has been studied in the context of storm-driven erosion of beaches and dunes. It has been shown by different authors (Vousdoukas et al, 2012; Coco et al, 2014; Splinter et al, 2014; Karunarathna et al, 2014; Dissanayake et al, 2015) that storms occurring in quick succession may result in greater beach erosion than the cumulated erosion induced by single storms of far higher return periods. In micro-tidal environments, such as the Mediterranean Sea, wave storms are the principal driver of short term coastal erosion and flooding; it is important to understand the occurrence of clustering. Regional differences are significant. Sartini et al (2015a) linked the seasonality of wave storms to local features of atmospheric pressure over the Mediterranean basin, strongly suggesting that the local typical meteorological conditions determine different temporal regimes of storm waves

Objectives

Results

Conclusion