# Global analysis of temporal clusters of storm surges

## TL;DR

This paper studies how often storm surges cluster in time globally, identifying regions with frequent events and showing that many locations don't follow expected statistical patterns.

## Contribution

The study introduces a global analysis of storm surge clustering dynamics and challenges the Poisson distribution assumption in frequency analysis.

## Key findings

- 92% of coastal locations show significant temporal clustering for 1-year return period storm surge events.
- Two distinct clustering regimes are identified: short (intra-annual) and long (inter-annual) timescales.
- Over 80% of stations analyzed do not follow a Poisson distribution for storm surge frequencies.

## Abstract

Temporal storm surge clustering refers to a series of events affecting the same region within a short period of time, which can strongly influence coastal flooding impacts and erosion. Here, we analyze global storm surge clustering from tide gauges and a state-of-the-art global model hindcast to identify geographical hotspots of extreme storm surge clusters and assess event frequencies. We study the spatial distribution as well as the contribution of different event intensities to clustering. On average, globally, 92% of coastal locations show significant temporal clustering for 1-year return period events, and 25% for 5-year return level events, although notable spatial differences exist. Our results reveal two distinct clustering regimes: (i) short timescale clustering, where events occur in rapid succession (intra-annual), and (ii) long timescales (inter-annual), providing varying recovery times between events. We also test the validity of assuming a Poisson distribution, commonly used in storm surge frequency analyses. Our results show that >80% of the stations analyzed do not follow a Poisson distribution, at least when including events that are not the most extreme but exceeded, for example, the 1-year return level. These findings offer insights into temporal clustering dynamics of storm surges and their implications for coastal hazard assessments.