Quantifying the relationship between flood and wind damage over North-West Europe, in a present and future climate

Strong winds and extremes in precipitation are capable of producing devastating socio-economic impacts across Europe. Although it is well known that individually these drivers cause billions of Euros of damage, their combined impacts are less well understood. Previous work has typically either focused on daily or seasonal timescales, demonstrating that compound wind and precipitation events are commonly associated with passing cyclones or particularly wet and windy years respectively. This study systematically investigates the relationships between national wind and flood damage metrics at all timescales ranging from daily to seasonal during the winter season. This work is completed using high resolution meteorological reanalysis and river flow datasets to explore the historical period (1980-present). As well as this, data from the UKCP18 climate projections at 2.2km and 12km resolution is used to understand historical sampling uncertainty, and the possible impacts of future climate change.

The correlation between national aggregate wind gusts and precipitation peaks at ~10 days; whereas, the correlation between national aggregate wind gusts and river flows peaks at ~3 weeks. When using more impact focussed metrics of compound wind and flood events, such as storm severity and flooding indices, the strongest correlations are seen at seasonal timescales. Results show the historical correlation between wind and flood damage becomes weaker as the definition of the metrics become more impact focussed, and this is true across all timescales from daily to seasonal. This change in relationship is of key importance to the insurance industry who require actionable information based on both the meteorological hazards and on the exposure of their portfolios. The work is designed to support climate analytics for financial institutions, as part of the UK Centre for Greening Finance and Investments (UKCGFI). Results incorporating the impacts of climate change on compound wind and flood events will also be discussed.