Past and Projected Weather Pattern Persistence with Associated Multi-Hazards in the British Isles

Paolo De Luca,Colin Harpham,Christian L E Franzke,John K Hillier,Gregor C Leckebusch,Robert L Wilby

doi:10.3390/atmos10100577

Abstract

Hazards such as heatwaves, droughts and floods are often associated with persistent weather patterns. Atmosphere-Ocean General Circulation Models (AOGCMs) are important tools for evaluating projected changes in extreme weather. Here, we demonstrate that 2-day weather pattern persistence, derived from the Lamb Weather Types (LWTs) objective scheme, is a useful concept for both investigating climate risks from multi-hazard events as well as for assessing AOGCM realism. This study evaluates the ability of a Coupled Model Intercomparison Project Phase 5 (CMIP5) multi-model sub-ensemble of 10 AOGCMs at reproducing seasonal LWTs persistence and frequencies over the British Isles (BI). Changes in persistence are investigated under two Representative Concentration Pathways (RCP8.5 and RCP4.5) up to 2100. The ensemble broadly replicates historical LWTs persistence observed in reanalyses (1971–2000). Future persistence and frequency of summer anticyclonic LWT are found to increase, implying heightened risk of drought and heatwaves. On the other hand, the cyclonic LWT decreases in autumn suggesting reduced likelihood of flooding and severe gales. During winter, AOGCMs point to increased risk of concurrent fluvial flooding-wind hazards by 2100, however, they also tend to over-estimate such risks when compared to reanalyses. In summer, the strength of the nocturnal Urban Heat Island (UHI) of London could intensify, enhancing the likelihood of combined heatwave-poor air quality events. Further research is needed to explore other multi-hazards in relation to changing weather pattern persistence and how best to communicate such threats to vulnerable communities.

Highlights

Persistent weather patterns can translate into hazards such as heatwaves, poor air quality, drought, wildfires and episodes of flooding [1,2,3,4], with significant socio-economic losses [5,6]
Overall, blocking episodes are projected to decrease for the British Isles (BI) in DJF and JJA by 2061–2090 (RCP8.5) [70]. We extend these analyses by assessing the ability of a Coupled Model Intercomparison Project Phase 5 (CMIP5) [71] multi-model sub-ensemble (MME) of 10 Atmosphere-Ocean General Circulation Models (AOGCMs) at reproducing historical seasonal persistence of daily Lamb Weather Types (LWTs) over the BI [33,34,35,36]
We investigate how persistence and seasonal frequencies are projected to change within the full 21st century under RCP8.5 and RCP4.5, with persistence assessed for both the MME mean (MMEM) and individual AOGCMs

Summary

Introduction

Persistent weather patterns can translate into hazards such as heatwaves, poor air quality, drought, wildfires and episodes of flooding [1,2,3,4], with significant socio-economic losses [5,6]. Examples of such impactful episodes include the 2003 and 2010 European summer heatwaves that led to more than. Summer 2013 in eastern China, was the hottest ever recorded in that region, with persistent and widespread heatwaves and droughts causing severe socio-economic impacts amounting to 59 billion RMB in losses [11]. Natural hazards can compound in various ways (i.e., occur simultaneously, as cascades or cumulatively) over a sufficiently long time-frame [22], and their combined socio-economic impacts can exceed what was originally planned for, putting societies and economies under stress [15]

Methods

Results

Conclusion