Daily synoptic conditions associated with occurrences of compound events in estuaries along North Atlantic coastlines

Abstract

Coastal compound flooding events occur when extreme events of rainfall, river discharge and sea level coincide and collectively increase water surface elevation, exacerbating flooding. The meteorological conditions that generate these events are usually low-pressure systems that generate high winds and intense rainfall. In this study, we identify the types of synoptic atmospheric conditions that are typically associated with coastal compound events using a weathertype approach, for the North Atlantic coastlines (encompassing northwest Europe and the east coast of the United States). Compound events are identified along the estuaries of the study region from 1980 to 2014 based on an impact function defined by water surface elevation that resulted from the combination of river discharge and sea level. We find that compound events are more frequent along European as opposed to U.S. coastlines. In both cases, they are associated with a few dominant weather patterns. European hotspots of compound events are concentrated in the west coast of United Kingdom, the northwest coast of the Iberian Peninsula and around the Strait of Gibraltar.These areas share the same weather patterns which represent the main pathways of storms that cross the North Atlantic Ocean. In the case of U.S. locations, the areas with highest number of compound events are located mainly in the Gulf of Mexico and along Mexico and along the mid-eastern U.S. coastlines. In these areas, compound events are produced by transitional weather patterns, which describe storms that travel northward parallel to the coastline. Splitting the occurrence of compound events in the corresponding weather types discriminates the interannual variability based on the relationship with dominant climate indices in the North Atlantic Ocean.

Historic Spatial Patterns of Storm-Driven Compound Events in UK Estuaries

“…Catchments respond quickly to rainfall and peak river discharges are likely to occur on the same day as extreme skew surges (Svensson and Jones 2004). Fewer annual mean compound events were identified on the east coast of Britain, which has previously been identified due to East coast surge and precipitation events being driven by different storm patterns (Svensson and Jones 2002;Zong and Tooley 2003;Camus et al 2022). Calculating annual mean compound events is a valuable and practical metric as this can identify regions where there is a higher potential for compound flooding events as they have already occurred.…”

The influence of future weather pattern changes and projected sea-level rise on coastal flood impacts around the UK

“…Targeted model development and a greater focus on early warning systems could be a beneficial adaptation measure. Specific weather types have been linked to high impact fluvial flooding (Pope et al 2022) and compound flooding in estuaries along North Atlantic coastlines (Camus et al 2022). Extreme sea levels are the result of the interaction between the local time-mean sea level, the tides, the storm surge and sea-surface waves, the latter of which are a direct consequence of cyclonic systems that vary in size, speed and trajectory.…”

On the potential use of weather types to describe the interannual variability of annual maximum discharge across the conterminous United States

“…Based on this brief review, WTs can provide useful information to understand the synoptic drivers of climate variables like precipitation and temperature. Given that these two variables are the fundamental drivers of flooding through their connection to various contributing factors such as antecedent wetness (Kim et al, 2019; Wasko & Sharma, 2017), snowmelt (Li et al, 2019; McCabe & Clark, 2005) and evapotranspiration (Rossi et al, 2016) as well as surface runoff, one research question that has received limited attention in the literature is the suitability of WTs in describing the changes in flooding by modulating precipitation and temperature (e.g., Armon et al, 2018; Camus et al, 2022; Gilabert & Llasat, 2018; Knighton et al, 2019). In the United States, Knighton et al (2019) identified teleconnections between synoptic‐scale climate variables and precipitation and discharge extreme events over the eastern United States, suggesting that geopotential height and integrated vapour transport are key variables for regional patterns of extremes.…”

“…In the United States, Knighton et al (2019) identified teleconnections between synoptic-scale climate variables and precipitation and discharge extreme events over the eastern United States, suggesting that geopotential height and integrated vapour transport are key variables for regional patterns of extremes. Camus et al (2022) characterized 49 daily WTs in the eastern United States and identified a few dominant patterns associated with coastal compound flood events that occurred along the coast lines in the Gulf of Mexico and the U.S. East Coast.…”