Storm types and antecedent conditions during local and regional floods in the United States
Abstract
Both local and regional floods with potentially widespread impacts result from a combination of precipitation-triggering storms with certain antecedent conditions. But do these flood generation mechanisms and their interplay differ for local and regional events? Here, we investigate this question by assessing differences in the compounding drivers of local and regional floods in the United States. To do so, we develop two new classification schemes, one for storm types and another one for antecedent conditions.
We find that the dominant storm type triggering floods in the United States is frontal events, in particular those related to mesoscale convective systems. We also show that the importance of different storm types varies by season. Specifically, frontal mesoscale convective systems are most important in summer, non-frontal and extratropical-cyclone related storms in winter and spring, and tropical cyclones in fall. Our comparison of the drivers of local and regional events shows that local and regional floods are clearly distinct in terms of antecedent conditions. Regional events are mostly related to wet antecedent conditions in some cases combined with snowmelt, while local events are more likely to develop under dry surface conditions and driven by precipitation. In contrast, the relative importance of different storm types only weakly differs between the two types of events. Over all regions and seasons, regional events are most often the result of a frontal storm combined with wet antecedent conditions. We conclude that jointly considering multiple flood drivers within a compound event framework is crucial to understand the differences in the drivers of local and regional floods. Consequently, regional flood risk and change assessments should account for the compounding nature of atmospheric and land-surface flood drivers.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMNH45A..04B