Quasi-Linear Convective Systems and Derechos across Europe: Climatology, Accompanying Hazards, and Societal Impacts

Abstract

Abstract In this work, we use 8 years (2014–21) of Operational Programme for the Exchange of Weather Radar Information (OPERA) radar data, ESWD severe weather reports, and arrival time difference (ATD) lightning detection network (ATDnet) data to create a climatology of quasi-linear convective systems (QLCSs) across Europe. In the first step, 15-min radar scans were used to identify 1475 QLCS polygons. Severe weather reports, lightning data, and morphological properties were used to classify QLCSs according to their intensity into 1151 marginal (78.0%), 272 moderate (18.5%), and 52 derecho (3.5%) events. The manual evaluation led to the recognition of QLCS morphological and precipitation archetypes, areal extent, duration, speed, forward motion, width, length, accompanying hazards, injuries, and fatalities. Results indicate that QLCSs are the most frequent during summer in central Europe, while in southern Europe, their occurrence is extended to late autumn. A bow echo feature occurred in around 29% of QLCS cases, while a mesoscale convective vortex occurred in almost 9%. Among precipitation modes, trailing and embedded stratiform types accounted for around 50% of QLCSs. The most frequent hazard accompanying QLCSs was lightning (taking up on average 94.4% of the area impacted by QLCS), followed by severe wind gusts (7.9%), excessive precipitation (6.1%), large hail (2.9%), and tornadoes (0.5%). Derechos had the largest coverage of severe wind reports (49.8%), while back-building QLCSs were the most prone to excessive precipitation events (13.5%). QLCSs caused 104 fatalities and 886 injuries. Severe wind gusts were responsible for 73.6% of fatalities and 87.6% of injuries. Nearly half of all fatalities and injuries were associated with only the 10 most impactful QLCS events, mostly warm-season derechos. Significance Statement Each year, severe storms in the form of quasi-linear convective systems (QLCSs) lead to immense socioeconomic impacts across densely populated Europe. As indicated in our work, 10 derechos out of 1475 QLCS events were responsible for nearly half of all injuries and fatalities. Despite such importance, climatological aspects of QLCSs have been poorly understood across Europe. However, recent improvements in coverage and quality of radar data within the OPERA project opened an opportunity to perform a pan-European study of QLCSs. Thus, in our work, we use 8 years of OPERA, lightning, and severe weather reports data to construct a climatology of QLCSs, including derechos. We evaluate their spatiotemporal variability, life cycle, severity, archetypes, morphological features, accompanying hazards, and social aspects.

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