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

Quasi-Linear Convective System (QLCS) is a type of convective mode characterized by a linear organization of convective cells known for generating severe weather at midlatitudes, including Europe. In this work, we created a radar-based climatology of QLCS in Europe using 8 years (2014–2021) of Operational Programme for the Exchange of Weather Radar Information (OPERA) radar data, lightning detection network (ATDnet) data, and severe weather reports (ESWD). First, 15-minute OPERA radar scans were examined, identifying 1475 QLCS cases. The manual evaluation of each QLCS allowed us to recognize their  features such as morphological and precipitation archetypes, areal extent, width, length, duration, speed, and forward motion. In the next step, 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. We found that QLCSs are the most common during summer in Central Europe, while in the southern part of Europe, their frequent occurrence is extended to late autumn. Our study reveals that the bow echo morphological archetype was present in around 29% of QLCS cases, and a mesoscale convective vortex developed in almost 9%. Among precipitation modes, around 50% of QLCS were organized into trailing and embedded stratiform types.  Using severe weather reports we found  that the most common QLCS-related threat 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%). Moreover, derechos had the most extensive coverage of severe wind gusts (49.8%), whereas back-building QLCSs were mainly associated with excessive precipitation events (13.5%). QLCSs caused 104 fatalities and 886 injuries. Ten of the most impactful events were responsible for nearly half of QLCS-related fatalities and injuries.