EMMA-Tracker v1.0: a mesoscale convective system tracker and 27-year European observational climatology

Abstract

Abstract. Investigating how mesoscale convective systems (MCSs) over Europe will change in a warming climate relies on robust projections from climate models. To confidently use these projections, researchers must first understand model capabilities and uncertainties through strict, process-based evaluation against past observations. However, a lack of suitable reference datasets currently hinders this evaluation. Existing observational trackers often use variables unavailable in European climate model ensemble output or group mesoscale convection together with co-occurring synoptic-scale fronts. Because climate models represent synoptic and mesoscale dynamics through fundamentally different physical pathways, accurately evaluating a model's convective performance requires a benchmark that strictly isolates mesoscale processes. To address this, we introduce the EMMA-Tracker (Evolution-based MCS Model Assessment), an algorithm purpose-built to evaluate models using only standard output variables. We apply this tracker to IMERG precipitation and ERA5-derived atmospheric instability to generate a 27-year (1998–2024) warm-season climatology – the longest reference dataset of European MCSs to date. Following the initial tracking, EMMA applies post-processing filters to retain only distinct MCSs, systems that maintain a clear shape and steady movement, remaining structurally distinct from any co-occurring synoptic triggers. Our results show that these distinct MCSs are the dominant driver of extreme hourly precipitation. Their contribution to hourly warm season precipitation systematically increases with hourly precipitation intensity, accounting for over 60 % of heavy precipitation (P99.9) across most of continental Europe and 80 % over parts of the Mediterranean. The EMMA-Tracker provides both an observational reference for climatological studies and a targeted, process-oriented benchmark for evaluating regional and convection-permitting climate models.