Reconstruction of tornado environments in Romania (1981-2020) using the ERA5 reanalysis

The general interest in tornado studies has been stimulated by scientific challenges, such as a better understanding of their genesis and development, and by applications and practical issues, such as forecast, building engineering, and risk analysis. This context justifies the interest in reconstructing tornado characteristics based on different approaches. The recently released ERA5 reanalysis data set at 31 km-horizontal resolution, and hourly temporal resolution holds significant potential for many climate applications. In this paper, the tornado environments in Romania between 1981-2020 are reconstructed using a series of thermodynamic and kinematic parameters (e.g., 0-1 km bulk wind shear, 0-6 km bulk wind shear, 0-500m mixed-layer CAPE, ML WMAX*SHEAR) calculated based on ERA5 data. A previous paper on the climatology of tornadoes in Romania showed that in the 1980s there was a minimum in the tornado activity (1 tornado report) followed by a period with a large number of reports (138 reports, approximately 4 tornadoes per year). The aim of the paper is twofold. First, we want to investigate the changes in the occurrence of tornado environments in Romania and thus understand if the minimum in tornado reporting in 1980 is due to tornadoes being ignored by the researchers and meteorologists (and reported as swerve wind events) or natural variability. Second, to study the spatial and temporal variability of the tornadoes in Romania in relation to large-scale patterns. The results show that the frequency of occurrence of tornado environments has increased in Romania since 1980, especially over southeastern Romania. This work has been financed within project „Dezvoltarea Centrului de Competență pentru Adaptarea Comunităților Locale la Schimbările Climatice prin parteneriate de tip public-privat în domeniul CDI” cod 3/16.11.2022 finanțat prin Planul Național de Redresare și Reziliență Apel nr. PNRR-III-C9-2022 – I5"