Synoptic climatology of atmospheric fronts in the ERA5 output for Europe

This study extends our previous research focused on the climatology of atmospheric front occurrences over the European continent and their association with short-term, day-to-day variability in near-surface air temperature. The analysis conducted across different seasons and various European subregions has revealed that temperature responses during frontal passages display a high degree of spatial and temporal complexity. These findings imply the involvement of multiple atmospheric processes that interact in ways not yet fully understood, thereby indicating the need for further, more detailed investigation. One particularly noteworthy and counterintuitive observation pertains to the southern half of Europe, where several areas tend to experience a temperature decrease following the passage of a warm front during both the winter and summer seasons. This phenomenon contradicts the typical expectation of warming associated with warm fronts and highlights the importance of examining the broader dynamical context in which these events occur.

In the present contribution, we aim to deepen the understanding of the relationship between atmospheric fronts and short-term temperature variability by considering the broader framework of atmospheric circulation. To achieve this, we utilize an objective method to identify atmospheric fronts and extract the horizontal wind vector at the 850 hPa geopotential height level, which provides information on the local circulation conditions. Additionally, we characterize the synoptic-scale circulation using the Jenkinson–Collison classification system, which is applied to each time step and each grid point where a front is identified. This classification is derived from gridded ERA5 sea level pressure fields at instantaneous time steps.

Ultimately, our results will provide new insights into the mechanisms governing high-frequency temperature variability across Europe. Moreover, this study contributes to the development of methodological approaches by integrating two independent yet complementary frameworks for describing atmospheric circulation: the objective identification of fronts and the systematic classification of circulation types.