A Cold Frontal Life Cycle Climatology and Front–Cyclone Relationships Over the North Atlantic and Europe

Abstract

Atmospheric fronts and cyclones play an important role in day-to-day weather variability, especially in the mid-latitudes and during the winter season. Severe rainfall and windstorm events are often associated with the passage of a front or a cyclone. While there are many studies of individual fronts and climatologies of instantaneous fronts, there is no climatological study considering the whole frontal life cycle over time. Therefore, we use a front and cyclone tracking algorithm, together with a widely used front detection method, to detect and track cold fronts and cyclones over the North Atlantic and Europe in the extended winter season (October–March) in the ERA5 reanalysis data set. This enables a climatological study providing statistics of the frontal life cycle based on thousands of fronts. Several life cycle characteristics and frontal parameters are defined to investigate the frontal life cycle and the conditions and processes in the frontal region. Fronts are linked to their parent cyclone to study relationships between frontal and cyclonic properties. Cold fronts primarily develop over the Western North Atlantic and are found to decay at or soon after landfall on the European coast in most cases. Cold fronts tracked over the North Atlantic are found to last over 1 day longer and travel up to 1500 km farther on average than cold fronts tracked over the Mediterranean and over land. Cold frontal life cycle characteristics are strongly dependent on the North Atlantic Oscillation, with cold fronts appearing in a positive phase lasting longer and travelling faster and farther. Stronger cyclones are related to stronger frontal wind speeds at the surface as well as in the cold and warm sectors. The relationships between frontal and cyclonic properties are found to weaken over the course of their life cycle.