An updated climatology of atmospheric blocking in the eastern Atlantic-European region

Atmospheric blocking is an important aspect of weather in middle latitudes. Stationary, long-lasting weather patterns can lead to extreme conditions, such as very high temperatures or heavy rainfall. This study provides an updated climatology of blocking in the eastern Atlantic-European region, with the aid of a modified PV-theta wave-breaking index at the latitude of the climatological storm track. The seasonal and spatial variability of the blocking index, the blocking frequency, duration, and strength of blocking episodes are examined for the period 1979-2019 using ECMWF ERA5 datasets. The blocking index, a measure of possible reversals of potential temperature field, is characterized by a high day-to-day variability, especially in the vicinity of the Atlantic jet. Despite the different methodology, the higher spatial resolution and the most recent period covered by ERA5 data, no considerable differences in blocking frequencies were found with previous analyses. The longest events coincide with blocking frequency maxima while the strength of blocking episodes is generally independent of the blocking frequency. Indeed, the strongest blocking episodes were found over the eastern Atlantic where blocking is less frequent. A small decrease in mean strength of blocking episodes was found compared to previous studies for all longitudes. Finally, regarding the evolution of daily intensities of blocking episodes, no evidence is found that a typical evolution of strength during a blocking event exists.