An updated climatology of atmospheric blocking in the eastern Atlantic‐European region. (20th October 2022)

• Record Type: Journal Article
• Authors: Toumpos, Michalis; Flocas, Helena A.; Kouroutzoglou, John; Hatzaki, Maria
• Is Part Of: International journal of climatology. Volume 42:Number 16(2022)
• Page Start: 10153
• Page End: 10172
• Publication Date: 2022-10-20
• Subjects: duration -- ERA5 datasets -- frequency -- local and instantaneous blocking -- PV‐θ wave‐breaking index -- sector blocking -- strength; Climatology -- Periodicals; Climat -- Périodiques; Climatologie -- Périodiques; 551.605
• DOI: 10.1002/joc.7889
• Languages: English
• ISSNs: 0899-8418

Abstract

Abstract: 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‐ θ 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. Abstract : A more recent climatology of blocking is presented over the Euro‐Atlantic domain, being benefited by the use of the long and high‐quality ERA5 dataset for the period 1979–2019. Despite the different methodology, the higher spatial resolution and the most recent period, no significant difference in blocking frequencies was found with previous analyses, contrary to a small decrease in strength of blocking episodes. Furthermore, the longest events coincide with blocking frequency maxima while higher frequencies of sector blocking events do not lead necessarily to stronger events.