Do Atlantic‐European Weather Regimes Physically Exist?. Issue 20 (25th October 2021)

• Record Type: Journal Article
• Authors: Hochman, Assaf; Messori, Gabriele; Quinting, Julian F.; Pinto, Joaquim G.; Grams, Christian M.
• Is Part Of: Geophysical research letters. Volume 48:Issue 20(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-25
• Subjects: subseasonal variability -- extratropical weather regimes -- climate dynamics -- Europe -- Euro‐Atlantic; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL095574
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The subseasonal variability of the extratropical large‐scale atmospheric flow is characterized by recurrent or quasi‐stationary circulation anomalies, termed weather regimes. Despite the usefulness of these regimes in numerous meteorological and socioeconomic applications, there is an ongoing debate as to whether they represent physical modes of the atmosphere, or are merely useful statistical categorizations. Here, we answer this question for wintertime Atlantic‐European regimes. We argue that dynamical systems theory applied to a refined regime definition provides strong evidence in support of most weather regimes being physically meaningful. This finding underpins the broad relevance of weather regimes, for understanding the response of the atmosphere to external forcing, supporting subseasonal weather forecasting, and down scaling of climate projections. Plain Language Summary: The weather situation over the North Atlantic and Europe region is dominated by steady large‐scale atmospheric circulation patterns that occur repeatedly, often termed weather regimes. Despite their usefulness in weather forecasting, it is questioned whether these regimes have a clear physical grounding, or are merely useful statistical classifications. By showing that the atmospheric circulation indeed settles down in a comparably steady state during certain regimes, we provide strong evidence in support of their physical foundation. This finding underpins the broad relevance of weather regimes in supporting weather forecasting several weeks ahead and, in addition, understanding the impacts of climate change on our atmosphere. Key Points: We assess the physical grounding of Atlantic‐European winter weather regimes (WR) using dynamical systems (DS) theory Most WR display distinct and predictable flow characteristics at their maximum stage, and unpredictable flow at onset and decay The agreement between the statistical classification and the DS analysis provides strong evidence for most WR being physically meaningful