Wintertime North American Weather Regimes and the Arctic Stratospheric Polar Vortex. Issue 24 (27th December 2019)

• Record Type: Journal Article
• Authors: Lee, S. H.; Furtado, J. C.; Charlton‐Perez, A. J.
• Is Part Of: Geophysical research letters. Volume 46:Issue 24(2019)
• Page Start: 14892
• Page End: 14900
• Publication Date: 2019-12-27
• Subjects: stratosphere -- weather regimes -- polar vortex -- cold -- stratosphere‐troposphere coupling; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2019GL085592
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The impact of the Arctic stratospheric polar vortex on persistent weather regimes over North America is so far underexplored. Here we show the relationship between four wintertime North American weather regimes and the stratospheric vortex strength using reanalysis data. We find that the strength of the vortex significantly affects the behavior of the regimes. While a regime associated with Greenland blocking is strongly favored following weak vortex events, it is not the primary regime associated with a widespread, elevated risk of extreme cold in North America. Instead, we find that the regime most strongly associated with widespread extremely cold weather does not show a strong dependency on the strength of the lower stratospheric zonal mean zonal winds. We also suggest that stratospheric vortex morphology may be particularly important for cold air outbreaks during this regime. Plain Language Summary: During winter, the strength of the winds 10–50 km above the Arctic can affect the weather patterns at the surface. Generally, this influence is strongest over the North Atlantic and Europe. However, we show that the strength of stratospheric winds has a significant impact on weather patterns across North America. Our results indicate that knowledge of the stratospheric winds can provide a greater understanding of the evolution of likely weather in this region on longer time periods, including both severely cold weather (and its associated impacts on energy consumption, transport, and human health) and an unusual absence of severe cold. Key Points: The behavior of three of four regimes over North America is significantly linked to the strength of the lower stratospheric polar vortex A regime associated with Greenland blocking shows the strongest relationship with the stratospheric polar vortex strength The regime most strongly associated with widespread severe North American cold does not show a dependency on stratospheric vortex strength