Drivers of North Atlantic Polar Front jet stream variability

Abstract

Polar front jet stream variability is responsible for instances of extreme weather and is crucial for regional climate change. The North Atlantic Polar Front jet stream is of particular significance to the heavily populated areas of western Europe and eastern North America as storm track variability, atmospheric modes of variability such as the North Atlantic Oscillation (NAO), temperature and rainfall are all intimately linked with jet stream changes. Although seasonal and interannual variability are often attributed to internal variability, there are several possible drivers of polar front jet stream changes that are reviewed in this study. Cryospheric effects from sea-ice extent and snow cover, oceanic effects from North Atlantic sea-surface temperatures and tropical influences such as the El-Niño Southern Oscillation, and stratospheric effects due to stratospheric circulation variability, solar variability, volcanic eruptions and the Quasi-Biennial Oscillation are all identified in the literature as factors that impact on the Atlantic Polar Front jet stream. These drivers of jet stream variability can oppose or reinforce one another, and there are some indications of possible nonlinear interactions between them. We also review the modelling of jet stream variability. While a consensus has now been reached that some observed drivers can be reproduced in climate models, we conclude that improved understanding of more recently identified drivers of the Atlantic extratropical jet stream is crucial for making progress in regional climate predictions on all timescales from months to decades ahead. © 2015 Royal Meteorological Society

A 133-Year Record of Climate Change and Variability from Sheffield, England

“…Supplementary Figure S5 highlights the difference between the NAO and EA in terms of winter correlations with mean temperature and precipitation and shows that for WP, the EA is a better indicator of storms that result in precipitation at WP (central England) than the NAO, which has significant correlations across the western coastlines of the UK and Ireland, indicating a more north-easterly storm track. This lends credence to the idea that more relevant jet-stream indicators [33,48] than that of a one-dimensional index would be useful in explaining climate variations.…”

“…There have also been two record wet (2002 and 2012) and dry (2003 and 2011) years since the turn of the century which again illustrates the importance of natural variability in the WP record which, like for the wider-European region as well, arises due to subtle changes in the polar front jet stream [33].…”

“…The EA-WR positive correlation with mean temperature during spring has been identified as persistent in time across North-western Europe since 1950 [49] and is associated with a blocking pattern centred above the UK which whilst variable in spring, would usually be associated with drier, warmer conditions. The negative sea-ice relationship with temperature in autumn (positive for the 10th percentile temperature indices) is possibly due to the sea ice loss influencing the jet stream position, although there are multiple competing factors on European (and therefore WP) climate variability [33][34][35]50].…”

Drivers and potential predictability of summer time North Atlantic polar front jet variability

“…Hall et al 2015). The Atlantic Multidecadal Oscillation (AMO; Enfield et al 2001) is a mode of North Atlantic sea surface temperature (SST) variability with a period of 65-80 years.…”

“…Stratosphere-troposphere coupling exerts a potential influence in winter on the PFJ through a range of factors (Kidston et al 2015;Hall et al 2015). However, in the summer hemisphere the stratospheric polar vortex breaks down, and easterly flow prevails, which prevents propagation of Rossby waves and so this coupling does not occur and therefore predictors of variability such as the quasi-biennial oscillation (QBO) and the impact of tropical volcanic eruptions, to name but two, are unable to exert a summer-time influence via the stratospheric pathway.…”