The tropical Pacific influences the North Atlantic jet stream
The location of the jet stream influences European weather at all times. A new study links its position both to local weather systems and to the far-away Pacific Ocean. Lead author Erica Madonna explains.
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Written by Erica Madonna from the and the Geophysical Institute at the University of Bergen.
Jet streams are narrow bands of strong winds that shape midlatitude聽weather and climate. For example, the North Atlantic jet exhibits聽frequent north-south shifts that profoundly affect precipitation and聽temperature over Europe.
Occasionally, the jet may stay fixed in one聽position for longer periods. For example, the 2009/2010 winter saw a聽remarkably stable southern North Atlantic jet. This coincided with a strongly negative North Atlantic Oscillation (NAO) index, meaning that the pressure difference between the Icelandic low and the Azores high was smaller than normal.
Previous studies argue that persistent southward聽shifts in the jet聽reflect changes in dynamics linked to convection in the tropical聽Pacific, while frequent shifts on daily timescales arise from the action聽of upper-level eddies in the jet region.
In this聽, we bridge the climate (year-to-year聽variability) and weather (day-to-day variability) perspectives to聽demonstrate that,聽whenever the North Atlantic jet (black contours in the聽schematic) shifts south, it consistently shows evidence of a tropical聽influence (stronger heating, in red) and weaker eddies (in blue).
Winter聽2009/2010 was, in fact, the result of consecutive episodes of southern聽jet shifts each lasting several weeks.
Reference
Madonna, E.;聽Li, C.;聽Wettstein, JJ. (2019):聽.聽Atmos Sci Lett. 2019;e937.聽
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