The jet stream that brought in Storm Eunice is moving northwards

Date:
February 22, 2022
Source:
University of Southampton
Summary:
The Northern Hemisphere Jet Stream, which this week brought storms
Dudley, Eunice and Franklin to the UK has been getting faster and
moving northwards over the past century.



FULL STORY ==========================================================================
New research shows that the average winter northern hemisphere jet stream position over the North Atlantic and Eurasia has moved northwards by
up to 330 kilometres and the mean winter jet speed has increased by 8%
to 132 miles per hour, during the 141-year period from 1871-2011.


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Just this week the jet stream has brought storms Dudley, Eunice and
Franklin to the UK. Jet streams are fast bands of air which flow around
the globe around ten thousand metres above Earth's surface. They have a significant influence on storm activity and temperature patterns across
the northern hemisphere which can impact the weather through strong winds
and flooding events. This is the longest regional study of the northern hemisphere jet stream and the trends observed are potential indicators
of climate change.

The study, published in Climate Dynamics, provides a comparison of the
Northern Hemisphere jet stream across oceans and continents and finds that
jet stream trends vary on a regional and seasonal basis. Between 1871 and
2011 the average winter movement in jet stream latitude over the North
Atlantic was from 44DEG to 47DEG north with a 10 mph increase in speed to
132 miles per hour, but no increases were observed over the North Pacific.

The study was led by Dr. Samantha Hallam, from Maynooth University in
Ireland whilst undertaking a PhD at the University of Southampton. Dr
Hallam said: "Significant increases in winter jet latitude and speed
are observed over the North Atlantic and Eurasia. These changes are
consistent with the decreasing temperature and increasing pressure
gradients observed between the equator and the Arctic over the period,
and likely associated with the warming Arctic winters." "Over the North Pacific, no increase in jet latitude or speed are observed, however,
changes in the North Pacific sea surface temperatures explains over 50%
of the variability in jet latitude." The results highlight that northern hemisphere jet variability and trends differ on a regional basis across
the North Atlantic, North Pacific, Eurasia and North America. This is
important for making climate predictions and in developing plans to
combat climate change.

These findings are the result of a statistical analysis of the 250mb
jet stream using the Twentieth Century Reanalysis dataset.

The research was supported by the Marine Institute and funded by the Irish Government under the JPI Climate and JPI Ocean joint call and the Natural Environmental Research Council, and involved collaboration between The
Irish Climate Analysis Research Units (ICARUS) at Maynooth University
in Ireland, University of Southampton, UK and National Oceanography
Centre, UK.

========================================================================== Story Source: Materials provided by University_of_Southampton. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Samantha Hallam, Simon A. Josey, Gerard D. McCarthy, Joe"l
J.-M. Hirschi.

A regional (land-ocean) comparison of the seasonal to decadal
variability of the Northern Hemisphere jet stream 1871-2011. Climate
Dynamics, 2022; DOI: 10.1007/s00382-022-06185-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220222085607.htm

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