Summer extremes of 2018 linked to stalled giant waves in jet stream 

Posted: April 30, 2019 by oldbrew in Natural Variation, research, Temperature, weather, wind
Tags: ,

Omega blocking highs can remain in place for several days or even weeks [image credit: UK Met Office]


Atmospheric blocking is a well-known weather phenomenon. The report below says ‘In recent years, the scientists observed a clear increase of these patterns’. But scientists have also reported a 20 year decline in solar magnetic fields and solar wind micro-turbulence levels. Coincidence, or possibly not?

Record breaking heatwaves and droughts in North America and Western Europe, torrential rainfalls and floods in South-East Europe and Japan – the summer of 2018 brought a series of extreme weather events that occurred almost simultaneously around the Northern Hemisphere in June and July, says IOP Publishing.

These extremes had something in common, a new study published today in Environmental Research Letters by an international team of climate researchers now finds.

The events were connected by a newly-identified pattern of the jet stream encircling the Earth. The jet stream formed a stalled wave pattern in the atmosphere, which made weather conditions more persistent and thus extreme in the affected regions.

The same pattern also occurred during European heat waves in 2015, 2006 and 2003, which rank among the most extreme heatwaves ever recorded. In recent years, the scientists observed a clear increase of these patterns.

The jet stream, about 10 km up in the atmosphere, steers large scale weather systems from west to east around the world. The wind system can develop large meanders, so-called Rossby waves, and occasionally these waves stay in place for weeks. Under these conditions warm sunny days can turn into a heat wave and drought, and rainy days into a flood.

“Our study shows that the specific locations and timing of the 2018 summer extremes weren’t random, but directly connected to the emergence of a re-occurring pattern in the jet stream that stretches around the entire Northern Hemisphere,” said lead author Kai Kornhuber from the University of Oxford and the Potsdam Institute for Climate Impact Research (PIK).

Identified wind pattern was also present during past summers with extreme weather

“We find a strong relation between the pattern and persistent heat extremes in Western Europe, North America and the Caspian Sea region. This pattern was present during other years with extreme weather events such as the heat waves in Europe during summer 2015, 2006 and 2003. Moreover, its frequency and duration have in fact increased over the last two decades.

“In the two decades before 1999, there were no summers that saw a stalling wave pattern lasting for two weeks or more, but since then we have seen already seven such summers,” said co-author Dim Coumou, from Vrije Universiteit Amsterdam and PIK.

The observed wave pattern is anticipated to re-occur more frequently in future because of climate change and human-caused global warming. There is a physical reason behind this: Land masses tend to heat up faster than the ocean areas. This leads to a more pronounced temperature contrast between land and ocean areas.

“The stalling wave pattern may be favoured by this increased land ocean temperature contrast. Another relevant aspect could be the cooler than normal North Atlantic, likely a result of a slowdown of the Atlantic Meridional Overturning Circulation, commonly known as Gulf Stream System. However, this needs further investigation,” said Stefan Rahmstorf, who leads the Earth System Analysis research department at PIK.

Continued here.

Comments
  1. Phoenix44 says:

    Once again claiming that extremely short run records “prove” something in chaotic non-linear complex systems.

    Do they not understand what they are studying?

    In such systems, you will see things happening for the first time and then happening two or three times again quite soon after, even though they may never have been seen before. That’s exactly how these systems work.

  2. oldbrew says:

    See also Jaime Jessop’s 2014 article (under ‘Related’, above).

    Climate Wars – CO2 vs. Solar in the Battle to Lay Claim to Jet Stream Anomalies
    https://tallbloke.wordpress.com/2014/02/23/jaime-jessop-climate-wars-co2-vs-solar-in-the-battle-to-lay-claim-to-jet-stream-anomalies/

  3. JB says:

    “Do they not understand what they are studying?”

    From our POV, apparently not. But then isn’t the purpose of studying to gain understanding? When they get a handle on what’s causing the hi/lo standing wave pattern instead of the presumed negligible forces they’ll be on to something.

  4. Stephen Richards says:

    HH Lamb found that global cooling initiated anticyclonic blocking. Hence the extremely cold winters and hot summers of the 1600,1700,1800

  5. Stephen Richards says:

    oldbrew says:
    April 30, 2019 at 3:50 pm
    See also Jaime Jessop’s 2014 article (under ‘Related’, above).
    Climate Wars – CO2 vs. Solar in the Battle to Lay Claim to Jet Stream Anomalies

    Jaime is another one banned from twitter for criticising a UK MP.

    Get rid of these parasites, please

  6. oldbrew says:

    Stephen Richards says: May 1, 2019 at 8:37 am

    Paul Homewood looked at HH Lamb’s work here:
    https://notalotofpeopleknowthat.wordpress.com/2012/06/28/hh-lambclimate-present-past-futurevol-2in-reviewpart-ii/

    Under the paragraph heading ‘Effects of a cooler climate’, Lamb says:
    Much smaller changes over middle latitudes, where the most significant feature has been the very awkward type of variability from year to year, associated with the behaviour of blocking systems and meridional circulation patterns.

    PH adds a comment:
    [While the droughts referred to are well known, it is interesting to learn about the increase in blocking patterns, which Hansen and co would like to blame nowadays on warming].

  7. oldbrew says:

    DOES THE SUN AFFECT OUR WEATHER AND CLIMATE?
    INSIDE THE THERMOSPHERE CLIMATE INDEX

    Martin Mlynczak, at NASA’s Langley Research Center, has developed something called the Thermosphere Climate Index (TCI), which measures the temperatures at the top of Earth’s atmosphere. Although SABER has been in orbit for only 17 years, Mlynczak and his colleagues recently calculated TCI going all the way back to the 1940s. “SABER taught us to do this by revealing how TCI depends on other variables such as geomagnetic activity and the Sun’s UV output—things that have been measured for decades,” he explained. (See the accompanying graph of TCI data, courtesy of NASA.)

    As 2019 begins, the Thermosphere Climate Index is on the verge of setting a Space Age record for cold, which reflects the historic low in solar activity in the current cycle.

    So, recent data has proven that temperatures in the uppermost portion of the atmosphere vary substantially, in parallel with solar activity. Recent research proposes a mechanism by which these changes can have a significant effect on weather patterns in the lower atmosphere.

    https://thecommentarygazette.com/2019/04/11/the-old-farmers-almanac-for-april-11-does-the-sun-affect-our-weather-and-climate/

  8. craigm350 says:

    Reblogged this on WeatherAction News and commented:
    “In the two decades before 1999, there were no summers that saw a stalling wave pattern lasting for two weeks or more

    Conveniently this just missed the summer of 1976  but “1980 (Spring):
    1. The period of 8 weeks from the 2nd April 1980 was regarded as the DRIEST such spell at the time, the only other previous dry spell being August to October, 1959. This in the EWR series.”

    https://www.webarchive.org.uk/wayback/en/archive/20130428155009/http://booty.org.uk/booty.weather/climate/1975_1999.htm

    Okay it is spring, not summer, but blocking highs are noted throughout the seasons. This contempory report from The Times in May 1980 which funnily enough also discusses blocking highs during the LIA;

    Trying to pin down the change in the weather
    Burroughs, W. J.
    The Times (London, England), Wednesday, May 21, 1980

    Surely you’d want to look at the phenomena in its entirety?

  9. oldbrew says:

    NASA tries to gloss over the impressive growth of Greenland’s biggest glacier since 2016 – 30 metres taller in one year. Reason: the water got colder, 3 years in a row. Cue mutterings about natural cycles, which of course are never mentioned as a cause of warming.

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