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Posted
  • Location: Broxbourne, Herts
  • Weather Preferences: Snow snow and snow
  • Location: Broxbourne, Herts

    La Soufriere Volcano in St Vincent has exploded into life causing havoc for those in St Vincent and even impacting the sunshine and beautiful beaches of Barbados.

     

    Its last three explosions were in 1812, 1902 and 1979

    The average annual CET for the ten years preceding each explosion was greater than for the ten years of and succeeding the explosion.

    I wonder if the comparison of annual CETs for 2021-2030 against 2011-2020 will make it four times in a row? 

     

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    Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

    Possibly but unlikely to be a direct result.

    Generally speaking you need a VEI6 eruption for global climate impact while even the 1902 eruption was VEI4 (and so far it looks VEI3/4).

    1902 was around a fairly deep solar minima (the 1912 one was the deepest on record).

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    Posted
  • Location: Broxbourne, Herts
  • Weather Preferences: Snow snow and snow
  • Location: Broxbourne, Herts

    i agree regarding global impact.  I just wonder if the location of La Soufriere might be a factor on on how weather systems that ultimately impact upon us develop.

    Am I right in believing we are in a fairly deep solar minima now?



     

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    Posted
  • Location: County Londonderry 36m ASL
  • Weather Preferences: Proper winter/Proper summer
  • Location: County Londonderry 36m ASL

    Interesting thread. Be one to keep an eye on as time passes to either confirm or refute your idea. It does look localised to me though, not like Mount Pinatubo or Eyjafjallajokull with affects over wide geographic areas.

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    Posted
  • Location: Irlam
  • Location: Irlam

    Isn't there a thread for volcanic activity here?  We had a really daft thread opened very recently about that Icelandic volcano erupting. Is this going to happen every time a volcano erupts and speculation on what it may do to the weather? 

     

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    Posted
  • Location: Rossland BC Canada
  • Location: Rossland BC Canada

    The 1902 eruption of this volcano was a day or two before the much larger eruption of Mont Pelee on Martinique (May 8, 1902) which destroyed a city of 30,000 people; whatever impact there was on the weather regionally or globally would be more down to that larger eruption. The year 1904 was unusually cold in eastern North America. You would expect a dust veil in the Caribbean to move mostly to the west-northwest although right now this particular one has been drifting more to the east. The atmosphere between the surface and at least 300 mb usually has an easterly component in that region, above maybe 200 mb more westerly. Unless it's a huge eruption most of the ash cloud produced would probably flatten out around 400-600 mb levels. 

    I've read a theory that the cause and effect of cold weather may be partly the reverse of the dust veil logic, that is to say, if the atmospheric pressure goes into a cycle which will load up cold in the mid-latitudes, it stresses the crust and volcanoes erupt more frequently or more impressively. Don't know if there's anything to that or not. One indicator is that when Krakatoa erupted in August 1883, it had already been anomalously cold in many parts of the northern hemisphere for about a year, for example March 1883 was a very cold month. That obviously cannot have been caused by the volcanic dust veil. In fact the average lag time from major eruptions to postulated effects is on the order of 1 to 4 years. The cold of 1885 to 1888 (more notable in North America) might have been more Krakatoa's work than cold in 1883 or even parts of 1884. The Tamboro eruption was in April 1815 and its effects began to show up (at least the postulated effects) around late 1815 and early 1816. Pinatubo is sometimes blamed for colder weather in 1992 (once again mostly in North America), but I'm not really convinced it had much to do with that, the dust veil was relatively minor and the cooling was quite strong (the summer of 1992 was probably the worst one in decades in eastern North America). 

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    • 2 weeks later...
    Posted
  • Location: Alston, Cumbria
  • Weather Preferences: Proper Seasons,lots of frost and snow October to April, hot summers!
  • Location: Alston, Cumbria

    There has been quite a few high-profile big eruptions in recent months, each of which has led to volcanic dust ejected to over 10,000 metres' elevation: La Soufriére is the latest, with dust reaching over 13,000 metres' elevation. In March there was Sangay in Ecuador (dust reaching over 12,000 metres) and Mount Sinabung (Sumatra) blew its top at the beginning of March , again with dust reaching over 12,000 metres. At the end of November/ early December 2020 two powerful volcanoes (Semeru and Lewotowo in Indonesia) blew their top and each pushed volcanic dust to over 14,000 metres. The impact of these volcanoes, all fairly close to the Equator and in the vicinity of the Intertropical Convergence Zone (ITCZ) will have been significant. 

    In terms of cooling the globe, even quite large amounts of dust don't have a major impact directly. The upper atmosphere ends up absorbing heat from the Sun that otherwise would reach the surface- and that warmed upper-air eventually descends in the subtropical high-pressure belts or finds it's way into the Westerlies. However, just half a degree of warming of the Equatorial upper- atmosphere (combined with a similar amount of cooling below) leads to a weakening of the ITCZ by reducing the temperature lapse- rate in the atmosphere in a part of the world normally conducive to deep convection. Since it is deep convection that normally drives the ITCZ then volcanic dust in the high- atmosphere over the Equator such that there is a 0.5C warming aloft and 0.5C cooling near the surface could weaken the ITCZ- and the attendant Hadley Cell- by 10% or more. Since the atmosphere is often conditionally unstable a reduction of the temperature gradient between the top and bottom of the atmosphere by 1C- or just under 1% (the top of the troposphere over the Equator is often below -80C but near 27C at the surface) has a much bigger impact than a 1% drop in the atmospheric temperature lapse- rate would suggest. In addition to this, La Nina has been dominant in the eastern Equatorial Pacific- with relatively cool ocean- surfaces further reducing surface temperatures near that part of the ITCZ.

    Thus, there has been less convection along the ITCZ, a weaker Hadley Cell and (crucially) weaker transfer of Westerly Atmospheric Angular Momentum to higher latitudes aloft. So, you end up with a situation whereby a series of powerful volcanoes like La Soufriére (with the help of La Nina) leads to weaker Westerlies and a weaker, wavier Circumpolar Vortex in higher latitudes and (with it) a higher propensity to High-Latitude Blocking Highs that displace the Westerlies from countries like the UK and allow much colder air to penetrate south from high latitudes. Thus, indeed there is a link between powerful volcanoes (if they erupt near the Equator) and increased cold- spells in mid- latitudes, though not so much for the reasons that one might first suspect. 

    It could be that these volcanoes, along with La Nina, have helped to bring about the coldest winter since 2010-11 and also the almost three weeks of dry cold weather with plant-decimating late spring frosts across large areas of western Europe this month. 

         

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