Those Wretched Winds That Have To Blow To Stop The Earth Slowing Down!

[iapennell]

This is an appropriate point in the year to have this topic when the strengthening Circumpolar Vortex and the consequent increase in vigour of mild south-west winds wreck the potential for another cold snowy Christmas/Winter (Yet Again)!! All that hope for increased snow-cover over Eurasia to bring about a hard winter- dashed once again. Storm Barbara is about to descend upon the North of Britain to give a reminder of last December's catastrophic flooding over the Festive Period. And this keeps happening every December!

A little look at some basic meteorology and some physics is in order to get to a correct prognosis: Once you have a prognosis you can then think about whether we have the technology to stop this happening in future so that future generations can (more than Bing Crosby sang in his song) not only dream of a White Christmas (like the ones we used to know) but to make them a possibility for our grandchildren and their children!

Two major (and fundamental) controls on the global weather systems have conspired against White Christmases in recent times: Firstly rising CO₂ levels have led to a warming of the planet as more heat is absorbed globally over the years than has been lost to space; this is a consequence of CO2 being a greenhouse gas that re-absorbs long-wave heat radiation emitted by the Earth's surface and re-radiating much of this heat downwards leading to a small warming effect of the surface and lower atmosphere. As the Earth gets warmer the extra heat finds its way into the oceans and is transported to high latitudes leading to milder winters. At the fringes of the Arctic (and Antarctic) the reduction in sea-ice takes place earlier in the summer due to this warming and the darker ocean and land surfaces absorb the Sun's energy rather than reflecting it back into space- making oceans and lands at higher latitudes warmer still. The extra warmth arising from more solar energy absorbed by ice-free sub-arctic seas in late spring/summer means these waters stay warmer and fail to freeze until well into December, the open water warming rather than cooling any very cold air-masses passing over them. This all means that even the Arctic loses some of it's potential to deliver very cold conditions further south even if the pressure-patterns were to be favourable for Arctic winds to blow southwards: And the indications are that recent winters (2009/10 and 2010/11 notwithstanding) have been even less favourable for the right weather-patterns to deliver cold and snow than even their earlier unfavourability for cold in Britain; this naturally brings us onto the second major control on the weather in early winter over Britain.

The fact that planet Earth rotates once every 23 hours and 56 minutes (our days are only 24 hours' long by virtue of the fact that the Earth moves in its orbit round the Sun and so it takes 24 hours for the Earth to catch-up its position relative to the Sun, as it were) has major implications for our weather: If the Earth did not rotate (or only rotated very slowly with a day lasting a month, for example) cold air over the Poles would flow directly towards the Equator and return to high latitudes aloft; there would be no depressions in middle or high-latitudes- only a broad area of high-pressure which would be highest at the surface in the Arctic and Antarctic. However, since the Earth does rotate at the rate it does the air moving north and south away from the Intertropical Convergence Zone (the zone of hot moist rising air near the Equator) retains the west to east movement it had when first rising in the Intertropical Convergence Zone (ITCZ) as it moves to higher latitudes where the Earth rotates more slowly. The result is a band of very strong westerly winds at high altitudes over about 30N (and 30S), which is the subtropical jet-stream and air coming from the Equator to the south of it aloft (in the Northern Hemisphere) cannot penetrate this zone of very strong westerly winds and is forced to descend. This results in the subtropical high-pressure belts near the surface centred on roughly 30 to 35N (in the Northern Hemisphere). Further north towards the poles any further northwards movement of air over areas where the Earth's rotation speed is much lower results in very strong Westerlies, so strong in fact that descent of this air would carry the westerly momentum towards the surface and frictional drag on the air below would result in lower-level air moving towards the subtropics (this is similar to the mechanism by which strong Westerlies blowing over the ocean leads to ocean currents moving from west to east at the surface but more north-west to south-east some ten or more metres below the surface of the ocean. The progressive change in ocean-currents at depth -and of wind-direction descending through the troposphere- is called the Ekman Spiral and it is a feature of fluid dynamics on any large rotating body). This initial process results in surface air-pressure falling north of subtropical high-pressure belts (in the Northern Hemisphere) and with lower pressure to the north surface winds blow northwards from the subtropical-high to become increasingly deflected by the Earth's rotation as the air moves over land and seas that rotate closer to the axis of the Earth's rotation and so they become surface south-westerlies. It is these south-westerlies that bring mild moist air to Britain at this time of year and wreck so many of our Christmasses!! However, at high-latitudes surface pressure is higher over very cold and frozen lands and seas and air flows equator-wards from these and, deflected by the Earth's rotation, become the Polar Easterlies and the is a return flow of air aloft from sub-polar regions towards the central Arctic; these Polar Easterlies meet the surface south-westerlies further south along what is called the Arctic Front but there are other constraints (again to do with the Earth's rotation) that greatly limit how far south these Polar Easterlies can get although other factors such as sea-surface temperatures and Arctic pack-ice extent also play a big role too!

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[iapennell]

(CONTINUED

Now the higher-latitude south-westerlies impart westerly atmospheric momentum to the underlying surface through friction whilst at the same time the north-easterlies in the tropics and at very high latitudes result in the atmosphere overall gaining Westerly momentum- again through friction with the underlying surface: If there are more (or stronger) easterlies over the Northern Hemisphere there is a net increase in westerly momentum for the atmosphere as a whole, this process cannot go on for long because the resultant very strong westerlies aloft at higher latitudes results in deeper depressions forming with the result being this excess and accumulating westerly atmospheric momentum is transferred back to the surface. This, in essence, explains why we always have this problem with strong Westerlies coming off the North Atlantic at this time of year!

Of course, this is not the whole story. The strength of the NE Trade Winds is greater in winter, the Polar Easterlies are stronger and there are easterlies over Russia and Mongolia at this time of year due the Siberian High. Thus a lot of Westerly atmospheric momentum accumulates into the atmosphere and so this demands for a zone of stronger Westerlies in the fewer locations not affected by easterlies. With favourable baroclinic temperature gradients between the Arctic and far North Atlantic this country is thus right in the firing-line for strong Westerlies off the North Atlantic in December! 

Edited December 22, 2016 by iapennell

[Methuselah]

Hi Ian, and a merry Christmas to you...

Are you saying that (having accounted for the slowing of Earth's rotation, due to the gravitational drag due to the Moon, Solar System and Universe as a whole) that the Coriolis Effect will ensure that (on average) high-latitude westerlies will inevitable overpower any transient easterlies?

If so, then isn't it a wee bitty obvious?

PS: I'm not intending to come across as being rude. I am genuinely interested.

[iapennell]

39 minutes ago, Ed Stone said:

Hi Ian, and a merry Christmas to you...

Are you saying that (having accounted for the slowing of Earth's rotation, due to the gravitational drag due to the Moon, Solar System and Universe as a whole) that the Coriolis Effect will ensure that (on average) high-latitude westerlies will inevitable overpower any transient easterlies?

If so, then isn't it a wee bitty obvious?

PS: I'm not intending to come across as being rude. I am genuinely interested.

@Ed Stone First of all, all the best for Christmas for you and your family. 

You certainly have a point about the tidal impacts of the Sun and Moon but this is very slight. I recently read a book written by the late Patrick Moore on the subject of different ways in which our planet could meet its end, one of these being the likelihood of the Moon colliding with the Earth. In the chapter on The Menacing Moon he discussed that lunar and solar tidal influences would take so long to slow the Earth's rotation that it would take 50 billion years for the length of day to increase to a length of 47 of our current days. This means a rate of increase in day- length of just a few millionths of a second annually. In other words that is neither here nor there.

On an annual basis seasonal changes in global winds, cooling at high latitudes leading to strong Westerlies aloft after increases in easterlies over low latitude continents, leads to increases in the length of day by 1 to 2 milliseconds but this reverses in the spring as the low latitude easterlies weaken and excess Westerly Momentum is returned to the surface in higher latitudes. 

Significant changes in the Length of Day occur in association with periods of sharp global cooling when tropical easterlies strengthen but the colder oceans of higher latitudes discourage intense cyclogenisis over them. In such situations the westerlies strengthen aloft in lower latitudes leading to mountain torque removing much excess Westerly Atmospheric Momentum in the winter months. However, in this situation with more extensive cold -air highs near the surface at high latitudes there is convergence aloft and the dynamic creation of lower pressure and depressed thickness heights right up into the mesosphere over mid-latitudes which means excess westerly atmospheric momentum is transferred upwards to the edge of space, whereby some could be lost to atmospheric diffusion to space. However,  most Westerly Atmospheric Momentum shunted up into the mesosphere in winter at times of global cooling is returned to the surface (lower mid-latitude mountains) in spring.

Unfortunately this is not the situation with the global climate at present, unfortunately being for those wanting snow and crackly hard frosts at Christmas. There is far too much higher latitude ocean warmth that actively invites excess Westerly Atmospheric Momentum to make surfacefall upwind of Britain!! 

[hillbilly]

Lots of technical reading but we can get lots of stormy weather for much of the extended winter and for all the 'non wintery 'xmas periods we have had it is not a period that I have as a stormy one in past memories.

[iapennell]

@Ed Stone PS. The name of the book I was referring to is called "Countdown: How Nigh Is The End" written by the famous Patrick Moore (who used to present "The Sky at Night" on BBC2, I recall; sadly he died a year or two back). He makes reference to the Moon slowing down the Earth's rotation ever so slightly but that in 50 billion years our days would be 46 days' long and that this would be the time it takes for the Moon to orbit the Earth by then- the Earth loses angular momentum through interaction with the Moon but that this is transferred to the Moon whose orbital angular momentum about the Earth increases by the same amount. By AD 50,000,000,000 the Moon's orbit will have receded to about 330,000 from the Earth; Patrick Moore in his chapter on The Menacing Moon then explains that the Moon will not be slowing the earth's rotation down by this point because the duration of the Moon's orbit and the length of day would be the same length, but Patrick Moore then explains the Moon is "not the only factor slowing down the Earth's rotation" and that tidal interaction with the Sun would continue to do this, leading to the Earth taking longer to rotate on it's axis than the Moon takes to orbit the Earth. Once that happens, the Moon will try to speed the Earth up and in the process loses absolute orbital momentum and this means the Moon draws in again towards the Earth. As the Moon draws in it orbits faster and tries to drag the slowly-rotating Earth around (with little effect) and eventually after billions more years the Moon would get to within the Roche limit-leading to huge forces between Earth and Moon with the result being that the Moon ends up breaking into little fragments rather than colliding directly with the Earth (which would destroy both the Earth and the Moon).

However, Patrick Moore then points out the one obvious flaw in this theory that there will not be an AD 50 billion because the Earth will be destroyed by the Sun turning into a Red Giant Star long before then!!

The central Law of Conservation of Angular Momentum states that the total angular momentum of any rotating body remains constant without any outside force acting upon it. This means the Earth and atmosphere have to maintain the same total Angular Momentum in the absence of outside influences. However there are outside forces that act chiefly to slow the Earth's rotation down, the tidal effects of the Sun and Moon being two of them. Other forces operate such as the diffusion at the top of the atmosphere to space (mostly of helium and hydrogen), if the diffusing gases at the top of the atmosphere have stronger westerly momentum then that constitutes a loss of total Angular Momentum of the Earth and its atmosphere (though if one also factors in the gases that have escaped to space the total Angular Momentum of the Earth, atmosphere and the diffused gas-  with reference to the axis of Earth's rotation will not have changed- the Law of Conservation of Angular Momentum holds). Other forces acting from outside the Earth-Atmosphere system include the impact of Solar Storms which- through the interaction with Earth's Magnetic Field- tend to have a small effect in adding to the total Angular Momentum of the Earth Atmosphere system; meteorites large and small slam into the upper atmosphere at great speed and these will either impart to (or subtract from) the total Angular Momentum of the Earth Atmosphere system. Neither is deep space totally free of trace gases and dust particles and these will have a small effect on our rotating Earth in slowing the Earth's rotation down (and also reducing by a small amount the orbital Angular Momentum of our planet as well, though this is likely to be more than countered by the fact the Sun rotates on its axis every 28 days whilst the Earth takes a year to orbit the Sun- the Sun must be imparting a very small amount of this momentum to Earth's orbit pushing our orbit outwards).

It is believed by some astronomers that our Solar System- in its 330 million-year orbit around the centre of our galaxy travels through dust-lanes in the spiral arms of The Milky Way. These astronomers believe this is a possible cause of  Ice Ages because the dust falls on the Sun, causing it to run riot whilst Earth is shielded from it and then go "off the boil" as it were (with subdued convection); this could cause the Sun's total radiation to drop 2 to 3%- leading to an Ice Age (this, by the way, was a theory around in the 1970's and how much verified this is by more recent findings it would be interesting to discover!). However, if the Earth did encounter excessive quantities of dust in its orbit coming from outside our Solar System the impact on the total Angular Momentum of the Earth Atmosphere system would be substantial and there would be a considerable force slowing the Earth down. Even if it lasted just a year, the impact on our weather-patterns would be very dramatic indeed.            

[iapennell]

2 hours ago, hillbilly said:

Lots of technical reading but we can get lots of stormy weather for much of the extended winter and for all the 'non wintery 'xmas periods we have had it is not a period that I have as a stormy one in past memories.

Late December not stormy? I live in the North Pennines and can recall west or south-westerly gales in late-December in 1983 (very bad ones), 1986, 1991, 1997, 1998 (severe gales), 2011 and (particularly) 2013. Late December last year was very wet as well as stormy.

[seaside 60]

I suppose that puts a flaw in trying to find  a live forever potion, reading this its all pretty much doom and gloom then lol...

By the way the last post is all very interesting, inc the bit about solar dust pos casing ice age/

 

[iapennell]

So we have two fundamental controls on our weather at this time of year, firstly increased CO2 levels have led to an increase in the outgoing radiative heat being retained by the Earth (i.e. absorbed in the atmosphere and re-radiated back down towards the surface); hence for quite a few decades now the picture has been an excess of incoming radiation from the Sun over outgoing radiative heat loss to space as averaged over all latitudes during the course of a year. This extra warmth is stored in the oceans and transported by the global winds to high latitudes in winter- leading as it does to anomalously high temperatures, particularly in regions where the sea nearby fails to freeze over. Consequently, airstreams reaching Britain during the winter months have been warmer than the corresponding airstreams in the past. The Arctic, for example, has lost some of its potency as a source region of extremely frigid air-masses (in early winter especially).

The fact that the Earth rotates and the need for the Earth-Atmosphere system to conserve Angular Momentum results in surface Westerlies in the winter months that need to counterbalance easterlies elsewhere in the Northern Hemisphere: Physical forces from outside the Earth are insignificant in these recent times of global warming and with warm higher-latitude oceans (with their strong baroclinic zones on their northern borders) enticing excess Westerly angular momentum in the atmosphere towards the surface (rather than pushing it up into the mesosphere) in the winter months it means north-west Europe will inevitably be in the firing line for strong mild west or south-west winds coming off the North Atlantic at this time of year. And with the effects of global warming meaning the North Atlantic is overall warmer than usual for December this means particularly mild (and wet) weather reigns supreme: Temperatures above 10C have occurred far more frequently over lowland Britain in late December than temperatures below 0C over the last 30 years!

So, is there anything that can be done to stop and hopefully reverse this trend? The obvious solution is for the entire Global Community to work towards the decarbonisation of their economies and the reduction of carbon dioxide levels in the atmosphere in an attempt to stop global warming getting out of hand but (understandably) most countries are reluctant to impose measures that would stifle their economies and threaten the stability of their power-supplies. Planting trees on a very large scale (preferably ones that have light-coloured leaves) will go some way towards mopping up excessive amounts of CO₂ in the atmosphere but is not going to reverse the trend towards higher CO₂ levels alone. I have discussed geoengineering on other threads on this Site in the past and aside from planting light-coloured trees on a grand scale the only other cost-effective solution that has a real chance of success (and which I have gleaned from extensive discussion on this Forum, though Environmentalists will vehemently object!) is the regulated injection of sulphur dioxide into the Stratosphere where it can reduce the amount of insolation reaching the surface of the Earth. None of these measures are a permanent fix however and in the longer term using technology to switch to a zero-carbon economy (without damaging the economy) and helping other countries do the same is the best chance we have of safeguarding our futures and enabling our grandchildren (and their children) to experience the joy of snow at Christmas.

Wind, rain and mild weather at Christmas have become more frequent in recent years (overall); as the climate has warmed and the edges of Arctic ice at this time of year receded polewards the Westerlies have pushed northwards and have become stronger: The more northward-displaced Westerlies have to blow stronger and harder to counterbalance easterlies elsewhere (in order that there is a balance with Westerly angular momentum being removed from the global atmospheric circulation at the same rate it is added) because the Westerlies blow even closer to the axis of the Earth's rotation- the effect is analogous to that of a see-saw- a light person far from the centre can hold up a heavy person the other side of (but close to) the centre of the see-saw. Helping reduce CO2 levels will encourage the polar ice to creep a bit further south once more which would push the Westerlies into somewhat lower mid-latitudes in winter- these Westerlies, then blowing further from the axis of the Earth's rotation will not then need to blow as hard to counterbalance easterlies elsewhere across the Northern Hemisphere. Britain then might get more respite from Christmas wet and wind, along with more chance of that white stuff that makes Christmas much more joyful! There is a serious side to tackling global warming because not only is persistent wind and rain at this time of year a nuisance for many, but greater storm frequency means more flooding, more coastal erosion, more sinkholes opening up under unsuspecting communities (these seem to be happening more frequently in recent years) and this is a major threat to coastal communities even without the consideration of what happens when the Greenland Icecap goes into terminal decline because of modest global warming.

Another solution to mild, wet and stormy winters is using the best technology available to tackle the Westerlies head on by addressing an underlying cause; the need for the atmosphere to shed excess Westerly momentum accumulated elsewhere. The most practical solution is the planting of trees in locations prone to frequent Westerly gales in winter (the trees need to be quite sturdy)- obvious locations include western Scotland, western Ireland and coastal areas of British Columbia (including Vancouver) in Canada. The mountain chain that separates Spain and Portugal also gets strong westerly winds at times in the winter, particularly towards the northern end of these mountains so the planting of trees here (ones able to cope with hot dry summers) would also help to relieve the atmosphere of excess Westerly momentum. These trees would serve a dual purpose- that of removing carbon dioxide from the air (ideally heir leaves should be light in colour so they don't absorb too much heat from the Sun and so add to the global warming problem rather than being a solution to it), whilst acting as a major sink to accumulated Westerly Momentum in the atmosphere by impeding the force of strong Westerly winds. This in turn would lessen the "need" for strong/persistent westerlies elsewhere in higher latitudes at this time of year.

If all this could be done in the next 15 to 20 years then future generations might be spared a long run of dreary mild and wet winters and (crucially) spared the likes of what happened in December last year when much of northern Britain was under water at times!

[Snowologist]

Fascinating read. Now thinking of the solutions of planting trees in areas of the westerlies,  what would happen if trees were planted in the areas of the easterlies? 

Now in the polar regions it is currently too cold to support tree growth but as temperatures rise and this could lead to the northward spread of the boreal forests, would this lead to any effects on the westerlies?

[iapennell]

@Good doing Weather The temperature regime in the zones affected by the Polar Easterlies is likely to remain too chilly for big trees to grow quickly: Areas currently affected by Polar Easterlies for much (or all) of the year include Iceland, Alaska, parts of northern Canada, Greenland and the Kamchatka area of Siberia. With increases in CO₂ levels in the atmosphere some of these locations will come under the influence of westerlies, at least during the summer, and trees could be planted, though with limited success (much of Siberia, Alaska and northern Canada is covered with the very short trees that make up the taiga in any case).

In winter most of these locations will remain under the influence of Polar Easterlies so it would not be helpful to have more trees here anyway: Easterly winds add Westerly atmospheric angular momentum to the atmosphere through their frictional interaction with the underlying surface and that is certainly the last thing you want to do if you want to decrease the strength of the Westerlies (and storm intensities) in winter in the latitudes of the UK!

Another interesting point, forests in high latitudes tend to be dark spruce or coniferous types that reduce the albedo of the landscape and hasten the onset of snow-melt (leading to more dark ground absorbing the Sun's heat), so if we want to be serious about tackling global warming and decreasing the strength of higher-latitude Westerlies in winter mid-latitude locations between 40 and 65N should be re-forested with deciduous and evergreen trees that have light coloured leaves. These trees would suck CO₂ from the air and help modify the strength of the Ferrel Westerlies; at high-latitudes (north of 65N) cutting down whatever trees there are would help serve to forestall global warming by increasing the local albedo of (normally) snow-covered land and removing an impediment to prevailing easterlies locally (which, if left in place, would lead to an increase in Westerly atmospheric angular momentum). That said, the effect of Polar Easterlies on the global atmospheric angular momentum budget is low because they blow really close to the axis of the Earth's rotation and cover a relatively small area.

A better proposal might be discouraging tree planting in the Northern Hemisphere North-easterly Trade Wind belt (roughly 10 to 30N) and encouraging deforestation in this broad zone that extends across southern Asia, northern Africa, Mexico, central America and northernmost parts of Columbia and Venezuela. Anything that increases frictional resistance to prevailing easterlies in those locations leads to a sharp increase in the Westerly momentum of the Northern Hemisphere atmospheric circulation because such frictional impacts are important so far from the axis of the Earth's rotation (and if we want to put paid to the kind of wretched Christmas conditions we have had in Britain for four years in a row now the last thing we want is large tall forests clogging up the Trade Wind Belt). Large parts of the NE Trade wind belt are too hot and dry to support forests, the Sahara and much of sub-Saharan Africa being a case in point:  However that is not the case for much of SE Asia and central America that gets rain in summer but are affected by stiff NE Trade Winds in the winter months- trees can and do grow here, locally in thick jungles. These tropical-zone trees also tend to be dark green and absorb the Sun's heat, whereas if they were cut down the land could be used for farming or much lighter-coloured savannah could take over. 

Deforestation is not a universal wrong and nor is forest-planting a universal good; it depends on the colour of the leaves on the trees planted and on where in the world forest-planting is done as to the impact on the global climate and the Westerlies in higher latitudes!

I have discussed at length how erecting barriers facing the wind over mid-latitude oceans could also slow down the Westerlies and result in the removal of Westerly atmospheric angular momentum from the atmosphere on another thread recently. The difficulty in establishing anything solid over the oceans is not, of course, to be underestimated but ocean surfaces still represent some 40% of all the surface of the Earth between 40N and 65N- those locations most likely to get strong westerlies in winter. Moreover, the strongest and most persistent Westerlies occur over the oceans in winter in the Northern Hemisphere so any serious attempt to weaken the higher-latitude Westerlies and give Britain a chance of better Christmases in future will need to give serious thought to practical ways of increasing surface friction and surface roughness to the regions that get westerly winds more or less continuously.  

Edited December 23, 2016 by iapennell

[hillbilly]

On ‎23‎/‎12‎/‎2016 at 02:52, iapennell said:

Late December not stormy? I live in the North Pennines and can recall west or south-westerly gales in late-December in 1983 (very bad ones), 1986, 1991, 1997, 1998 (severe gales), 2011 and (particularly) 2013. Late December last year was very wet as well as stormy.

Sorry it seemed to me you were suggesting it was this time of year that it got stormy.I was not suggesting it is always quiet at this time but stormy weather can be any time from October to April  and 7 stormy or very windy ends of the year out of 35 years is probably similar in any of the above months .

[iapennell]

Actually THIS is the root cause of strong south-west and westerly winds heading our way in late December- very strong Westerlies in the Stratosphere and upper troposphere over (and just polewards) of the latitudes of Britain: It is a sight for sore eyes for those who hope for cold weather at this time of the year! Now imagine what could happen if we could somehow make the very strong Westerlies (the dark red in this example are winds averaging 90 metres per second- or 200 mph from the West) disappear: Several methods of achieving this result include the following:

1) Exploding of large quantities of soot and dust into the stratosphere about October-time over the Arctic- there is still a little weak sun by day at elevation over the Arctic and dust here would serve two purposes. First would be the warming of the Stratosphere as the Stratosphere absorbed more solar radiation- this would lead to a weakening of the Westerlies on the fringes of the Arctic. Secondly little insolation would reach the surface and that would hasten seasonal cooling below leading to more pack-ice: Result- more high-pressure over the Arctic going into winter.

2) Build a very high wall over mountainous areas of Alaska- up to 20 km high. Such a wall would operate as a barrier impeding the flow of strong upper Westerlies going into winter. That would greatly diminish the intensity and frequency of wild wet and stormy conditions at Christmas over Britain and it would dramatically increase the likelihood of much colder weather from the Arctic or from Russia.

3) Drill a deep hole into the fault-line separating the Eurasian and North American plates in the far north of Iceland: Drill down enough and far enough until the magma welling up from below is reached in order to provoke a truly massive volcano- so much lave would be poured out (and so explosively) that heat from the lave would warm the upper atmosphere and lead to a weakening of the Circumpolar Vortex. The volcano produced would also pump tonnes of ash into the Stratosphere which would block out the weak winter sunshine on the fringes of the Arctic leading to cooling below. The results would be similar to the first method- leading to increased high-latitude blocking.

4) Only as a last resort (and if all else fails or the technology and man-power cannot be accessed to do the above) explode a powerful H-bomb in the Arctic Stratosphere around November-time. This would warm the Arctic Stratosphere dramatically; weaken the steep winter-time temperature gradients in the Stratosphere on the fringes of the Arctic encouraging high-latitude blocking to occur- with higher-latitude depressions pushed into lower latitudes. A man-made Sudden Stratospheric Warming over the Arctic would have the same impact as a naturally-occurring one; the only problem is dealing with (and mitigating the effect of) any radiation fallout afterwards.

BTW the Russians and Americans tested H-bombs over Pacific islands in the 1960's without causing mass deaths (even though there were local ecological effects). If this is too much one could have lots of 1000-tonne TNT bombs dropped from a myriad high-flying aircraft timed to explode at the right height- this would alleviate radiation concerns and there would still be a Sudden Stratospheric Warming- of sorts!

And a Merry Christmas to you all. If I think of any other (more practical) ways of smashing the hated Ferrel Westerlies I will let you know and we can have a healthy discussion about them. All the best for 2017 to users of this Forum!