The Sudden Stratospheric Warming 2011/2012

redsunset wrote: »

I came across this from an Italian website so here it is translated,gives some good info in helping to understand. Excuse some sentences that are difficult to understand because of dodgy translation.

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The QBO positive in conjunction with the low solar activity leads to a Stratospheric Polar Vortex ( VPS) is completely blocked, due to the semi-block full of "Brewer Dobson Circulation" that stratospheric level, is a real current hemispherical sundial can connect with the polar equatorial regions. In short, when the BDC is very weak, the VPS is very strong and cold as well as affected by stratospheric zonal wind very intense. Thus the entire structure of the polar vortex (VP) is very compact, with very few opportunities to exchange major meridians (Europe swept by the flow of warm ocean zonal matrix). In such a context, in fact, the large planetary waves, whose propagation is prerequisite for the cold air down from high to medium-low latitudes, enter into serious crisis. In other words, because of the high-speed stratospheric zonal, the heat flows from the array of tropical troposphere to the stratosphere polar penetrate up through the propagation of Rossby waves, are strongly divergent.
A similar situation is greatly aggravated by Nina moderate / strong central in nature. The strong trade winds, related to the Walker circulation that blow constantly on the ground over the years affected by the phenomenon of the Nina, potently inhibit the development of the Convention on much of the deep Pacific, being the largest ocean on the planet, turns out to be crucial for As regards the complaints against the VP. The reduction of air deep concern to the Convention has 2 effects:
1) further reduction of the strength of the BDC that much depends on the convective Pacific and in particular the amount of water vapor which, through the tropopause, the stratosphere Equatorial penetrate;
2) reduction of heat that flows from the troposphere into the stratosphere polar penetrate through the "breakthrough" in the layer of Rossby waves. Said terms "playful", the tropical heat of the Convention is a fuel for the formation of large, long waves can break into the stratosphere.
The situation described so far is "photographed" by some key images. First of all I report an image, captured by the satellite OMI-AURA, representing the amount of ozone in the polar stratosphere in early December. In this regard, remember that ozone transport from equatorial latitudes (where it originates) to the polar is related to the intensity of the BDC. Therefore the amount of ozone in the VPS is a good index to measure the strength of the BDC.



You can easily see the ozone hole just above the North Pole.
Secondly carry the image from ECMWF carriers on the EP-FLUX. In two words, remember that these vectors represent the amount of heat fluxes and momentum from the troposphere to penetrate the polar stratosphere. Therefore, the longer vectors indicate a good propagation and vertical flow of heat from the trope of the layer (good wave propagation).



You will notice that until mid-December (red circle) patterns were completely different, a symptom of a VPS in great shape. Precisely in this period were reached in the polar stratosphere temperatures very low, near-record. In the second half of the month but something has changed since the first heat fluxes have been able to penetrate in part into the stratosphere (green circle). This forcing, started as told in the middle of the month and due in large part to the action of the continuous wave 1 (wave-Pacific), will in the coming days to less warming of the first season.
As I have repeatedly pointed out in comments made ​​in the weather , the disorder is not at all associated with a dynamic thrust of the wave 1 (elevation of the Aleutian hp), but to a particular location of the lower middle VPS that has allowed the vortex semi-permanent Aleutian taking a particularly favorable position. Specifically, the continuing dynamic action induced by the tropo-wave 3 (Asian wave) led the Polar Vortex in the lower stratosphere, to assume a configuration with a major axis ellitticizzata highly favorable (Canada-Eastern Siberia). This location has enabled VPS elliptical same "catch air" right where you are in fact the only obvious sources of heat in the Pacific under the like Nina (+ SSTA in the western Pacific).



This trend is clearly perceptible even from paper to 500hPa (with which you certainly more familiar). In this regard, the red arrow represents the pressure exerted by the wave 3 resulting ellitticizzazione the VP (the axis of the ellipse is highlighted by orange arrow).
That dynamic has allowed, as mentioned, discrete inflow of heat by the wava 1 and the resulting first discrete stratospheric warming of the season, as well detectable by the following paper 10 hpa:



As mentioned repeatedly, the upcoming minor warming (however weak) will have major repercussions in the troposphere. The main effect will be to produce a rotation axis of the polar vortex with major redistribution of vorticity. In particular, the translation of warming from eastern Siberia to Canada will produce a major shift of vorticity of the VP to the Euro-Atlantic sector.



The figure shows the shift of warming on Canada resulting in migration of the centers of vorticity towards the European sector.

In this phase of migration of arctic masses there will be a weak recovery in wave 2 (wave-Atlantic), with the hp of the Azores which will be facilitated to gain ground toward higher latitudes temporarily. This ripple will produce later this year a rapid and very weak foray into the Arctic Mediterranean, whose implications do not seem yet to be fully framed by the models.
In the next phase (beginning of new year), the successful transition of the masses on the Arctic sector Euro Russian by the desplacement layer, an inevitable result of the strengthening of the polar jet over Europe, with a consequent increase in the zonal velocity. This phase will therefore very likely that your hp interference ocean on our country will therefore be affected by weather and mild temperatures for the period, especially during the day (in fact the strong temperature inversion, however, guarantee low temperatures at night, especially in areas internal and in the Po Valley). The persistence dell'anticiclone on Italy, however, should not be very durable. In fact, the propagation of the warming even at lower altitudes would produce a further lowering of the polar jet over western right, favoring the entry of our country short fronts the Atlantic / North Atlantic. It should still be a minor ripple, not able to make big jerks.
Meanwhile, because of the changed position of the VPS is expected to witness the interruption of the inflow of heat from the wave 1 and the upper stratospheric warming quotas should be gradually reabsorbed. Therefore, it should embody a kind of zero at the end of baric disturbances introduced by the previous situation of forcing.
So far the forecast should have a good chance of success. For the later can only make assumptions without much qualitative feedback especially temporally. However I will try to draw a trend line based on some considerations.
First of all is to include the imminent passage of the QBO at 50 hPa in negative territory, proven step by ECMWF forecasts on the trend of zonal wind:



From this paper shows clearly how in 10 days, the share of the equator and 50 hpa (red circle) is already on the QBO value neutral.
The passage of the QBO in the negative at this stage may not have large seasonal shocks as the consequent strengthening of the BDC will have no effects in the polar stratosphere immediately. In fact, the air particles that move from the equator to the poles through the BDC take between 3 to 4 months to get the pole. Therefore, the stratosphere will continue to be locked down. However there are other effects induced by the passage of the QBO negative, in this context, may still be interesting.
First, when the eastern tropical wind regime (QBO-), the tropical easterlies tend to restrict the width of the planetary wave -guides in the extratropical lower stratosphere, favoring a larger amplitude wave and a slower phase. Secondly, the QBO-is able to make an increase in convective activity in the Pacific, especially in areas already covered by the Convention Deep (western Pacific under Nina like). This phenomenon is more exasperated by the low solar activity.
For these reasons I expect that the next tropospheric forcing of the stratospheric polar damage can be more effective than the previous one and therefore is a good time that we are waiting for a long.
The dynamics of the disorder among other things could be quite similar to that which produced the first warming of the season, due to the reactivation of the Wave 3 (Wave Asian). In fact, the wave 3 receives heat (energy) from the Atlantic jet, which, as mentioned above, is expected to sharp increase from next week. Specifically, the intense Atlantic jet, not just cross the continent of Europe, tends to slow for thermodynamic reasons, accumulating a lot of heat in this area (Eurasia).
The pressure-induced reactivation of tropowave 3 ellitticcizzazione induce a new VP, resulting in recovery of heat flow by the wave 1 (EP-FLUX new convergent). At this stage, as indeed said, the amount of energy and heat may be much larger. The heat developed by the new layer for propagation may be more enhanced by the strong interest that the average zonal speed the lower stratosphere for a long time. In short I think there's a good chance of being able to attend a stratwarming respectable, which could have implications in the troposphere also remarkable.
With regard to the timing, you should go for long enough. Let's say that straddles the end of the beginning of January you could have the first three waves of reactivation. This activation may favor, together with the location of the VP ellitticcizata, the slowing of the jet over Europe, with resumption of the Atlantic wave 2 (omega shape of the VP). This could cause a first down on its own arctic continent of Europe. From this point on, would share the flow converged layer with stratospheric beginning of the new disorder, which could last several days. In the third week of the month it reached maturity stratwarming, with implications in the troposphere, which began to take place in late January / early February.
I repeat once again that this is a trend, especially as regards the timing. Therefore, the changes may be considerable. Moreover, the stratospheric forecasts still do not begin to frame any favorable situation. The season is not as we know the good ones and there are these "attacks" even the smallest clues favorable. And then as they say, hope is always the last to die.

INTEGRATION:



From this image taken from ECMWF ENSEMBLE this morning we see that the models begin to frame the dynamics described at the end of the article. In particular, it is clear the pressure wave induced by the trope of omega-3 resulting in the disposal of the VP. This particular configuration could lead to the end of the first decade of January (maybe later), a first foray into the Arctic on our country, whose trajectory and the consequent implications would obviously all be evaluated. The important thing, which seems to be reflected among others in different emissions modeling today, is that the VP seems to be brought back to ellitticcizzarsi, resulting in recovery of heat flows converging in the stratosphere by the peaceful wave 1. This is a prerequisite in view of the end of the month stratwarming suggested to me.