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Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

Posted Images

I am copying this post across to this thread where it really belongs. My original post (from Monday) was more teleconnections related and only partly on the upcoming SSW but it was largely that part to which @Interitus replied. This is my response to his comments. I feel that this discussion should continue on here so that it does not disrupt the model thread as being slightly off topic there.  First Interitus' post:

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A couple of observations - 'uplift' from mountains doesn't produce 'vertical Rossby waves'. These would be orographic gravity waves - oscillations in the vertical which are restored to equilibrium through the density of the air parcels acting under gravity. They can increase in amplitude with height and reach a point where they break depositing their energy (possibly in the strat). But they are not planetary waves (wave 1, 2 etc) or Rossby waves. Rossby waves act in the horizontal plane perpendicular to the flow with the restorative force being the gradient of potential vorticity (typically north-south). This applies to the stationary waves from mountain torques also, where the height of the topography increases the amplitude of the wave, speed of the flow determines wavelength.

For winter 2009/10, the UK did experience cold weather after the SSW with a deeply negative AO - however the lowest AO and coldest UK weather occurred before the SSW on Feb 9th, as shown in the graph below (windspeed left axis, AO and CET right axis), with a healthy mid and upper strat vortex at the time -

2009-10.thumb.png.7e68f8e9abee6532907062a022df956d.png

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 Now my response:

I feel that I must respond to you as I largely disagree. Before I start, I should say that you have a most unfortunate habit of either misquoting long posts, cherry picking and quoting out of context or missing the main points being delivered in the post. You have actually managed to achieve all of these in only two paragraphs of your "observations"! While I respect that you have been specialising in the stratospheric processes for much longer than myself, some of your arguments are based on earlier theories which do not always reflect the latest thinking. Some of the interaction between the lower tropospheric teleconnective drivers and how they combine to influence the stratosphere, has, as I'm sure you realise, undergone significant change in recent years with an evolution of the understanding and considerable research being undertaken. This is gathering momentum with a number of new papers being published and a whole raft of them in the pipeline - not least various investigations into the early 2018 SSW events. As you have responded on this thread, I shall do likewise but I will copy this across to the strat thread afterwards so that other strat specialists can comment on this new theory and I will be facinated to hear what they have to say. 

Much of my last two main posts were centred around putting the recent theory on the influence of the Mongolian Mountains in helping to trigger major SSW events to the test. For those who wish to follow where we're at and the audit trail, here they are:

My post on page 6 of the model thread was entitled: "UPCOMING COLD SPELL - TELECONNECTIONS UPDATE WITH YET MORE ENCOURAGEMENT". 

Here's a direct link: https://www.netweather.tv/forum/topic/91032-hunt-for-cold-model-discussion-heading-into-christmas/?do=findComment&comment=3941269

My previous post entitled from December 13th was on page 295 of the previous model thread:  "A MAJOR SUDDEN STRATOSPHERIC WARMING (SSW) LATER THIS MONTH?  TESTING AN IMPORTANT RECENT THEORY".  

Here's a direct link: https://www.netweather.tv/forum/topic/90862-the-hunt-for-cold-model-discussion-late-november/?do=findComment&comment=3938049

I also referred back to two very long posts that Malcolm @Blessed Weather and I produced on a US forum Teleconnection thread back in April.  In fact you challenged Malcolm and myself to prove some of the links between Mountain Torque (MT) and SSW events back in February/March 2018 immediately after that SSW.  We had been looking into a number of papers on earlier SSWs.  Since then we have not only found some extremely strong evidence but we have built up a library of many 100s of Teleconnection related papers on the US forum. Here's a link to the main topics index (just click on the heading):   INDEX TO PAPERS AND PRESENTATIONS  . It has become so big that we have had to split it into two this week.

The main paper that we're both referring to is:  Orography and the Boreal Winter Stratosphere: the Importance of the Mongolian mountains  (click on the title for a link to the portal abstract where there's a link to the full paper).

This amazing paper was researched and published "before" the 2018 SSW but so much of the theory almost perfectly fitted into the timing of teleconnection interactions in the build up to and the triggering of the major SSW and the secondary warming.  I note that you referenced this paper about 3 months after Malcolm found it and I reviewed it. - so you must have read it but it seems that you are dismissing some of the findings although you do not directly say that - very puzzling. I will not repeat my very detailed review of that paper again now but I will quote from it in relation to several of your rather erroneous comments. 

This on rossby/planetary waves and gravity waves:  

"3.3 Impacts on Wave Activity Orography induced anomalies in EP flux divergence can be caused either by a change in wave activity amplitude or by changes in wave propagation pathways. If changes in wave amplitude were the dominant cause of the orography induced anomalies in EP flux divergence, then the pattern of anomalous EP fluxes would be nearly identical to that in the control just with reduced amplitude. Figures 2f and g show that, near the band of latitudes spanned by the mountains (⇠30-55N), the presence of the Mongolian or Tibetan mountains produces a strong increase in wave activity propagating upwards from the surface into the upper troposphere; however the orography induced EP flux anomalies have generally different propagation pathways from the troposphere to the upper stratosphere than the climatology (c.f. Figures 2f and g with Figure 2d). Mountains thus also induce changes in wave propagation paths. Additionally we find that orography induced anomalies in wave amplitudes for Z at 10 hPa (for wavenumbers k = 1, 2) are inconsistent with the changes in EP flux divergence across the three experiments (see supplemental Figure 196 S2), further suggesting that the orography induced changes in EP flux divergence cannot be attributed solely to the orography acting as an additional source of Rossby waves. –7– Confidential manuscript submitted to Geophysical Research Letters. Since changes in wave amplitude alone cannot explain the changes in EP flux divergence, we examine orography induced anomalies in KS (Figures 2f-h), which can alter wave propagation pathways and thus EP flux divergence. Between ⇠55-80 200 N and 10 hPa the Mongolian mountains induce a change in KS with a positive poleward gradient. This would act to deflect wave activity poleward relative to the control case and thus cause an increase in EP flux convergence poleward of ⇠50N, consistent with the orography induced anomalies in EP flux vectors and convergence in this region (Figure 205 2b). The mountains also generally increase KS in the stratosphere, which will allow more wave activity to propagate vertically into the stratosphere, where it can converge. Orography induced changes in KS are primarily due to changes in the meridional gradient of potential vorticity (qy ) and the zonal wind (u), and not changes in buoyancy ( f 2 0 /4N2H2).  The change in KS due to the Tibetan mountains has a similar spatial structure to the changes due to the Mongolian mountains, but are of smaller magnitude (Figure 2g), consistent with the smaller changes in EP flux divergence and u. Compared to Mongolia or Tibet, the Rockies have a much smaller impact on KS (Figure 2h), consistent with the small impact of the Rockies on the stratospheric zonal wind. These results indicate that changes in refractive index are of central importance for the impact of orography on the wintertime stratospheric circulation. The changes in KS stem from changes in the circulation of the upper troposphere associated with the various orographic features. As shown by White et al. [2017], the Mongolian mountains have a greater impact on the upper tropospheric wintertime circulation than the Tibetan plateau."

Now I won't for one minute admit to understanding the maths and equations (perhaps you do) but I always read the abstract, the introduction and conclusions when I read any paper and if I wish to learn more then I carefully read the full text. I discussed this with Malcolm and this is a decent short summary of that section:   

  • Rossby Waves are a bit of a red herring and (in hindsight) probably shouldn't have been mentioned although many authors do not distinguish between Rossby waves and Planetary waves..
  • Planetary Waves 1 and 2 impacting on EP-Flux convergence/divergence is what it relates to. 
  • This is NOT the amplitude of the Waves but by the mountains altering the propagation pathways of the waves poleward and by also allowing more waves to propagate vertically into the stratosphere.
  • Gravity waves can be part of the process but it is much more than that - there's another whole section on that

 

The main points here and also described in several other recent and some earlier papers which I reviewed in my very long April post, is that the Himalayas obstruct the southerly Asian jet stream. It's the interception by the high Himalayan peaks which are easily high enough to penetrate the lower portion of the jet stream. It doesn't matter whether it's a due west to due east jet flow (as recently and now) or a more south west to north east flow.  I feel that this is where several scientists have misunderstood this "new" theory (or in some cases are not prepared to entertain something that rather challenges conventional wisdom). The recent theory is not suggesting that the jet stream passes directly over the Mongolian range. In fact it very rarely does. It's the channeling and funneling which guides the flow northwards as it rushes down the lee side of the highest Himalayan peaks across the high Tibetan Plateau until it hits the Altai range and this where the extraordinary uplifting is produced (my long post back in April thoroughly examined the whole unique geography of the region with many maps and charts). It simply cannot be a coincidence that the strongest EAMT usually appears at 40N to 45N precisely where the Altai range blocks the flow.  I also explained that the traditional thinking of "only" mountain ranges which are perpendicular to the largely west to east jet stream (like the Rockies and Andies) is not the be all and end all to mountain torque and vertical propagation - in fact very far from it.  Back in 2002 the leading proponent of the GSDM (Global Synoptic Dynamic Model) and the GWO (Global Wind Oscillation) Dr Klaus Weickmann realised that EAMT (East Asian Mountain Torque) had far more impact on vertical propagation than NAMT (North American Mountain Torque) and he even refers to the unique properties of the Tibetan Plateau.  Following through on the development of the latest theories makes for fascinating reading right through to this Mongolian Mountain paper. The authors are currently completing even more research in this field and I imagine the early 2018 SSW and the highly likely late 2018 SSW events will feature heavily as they present further evidence to back up their theories..

Aside from this paper, there also appears to be a link between gravity wave drag (gwd) and EAMT.  Here's a gwd chart that I've rarely seen shown in any post with the MT chart for the same date alongside:

grw1.thumb.PNG.8589a19c2440b5cf11ab36bf671abb2a.PNG   mt13.thumb.PNG.daa5669d414a7b8be0c43b476a2634e6.PNG

They are at their global greatest in the east Asian mountains.  In fact almost all the activity or gwd appears in the sub tropics - mostly in the N Hem (all year round) but in the S hem to a lesser extent in their winter where I've noted some over Antarctica in July and a little around 70S to 75S on the edge of that continent (some pretty high mountain there), mostly in their winter but a little at other times (as can be seen). More recently, most gwd has centred around 40N and there is a partial correlation with EAMT which seems to follow changes in gwd several days afterwards.  Follow the blue and yellow blobs at 30N to 50N right through.  Overall, the point here is that whatever the more significant factor (which might well vary during different episodes) the strongest EAMT spikes appear over the Mongolian Mountains and especially the Altai range.  The vertical propagation on occasions can be so strong that it influences the lower mesosphere and with waves breaking from very high levels.  A prolonged +ve EAMT event (over a few days) can potentially send up successive or multiple impacts with breaking from above and below.  It is essential that this new theory is thoroughly investigated.  I said in my posts that I am putting this theory to the test with the upcomng anticipated SSW.  

Several of the EAMT/Asian Monsoon papers I've read focused heavily on gwd and affirmed that much of the uplift was generated by the EAMT/gwd combo. This is far more in relation to tropospheric impacts and more in the summer half of the year. I've also read a paper on gravity waves and their impact in the tropics and in relation to ENSO and that's another area to study (gws and kelvin wave activity). These are the papers on gws and gwd which are in the Research Portal.  Again just click on the title for a link to the abstract where there's a direct link to the paper:

Gravity Waves (and Gravity Wave drag):

A comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings

Circumglobal Propagation of Successive MJO Events in MERRA-2 - Presentation

Convective Adjustment, Gravity Waves and Diurnal Regulation of Tropical Cyclogenesis - Presentation

Coupling of Stratospheric Warmings with Mesospheric Coolings in Observations and Simulations

Dynamical control of the mesosphere by gravity wave drag

Effects of Parameterized Orographic Drag on Weather Forecasting and Simulated Climatology Over East Asia During Boreal Summer

Gravity wave drag

Gravity Wave Effects on Polar Vortex Geometry During Split-Type Sudden Stratospheric Warmings

Gravity wave refraction by three-dimensionally varying winds and the global transport of angular momentum

Improving weather forecasts via impacts of turbulent orographic form and small-scale orographic gravity wave drag on boundary layers

Interannual variability in the gravity wave drag – vertical coupling and possible climate links

Kelvin Waves - A Learner's Guide

Mountain Waves and Downslope Winds

On the importance of gravity waves in the middle atmosphere and their parameterization in general circulation models

Parameterized Gravity Wave Momentum Fluxes from Sources Related to Convection & Large-Scale Precipitation Processes in Global Atmosphere Model

Propagation of planetary‐scale disturbances from the lower into the upper atmosphere

Regional Variations in Gravity Waves, Latent Heating, and the Tropical Circulation

Role of gravity waves in vertical coupling during sudden stratospheric warmings

Studies of atmospheric angular momentum

The Challenge of Classifying Propagating Synoptic Disturbances in the African Tropics – Examples from the DACCIWA Field Campaign - Presentation

The physics of orographic gravity wave drag

The roles of planetary and gravity waves during a major stratospheric sudden warming as characterized in WACCM

The whole atmosphere response to changes in the Earth’s magnetic field from 1900 to 2000

Toward a Physically Based Gravity Wave Source Parameterization in a General Circulation Model

Variability of African Easterly Wave Structures- Presentation

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

Why do Earth's equatorial waves head east?

I will not review any of these papers now (some readers will be relieved to hear) but in due course some of them can be reviewed on the teleconnections threads (here or across the pond). .

Finally, the part where you misquoted me the most was my reference to the 2009/10 winter. Firstly, as we know, every SSW is different and one should use analogue years with great caution.  The references that I made to that winter was in relation to how well primed the troposphere and surface was to SSW impacts. The difference in the main SSW itself was, as you say, the upcoming event (assuming it does happen which now seems almost certain) will be over 1 month earlier.  I have been referring to the blocking in Russia (right now and expanding HP to come over the next week to days) and another precursor to an SSW is the Asian blocking - probably no coincidence that the powerful jet streak over south and east Asia is propping up that HP.  Then I added in the MJO, AAM, torque factors plus the major "pattern re-set" and a fairly cold and blocked period is expected even without the assistance of an SSW.  To get an early season SSW plus these other teleconnections playing ball more or less simultaneously is particularly encouraging for those looking for cold.  Overall, I am prepared to accept that you may have misunderstood my comments in relation to the 2009/10 winter but most of your "observations" were really pretty wide of the mark.   David ? 

Edited by Guest
check charts, links and correct typos
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SOME USEFUL LINKS TO PAPERS AND PRESENTATIONS

I've noticed a number of references to SSW papers and the majority of these are already in the Research Portal that we have built up across the pond.  I felt that you might appreciate a list them now - just click on the title to go to the portal abstract and then you can decide if you wish to link to the full paper from there:

 

Sudden Stratospheric Warming (SSW):

A climatology of polar winter stratopause warmings and associated planetary wave breaking

A comparative study of the major sudden stratospheric warmings in the Arctic winters 2003/2004 – 2009/2010

A Dynamical Model of the Stratospheric Sudden Warming

A sudden stratospheric warming compendium

Blocking high influence on the stratospheric variability through enhancement and suppression of upward planetary-wave propagation

Blocking precursors to stratospheric sudden warming events

Breaking planetary waves in the stratosphere

Changes in Frequency of Major Stratospheric Sudden Warmings with El Niño/Southern Oscillation and Quasi-Biennial Oscillation

Characterizing Stratospheric Polar Vortex Variability With Computer Vision Techniques

Consequences of Arctic Amplification: Role of the Stratosphere - A Discussion

Coupling of Stratospheric Warmings with Mesospheric Coolings in Observations and Simulations

Defining Sudden Stratospheric Warmings

Defining Sudden Stratospheric Warming in Climate Models: Accounting for Biases in Model Climatologies

Different ENSO teleconnections and their effects on the stratospheric polar vortex

Dynamic coupling of the stratosphere with the troposphere and sudden stratospheric warmings

Dynamical control of the mesosphere by gravity wave drag

Dynamics of 2013 Sudden Stratospheric Warming event and its impact on cold weather over Eurasia: Role of planetary wave reflection

Effect of Madden–Julian Oscillation Occurrence Frequency on the Interannual Variability of Northern Hemisphere Stratospheric Wave Activity in Winter

Effects of stratospheric variability on El Niño teleconnections

El Niño, La Niña, and stratospheric sudden warmings: A reevaluation in light of the observational record

Enhanced seasonal forecast skill following stratospheric sudden warmings

Extraordinary Features of the Planetary Wave Propagation During the Boreal Winter 2013/2014 and the Zonal Wave Number Two Predominance

Gravity Wave Effects on Polar Vortex Geometry During Split-Type Sudden Stratospheric Warmings

Hindcasting the January 2009 Arctic Sudden Stratospheric Warming and Its Influence on the Arctic Oscillation with Unified Parameterization of Orographic Drag in NOGAPS. Part I: Extended-Range Stand-Alone Forecast

Identification and Classification of Sudden Stratospheric Warming Events

Impact of the Stratosphere on the Winter Tropospheric Teleconnections between ENSO and the North Atlantic and European Region

Life Cycle of the Northern Hemisphere Sudden Stratospheric Warming

Linking stratospheric circulation extremes and minimum Arctic sea ice extent

MJO‐Related Tropical Convection Anomalies Lead to More Accurate Stratospheric Vortex Variability in Sub-seasonal Forecast Models

Influence of subtropical Rossby wave trains on planetary wave activity over Antarctica in September 2002

Influences of the 11-year sunspot cycle on the stratosphere – and the importance of the QBO

More Frequent Sudden Stratospheric Warming Events due to Enhanced MJO Forcing Expected in a Warmer Climate

Multi‐decadal variability of sudden stratospheric warmings in an AOGCM

No robust evidence of future changes in major stratospheric sudden warmings: a multi-model assessment from CCMI

Northern Hemisphere mid‐winter vortex‐displacement and vortex‐split stratospheric sudden warmings: Influence of the Madden‐Julian Oscillation and Quasi‐Biennial Oscillation

Northern Hemisphere Stratospheric Pathway of Different El Niño Flavors in Stratosphere-Resolving CMIP5 Models

Observed connection between stratospheric sudden warmings and the Madden-Julian Oscillation

On the Relationship between ENSO, Stratospheric Sudden Warmings and Blocking

On the reproducibility of the September 2002 vortex splitting event in the Antarctic stratosphere achieved without satellite observations

Orography and the Boreal Winter Stratosphere: the Importance of the Mongolian mountains

Planetary‐scale wave activity as a source of varying tropospheric response to stratospheric sudden warming events: A case study

Preconditioning of Arctic Stratospheric Polar Vortex Shift Events

Progress in research of stratosphere-troposphere interactions: Application of isentropic potential vorticity dynamics and the effects of the Tibetan Plateau

Revisiting the ENSO–SSW Relationship

Role of Finite-Amplitude Eddies and Mixing in the Life Cycle of Stratospheric Sudden Warmings

Role of gravity waves in vertical coupling during sudden stratospheric warmings

Rossby Wave Propagation into the Northern Hemisphere Stratosphere: The Role of Zonal Phase Speed

Separating the stratospheric and tropospheric pathways of El Niño–Southern Oscillation teleconnections

Simulations of the Boreal Winter Upper Mesosphere and Lower Thermosphere With Meteorological Specifications in SD‐WACCM‐X

Snow–(N)AO Teleconnection and Its Modulation by the Quasi-Biennial Oscillation

Solar and QBO Influences on the Timing of Stratospheric Sudden Warmings

Sudden Stratospheric Warmings and Anomalous Upward Wave Activity Flux

Sudden Stratospheric Warming: Causes & Effects

Sudden Stratospheric Warmings – developing a new classification based on vertical depth, applying theory to a SSW in 2018, and assessing predictability of a cold air outbreak following this SSW

The association between stratospheric weak polar vortex events and cold air outbreaks in the Northern Hemisphere

The Downward Influence of Sudden Stratospheric Warmings: Association with Tropospheric Precursors

The Influence of the Solar Cycle and QBO on the Late-Winter Stratospheric Polar Vortex

The MJO‐SSW Teleconnection: Interaction Between MJO‐Forced Waves and the Midlatitude Jet

The preconditioning of major sudden stratospheric warmings

The Role of Zonal Asymmetry in the Enhancement and Suppression of Sudden Stratospheric Warming Variability by the Madden–Julian Oscillation

The roles of planetary and gravity waves during a major stratospheric sudden warming as characterized in WACCM

The stratopause evolution during different types of sudden stratospheric warming event

Three Types of Synoptic Events and Their Associated Troposphere-Stratosphere Coupling

Toward a Physically Based Gravity Wave Source Parameterization in a General Circulation Model

Tropospheric Precursors and Stratospheric Warmings

Tropospheric and Stratospheric Precursors to the January 2013 Sudden Stratospheric Warming

Upward Wave Activity Flux as a Precursor to Extreme Stratospheric Events and Subsequent Anomalous Surface Weather Regimes

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

What is a Polar Stratospheric Warming?

What is the GSDM and how does it help with subseasonal weather forecasts?          (A YouTube Presentation) 

What kind of stratospheric sudden warming propagates to the troposphere?

Zonal Phase Speed, Wave Propagation into the Stratosphere, and Atmospheric Blocking

 

Stratospheric Polar Vortex (SPV):

Characterizing Stratospheric Polar Vortex Variability With Computer Vision Techniques

Defining Sudden Stratospheric Warming in Climate Models: Accounting for Biases in Model Climatologies

Different ENSO teleconnections and their effects on the stratospheric polar vortex

Effect of Madden–Julian Oscillation Occurrence Frequency on the Interannual Variability of Northern Hemisphere Stratospheric Wave Activity in Winter

Gravity Wave Effects on Polar Vortex Geometry During Split-Type Sudden Stratospheric Warmings

Impact of the Stratosphere on the Winter Tropospheric Teleconnections between ENSO and the North Atlantic and European Region

Linking stratospheric circulation extremes and minimum Arctic sea ice extent

More persistent weak stratospheric polar vortex states linked to cold extremes

Near-term Climate Predictions of the North Atlantic Region - YouTube Presentation

No robust evidence of future changes in major stratospheric sudden warmings: a multi-model assessment from CCMI

Northern Hemisphere Stratospheric Pathway of Different El Niño Flavors in Stratosphere-Resolving CMIP5 Models

On the reproducibility of the September 2002 vortex splitting event in the Antarctic stratosphere achieved without satellite observations

Planetary‐scale wave activity as a source of varying tropospheric response to stratospheric sudden warming events: A case study

Preconditioning of Arctic Stratospheric Polar Vortex Shift Events

Progress in research of stratosphere-troposphere interactions: Application of isentropic potential vorticity dynamics and the effects of the Tibetan Plateau

Role of Finite-Amplitude Eddies and Mixing in the Life Cycle of Stratospheric Sudden Warmings

Snow–(N)AO Teleconnection and Its Modulation by the Quasi-Biennial Oscillation

Stratosphere-troposphere evolution during polar vortex intensification

Stratospheric Harbingers of Anomalous Weather Regimes

Stratosphere‐troposphere exchange

The association between stratospheric weak polar vortex events and cold air outbreaks in the Northern Hemisphere

The Influence of the Solar Cycle and QBO on the Late-Winter Stratospheric Polar Vortex

The stratopause evolution during different types of sudden stratospheric warming event

The stratospheric pathway for Arctic impacts on midlatitude climate

Tropospheric Cooling as a Mechanism for Stratospheric Polar Vortex Disturbances

Upward Wave Activity Flux as a Precursor to Extreme Stratospheric Events and Subsequent Anomalous Surface Weather Regimes

Varying stratospheric responses to tropical Atlantic SST forcing from early to late winter

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

What is a Polar Stratospheric Warming?

What is the Polar Vortex?

What is the Polar Vortex and How Does it Influence Weather? - Essay

 

Some titles are repeated under both headings.  There are also headings under Stratopshere and Coupling amongst others - here's the link to the full index:

 

INDEX TO PAPERS AND PRESENTATIONS      

 

I hope this is useful,  David :)  

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Didn't we have prior to the recent east QBO a double Westerly QBO is it possible that QBO is is also important in vortex disruption.

Because the QBO had a double season which does not seem to show ever in any records or data.

Is there any evidence of this ever happened before.

The stratosphere seems sensitive to solar minimum especially flat lined minimum.

And also February stratospheric warming event was the strongest ever recorded against the data collection.

But in a true minimum could this have been the normal.

 

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^^ Thanks for continuing the above discussion in this thread David. I know that the Mongolian Mountain paper you refer to above raised our eyebrows when we discovered it earlier this year. After all, the following is quite some claim: 

"The Mongolian mountains decrease the boreal winter stratospheric jet strength by ∼1/3 and increase the frequency of major sudden stratospheric warmings from 0.08 year to the observed 0.60 year."

When we looked at the factors building up to the Feb 2018 SSW it certainly appeared to us that the Mongolian Mountains had played their part in bringing about the final downfall of the SPV.

It would be most welcomed if others on here could find the time to take a look at the paper and give any comments they may have. Many thanks.

Edited by Blessed Weather
Deleted reference to another forum.
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20 minutes ago, ArHu3 said:

ecmwf10f216.gif

 

Yesterday's EC going for a split by day 9

I posted this yesterday Arhu?

anyway, yesterday’s ec op is confirmed technical ssw by day 10 (as expected ) and the heights at the very top are crazy split at that timescale 

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10 minutes ago, bluearmy said:

I posted this yesterday Arhu?

anyway, yesterday’s ec op is confirmed technical ssw by day 10 (as expected ) and the heights at the very top are crazy split at that timescale 

Busy day at work, so I guess I missed it but this is today's so the split is still there 

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34 minutes ago, ArHu3 said:

Busy day at work, so I guess I missed it but this is today's so the split is still there 

the same arhu - this mornings Berlin is yesterday’s noon run .... I posted it from another site 

anyway, the 00z run is on the same page, a little less amplified and the split at 10hpa delayed around 36 hours. Again, splitting from the top rather than the bottom (this a major difference between the ec and gfs which splits upwards and obviously promotes uncertainty )

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21 hours ago, Interitus said:

Obliteration of the strat on the GFS 06z - reversal from 264 hrs (29/12 06z) down to -18.7 m/s at t372

Since this run the minima have been -10.6, 1.8 and 3.2 m/s ...er...

The 00z GFSFV3 para was 4.5 m/s ... hmm.

Would look at more from the para but the source (NOMADS) seems to miss or discard the data very quickly.

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7 minutes ago, Interitus said:

Since this run the minima have been -10.6, 1.8 and 3.2 m/s ...er...

The 00z GFSFV3 para was 4.5 m/s ... hmm.

Would look at more from the para but the source (NOMADS) seems to miss or discard the data very quickly.

These GFS strat forecasts seem to be all over the place?

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2 hours ago, Don said:

These GFS strat forecasts seem to be all over the place?

Yes I’m curious as to why strat forecasts at such range would be any more reliable than typical tropospheric forecasts? After all, the cause of the SSW is as a direct result of goings on within the troposphere if my understanding is correct. We all know not to trust the models beyond 120-144hrs so can’t help but be circumspect of these long range stratospheric forecasts.

Question for the experts, assuming we get a SSW, what impacts length of time for effects to filter down into the troposphere? Lots of nervous people in the cold hunt thread but surely eye candy charts won’t even be shown yet as they are out of reach. I’ve read various sources that suggest it typically takes a week or two for the effects to filter down into the troposphere. Based on that, and assuming PV split around Boxing Day (as per tweet above), realistically, we should expect to see less Atlantic influence and more HL blocking being picked up by the models from around 7th Jan?

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Could GFS be ineffective at resolving crucial wave-2 forcing from above 10 hPa due to lower resolution than ECM and GloSea5..?

I’m not sure if it’s lower in the first place these days - if anyone knows and can share that’d be much appreciated.

 

Regardless, ECM and GloSea5 have my trust over GFS.

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5 minutes ago, Altostratus said:

Yes I’m curious as to why strat forecasts at such range would be any more reliable than typical tropospheric forecasts? After all, the cause of the SSW is as a direct result of goings on within the troposphere if my understanding is correct. We all know not to trust the models beyond 120-144hrs so can’t help but be circumspect of these long range stratospheric forecasts.

Question for the experts, assuming we get a SSW, what impacts length of time for effects to filter down into the troposphere? Lots of nervous people in the cold hunt thread but surely eye candy charts won’t even be shown yet as they are out of reach. I’ve read various sources that suggest it typically takes a week or two for the effects to filter down into the troposphere. Based on that, and assuming PV split around Boxing Day (as per tweet above), realistically, we should expect to see less Atlantic influence and more HL blocking being picked up by the models from around 7th Jan?

I don’t have the time for a full reply right now - and we should still be cautious of any model output at such a range without some ensemble consensus (which fortunately we do have to a large extent at the moment). But the primary reason that stratospheric modelling should in theory be more accurate is that it is an easier environment to model - you don’t have large geographic features like bodies of water and big mountains in the way, you’re essentially dealing with a flat “surface”. Of course, there is always the argument that as tropospheric behaviour can affect the stratosphere, it is still open to the same flaws, but generally the physics of the situation should be easier to handle

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6 minutes ago, snowking said:

I don’t have the time for a full reply right now - and we should still be cautious of any model output at such a range without some ensemble consensus (which fortunately we do have to a large extent at the moment). But the primary reason that stratospheric modelling should in theory be more accurate is that it is an easier environment to model - you don’t have large geographic features like bodies of water and big mountains in the way, you’re essentially dealing with a flat “surface”. Of course, there is always the argument that as tropospheric behaviour can affect the stratosphere, it is still open to the same flaws, but generally the physics of the situation should be easier to handle

Yup completely agree with the environment being easier to model as less variables etc but I was specifically referring to forecasting SSW events - the initiator for these comes from the troposphere so surely usual limitations apply.   

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6 minutes ago, Altostratus said:

Yup completely agree with the environment being easier to model as less variables etc but I was specifically referring to forecasting SSW events - the initiator for these comes from the troposphere so surely usual limitations apply.   

And is the strat being modelled in its own right, or is it just an 'oops, I almost forgot' forecast, stuck on like an afterthought? If it's the latter, would strat forecasts not merely flap around in response to the latest tropospheric expectations...?

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There is quite a big difference around day 10 between the GFS and ECM regarding wave 1 displacement position and therefore influx and angle of warming. The ECM is far further west at 1 hPa. Significant differences like this will make a difference on the baroclinic tilt and forecast wave 2 activity that the displaced residual vortex will further down towards the troposphere. And because of this there will a certain amount of unreliability with medium range trop forecasts

NH_TMP_1mb_222.gif

ecmwf1f240.gif

NH_HGT_1mb_222.gif

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20 minutes ago, chionomaniac said:

There is quite a big difference around day 10 between the GFS and ECM regarding wave 1 displacement position and therefore influx and angle of warming. The ECM is far further west at 1 hPa. Significant differences like this will make a difference on the baroclinic tilt and forecast wave 2 activity that the displaced residual vortex will further down towards the troposphere. And because of this there will a certain amount of unreliability with medium range trop forecasts

NH_TMP_1mb_222.gif

ecmwf1f240.gif

NH_HGT_1mb_222.gif

What would you put your money on ECM or GFS chino ?? Or could there be a middle ground ? 

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