Why the Stratosphere Gave a False ENSO Signal in the Spring

[HM]

The latest and greatest trend these days is to blame everything on the sun, especially when it comes to ENSO changes. While I do agree that it is changes in the IMF/geomag activity that dictate ENSO, I want to concentrate solely on the physical and terrestrial effects instead. So from this point on, I hope you don't read anything that says, "because of the sun" for an explanation, or otherwise I'm a liar.

Back in 2009, when I made a call for El Niño to form, one of the factors used in determining the potential SST warming was the QBO. However, for this particular spring, the warming cannot be traced back to the QBO. The latest 30mb and 50mb numbers indicate that we are in a solid downwelling +QBO wave.

30mb QBO

2010 -16.02 -16.98 -19.68 -23.57 -26.28 -25.05 -9.84 1.45 6.58 10.83 12.16 10.97

2011 9.18 10.05 10.44 10.71

50mb QBO

2010 1.74 0.78 -0.34 -6.57 -12.68 -17.59 -18.32 -12.51 -4.30 4.07 8.58 8.51

2011 6.00 6.02 6.31 6.25

As a reminder, here is the classic temperature graphic showing how the QBO affects temperature through the thermal wind:

The +QBO, through equatorial profiles generally veering, produces an equatorial warm anomaly over the stratosphere. By weakening the z-circulations, the sinks across the subtropics cool. So while this cool anomaly in the subtropics has been occurring, the equator has been very cold. Here are temperature anomalies for the first half of May:

50mb Temp Anomaly May 1-15

30mb Temp Anomaly May 1-15

Here is the cold represented graphically from 25S to 25N:

This cold turn-about in April and the SST warming across the Tropical Pacific is no coincidence. Yes, climatologically, this is the time when the cooling, or warming if opposite phase, likes to weaken and is sensitive to smaller-scale forcings. However, this warming has been coming on a bit stronger than one would expect with the prevailing global conditions and the usual ENSO climo. The cold air over the Equator is fueling the convective waves that are responsible for the westerly wind anomalies and the subsequent warmings.

So, what else causes cold equatorial stratospheric temperatures? How about the other common scapegoat, La Niña?

Nope...

La Niña may cool global tropospheric temperatures, but the lack of widespread equatorial convection, normally expected, allows the growth of ozone in the stratosphere-a warming agent. In fact, between the +QBO and the La Niña, the upper level westerly winds and warming should be a no-brainer. It is the exact opposite phases that favor equatorial convection, enhanced water vapor flux and destruction of ozone, cooling the stratosphere.

So then what the heck is it already? Drum roll please...it was the final warming. The early and strong arrival of the final warming in April has been the driver of the cold equatorial stratospheric temperatures. If you refer back to the 30mb and 50mb temperature graphics, you will notice the polar areas are blazing still. Yes, the switch to summertime circulation is suppose to happen in the spring, but the speed and intensity of this feature was more robust than normal.

This was a record setting final warming folks. I've never seen anything like it and the graphs show it nicely:

North Pole min temps at 30mb

North Pole min temps at 50mb

Absolutely stunning. A huge anomaly like that, coming on so fast, displaced the remnant higher potential vorticity and more dense air away from the northern latitudes and into the tropical regions. This happens usually in a very slow, weaker and more compact setup during this time of year...not like what has happened in 2011. Ever since then, the instability has been enhanced over the Tropics, creating very coherent and and strong MJO waves.

Can this warming mature into more than just neutral or warm neutral? Yes, but the window of opportunity is brief, climatologically speaking. If the -QBO wave waits to come on and the remnant cold pool over the Equator can remain strong enough to allow continued WWBs, then the warm pool can easily slosh eastward this summer. The unique stratospheric setup we have now allows for two things to happen simultaneously for SST warming:

1. It allows the sinks to be weaker in the Subtropics, reducing the trade winds across the Equator and PDO-effect

2. Allows for coherent MJO waves to thrive in the cold anomaly across the Equator that kick off WWBs

The oncoming -QBO wave will sustain or redevelop the cold anomalies over the Equator; however, it will intensify the z-circulation and warming in the Subtropics. This combined with the -PDO would likely cap development. On the other hand, if the +QBO wave sustains much longer than normal, it would likely eat away at the cold anomalies in the lower equatorial stratosphere eventually (especially as we move deeper into summer). That would begin to tamper with warming, too. How long can this unusual setup hold?

[CoastalWx]

Cool stuff man. I was aware of the warm stratosphere, but never realized how cold it was in the tropics wrt the stratosphere. That's one hell of a reversal in a month up in the poles.

[HM]

Cool stuff man. I was aware of the warm stratosphere, but never realized how cold it was in the tropics wrt the stratosphere. That's one hell of a reversal in a month up in the poles.

Agreed...

The true La Nina/+QBO/low sun HT relationship idea certainly worked from mid winter on. The lack of a mid-winter warming and the intense cold stratospheric vortex fueled this final warming by just increasing wave amplitude. That is represented well in the swing in temp anomalies you noted.

This is a very odd stratospheric setup so enjoy it while it lasts!

[phil882]

The oncoming -QBO wave will sustain or redevelop the cold anomalies over the Equator; however, it will intensify the z-circulation and warming in the Subtropics. This combined with the -PDO would likely cap development. On the other hand, if the +QBO wave sustains much longer than normal, it would likely eat away at the cold anomalies in the lower equatorial stratosphere eventually (especially as we move deeper into summer). That would begin to tamper with warming, too. How long can this unusual setup hold?

Great work as always HM. Just drawing conclusions from your work, are you suggesting that regardless on what the QBO decides to do as we progress further into the Summer and Fall, it will not perpetuate the current pattern of strong eastward propagating MJO's (along with associated WWB) that have been eating away at the cold SSTA across the equatorial Pacific? What would it take to keep the positive feedback cycle going in order to allow a substantial change in the ENSO state (say towards something other than just a weak El Nino)?

[HM]

Great work as always HM. Just drawing conclusions from your work, are you suggesting that regardless on what the QBO decides to do as we progress further into the Summer and Fall, it will not perpetuate the current pattern of strong eastward propagating MJO's (along with associated WWB) that have been eating away at the cold SSTA across the equatorial Pacific? What would it take to keep the positive feedback cycle going in order to allow a substantial change in the ENSO state (say towards something other than just a weak El Nino)?

Thanks a lot Phil. Good question. I suppose I did say that it cannot last by suggesting that whatever the QBO decides to do would be detrimental. As we press forward, ultimately the current unusual stratospheric setup is going to breakdown. It may be as simple as the N. Pole temps coming back to normal, the subtropical sinks warming from the upcoming -QBO or the equatorial temps rising from the ongoing +QBO.

I would imagine that if we continue to have a high frequency/amplitude MJO cycle, that it would be a positive feedback to the cooling equatorial stratospheric temperatures. The sun going back into the crapper will do the same thing. I suppose if these two features can go as long as possible, that would help sustain the unusual stratospheric setup through feedback processes...

But even then, it is only a matter of time. But, the longer this takes, the stronger the warming.

[skierinvermont]

Excellent write up. I noticed the final warming occurred earlier and stronger than usual this year but it didn't occur to me to connect that to the unusually rapid decay of La Nina.

A couple questions...

If a cooler stratosphere causes more pronounced MJO activity, has anybody tried to connect the cooling stratosphere (associated with declining stratospheric ozone and an increasing greenhouse effect) with the evidence that ENSO acitivity/amplitude has been more pronounced this century than previous?

Any idea what set off the stronger early final warming this year?

[Supercane]

Great post, HM. I'm not sure I follow why west QBO warms the equatorial stratosphere while east QBO cools it? I understand it has to do with the thermal wind, but I thought thermal wind was a consequence of temperature gradient, not a cause. I suppose that may be getting into what drives the QBO in the first place.

Also, you mention that the solar activity is not to blame for the recent ENSO warming. Based on history, I agree, as rising/high solar activity seems to correlate with La Niña persistence. However, I've noticed that rising/high solar activity also correlates with El Niño persistence. Am I mistaken, or have you noticed this before too? I'm trying to figure out why that would be the case. My best guess is that rising/high solar activity = decreased cosmic rays = decreased cloud enhancement/formation in tropics = increased stability in tropics (lower MJO amplitude?) = ENSO (warm or cool) persistence. I could obviously be wrong.

[HM]

Excellent write up. I noticed the final warming occurred earlier and stronger than usual this year but it didn't occur to me to connect that to the unusually rapid decay of La Nina.

A couple questions...

If a cooler stratosphere causes more pronounced MJO activity, has anybody tried to connect the cooling stratosphere (associated with declining stratospheric ozone and an increasing greenhouse effect) with the evidence that ENSO acitivity/amplitude has been more pronounced this century than previous?

Any idea what set off the stronger early final warming this year?

Thanks a lot man. To my knowledge, there hasn't been this connection/paper yet, but I also want to caution that I have not been actively searching for those topics either. Although through casual reading, I think I've read certain people in the past indirectly suggesting these sort of connections that you're alluding. I think the problem you're going to find with doing something like that is the fickle nature of MJO activity, held back by the seasonal cycle and ENSO-forcing. I think this would cut the correlation down on the stratosphere, but we won't know until someone tries.

As far as what set off such a ridiculous warming, my best guess is what I said to Coastalwx: http://www.americanw...post__p__695083

When you have all polar vortex contributors suggesting a very cold vortex and lack a mid-winter warming, you set the stage for an early final warming. This is usually the general rule of thumb in any winter. This year, we had an amazing mountain torque shot right around astronomical spring (which is important too I think) with an already susceptible polar vortex for early destruction. I think if you destroy the vortex mid-winter and it builds back, it still has the momentum of building on the night jet in late winter, which usually delays the final warming.

[Alpha5]

Great post, I'm curious though...

What causes that major shift in polar temperatures. I understand its an extremely anomalous situation, but what could be causing the final warming to occur so radically?

[Amped]

Look forward to your hurricane season forecast.

[k***]

Yay MJO waves!

[HM]

Great post, HM. I'm not sure I follow why west QBO warms the equatorial stratosphere while east QBO cools it? I understand it has to do with the thermal wind, but I thought thermal wind was a consequence of temperature gradient, not a cause. I suppose that may be getting into what drives the QBO in the first place.

Also, you mention that the solar activity is not to blame for the recent ENSO warming. Based on history, I agree, as rising/high solar activity seems to correlate with La Niña persistence. However, I've noticed that rising/high solar activity also correlates with El Niño persistence. Am I mistaken, or have you noticed this before too? I'm trying to figure out why that would be the case. My best guess is that rising/high solar activity = decreased cosmic rays = decreased cloud enhancement/formation in tropics = increased stability in tropics (lower MJO amplitude?) = ENSO (warm or cool) persistence. I could obviously be wrong.

Thanks... Thermal "wind" is a bit of a misnomer because it is actually a shear vector. Generally, in the mid-Latitudes, a veering profile, or westerly horizontal shear, means warm air advection. However, the entire QBO process is a bit different. Keep in mind, there are still horizontal and vertical gradients in temperatures at this level of the atmosphere in the Tropics. Yes, the free troposphere for the most part is hydrostatic/barotropic, but the upper troposphere and lower stratosphere have a symmetrical band of wind with a T-gradient. The source of the wind is the upwelling gravity waves from the major uplift centers along the equator where the Coriolis force cannot carry them horizontally fast enough before they upwell into the stratosphere. As westerly momentum is added, surf zones form north/south of the band of westerly flow, produce eddies and tropopause depressions near/along the Equator. I believe this is one of the direct ways to warm the layer. Westerly momentum added over top the deep tropical easterlies is a natural warm air advection process, which limits convective growth and favors warmer air aloft. Radiative properties with water vapor/gases are the most important and this has a lot to do with cloud type/distribution. Added cirrus carried downstream from the Indonesian convection from the upper level winds is another, less complicated way, to affect temperature.

By the way, I didn't say solar activity had nothing to do with it. I just didn't want to say, "it's because of the sun" and that's it. I wanted to show a more direct cause/effect within our atmosphere and not concentrate on an even bigger picture. As far as what connections you've made, I think solar activity can lengthen/shorten climatic cycles here on Earth but I am not sure it is as simple as you're making it. Also, I think cosmic rays are bit overrated, but not without some merit, and generally are being mistaken for something that is much more important. This is because cosmic rays are a good proxy for geomag/solar factors as well as GLAAM changes from the solar wind.

[HM]

Great post, I'm curious though...

What causes that major shift in polar temperatures. I understand its an extremely anomalous situation, but what could be causing the final warming to occur so radically?

Thanks...

I tried taking a stab at that question already in coastalwx and skier's replies but... I think it was a uniquely-timed East-Asian wave response (+MT) during the equinox in an already susceptible stratospheric setup (because of the lack a mid-winter disturbance/very cold vortex). What was a regular East-Asian disturbance turned out to be the thing that got the ball rolling with the introduction of sunlight (increasing polar sunlight). The highest amount of ozone typically occurs over the Mid Latitiudes in early spring and combined with the effects from ENSO/QBO, managed to add onto the supply. When you slow down the night jet during that time of year, it is going to become the final warming. You are not going to rebuild the vortex with the introduction of sunlight and a whole mess of ozone piling in from the Mid Latitudes because of the weakening jet. So my guess is it was the unique timing of everything (although I suppose that could always be the same lame answer for anything haha).

[HM]

Yay MJO waves!

I know you are rooting for this so that the Pacific can have a better turnout this season (let's get those ACE values up)!

You can thank the Final Warming for this. Hopefully this unique setup continues, just for the sake of sheer fascination.

[Amped]

Good old 30hpa

[cooling climate]

A much more active sun during March and April compared to what we have

seen this last few years coinciding with a +QBO. Its as straight forward and

simple as that.

[wxmx]

A much more active sun during March and April compared to what we have

seen this last few years coinciding with a +QBO. Its as straight forward and

simple as that.

What's the mechanism?

[Amped]

A much more active sun during March and April compared to what we have

seen this last few years coinciding with a +QBO. Its as straight forward and

simple as that.

Good job talking about exactly what HM didn't want this thread to be about.

[HM]

Latest weekly ENSO numbers:

Niño 4: -0.2

Niño 3.4: -0.2

Niño 3: 0.0

Niño 1.2: +0.5

As this latest MJO wave subsides, the tendency is beginning to drop in the AAM and the atmospheric winds have responded.

All the latest trend charts from the equatorial stratosphere remain well below normal. Some levels are still flirting with record territory.

[nzucker]

Latest weekly ENSO numbers:

Niño 4: -0.2

Niño 3.4: -0.2

Niño 3: 0.0

Niño 1.2: +0.5

As this latest MJO wave subsides, the tendency is beginning to drop in the AAM and the atmospheric winds have responded.

All the latest trend charts from the equatorial stratosphere remain well below normal. Some levels are still flirting with record territory.

It still looked as if there were a little more warming on the latest NOAA SST anomaly maps:

http://www.osdpd.noaa.gov/data/sst/anomaly/2011/anomnight.5.23.2011.gif

The -PDO configuration in the North Pacific has strengthened, however, and the SOI has gone back into positive territory. So there's definitely some signs that the La Nina is regaining control. Global temperatures also remain quite low with AMSU Channel 5 down to 2008 levels.

[skierinvermont]

Global temperatures also remain quite low with AMSU Channel 5 down to 2008 levels.

This is a little misleading to posters not too familiar with AMSU CH5 considering for the past two months as a whole global temps have averaged a solid .3C warmer than 2008. Even over the last two weeks they have averaged a solid .3C-.4C warmer. Even on the latest daily update that I see, they are still .1C warmer. Ch5 temps bounce around a lot so it's not very meaningful to look at single days. But even if we do, 2011 is still .1C warmer than 2008 on the latest daily.

Also, as I'm sure you are aware, but others may not be, global tropospheric temperatures usually lag ENSO by 5-6 months.

[nzucker]

This is a little misleading to posters not too familiar with AMSU CH5 considering for the past two months as a whole global temps have averaged a solid .3C warmer than 2008. Even over the last two weeks they have averaged a solid .3C-.4C warmer. Even on the latest daily update that I see, they are still .1C warmer. Ch5 temps bounce around a lot so it's not very meaningful to look at single days. But even if we do, 2011 is still .1C warmer than 2008 on the latest daily.

Also, as I'm sure you are aware, but others may not be, global tropospheric temperatures usually lag ENSO by 5-6 months.

Well if you're not familiar with it, then go look it up!

I never said the entire year was averaging as cold as 2008, but the current temperatures on the AMSU Discover site show us about even with 2008 (as of yesterday). Of course it's not meaningful to look at single days, but 2011 is distinguishing itself as a cooler year relative to today's climate. And yes, we're still in the lag period for the switch to neutral ENSO conditions, although the GFS initializations show the anomaly down to .18C (again, yesterday's data) whereas we were recently as high as ~.25C, and I assume these numbers would be affected much more quickly by ENSO. We've already seen the cold anomalies over the Tropical Pacific fade on the GFS maps in the past 2 months, an area that was consistently coming in below average for air temperatures when the La Nina was going. Interestingly, and I have no idea why, almost all the cold anomalies in the world are coming from Antarctica, and the warm anomalies are mostly in the Northern Hemisphere. Very strong distribution of anomalies on the GFS charts with the NH being MUCH warmer than the SH.

In terms of ENSO, it looks as if the trade winds are back in control if this chart is accurate:

We're going to need another push of westerly winds to get into a weak El Nino for Winter 11-12. Many are praying, I am sure.

[HM]

It still looked as if there were a little more warming on the latest NOAA SST anomaly maps:

http://www.osdpd.noa...t.5.23.2011.gif

The -PDO configuration in the North Pacific has strengthened, however, and the SOI has gone back into positive territory. So there's definitely some signs that the La Nina is regaining control. Global temperatures also remain quite low with AMSU Channel 5 down to 2008 levels.

Yes, agreed about the PDO. As expected, mainly a waxing/waning situation with enso-neutral conditions. However, the warming periods will continue to receive extra aid as long as the stratosphere stays as cold as it is across the equatorial Pacific. I still don't believe we go into basin-wide El Niño conditions here but warm-neutral and weak El Niño's probabilities have certainly increased since late winter. Neutral is probably the most realistic call at this point.

[A-L-E-X]

Yes, agreed about the PDO. As expected, mainly a waxing/waning situation with enso-neutral conditions. However, the warming periods will continue to receive extra aid as long as the stratosphere stays as cold as it is across the equatorial Pacific. I still don't believe we go into basin-wide El Niño conditions here but warm-neutral and weak El Niño's probabilities have certainly increased since late winter. Neutral is probably the most realistic call at this point.

I agree HM, and if you look at some of the analogs..... it looks like there's a pretty good chance we go into an el nino not next winter, but the winter after that. I think 3 of the 4 analogs we were looking at pointed in that direction for winter 2012-13 (1957-58, 1968-69, 1997-98).

[BethesdaWX]

This is a little misleading to posters not too familiar with AMSU CH5 considering for the past two months as a whole global temps have averaged a solid .3C warmer than 2008. Even over the last two weeks they have averaged a solid .3C-.4C warmer. Even on the latest daily update that I see, they are still .1C warmer. Ch5 temps bounce around a lot so it's not very meaningful to look at single days. But even if we do, 2011 is still .1C warmer than 2008 on the latest daily.

Also, as I'm sure you are aware, but others may not be, global tropospheric temperatures usually lag ENSO by 5-6 months.

Does it matter? We're at 2008 levels now, maybe a tad warmer, but its an irrelavent argument, what does this have to do with ENSO?

We're at 2008 levels, get over it dude: http://discover.itsc...h?amsutemps+002

Since you seem a bit confused or hooked on an irrelavent argument: We're currently at -20.10C on CH4 AQUA 14K, and the Average is -19.91C for this date. So we're -.19C right now compared to the long term avg, translating into -.09C when adding in the +.1C to the UAH final. The month to date on the AQUA is +.04C now but dropping, so May likely ends up near April, maybe a bit colder, if the expected difference between AQUA and UAH stand firm. This is an earlier warming max for ENSO

I think the point here is, the -PDO is present, La Nina is attempting to hold its ground, and a Healthy Nino is unlikely at this time. Trade winds in the forecasts look to resume a bit, and the high +Earth AAM wave is weakening.

The MJO is absolutely Dead

We also hve te +AMO and +IOD, which factor into the ENSO perhaps...not 100% sure on that

[HM]

I think the point here is, the -PDO is present, La Nina is attempting to hold its ground, and a Healthy Nino is unlikely at this time. Trade winds in the forecasts look to resume a bit, and the high +Earth AAM wave is weakening.

The MJO is absolutely Dead

The MJO and trade winds are cyclic and sort of a bad argument to use when analyzing their daily fluctuations and then talking long-term climatology and long-term ENSO forecasting. I wouldn't say the La Niña is holding its ground here but yes the SST will wax/wane with the intraseasonal variability. The situation is plainly neutral and will be governed by intraseasonal variability for the foreseeable future. Until I see the troposphere and stratosphere become better in-sync here, all bets are off as far as how far this warming will go. But I do agree that a healthy El Niño seems unlikely at this point.

[BethesdaWX]

The situation is plainly neutral and will be governed by intraseasonal variability for the foreseeable future.

Agree completely, thats what I was trying to convey (regarding MJO/AAM activity in more of a 10 day timeframe rather than farther out). Your knowledge base is definitely superior to mine, so really I'm more of a student here

With the equatorial stratosphere coming in quite chilly, I assume you meant that the ENSO SST's would have more tendancy to warm rather than cool despite intraseasonal variability being the governing factor??

I just see it very hard, after a strong El Nino and Hefty Nina, for the climate system to produce another strong nino. From what I've been taught, the climate system tends to balance itself out, so extremes are met with extremes, and regulation is acheived through this aspect(?).

[skierinvermont]

We're currently at -20.10C on CH4 AQUA 14K, and the Average is -19.91C for this date. So we're -.19C right now compared to the long term avg, translating into -.09C when adding in the +.1C to the UAH final. The month to date on the AQUA is +.04C now but dropping, so May likely ends up near April, maybe a bit colder, if the expected difference between AQUA and UAH stand firm. T

AMSU doesn't use a "long term" average. It uses a ~10 year average. We remain well above the long-term average.

I'm just correcting misinformation being spread in this thread. I don't know why you and zucker have brought global temps into an ENSO thread.

[nzucker]

AMSU doesn't use a "long term" average. It uses a ~10 year average. We remain well above the long-term average.

I'm just correcting misinformation being spread in this thread. I don't know why you and zucker have brought global temps into an ENSO thread.

Of course, skier must point out how warm it is, even when it isn't.

Show me the .2-.3C/decade and then we'll talk.

[A-L-E-X]

Of course, skier must point out how warm it is, even when it isn't.

Show me the .2-.3C/decade and then we'll talk.

LOL you guys definitely have a love/hate relationship (or maybe that's just how it seems on here).