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Messages - aslan

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1
Consequences / Re: 2017 ENSO
« on: February 22, 2017, 09:59:00 AM »
In general terms the IPCC forecasts for climate change induced changes in global precipitation patterns have erred on the side of least drama; so I would not be surprised if the recent drought in Venezuela, and the floods in Peru, that you have pointed-out may be as much related to high climate sensitivity to global warming (the attached AR4 image for scenario A1B shows this change in precipitation pattern by 2100) as to the ENSO cycle.


Yes there is probably also a global warming component in there ;)

Some cyclonic activity is occuring in the Southern Pacific, not too far from equator :



But the current cyclonic season in the SH is extraordinarly inactive and not helping much the El Niño.

2
Consequences / Re: Weird Weather and anecdotal stories about climate change
« on: February 20, 2017, 05:42:23 PM »
Downpours in Andalucía. But this kind of event usually occurs in Autumn or at the start of the Winter.

http://ccaa.elpais.com/ccaa/2017/02/19/andalucia/1487504063_160360.html?id_externo_rsoc=FB_CM

3
Arctic sea ice / Re: Arctic temperature layers and inversions
« on: February 20, 2017, 11:20:46 AM »
This appears to be somewhat related to the work done by Prof James G. Anderson and his group.

https://www.arp.harvard.edu/our-research

I also recall some hypotheses regarding the Hadley, Ferrell and Polar cells collapsing into one cell per hemisphere. I can't remember now (poor note keeping :-) ) but it might have been Jennifer Francis. The idea implied a drastically reduced temperature differential temperature between the equator and the poles.

Has anyone come across this and is there some reason why it must be one cell or three, not two?


It is not possible to have one cell, due to conservation of angular momentin. Coriolis deflects flow to the right in NH, to the left in SH -or to the west in each case-. If their is aire flow away from equator and toward Poles, at some point, air accelerates too much, and can't keep going northward. It exists some theories about a one cell circulation during equables climates, but the argument is very weak to say the least.

https://www.seas.harvard.edu/climate/eli/research/equable/hadley.html

http://www.to.isac.cnr.it/aosta_old/aosta2014/LecturesSeminars/Tziperman_2.pdf

Of course, that assumes that the arctic ice does actually stabilize. I saw a recent talk by Jennifer Francis where she said "there will always be ice in the arctic". I was immediately struck by the thought that that may not be true in any meaningful sense.  :(


Yeah, probably too optimistic, but reality is hard.

If the surface temp is above the 850 and 500mb temp, there's no longer a net inversion. An inversion, by definition, is a negative lapse rate or an increase in temperature with height. So, the mean state has switched from an inversion to essentially isothermal. With additional heating, the lower layers will exhibit a positive lapse rate. It's important from the perspective of cloud generation as it's easier to generate clouds and increase precipitation rates the less stable the atmosphere is with respect to buoyancy.

Low water clouds reflect more sunlight but trap infrared heat even better than high ice clouds. If you want confirmation of this, take a look at a visible satellite with low clouds overlain by jet cirrus. The cutoff for ice/water clouds is about -10C. Ice crystals tend to increasingly dominate past -10C and are virtually all ice below -20C except in certain circumstances -- like convective clouds. The phase transition between 253K and 263K is really important with respect to cloud water content. Of course, since the sun doesn't shine during the winter, having more water droplet-dominated clouds will increase DLWR -- acting as a net positive feedback.


Yes.



A view of the current difference of temperatures between 850 and 1000 hPa for last 3 months:


4
Arctic sea ice / Re: Arctic temperature layers and inversions
« on: February 18, 2017, 10:48:13 PM »
So we move and I was going topost to the freezing thread :D


Killer graph. That yellow line is showing almost 20 degC of warming!


I will speak about myself sorry ^^" But if is "fun", I never, when I wrote the post, I never realize the magnitude of the warming. I said 20°C, 30°C, but in my brain no connections happened, I was not aware of what I was writing (the global warming, the weed of the future...). It is when I read you, just minuts ago, that I understand I was speaking about full 20°C in 35 years. And it was like "Salva nos Domine" et "Eleison imas" in my head. And I was not able to believe I made no error so I double check, and I even plot the map from the reanalysis. For example this is the exact area (all things above 67.5°N) for the year 1983, a bit cool but not so much (the first low point to the left, after the small uptick of 1982):





And this is for 2017 :





If the reanalysis is not widely in error (really unlikely), yeah there is probably something around 15 - 20°C of warming.

Without trying to put me on the front scene, but I am worry by this change since 2012, when Kara sea remained open in the winter. I discovered Ostrov Vize this winter, and since then Ostrov Vize is one thing that keep me awake in the night. This year, it was localized, but some strong hints about a feedback from the cloud, the water vapor, and the open Ocean, were clearly visible.
I agree with jdallen, models are probably not able to fully simulate the feedbacks which are now at play, and we are probably in for a state change without gloves nor care. There is some papers about the clouds, the water vapor feedback, the permanent inversion in Arctic, but I am not aware of any paper which is really relevant for the last two winters and which anticipate such a fast state change.

http://www.nature.com/ngeo/journal/v4/n11/full/ngeo1285.html

http://geosci.uchicago.edu/~abbot/Code/Abbot-Tziperman-2008/abbot-tziperman-08b.pdf

https://www.atmos.washington.edu/~bitz/holland_etal2006GRL.pdf et http://www.geo.brown.edu/research/Fox-Kemper/classes/CU/ATOC6020_08/notes/08_05_Holland.pdf

http://www.atmos-chem-phys.net/16/14343/2016/acp-16-14343-2016.pdf

http://www.cesm.ucar.edu/events/wg-meetings/2010/presentations/amwg/kay.pdf

Etc... But to my knowledge nothing really pertinent for the current and ongoing crash. As jdallen said


It may be there are relevant papers we haven't seen, and yes, this implies a pretty scary feedback and an implied tipping point.  If ice drops much below 3M KM2, the additional heat uptake and H2O being injected into the atmosphere combined with that being imported from steady less dramatic changes further south may translate to a rapid state change in atmospheric circulation that no one has envisioned.

The short ride to to that new state will likely be very bumpy.


models are probably somewhat lost and we have to put more attention to what is happening in the Arctic now.

Merci beaucoup.


De rien ^^

5
Arctic sea ice / Re: Polar Vortex/SSW effects on Ice
« on: February 18, 2017, 07:42:36 PM »
Yeah sorry, my bad, I was not enough explict. Yeah, the sun rises earlier over the stratosphere, due to the altitude ;) But Sun is not high enough still to warm sufficiently the stratosphere, despite the ozone to suck up the UVs. To put in perspective, a radiative SFW (so one which is only achieve with the "strength" of the Sun and is its small arm muscles) only occurs around April -  May.

6
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 18, 2017, 07:34:55 PM »
Using the reanalysis, we can calculate also the mean of the downward radiation flux. Of course, it is the reanalysis, with a coarse resolution and its own limitations (especially discontinuities due to inclusion of varying kinds of data), but I think it is quite good nonetheless, if we look at the values after 1981 (start of the satellite era). So, the downward radiation flux, or the infrared emitted by the atmosphere toward Earth surface (one funny thing when you have some knowledge in physics, you know you are a being of light and that you are shining :D ). Data are for the whole above 69°N (radiation data are along a Gauss grid, I take values up to 69.5217°N, cell index 11), averaged according to surface (hoping I make no mistakes), for each day from 1st January, 1981 :



It is looking quite like the graph of the temperature according to the DNMI, which is not unexpected by the way. We are tempted to say, a warmer atmosphere radiates more energy, so what is the point?

Actually there is more in this. The mean level of radiation for Earth is around 5 - 6 km, so around 500 hPa, take or given a couple of hPa. Relationship between temperature and radiation is not linear, so we can calculate the flux of a black-body with our old friend, the equation of a black-body :

Flux = 5.67e-8 * T^4

The grid for the temperatures are not the same as the one for the radiation data, but I didn't care about this. The precision of the reanalysis is probably far worse than the small difference induced by averaging over a slightly different area. So I used the region above 67.5°N for the temperatures, calculate the radiation flux from the temperature and compare with DWLR, and averaged for the three months from November to January (February is still ongoing un 2017). The year of reference is that of January (ie., NDJ 2017 is the average of ND 2016 and J 2017) :



Values are roughly the same, so yeah 500 hPa is a good level. But correlation is not looking good actually... I look to other levels, but the correlation is not significantly better. As a side-note, the temperatures at 500 hPa :



So, what if we try with the precipitable water?



It looks way better...

So I detrend the series, to compare the cross-correlation. Anomalies of the downward radiation flux, explained by the anomalies of the black-body emmision :



Anomalies of the downward radiation flux, explained by the anomalies of the precipitable water :



Anomalies of the anomalies of the precipitable water, explained by the temperature at 500 hPa :



I will not try an argument about chickens and eggs. It is of course difficult to disentangled all the mechanisms ongoing. But at least the increasing of water vapor, linked to warming of the temperatures but also to the decrease of Arctic sea ice, is increasing downward radiations.

The major point is that a warming of 20°C or 30°C is not impossible at surface is thus not impossible. With global warming, the "thin" -a 2 km thick and 20°C inversion is massive for an inversion in the absolute, but compared to the whole atmosphere this it is not so thick nor so cold- the "thin" layer of permanent inversion is set to be destroyed, with only marginal warming above. Usually there is around 5 to 10°C between surface and 850 hPa. Even a 7-8°C lapse rate with a 850 hPa layer around 250K would imply a mean surface temperature a bit below 260K, around -15°C, barely enough cold for sea ice. This graph shows the warming of the Arctic layers :



The surface 1000 hPa is warming fast and is now warmer than the 850 hPa for the first time since 1981 (and probably since many millenniums...). And the strength of the inversion (or of the now non-inversion) taken as the difference between the 850 hPa and 1000 hPa temperatures :





I will post the spreadsheet with the data a bit latter ;)

P.S. : THe spreadsheet www.climatvisu.fr/Neven_ASIF/dlwr_out_2.ods

7
Arctic sea ice / Re: Polar Vortex/SSW effects on Ice
« on: February 18, 2017, 05:35:23 PM »
with 3 days out being as far as one dare peep some days?

Perhaps a bit exaggerated  :D but yes. This is not usual so you are not sure how things can unfold. For example, about the coming SSW, yeah it could be the SFW, but it opens some questions. The Sun has not yet rise over the Arctic, so how the stratosphere will stay warm until the end of March? Will waves activity continue during March to sustain the warming of the Stratosphere until the Sun rises and brings energy to the polar stratosphere? This is what happened last years, wave 1 after wave1, a continuous pile of wave 1 bringing again warmth to the polar stratosphere until the rise of the Sun. Of course, a dynamical breakdown of PV is forced by wave activity, but usually SFW occurs not too far away from the equinox, even if dynamically forced. But there is one big wave which comes, destroy everything with some lasting effects during 2 - 3 weeks, and then comes the Sun. And there is no need to pile up wave 1 over wave 1 to make the junction. For the 2016 SFW, I count at least four (4 !) waves 1 -perhaps even 5, I didn't try to count rigorously- during the end of February and the month of March. Speak of a fury...

And for this March, GFS is showing again the VP being almost perpetually assault by waves 1. So this leads to be more confident that, yes, what is coming is the SFW. But this is only a rationale by analogy (is this plain English?). For the moment, at least for me, I don't have a satisfactory explanation of the mechanisms of such extra early SFW, or if there is a reason why we are potentially seeing such an event two conservatives years.

I don't see also how the PV could get back in the saddle. But it is not again really satisfactory to say "I don't see". And for my brain, this is really frustrating because the rationale is not closed. If the train of wave 1 don't occur, the PV could in theory reestablish itself. But yes I don't see how in the middle of March such a mess could strengthen again. So I need to invoke the wave 1 activity and bet that GFS is true, without having any beginning of explanation of how it is possible to have such a fury of wave activity. And indirectly it implies that once the train of wave 1 is en route, it needs to continues at least until the end of March to make the ends meet. But there is nothing, to my knowledge, saying something like, if wave 1 starts to destroy the PV at the end February then the wave 1activity must continue until the end March. Actually it even sounds quite absurd xD Perhaps the PV is "feedbacking" itself trough the troposphere - stratosphere interaction, but is quite weak as an argument. And where is the wave 2 and eventually wave 3? GFS is not always showing something like a canonical wave 1. So, is it that an extra early SFW depends upon wave 1 activity? Or can wave 2 activity plays a role? This opens a lot more of questions. And there is also the vertical propagation of the wave, baroclinic, barotropic, how also this thins play together last year and perhaps -probably?- this year. Bref, actually, I am like a dog trying to bite its tail  :D

So yes it is really difficult to forecast what could happen... And I am not a weather model (not yet xD ) but I think that sometimes they can be quite lost yes. They were build upon assumptions and equations from the 20th century, and the way models are build is probably impeding their forecasts ability.

8
Consequences / Re: 2017 ENSO
« on: February 18, 2017, 08:55:20 AM »
Also, for the Venezuela the situation is dire. After enduring an historic drought in 2016, the warming of the Pacific is again reducing rainfalls amount in the country. The closest station is showing almost no rain in December and January:

http://ogimet.com/cgi-bin/gsynres?ind=82022&ndays=50&ano=2017&mes=2&day=18&hora=7&min=26

La repressa de Guri, the main dam of the country and the main electricity plant of the country, is again in a bad situation. El gobierno is relectuant to speak about the situation, saying some void words like this :

http://www.eldiariodeguayana.com.ve/natural-descenso-actual-las-aguas-del-embalse-guri/

But el nivel de Guri is probably below 260m above sea level now, which implies that electricity generation is probably reduced. At least is is not as bad as in 2016, when temperatures soared to records levels for months and months, accelerating the drying of country and increasing the consumption of electricity; to the point that in April 2016 the country nearly missed a total blackout. But the Guri was not able to replenish, lefting el nivel de Guri below su cota operativa at the end of the rainy season. And now that the dry season, even though the temperatures are near normal, the level is lowering at a worrisome pace.

9
Arctic sea ice / Re: 2016 (and historic) Polar Vortex/SSW effects on Ice
« on: February 18, 2017, 08:43:32 AM »
The way I read your string of thoughts, you seem to suggest that tropical turbulence – approaching the NH spring equinox - has now fired up the Jetstream. This stream of moist air has led to the atmospheric river now threatening the stability of the Oroville Dam. The subsequent upslope erosion (see  https://www.theatlantic.com/national/archive/2017/02/how-did-the-oroville-dam-get-so-bad/516429/ ) could spoil not only the spring in California, but also put Trump in a dire position to choose between more roads or better dams.


Yeah, it is true also that MJO is a player in this act also. The reccent PNA+ pattern with a jet-stream is forced by the strong convective activity in the Eastern Pacific.

The Arctic seems to be dominated with systems at the present that have High MSLP's. That will start to change again in about a week, very closely correlated to the 10 hpa Polar Vortex changes.


Usually the effects of a SSW / SFW take a week or two to reach the troposphere. In a very long range GFS is showing things in this range of idea :



Or things in this range of idea :



Common point being the warm high pressure over Arctic and cold pool being displaced to Canada. To speak like smart people, it is an attractor for a chaotic system. Which, by the way is probably the consequence of the SSW. Forecasts in the long range could be possible if we were paying more attention to the stable states emerging from the day to day apparent chaos of the maps. But for now we are for many factors in situation without precedent, so it is a bit of a terra incognita, lowering confidence in the forecast.

10
Consequences / Re: 2017 ENSO
« on: February 17, 2017, 11:40:23 PM »
Perú also is monitoring the situation. Since the start of February, the SENAMHI (the local MetOffice) has issued an alert for a coastal El Niño :

http://www.senamhi.gob.pe/load/file/02204SENA-71.pdf

https://www.facebook.com/notes/senamhi-peru/estado-del-sistema-de-alerta-alerta-de-el-ni%C3%B1o-costero/10154730059795860

And flooding are already occuring here and there in the country. These days, it is in Piura, with a Nivel 4 (alerta roja) :

https://twitter.com/maxprugue/status/832710807653801988

http://www.senamhi.gob.pe/?p=0140&tip_alert=022


11
Arctic sea ice / Re: 2016 (and historic) Polar Vortex/SSW effects on Ice
« on: February 17, 2017, 10:23:11 PM »
Very important info from aslan. I am still trying to understand some of it, but will be curious to see how it plays out in the next few days and weeks.

Yeah, in the end there is only one thing true, what happens in the real world. Thanks jdallen ;)

12
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 17, 2017, 08:19:26 PM »
This years uptick in sightings of folk of polar Stratospheric clouds also has me wondering. you need a really cold strat for them to form but you also need moisture up in the strat?

PSC's are also important in the destruction of Ozone and so , just as the hole over Antarctica appears to be mending?

The ozone hole over the UK , this time last year, is an example of what increased moisture/cooler upper strat will mean to the hemisphere?

To me it appears that the extra energy that increases in GHG's have placed into the climate system is impacting all layers of the atmosphere?


I am pretty confident we are totally off-topic xD but here we go.

There is a circulation of ozone in stratosphere, called the Brewer-Dobson circulation (Dobson like the Dobson Unit, a DU, it is the same guy). I don't know everything about this subject so I will try to stick with what I am sure. Ozone is mainly produced in tropical stratosphere, due to UVs radiations. It is also UVs radiations which destroy naturally the ozone. The Brewer-Dobson circulation mixes this ozone. In the tropics, in the stratosphere, there is upwelling. And near the poles, especially in winter hemisphere, there is downwelling. Ozone concentration is thus lowered in tropics, and raised in extratropics. This is the reason for the annual cycle of ozone in the stratosphere of the Northern Hemisphere :

https://ozonewatch.gsfc.nasa.gov/meteorology/figures/merra/ozone/toms_capn_2016_omi+merra.pdf

Brewer-Dobson circulation transport ozone from tropics to poles, but especially in winter, and the ozone being not destroyed due to the low sun, ozone accumulates.

But in the same time, the polar vortex isolated cold air of the stratosphere, away from the sun rays.

This is even more true for the Southern Hemisphere, where there is no planetary waves to disrupt the PV. So the polar stratosphere is isolated and cool down a lot. Molecules like CFC etc... responsible of the ozone depletion accumulate in the vortex, destroying the ozone. The very cool stratosphere in SH, with stratospheric polar clouds, explain why ozone depletion is mainly occuring in SH. We can thus this a broken seasonal cycle, with a first minimum in boreal summer (Feb.) then the start of a rise, and after a big crash when PV builb up:

https://ozonewatch.gsfc.nasa.gov/meteorology/figures/merra/ozone/toms_mins_2016_omi+merra.pdf

There is a feedback loop in this. Stratosphere is warm by the Sun energy sucked up by the ozone. So if there is less ozone, the PV is colder during the Spring, so the PV is stronger and last longer (some SFW in Southern Hemisphere lately occurred even in boreal summer...), so the ozone depletion is reinforced, etc...

Ozone depletion is also observed in NH when the polar vortex is strong. The biggest hole was reached during the winter 2011 I think:

https://ozonewatch.gsfc.nasa.gov/Scripts/big_image.php?date=2011-03-15&hem=N





But polar vortex being weaker and warmer in Northern Hemisphere, ozone depletion is weaker and is not producing a big hole like in SH.
There is at least one positive point with the polar vortex being shaken, it avoid us to be irradiated and burnt  :D

With global warming in troposphere, stratosphere is cooling -and it is a big fingerprint of greenhouses being at work-. This year, despite the disturbed PV, it was cold in stratosphere, and sometimes even record cold:



http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/

In theory, stratosphere should moistens a bit also, with a greater input from the tropical convection (Cbs overshoot reaching the lower stratosphre). But here is uncertainity regarding what is really going on with the stratospheric water vapor :

http://onlinelibrary.wiley.com/doi/10.1002/2014JD021712/full

http://onlinelibrary.wiley.com/doi/10.1002/2014JD021712/full

http://www.pnas.org/content/110/45/18087.full

www.sciencemag.org/cgi/content/abstract/science.1182488

It exists some theories about a feedback from polar clouds, in equable climates especially, but also in a not so distance future. For example :

http://www.nature.com/nature/journal/v357/n6376/abs/357320a0.html

http://onlinelibrary.wiley.com/doi/10.1029/98GL02492/pdf

http://climate.fas.harvard.edu/files/climate/files/huber_cpd-7-241-2011-print.pdf (there is a list of papers about PSCs at the beginning)

Stratospheric clouds are perhaps set to become more frequent, but observations are really not conclusive for now.

To me it appears that the extra energy that increases in GHG's have placed into the climate system is impacting all layers of the atmosphere?


Yeah, no doubt, we are totally messing with the whole atmosphere and not only troposphere.

P.S: If you are british, in the end of March 2011 it was even worst actually...


13
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 17, 2017, 07:13:54 PM »
Yeah, there is a study going with you :

http://www.nature.com/articles/ncomms5646

The figure I was searching (sorry, it is a bad scan, I was not able to find a fun version on Internet) from Peixoto  & Oort, 1992 (thanks D. for helping me with the reference...) : https://www.amazon.fr/Physics-Climate-Jose-P-Peixoto/dp/0883187124 (I think it is quite good also to stun people, in a literal and metaphorical way of meaning  :D )



Meridional transport of heat (sensible heat, in degree) from a/ total transport b/ transitory circulation (baroclinic lows in plain english) c/ stationary circulation (planetary waves so) and d/axisymetric circulation (Hadley cells, symmetric around an axis). Red is annual, blue is summer, yellow is winter. Axis scale change from one diagramm to the other.

And the same for water vapor (showing indirectly latent heat from water vapor condensing / evaporating) :



There is quite a bit spike in NH associated with the planetary waves (non symmetric stationary circulation). This is from the 90s but planetary waves have always been a factor in NH climatology. This waves are the reasons for the frequent SSW in winter (about one every two winters) and dynamical, early SFWs. With climate change and jets going wacko, stratosphere could be more often disrupted. There is also another factor, highlighted by Judah Cohen. Increased snow cover in Autumn (especially October and November) associated with the increase in moisture, can also disrupted the polar vortex. Increased snow reinforce the Siberian High, with the effect to enhance the planetary wave 1. And strong wave 1 generally leads to a broken VP during the winter. There is a review from Cohen of this subject (but I must confess I don't have read it wholly ^^" ):

http://web.mit.edu/jlcohen/www/papers/Cohenetal_NGeo14.pdf

This is an interresting area of research, but it is also a nightmare to find some dry ground in theses marshes.

After that, there is also of course others factors. The review has also a word or two about the tropics, without going through it in details (it is not a full lecture about the climate :D ). But yet, the tropical convection is also a factor for the stratosphere. QBO is primarily driven by propagation of waves from tropics, and currently there is no consensus about the evolution of the QBO under the hypothesis of a global warming. Some are saying that QBO will oscillate more rapidly, some more slowly, some are saying no change, or etc... And in the same time we have the QBO making some crazy stuffs. So, for this subject, it is anyone guess.

And last but not least, ozone depletion is also a factor.

14
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 17, 2017, 05:40:25 PM »
Antarctica also saw an early final warming at the end of its winter season? I imagine the Strat is far less complex in its operations than the Trop below and ,as such, I think it can be viewed as a single unit unlike the trop which is broken down into hemisphere and cells?


Nein Pamina. Early SFWs, of a dynamic kind, are specific to NH due to the wave activity, caused by the mountains in the flow. In NH winter, Rossby waves (wavenumber up to 8 - 9) are an important factor. I will search to retrieve a resource about this subject, I will post when I find it on Internet :p

The Rockies and Tibetan plateau disrupt the flow, and to a lesser extent Apalachians and Ural. In NH, there is two kind of SFW. One, early (March - April), and dynamically forced. This kind of SFW often brings an AO- pattern to simplify during the Spring (but it is really to simplify with an axe). On the other hand, there is a radiatively forced SFW. When the Sun rises, the ozone-rich, polar, region sucks in energy until the PV disappears. This king of SFW is often associated with an AO+ pattern during Spring (still, to simplify with an axe :D ). In SH, there is no such thing as wave activity. Flow around 40°S - 50°S  is away from any landmasses and can flow regularly. There is one occurrence of a dynamical SFW in the SH, in 2002, but this extremely rare. Often, it is a radiative SFW occurring around November - December -so very very lately-.

http://journals.ametsoc.org/doi/pdf/10.1175/JAS3979.1

http://journals.ametsoc.org/doi/pdf/10.1175/JCLI3907.1

http://journals.ametsoc.org/doi/pdf/10.1175/JAS3981.1

ftp://acd-ext.gsfc.nasa.gov/pub/papers/newman/o3_sh_02/2002_o3_hole.pdf

http://www.cpc.ncep.noaa.gov/products/outreach/proceedings/cdw29_proceedings/black.ppt

You can search for this scientists, Baldwin, McDaniel, Black. There is other names, but this three are often involved.


Should we see an unusual impact hitting the strat then I tend toward thinking it would reverberate around the whole of the strat impacting both regions? Only in Autumn can we see both polar vortex and this year the collapse of the polar vortex was occurring as the final warming was occurring in the southern hemisphere . Coincidence or more evidence for the Strat behaving oddly over recent years?


I don't know. QBO was probably disrupted in part due to the unusual behavior of the polar vortex in NH last year, but here you are at the borders of the knowledge (and of the madness I want to say).

15
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 17, 2017, 05:25:15 PM »
It is from an ozone project at NASA :

https://ozonewatch.gsfc.nasa.gov/meteorology/NH.html

And for SH :

https://ozonewatch.gsfc.nasa.gov/meteorology/

Plot shows forecast up to 192h. The fat of the SFW is still a tad after, in a longer range. The important thing is to look for a wind reversal, ie. zonal wind becoming negatif. If easterlies take place in stratosphere, wave guide and wave propagation are heavily disrupted. So there is, in this peticular case, a kind of razor thin threshold (which is an uncommon thing usually in atmospheric science  :D ). This can promote the building of "warm" high pressure other Arctic, like GFS is showing (but only as an example, an illustration. GFS at 348h in troposphere is too wacky for trying to even pin down a broad region from where these highs can come from...) :



One other thing is the restless activity of waves in stratosphere. At this time of higher, Sun is not yet shining over the PV and PV should be able to reestablish, but GFS don't let him this possibility. Its best foe, IFS the european, goes only to 240h and so only show the incipient SSW and still not the downward propagation of its consequences in troposphere. But currently, given its outputs, it is quite likely it will follow the GFS idea.

On the opposite side, an early SFW could promote cold weather other continents, helping the snow which is already under assault:



But I am not really convinced. For the moment, I still don't have a clear idea of how the month of March could unfold, but at least I am not optimistic. Currently, given tropical convection and stratosphere activity, I tend to think that cold in troposphere wil be displaced to a pool circumscribe to Canada and Estern Siberia, but weather is weird. If we go for the earliest SFW recorded, by definition we have no precedent, leaving us to guess more than to forecast. It is difficult to find clues in these marshes.

16
Consequences / Re: Global Surface Air Temperatures
« on: February 17, 2017, 01:43:20 PM »
Yeah I agree, I even think the flip was already perceptible in 2013. The first thing that caught my attention in 2013 was the rise of CO2. The annual rise was the 3rd highest at the time (behind 1998 and 1987). It is a “proxy indicator" but this really caught my attention during 2013. And the year ends with the 3rd highest mean annual temperature. All of this despite marginally cold conditions in the Pacific. I am extremely cautious calling this an acceleration. We criticize the denialists for emphasizing a slowdown which was never significant, so I don't want to overreacting to an acceleration which is still in its infancy and not statistically significant.
But this is really disturbing to see near record warmth on an almost perpetual basis since 4 years, despite all the ups and downs in the Pacific. The year 2017 is actually set to be a top 3 again, yes.
I am not sure also how to explain. This does not look to be tied strongly to the Pacific, because we are riding the warmth no matter the state of ENSO. But it looks like that tropics are more involved. I think this may be tied to a reduction of aerosols load in the atmosphere, following a reduced use of coal worldwide. But this is only a guess. We will see but the trend is really disturbing.
In the opposite direction, it is true also that we were running  a bit below the trends in climate models. Given the major El Niño in 2016, the yearly record was not so extraordinary compared to the forecasts ( https://www.climate-lab-book.ac.uk/comparing-cmip5-observations/ ):
But the trend being really high (0.2°C per decade, at least), this is not really comforting...

17
Consequences / Re: Global Surface Air Temperatures
« on: February 17, 2017, 11:16:35 AM »
Also, temperatures in tropics are warming fast and furious. For the Southern Hemisphere, we are all aware that weather is overheating, especially in Australia. But in the vast region going from Sahara to India, in the Northen Hemisphere, temperatures are already extraordinary warm. And fact is that this is endogenous warmth, which tends to accumulate months after months. So that a warm February is often follow by a warm March etc... And even more in the context of ongoing record warmth globally. Last year, when wolrd reached its warmest temperature ever in July - August (54°C around Kuwait), warning signs were visible with extremes heat in the Spring from Senegal to India. I am not aware of many monthly records, but we are still mid month. Usually, records occurs later in February in the Northern Hemisphere. But temperatures are already extraordinary high for this time of year, and if this is not monthly records this is often records for a first part of February. One point is that warmth is really widespread, from Atlantic to Pacific through all Africeurasia or I don't know how is called this continent, like in 2016. Records in tropics occured in other years of course, especially 2005, 2006, 2010, but here near record are showing about everywhere in the tropical band, like in 2016 and a bit like 2015 (but to a lesser degree of warmth in 2015). We will see, but this is not boding well also...

For example, Yelimane reached 42°C the 16th (presumptive record, 44.3°C 02/28/2010), Karachi 34.5°C the 15th (presumptive record 36.5°C the 02/27/2016), Bhuj-Rudramata 37.5°C the 15th (presumptive record 39.2°C the 02/29/2016), Save 40.4°C the 15th (presumptive record 41°C the 02/20/2016, national record for Benin 44.5°C the 04/28/1952 -monsoon comes early in Benin-).

The most extraordinary is Sarh, in Chad :

http://ogimet.com/cgi-bin/gsynres?ind=64750&decoded=yes&ndays=20&ano=2017&mes=02&day=15&hora=06

There is no obvious indication that reports coul be in error (the SYNOP from the 13th at 15Z is erroneous of course, but the others don't look in error to me). Max T is 44°C, 43.7°C and 41.2°C for a synoptic hour. In the same time, GFS is showing T850 above 28°C in the region, with a small thermal low. If it is valid, Sarh fall short of the hemispheric record of February, but the 11th of the month ! Hemispheric record is probably a 45°C reading in Sudan, the 25th of February in 2005.

Oceanic temperatures are lower than in 2016 apparently, so this will perhaps temper the seasonal rise of temperatures. And a stronger temperature gradient between Ocean and Land can possibly lead to a stronger monsoon, tempering even more the warmth. But it does not need a lot of imagination to construct an idea of what this mean in May or June after 4 months of seasonal rise if the start of the rise is already above 40°C....

18
Consequences / Re: Global Surface Air Temperatures
« on: February 16, 2017, 09:33:03 PM »
NASA just reported a January anomaly being third warmest such on record behind 2016 and 2007.The anomaly was +0,92oC above the 1951-1980 average. January 2016 had an anomaly of +1,13o while January 2007 was +0,96o warmer. The gap to January 2015 at fourth place is quite large, almost 0,1oC (was +0,82oC warmer).

In addition, NASA has made BIG changes to some months in 2016! For. ex, November was down from +0,95o to +0,89o. February also looks significantly lower and the annual anomaly is now down to +0,98oC.

//LMV

NASA again dropped Arctic stations because they are warming too fast. So the algorithm assumes theses ones are in error. It is something like, if the anomalie is above a threshold of x °C during y months, so throw out this station. Ostrov Vize for example, near the epicenter of the "oceanification" of the Arctic was discarded after measuring records after records. NASA will probably fix it but in the mean time, Ostrov Vize are available in the raw and unadujusted data :

https://data.giss.nasa.gov/tmp/gistemp/STATIONS/tmp_222200690000_7_0_1/station.txt

But no longer in the homoginized data set :

https://data.giss.nasa.gov/tmp/gistemp/STATIONS/tmp_222200690000_5_0_1/station.txt

Denialists are always complaining that scientists are alarmiosts, will in fact it the contrary. They are extremly conservative...

19
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 15, 2017, 10:50:54 PM »
The Canadian Ice Service is still showing massive amount of thin and medium first year sea ice with some patches of gray ice embedded. There is virtually no thick first year sea ice. As a remainder, for the Canadians, thin is up to 70 cms, medium is up to 120 cms, thick is above 120 cms :



Again, it is looking really bad.

In January 2017, downward infrared radiations were again quite high. Not as high as in January 2016, but it is quite close :





The normal :



And fact is that snow and ice are not so white for snakes (if any one is living on the sea ice  :D )

https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes



I am not sure how much this is a factor, but at least it is not helping...

For the MJO, yes a very big spike is ongoing. This is probably boosting the positive PNA pattern, which in the end is bringing record warmth to western Canada. In the same time, GFS is showing wave 1 after wave 1 into the stratosphere :



Ok it is 384h and even for the stratosphere forecast are a bit uncertain, but nonetheless the possibility of a very early SFW is gaining ground. At least VP is going to be heavily disrupted. Big changes in the synoptic situation are likely for March.

20
Consequences / Re: CA Drought Emergency Declared
« on: February 15, 2017, 11:28:45 AM »
An NYT article with some good scientific references :

https://www.nytimes.com/2017/02/14/opinion/what-californias-dam-crisis-says-about-the-changing-climate.html

The "funniest" part is about the reference in the 80s, warning of both drier and wetter conditions, especially for Cali. Thirty years later, this prediction is showing to be quite accurate...

21
Consequences / Re: 2017 ENSO
« on: February 14, 2017, 07:13:17 PM »
As forecasted -and shown by AbruptSLR-, extremely strong MJO is ongoing, with reinforced convective activity in the central and eastern Pacific. This will help the nascent El Niño for sure. Some models like GFS are even showing the MJO to linger in phase 7 - 8 for some weeks.



It only lacks some twins cyclones in the Pacific now :D

22
Consequences / Re: CA Drought Emergency Declared
« on: February 14, 2017, 12:03:47 PM »
5 years of drought and then this. Higher probability of extreme weather events indeed.
Must say the helicopter footage is quite scary.


Yep, hydrological cycle on steroids. Oroville storage went from 35-40% of its capacity to more than 100% in less than two months. Speak of a whiplash effect...


23
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 14, 2017, 10:58:56 AM »
And also a monthly heat record in Island, with +19.1°C the 12th ( ! ), and in the first half of February... This was due to a foehn effect. It breaks old record of 18.3°C in 2005, the 21th; and 18.1°C in 1998, the 17th.

https://www.facebook.com/geoclimat.org/photos/a.832272180166905.1073741826.832246480169475/1355999204460864/?type=3&theater

24
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 14, 2017, 09:52:57 AM »
Models are forecasting a major SSW for the end of the month. It is still in the 240h - 384h range, and so IFS -the european model- still does not show a major SSW. But the warming is gaining ground in this model also, with a wind reversal down to around 2 - 3hPa. And tomorow the forecast will probably show a wind reversal at 10 hPa also. The activity of the wave 1 is really strong and it is certain that in the coming days the IFS will also show a major SSW. In contrast with the displacement event earlier this winter, the baroclinic nature of the wave 1 is clear this time, with the minimum of the PV being displaced westward and somewhat poleward with height, and being almost 180° apart beetween lower stratosphere and higher stratosphere. In the end, the PV is set to be twisted and torn apart by the wave 1.



But the most unbelievable thing is the constancy of GFS to depict this event as a SFW... Every run, up to 384h, shows the end of the polar vortex. The wind forecast at 10 hPa and 384h :



And the temperature forecast :



Where are you, PV?

We will see what the IFS tell us in the coming days, but if this is the SFW and not SSW, this will be the earliest one, beating out the record of 2016... Crazy. This plot goes only to 192h, so the SSW is still not visible, but to put in perspective a SFW in the end of February...

https://ozonewatch.gsfc.nasa.gov/meteorology/figures/merra2/wind/u60n_10_2016_merra2.pdf

Atop this SSW looking like a SFW, global temperatures are still extremely high and forecasted to remain in the same range in coming weeks, and models are pointing out to an early retreat of the snow. March is set for some suprise in the synoptic situation.

May you live in interresting times, as the old say goes...

25
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 12, 2017, 01:52:18 PM »
Svalbard finally dip below zero degrees Celsius around 02UTC this day, ending a remarquable streak of above freezing temperatures. It has been since the early hours of the 05th February that the airport was above zero. During one full week, or 169 hours, the airport was above freezing. This is the longest streak in any winter months, beating out the previous thawing period of 155 hours at the end of December 2015 and the start of January 2016. Needless to say, this will be the February month with the lowest freezing days total for the station.



And the month to day is more typical of a February month in Deutschland with a Tnm of -2.5°C, a Tm of 0.2°C and a Txm of 2.8°C. A strong cooling is likely in the coming days, and beating out the monthly record of -1.4°C in February 2014 seems highly unlikely, but still this is remarquable for the a first half of February.

26
Arctic sea ice / Re: The Slow Transition
« on: February 11, 2017, 10:45:29 PM »
Yep, the two subjects are tied. Still, the inability of this winter to built back a slab of ice which is 2 m thick is, in my opinion, a counter argument to the slow transition. C. Reynolds had a nice idea and put some good work. But the premisses of his hypothesis is that the winter will be able to erase the memory of the system if I am say, at least for some times. And so, it will still need some mighty weather during the summer to demolish the sea ice. So the minimum sea ice trend will tend to flatten somewhat, being more subjected to year to year variability.

But this winter it is clearly not the case. Chukchi sea was still open in early - mid January, and there is no way sea ice will be able to consolidate before the melting season. Over the freezing thread of this winter, about everyone agrees saying that the conditions at the start of the melting season will be the worst ever and that even a non-conducive weather pattern this Summer can lead to an extremly low sea ice minimum. And we are only in 2016 - 2017. Which bring us back to the winter. What we are seing is the transtion of the Arctic region to a oceanic climate (as a side note, Svalbard was almost in line with a continental climate in 2016, and not too far away from a subpolar oceanic climate, temperatures wise ...). And this is linked to stormier Arctic, to lapse-rate feedback, to clouds feedback, and so on, during the winter season. With to understand and acknowledged the factors playing for an ice free winter to refute the slow transition theory. There is no indications that that the winter will be able to maintain the rate of ice growth. Summer is probably going to be ice free in 5 - 10 years from now, and Winter will probably be ice free beetween 2050 an 2070 depending on emissions path, unknown unknowns etc...

27
Arctic sea ice / Re: The Slow Transition
« on: February 11, 2017, 06:22:42 PM »
This winter is making clear that Arctic is going to crash abruptly. We are almost at the end of the winter, and first year sea ice is still not consolitaded. Until this year, yes, the cold was enough to keep the ice growing and reach a "standard value", something like a slab of first year ice, a 14 millions km² by 2m thickness slab. But these year we are way beyond this. The first year sea ice is still 1m - 1.5m about everywhere and there is only 1 - 2 month left before melting season starts. There is no way this year will reach the equilibrium state of a slab of 14 millions km² by 2m.



For Canada Sea Ice Service, thin first year ice is up to 70 cms, medium is up to 120 cms, thick is above. This is in broad agreement with HYCOM :



And it is woth stressing again that Chukchi sea ice remains open in the polar night until the start of January...
It can seem crazy to think that the Arctic is ice free in winter, but it will probably the case in the second half of this century. We are all in denial -me too sometimes-; and acknolewding that Arctic can be ice free in winter brings to me a picture of a man at the edge of a cliff, looking down and seeing nothing than a dark abyss -yeah I am a visual guy-. But here we are, this winter 2016-2017 is shouting to us, yes it is possible, it is only a matter of time.

There is not a strong need for aditional forcings. A bit more of CO2, a bit help from oceanic circulation, yes probably. But the most important factor is already playing
In winter there is a quasi permanent inversion in the Arctic. This quasi permanent inversion means, for radiative reasons, that surface can warm widly while the free atmosphere barely becomes hotter :

http://www.nature.com/ngeo/journal/v4/n11/full/ngeo1285.html

With this, open waters means clouds and water vapor. Stratocumulus helps even more to destroy the surface inversion.
Only one uncertainty remains, the possible feedback from a stormier Arctic. If Arctic truly becomes a den for storms, wich is likely, this will fan the oceanic heat content, helping even more. The 2016-2017 winter was astonishing because the surface inversion was barely alive. With January 2016, January 2017 is the sole month were T at 1000 hpa were above T at 850 hpa over Arctic:



Again, even while we are only in 2017, Ostrov Vrangla and the Pacific side of Arctic was able to stay strong and open until early - mid January, making two third of the journey trough the "freezing season" without freezing.

28
Arctic sea ice / Re: Return of the Perfect Melt Storm synoptic
« on: February 11, 2017, 04:20:48 PM »
I am not speaking about ozone hole directly, even though it is a related subject. I am only mentioning the fact that there is a link between ozone chemistry, solar activity (and times to times, volcanic eruptions...), and the transport of ozone in stratosphere. And by the way, QBO is also a player of course. Emissions of chlore counpounds is mudding the picture, with the additional effect of a reduced O3 content in stratosphere (linked to a persistant AAO in Southern Hemisphere pecurlary) but this is not the main point. The Brewer Dobson circulation exists and is influenced by the QBO and the Sun, no matter what is going on with ozone depletion. And this can have a significant effect for the polar vortex in the end.

http://www.iup.uni-bremen.de/sciamachy/sparc/downloads/weberrsparc07.pdf
http://www.iup.uni-bremen.de/materials/icacgp/Weber_stratosphere.pdf
www.gps.caltech.edu/~kl/research/proposalreview_Amended.ppt
ftp://ftp.lpl.arizona.edu/pub/lpl/lon/stratosphere/hood_nas11.pdf (very, very, very heavy PDF. To be downloaded, otherwise the browser could hoist the white flag)

And I am not here to discuss pseudo magic theory neither.

(By the way, if you want to muse a bit : ftp://ftp.lpl.arizona.edu/pub/lpl/lon/stratosphere/ )

29
Arctic sea ice / Re: Return of the Perfect Melt Storm synoptic
« on: February 11, 2017, 02:49:54 PM »
Yep but here there is another explanation. Solar has an impact on ozone cycle, Brewer Dobson circulation, and so on the polar vortex (even though there is no sun over the polar stratosphere in winter of course... but more or less Sun modify the ozone cycle and so the Sun is forcing the polar vortex also). This can lead to a northward or southward displacements of the jets. Of course, variations of the global temperature as a consequence is small, but variations in the synoptic pattern can be quite significant. I hear what Gray-Wolf want to say but I'm really not convinced. Impact of the Sun is stronger in Winter than in Summer for one part. And no matter what happens to the Sun, jets are marching northward. Again, I am really not convinced that the 2007 Summer is of any help to forecast what can happen in the near future.

P.S. : As a side-note, there is also some hints that a prolonged low solar activity (over decades or centuries) can increase the frequency of El Niño, and a prolonged high solar activity can increase the frequency of La Niña, but this is rather hypothetical and true for the "old" climate by the way.

30
Arctic sea ice / Re: Return of the Perfect Melt Storm synoptic
« on: February 11, 2017, 12:55:13 PM »
I don't think that the 2007 pattern was the perfect storm, nor that we are going to see this pattern again. We are lost in this wild ride and trying to hold on, trying to grab some certainty. We climate change going on, an the sea ice going down, it is far more likely we are going to see more and more a "warm cyclonism" -still baroclinic and cold core in the definition but with rains and mild temperatures-. Heavy downpours in the end can be as much devastating that a good old high pressure area and a sunny summer. This was the case in 2016, and this will probably become a trend. The 2007 pattern implies that subtropical jet and polar jet (or thermally and eddy driven jet or etc..) are still somewhat no far away from where they are supposed to be in the 20th century climate. But jets are moving northward and at one point (as shown by the 2016 pattern), there is no more "room" to put an high over Arctic.

31
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 11, 2017, 01:03:19 AM »
And not just an arm of warm temps reaching towards the North Pole, but a whole bulge:

One of the few occasions that the actual conditions have turned out even warmer than forecasted.
A lot of cold coming to the whole Arctic next week but the forecasts differ a lot beyond 5 days. The undecipherable SSW stuff disrupting the NH atmosphere??


The "SSW" was actually quite weak and barely qualifies as a SSW. I am really reluctant to call this thing a SSW, it was looking way way more like a minor displacement event. The polar vortex was never disrupted (a major displacement event means that the polar vortex is torn apart and shred in small pieces). And average 10 hPa zonal wind at 60°N barely touch the zero threshold. Arctic oscillation is taking a hit but the negative AO signal is weak. And the NAO is even positive, and not heading toward sub zero values. Which is quite frankly not unexpected, weak displacement event can lead to an increase frequency of storms over Atlantic. What is surprising is the magnitude of the decoupling between NAO and AO. I don't know why NAO is able to remain in neutral / positive territory will AO is negative. This said consequences from this displacement event will probably not be long lasting and are probably not the main cause of the disturbance we are seeing in the models.

The real game changer will be the next SSW - probably a true one, a SSW in the definition, this time-. Polar vortex is going to take a severe hit, and an early SFW out of this is not out of question. In the meantime, MJO is coming back to life with a (very, very) very strong 7 - 8 phase. Among others things (for example, boosting the incumbent El Niño...), strong MJO signal will also probably help the positive PNA pattern and in the end but a more prominent factor in the weaking of the positive NAO. There is even what can be qualified as an ongoing tectonic shift in the tropics with the Walker cells being strongly affected by the MJO (such a signal in the tropics was not seen since November) and taking a bit of en El Niño look.

In the 5 - 10 days window, the cold and high pressure foretasted for Arctic are probably a reliable signal, but without putting too much emphasize on this. It will not be a long-lasting nor a strong signal. After 10 days, the real game comes with the disruption of the polar vortex and the building effects of strong tropical convection.

And looking forward, Mach should be really interesting. An early SFW seems likely; and going on with the shift in the tropical convection, this could have profound effects for the beginning of the Spring -hoping a cold and snowy March for Europe ^^ -.

The 10 hPa winds viewed by GFS at 348h:



The current state of the tropical convection:



And the forecasted one :


32
Arctic sea ice / Re: The 2016/2017 freezing season
« on: February 10, 2017, 11:16:04 PM »
Buoy near the North Pole hitting again (bis repetita non placent...) 0°C:

http://www.infoclimat.fr/mer/bouees.php?id=26565&jour=20170210

http://www.infoclimat.fr/mer/bouees.php?id=26566&jour=20170210

And Svalbard is on overheating mode. It has been since the early hours of the 5th that the airport is above freezing. The monthly record is still not reached (7°C in 2012) but this is the second worst thawing period for any winter month here, second only to the begining of January 2016. Before 2016, more than two or three day above 0°C in a row was unheard of in Svalbard in winter.

33
Arctic sea ice / Re: The 2016/2017 freezing season
« on: January 23, 2017, 11:20:49 PM »
Another view of the ongoing tectonic shift. Data from NCEP NCAR reanalysis is showing the end of the thermal inversion in Arctic... This is quite a change, and have huge implications for radiative equilibrium. We are now saying that at surface, clouds, water vapor and CO2 are now sufficient to break the thermal inversion :

http://www.nature.com/ngeo/journal/v4/n11/full/ngeo1285.html

To illustrate, the data from December. The map presents the difference between temperature at 850 hPa and at 1000 hPa for the month of December :



Positive : no or weak thermal inversion, surface warmer than lowest layer of free atmosphere. Negative : the reverse.

The situation is even worst than last year (so December 2015, speaking of December 2016 before) :



The trend of the difference between 1000 and 850 hPa is upward, to say the least. And December 2016 was the first month of December when the surface was warmer than the lowest layer of free atmosphere.



This imply that the warmth of Arctic is partly endogenous, and that Arctic is able to sustain itself trough the darkness of the polar night. This is also visible with the downward radiation flux, showing widspread high values. The map for 2016 :



And for the long term mean :



And this is a trend for January also. Despite a cooling at 850 hpa, and temperatures in free atmosphere being colder than in say 2012 or 2016, Ostrov Vize is still running for its warmest January and the highest temperature anomaly of any month. Record seems far from certain, but the point is still there (January 2017 is the last point, preliminary data up to the 23rd).



And at the other end, Ostrov Vrangela is way above normal, tough not near record, temperatures in altitude being really cold for January over Pacific side.
 
As one guy (I don't remember who ^^" ) said, Arctic is becoming an Ocean. More and more, humidity and clouds and CO2 are insulating the Arctic, to the point that we are now almost at the point where no matter how cold it is in free atmosphere, the open Ocean will help with a heavy coat. Of course, for the theoretical/universitary remark, it is probably not a tipping point in the sense that if we could cool enough Arctic, sea ice will probably recover. It is more like an hysteresis, to be precise with words. But in the end, Co2 building up and temperatures soaring, this is more or less equivalent to a "no comeback from here and onwards".

34
Arctic sea ice / Re: Stupid Questions :o
« on: January 23, 2017, 10:41:09 PM »
Yeah yeah, of course cyclone is not spinning the same way in NH and SH. And if you dig in the etymology of the word cyclonic and anticyclonic, it is quite two strange words. Cyclone comes from Greek and does not implies a priori a specific direction for the spin. Etymologically speaking, we could make a case that anticyclonic is cyclonic... It is worth remembering also that we are speaking about vorticity along z-axis. Vorticity along x and y axis are negligible in general ( excepted in tornadoes XD ). And, mathematically speaking, positive vorticity is counter-clockwise, and negative vorticity is clockwise. This said, when I speak about a cyclone, for me it is a positive spin in NH and negative spin in SH. Of course, there is a link between the vorticity and the local pressure anomaly. If you consider p', the field of the pressure anomaly (anomaly regarding a space mean p0, not a time mean), you can write something like this -k and v vector- :

-1/ρ0 * grad( p' ) = f0 * k ⋀ v

Or more simply, in NH positive spin around a low pressure anomaly (1025 hPa can still be cyclonic if embedded in a 1050 hPa anticyclonic rotation ...) and a negative spin around a low pressure anomaly (again, 1000 hPa can be quite anticyclonic). I'm note sure if there is a best way to describe this equation. Coriolis force and pressure gradient act together and you have something like a double entry table. If NH and convergent flow, positive vorticity. If SH and convergent flow, negative vorticity. If NH and divergent flow, negative vorticity. If SH and convergent flow, positive vorticity.

35
Arctic sea ice / Re: Stupid Questions :o
« on: January 22, 2017, 01:59:36 PM »
Aslan, thank you for your explanation, I'm very interested in understanding several of the points you've made.  I will be reading soon, unfortunately, I need to be reading for my job, not my hobby...

I apologize for my ignorance, I've not studied meteorology in depth.  As I understand tropical cyclones always spin counter clockwise in the northern hemisphere and clockwise in the southern.  I assume this has to do with the direction of heat transport and magnetic fields.

I'm inclined to believe the upper atmosphere behaves similarly.  But I also fear my assumption is baseless.

Thats what I was fishing for, now I need to read, to see my postulations are anywhere near the right track...

In either event, thank you!

The direction of the spin is imposed by the coriolis force only. In NH, cyclonic flow is counter-clockwise and anticyclonic flow is clockwise. The reverse is true for SH. Coriolis force is described by f, the coriolis frequency, such as :

f = 2 * ( earth rotation rate ) * sin( latitude )

And Earth rotation rate is 7.2921*10-5 s-1

For around 45°N (in radians, so pi/4), f is roughly equal to 1e-4 s-1, and for 45°S it is roughly equal to -1e-4 s-1. The change in sign is the only reason for the different direction of spin in NH and SH. You can also note that the multiplicative inverse of f, around 45°N or S still, is 3 hours approximately (10 000 seconds). This means that any flow lasting less than 3h will not feel the coriolis force. And given a standard speed of around 50 m/s (180 km/h), in 3 hours the flows will "travel" around 500 kilometers. This means that any flow lasting less than 3h and/or smaller than 500 kilometers will not feel the coriolis force. This is described by Rossby number :

Ro = speed / ( lengthscale * f )

If Ro < 1, the flow will be subject to Coriolis force. You can check that for example the flow in a bathtub will not be subject to Coriolis force.

In tropics, Coriolis frequency being small (and even nul at equator), flow are much rotationnal and much more divergent / convergent. Tropical cyclones are an exception, being very long lasting system and with very high wind speed. For example, in mid-latitudes, squall-lines have a lengthscale around 100 - 200 kilometers and are a the high end bounds of the mesoscale where Coriolis force remains marginal. In tropics, squall-lines can reach a lengthscale of up to 1000 kilometers and still being and still being at the high end bounds of the mesoscale where Coriolis force remains marginal.

There is no such thing as the geomagnetic field or differential temperatures advection in explaining the direction of the spin.

36
How can you said that positive PDO is bringing a strong subtropical jet now, while it was not the case this past winter with an even stronger PDO and en El Niño ?


at the risk of being too much off topic.  my observations show increased water vapor moving into the higher latitudes.  This appears to be operating well below the subtropical jet and is a function of reduced high-temp process/high altitude aerosol emissions from Asia.  These aerosols previously suppressed upper altitude water vapor buildup through strong precipitation signals.

lets move this to wierd weather (or another location if you prefer) to talk http://forum.arctic-sea-ice.net/index.php/topic,323.1350.html


So, to move ^^ There is also a possible connection with the aerosols, yes. Since 2013, coal consumption / emission is stalling while gas and oil are still on the increase globally. Even though the proofs are thin, I suspect the stall in coal can explain the reduced aerosols emissions, and so could also be a factor in the recent burst of global temperatures. For the water vapor, you quite can be right but I must said I don't have think about this actually. Nonetheless, the observation of more and more water vapor being advected to the poles is clear.

37
Arctic sea ice / Re: Stupid Questions :o
« on: January 21, 2017, 08:50:13 PM »
I suppose I phrased my question wrong (dang my stupidity)... ;)

Instead of high pressure vs low pressure in cyclonic spin, is it a function of heat transport down vs. up?

Do low pressure systems spin counter clockwise in the northern hemisphere due to heat being transported up thru the center?

Conversely do clockwise spin in northern hemisphere indicate cold transport down @/thru the center?

 Thanks for the wonderful response to my other stupid questions, BTW!

There is no direct link between stratosphere and troposphere. When you will know more about the subject you will see how troposphere and stratophere are connected, but by the way I strongly suggest you starting with the point of view that there is not such thing as of a direct link between low pressure center in stratosphere and low pressure center in troposphere. And I even more strongly suggest that you don't refer to low pressure area, excepted at surface. This can lead to epic confusion and epic fail. Above surface, no matter it is troposphere and stratosphere, it is better to speak about low geopotential and high geopotential (there is others terms possible, depending at which kind of surface you are looking at, but low / high geopotenial is a good start). And more generally, don't try to make direct link between low geopotential area in stratosphere and troposphere. There is baroclinic and batropic waves. In the case of baroclinic wave, center of low geopotential area is displaced to the west with height. For the rest I am not sure to understund.

But to help you. There is the difference between baroclinic and barotropic waves indeed. In baroclinic waves, there is warm temperatures and high humidity to the equator, and low temperatures and low humidity to the pole. With the southerly flow downstream of the low, geopotential heights rise (air is at higher temperatures and higher humidity, so the air expands, hence the higher geopotential height). And with northerly flow upstream of the low, geopotentials heights lower. This is the case for an extratopical cyclone (at 500 hPa, the trough is "behind" the low at surface). But it is also the case for large scale waves. Currently, stratosphere is under assault by a wave of wavenumber 1. Usually, this is a baroclinic wave. But for now, the tilt toward the west with height is not really persuasive, and this does not lead to be overly optimistic about the chance of a SSW in the definition.
Conversely, barotropic waves are vertically aligned and there is no such thing as differential temperature/humidity advection. This is the case for tropical cyclones and polar low for example. But at a wider scale, planetary waves often tend to become barotropic -despite the gradients in the mid latitudes-. Also, wavenumber 2 in stratosphere is more usually a barotropic wave, which means it is vertically aligned. Wavenumber 2 assault against polar vortex often lead to a split case of SSW (polar vortex being broken in two piece so).

38
Arctic sea ice / Re: The 2016/2017 freezing season
« on: January 21, 2017, 09:33:10 AM »

I am not sure how we translate past PDO behaviour with today's anomalies.

see: 


compare with today



While I do not disagree that the PDO is + and warm, the persistence of tropical water vapor is a much stronger signal than a normal El Nino year today.  Last year's El Nino was not acting like an El Nino.  Our current Atmospheric river in California has tropical water vapor translation stretching all the way to the pacific warm pool!  I have never observed this before, not during El Nino, NEVER.

We used to call atmospheric rivers 'pineapple express' because they originated from the region around hawaii.  This event is more accurately called a 'palm oil express'. 

https://earth.nullschool.net/#2017/01/17/1500Z/wind/surface/level/overlay=total_precipitable_water/equirectangular=-162.35,18.54,519

I am not disagreeing with you, but we must recognize that the earth systems are changing so rapidly now that our previous patterns/metrics are no longer communicating current system operations accurately.


Yeah, no problems, I fully understand your question and I agree with your point. How can you said that positive PDO is bringing a strong subtropical jet now, while it was not the case this past winter with an even stronger PDO and en El Niño ? I think the last winter, warmth was widespread. Even if the pattern was fitting pattern of ENSO and PDO, it was more like a huge toast of red about everywhere and the Hadley cell were not able to contract as it should be the case. We even saw a case of two hurricanes at the same time in the Atlantic and the Pacific... Currently, the pattern of SST are a bit more zonally oriented; and the transition to positive anomalies in the subtropical Pacific, to cold anomalies in subpolar Pacific, is more pronounced, and global temperatures are a bit lower, allowing a response which is more classical of positive PDO. But nonetheless I agree with your point, we should be really cautious when we use this "old" "rule of thumbs" if I may say. Atmospheric circulation is highly disturbed and nothing known about the climate of the 20th will go through the 21th century unscathed.

I'm looking for some background information on Arctic weather. I know storms are not uncommon in the Arctic but is there a trend change in frequency, duration or intensity?


Very, very difficult question to answer, but as everyone already said, it is quite possible. The regions with a gradient of temperature and humidity, the baroclinic zone, is changing rapidly and this can lead to more frequent storms for Arctic. This year, it is beyond doubt that it was the case. The baroclinic zone this year was totally broken, with a reverse gradient between Arctic and Russia during Automn -for the first time since at least 50 years according to the reanalysis-.

39
Arctic sea ice / Re: The 2016/2017 freezing season
« on: January 19, 2017, 05:30:55 PM »
The strong, well established subtropical jet is typical of La Niña.

Sorry, proof reading me a bit late... Typical of El Nino, or more exactly of the warm pacific (positive PDO). Cali floods are not typical of La Nina but here the Pacific is behaving according to positive PDO more probably than according to La Nina wich is barely alive. So to sum up forcings are more likely warm Pacific, heavily disrupted baroclinical zone (and so the possible positive feedback Neven speaking about) and tropical convection in Indonesia and N. Amazonia. For the strat it is more likely that the heavily disturbed baroclinic zone is weakening PV, and not the other way round (weak PV disrupting baroclinic zone).

40
Arctic sea ice / Re: The 2016/2017 freezing season
« on: January 18, 2017, 11:21:07 AM »
The Polar vortex is just as important as the storms coming in (IMHO) We know that the strat 'drives' weather via various mechanisms and so keeping tabs on it , and trop forecasts, so we can better gauge impacts on the ice.

Should we see a warming down to ground level then we could see a period of HP dominance over the ice and isn't knowing such might be on the horizon important?

Then there is WACCy and the PV disruption. Without the poorly formed , errant PV through early winter would we have seen the Polar Jet flinging storms into the basin?

I know we have separate threads but when it is a pertinent observation of atmospheric forcing then it belongs here as much as any other chart ( again IMHO).


It really does not look like a major warming is underway. The polar vortex is severely weakened but westerlies are not ready to surrender. And if the stratopheric polar night jet remains in place, wave guide and waves propagation and so on are not going to be modified :

https://twitter.com/splillo/status/821488732796755968

The displacement will probably bring some blocking patterns in February, but I really doubt the AO will go down to basement or that strong high pressure areas will be back over Arctic. It really does not looks like a major event underway. The PV is severly disrupted but the wave flux is too much "eaquator-oriented" int the stratosphere, probably as a result of unending westerly QBO and strong Brewer Dobson circulation. And so the PV, even displaced, is not looking like it will break up and be torn apart.

http://img11.hostingpics.net/pics/777795GFSOPNH0036041.png

Il plie, mais ne rompt pas.

In my opinion, about the early disruption in the season of the PV, in the Automn, wich was quite exceptionnal. Of course, all weather phenomenon are related, and probably the early disruption of the PV was a factor during the winter. But the troposphere was, until now at least, only weakly coupled to stratosphere. The two jets this winter are seperated (subtropical and polar or thermal and eddy jet, as you want). The strong, well established subtropical jet is typical of La Niña. Associated to this, the polar jet was displaced far to the North probably due to some combinaisons of tropical forcings (strong convective activity in Indonesia and in Venezuela - Northern Amazonia associated with a weak La Niña probably sent energy to the polar jet), heavily disrupted baroclinic zone (early and strong siberian cooling and extensive snow cover associated with extremely low arctic sea ice) and yes perhaps the early disruption of the PV, but I really doubt it was a major factor. In itself, the tropospherics forcings are quite enough to explain the strongs and well seperated jets.

And for the early SFW, I also really doubt it will be the case. If the PV is not able to explode now, it don't see why it will be more likely to explode in March. Perhaps the QBO is going to help, but for now the QBO is lost.

41
Arctic sea ice / Re: The 2016/2017 freezing season
« on: January 14, 2017, 11:55:48 PM »
We are now seeing a possible SSW ( Sudden stratospheric warming ) toward the end of the month now. This might serve to build a high over the basin for a period? With the pack taking a beating how would this 'settled period' play out over the pack? would we see rotation of the ice and so further mechanical weathering/fracturing of the ice just prior to sun up again?

Just a thought but ,after last years record early 'final warming' dare we believe that if this SSW does arrive it could prove to be an even earlier 'final warming' and so usher us out of winter as far as the strat is concerned?

SSW is really not a given. There is another factor, the QBO. Still in westerly phase, and no one knowing what the hell is going on with the QBO. The easterly phase which should have been starting at 10 hPa now seems to be at least delayed. And after the epic fail of the QBO last year, what is happening regarding the QBO is anyone guess. Westerly QBO are often not favorable to SSW. Models are showing strong wave 1 activity but still nothing reaching the definition of SSW (a reversal of westerlies at 10 hPa). Stratosphere will probably be disrupted in the coming weeks, but a "true" SSW with a broken vortex and a strong AO- seems really uncertain. I am hopping for a SSW with some snow and cold where I lived, but this is still a very uncertain outcome. A worst case scenario, with a weak displacement having weak effects followed by an early SFW following strong waves activity in stratosphere, associated with an early onset of the Spring, seems a far more likely outcome.

42
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 29, 2016, 11:28:39 AM »
does anyone have an explanation for this apparently open water lead that persists now for quite some time and despite the fact that temps are sufficiently low in barrow to overfreeze any open water by now ? hope it's not an optical illusion or something like that but it's been there for a while now :-)


Probably not an illusion... Canadian Sea ice Service is showing also a region of very weak ice near Point Barrow :



And satellite products are also showing a region of low sea ice concentration around Point Barrow :



Why ? probably because there is offshore wind, and the sea ice is extremely weak, and Arctic Ocean beneath probably still warm.

And weather forecasts are dire, showing advection of warm, moist air from the south. Chukchi is barely closed since the last few days, be will probably open here and there for the beginning of January. This is worrisome, Chukchi sea ice will never fully consolidated before Spring, allowing warm Pacific to easily reach the central pack during the melting season.

43
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 26, 2016, 12:04:16 AM »
with regards to studies of equable climates, posted this here 2 weeks ago

http://forum.arctic-sea-ice.net/index.php/topic,1611.msg96837.html#msg96837




Yep good discussion ;) In the end, a big part of the answer for equable climates probably lies in the cloud. High clouds and some refinements of clouds proprieties are particularly suspected for explaining equable climates, event though the exact picture is still not clear.

44
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 24, 2016, 04:44:49 PM »
Sorry I think I meddled my own posts ^^"

Off the coast of Norway?! Actually just north-west of me, off the Outer Hebrides (Scotland).


Actually yes but you get the idea XD

The second effect is advection of an atmospheric moisture column in from far to the south. This impacts the heat budget of the Arctic Ocean more subtly in the form of heat-trapping clouds and water vapor that re-radiate back down longwave radiation the ocean is trying to give off, warming the air over the ice and preconditioning the next melt season by keeping open water from cooling.


Yep. We can get a sense of it with flux data from the reanalysis. The downward longwave radiation flux is showing a big anomaly in Chukchi and Barents sea (such a surprise...). The normal for 12/15 to 12/20 :



And in 2016 :



Longwave radiations coming from the "sky" are extremely high this winter. In Chukchi, the difference is topping 80 W/m². For comparaison, this is usually the power necessary to heat a house in winter... And this is the consequence of a moist, cloudy winter in Arctic. Ostrov Vrangela has seen very high values of Nh (low cloud cover octas) :

http://ogimet.com/cgi-bin/gsynres?ord=REV&ndays=50&ano=2016&mes=12&day=24&hora=12&ind=21982

And low temperatures are roughly correlate to low values of Nh. The same is visible elswhere in the Arctic. It was already the case in 2012, when Barents sea remains open all the winter and allows the cloud cover to keep the region to an extraordinarly wam level.

And we can see the feedback nature of the clouds. High dlwrf is following approximately the edge of sea ice. Open sea is increasing the moisture in the boundary layer, increasing the cloud cover. There is also another important point, the quasi permanent inversion thermal inversion in Arctic : http://www.nature.com/ngeo/journal/v4/n11/full/ngeo1285.html
Strong inversion are especially sensitive to change in radiations flux.

This is probably the most important fact of this winter. Being able to maintain sea open in Chukchi despite polar night is a frightening sight. It implies without any doubt that Arctic is able to be stable in a ice free state in the short term with an increase in heat and moisture transport. The feedback loop of clouds and moisture will be able to coat the Arctic even in the polar night, and with a bit of help from moisture and heat transport, an Arctic winter ice free is possible. This is the message of the current haemorrhagia. Yes, a winter ice free is whithin reach, look at the Chukchi sea. On a longer term, this is also probably linked to the theory of Abott about equable climates.

http://www.seas.harvard.edu/climate/eli/reprints/Abbot-Tziperman-2008a.pdf

If first step is to destroy thermal inversion with shallow convection (stratocumulus), currently ongoing; the next step could well be an even steeper lapse rate with deep convection and an equable climate. Soon to be a hurricane in Arctic?

45
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 24, 2016, 11:49:45 AM »

It is really incredible (at least for me)!!! Not an earthquake involved? Just a cold front?

19-meter wave sets new record - highest significant wave height measured by a buoy
https://public.wmo.int/en/media/press-release/19-meter-wave-sets-new-record-highest-significant-wave-height-measured-buoy


Nop, no tsunami ^^ Only the storm Barbara. This was measured off the coast of Norway, so near the sea ice waves were smaller, around 2 to 5 meters probably, but it gives you a sense of what a powerful low can do. And waves this high will produce a long swell which is also a big problem for sea ice. Swells from Barbara produced near Norway are now reaching sea ice and with a high swell period (more than 20 seconds). The very long fetch due to low sea ice will allows the swell to be well developed with very very long wave periods, which can bring quite energetics waves to say the least : https://en.wikipedia.org/wiki/Swell_(ocean)#Swell_and_coastal_impacts



And of course it is a positive feedback loop. Low sea ice increase the fetch and reduced the resistance of the ice to waves, which enhanced the consequences of big waves crashing against the sea ice front.

19m is remarkable. Since significant height is the average of the highest third of the waves, there were presumably even higher individual waves in the series?


Yep. Waves of 20 - 30 meters are not unheard of, but are rare of course. North Atlantic is known for its deep lows (in 1993, the Baer Storm bottoms out around 915 hPa...) and big waves, sometimes greater than 20 meters.

46
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 24, 2016, 11:43:27 AM »

It is really incredible (at least for me)!!! Not an earthquake involved? Just a cold front?

19-meter wave sets new record - highest significant wave height measured by a buoy
https://public.wmo.int/en/media/press-release/19-meter-wave-sets-new-record-highest-significant-wave-height-measured-buoy


Nop, no tsunami ^^ Only the storm Barbara. This was measured off the coast of Norway, so near the sea ice waves were smaller, around 2 to 5 meters probably, but it gives you a sense of what a powerful low can do.



And of course it is a positive feedback loop. Low sea ice increase the fetch and reduced the resistance of the ice to waves, which enhanced the consequences of big waves crashing against the sea ice front.

19m is remarkable. Since significant height is the average of the highest third of the waves, there were presumably even higher individual waves in the series?


Yep. Waves of 20 - 30 meters are not unheard of, but are rare of course. North Atlantic is known for its deep lows (in 1993, the Baer Storm bottoms out around 915 hPa...) and big waves, sometimes greater than 20 meters.

47
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 23, 2016, 10:38:54 PM »
Here is the link to that buoy table, data is attached: it seems show a patch of positives peaking at +0.8ºC (far right column, Ta).


That's from day 320 though. The previous "spike".




Yep, 300234064010010 reached only 0.0°C I think. But another buoy, 300234062788480, reached 0.4°C being at 86.8336°N, 300234064015020 reached 0.8°C being at 87.568°N and 300234064011000 reached 0.2°C being at 88.3142°N if I'm not mistaken.

48
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 23, 2016, 10:34:22 PM »



Not to mention another interesting side effect of the big North Atlantic low:



https://twitter.com/GaetanHeymes/status/812402581704179713

Waves of 15.4 meters, 6 floors, high...



49
Arctic sea ice / Re: The 2016/2017 freezing season
« on: December 10, 2016, 11:28:43 AM »
using a flawed metric (extent instead of volume) and ignoring aerosol emissions do not have any impact, she grossly underestimates the projection of future sea ice loss. laughable (if it wasn't so deadly important) assertion that it would take ANY MORE emissions from today to cause an ice free September minimum.  (hint: it won't). Graphic is gross.

Thanks, Jai. That and more needs to be said. The article is not even up to forum standards. The gimmick though was well-intentioned: personal footprint <--> lost ice. However it is way too late in the day for mickey-mouse mitigation like (voluntary) air travel offsets to begin in 2027 etc.


Yep, and they failed to consider the inertia of the system and the fact that we are way out of balance. Reaching  a summer free sea ice is only a matter of time now, and even a matter of short time (a few years probably).

For Siberia, it was an extraordinary heat wave, bringing record heat and above freezing temperatures. SYNOPs are totally crazy, and are more like SYNOPs from a stormy day in Ireland than SYNOPs in Arctic Coast, far to the North of Siberia.

Omolon broke its December record, old value was set in 2010:

http://pogodaiklimat.ru/monitor.php?id=25428

And farther to the North, locally it was feeling more like Ireland Coast than Arctic Coast:

http://ogimet.com/cgi-bin/gsynres?ind=21978&decoded=yes&ndays=10&ano=2016&mes=12&day10&hora=00

Above freezing during 39 hours (!!!) and gusts up to ~145 kph... Ice melt is absolutly certain in this conditions. Even around the Kolyma, more famous for its gulags, its harsh winters, its wolves, its firs, than its sea resorts; it was above freezing:

http://ogimet.com/cgi-bin/gsynres?ind=25121&ano=2016&mes=12&day=10&hora=6&min=0&ndays=30

Warmest temperatures ever for December... I didn't check in details the data, and there is some gaps, but for example here at Buhta Ambarcik temperatures blow off the roof also:

http://ogimet.com/cgi-bin/gsynres?ind=25034&decoded=yes&ndays=20&ano=2016&mes=12&day=10&hora=06

The highest min for this station until now was probably a -4.7°C reading the 1st of December in 1973 (records go back to around 1948 - 1950). Now, the highest min is 0.7°C! Even acknowledging there is some gaps in the data, it is virtually certain it is the first time this station is above freezing in December for more than a day... The highest temp in December was until now a 3.6°C reading in 1966. Unfortunately, the Tx is lacking in the SYNOP, but the new Tx is at least 4.2°C since yesterday. Depending on the period and the method used for calculating the daily mean, this station register a Tm of around 2°C the 09th of December, 30°C above 1981-2010 normal and breaking the warmest Tm of -1.5°C set in 1996 (the 23th)... And it is the same elsewhere along the coast. Nearer to the Pacific (like in Pevek Apapelgino) no record was set, warm moist air coming from Ocean being able time to times to reach the Siberia. But for the Kolyma region, deep interior of Siberia, and Arctic Ocean, it was an extraordinary heat wave. And this pattern is set to continue according to models:

http://www.wetterzentrale.de/maps/ECMOPNH00_120_2.png

50
Arctic sea ice / Re: The 2016/2017 freezing season
« on: November 06, 2016, 12:38:07 AM »
...
And the trend:


...

Aslan, I am really intrigued by this nice time series. A question: why do you include only the sector of longitudes E120° to 270° ( 90° West I  guess).
Is it possible to get similar plots of specific and/or relative humidity at tropopause pressure altitude of 200 hPa. Just to see if indeed we can see the expected humidity increase (with a small drop of relative humidity, see link below) given the temperature plot that Zack Labe was showing.
http://m.earthobservatory.nasa.gov/Features/WaterVapor/water_vapor3.php


Yep, it's from the reanalysis:

http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl

Why 120°E to 270°WE? because plots from reanalysis are only possible over latitude - longitude box with a simple definition (from east to west and north to south). Extending the box would have taken into account snow lands or the open Atlantic. And I was too lazy to done my own calculations and integrate OLRs over the central Arctic stricto sensu ^^" One BIG caveat is the validity of the reanalysis before the satellite era for such parameters. Before the late 70s, data are probably totally unreliable.

Reanalysis also give humidity parameters. Near the surface, it is generally good with some caution, up in the atmosphere it is sometimes less reliable. Tropopause is lower in Arctic in October, generally around 300 hPa. So here it is for the level 400 hPa, acknowledging that data are more reliable in recent years:



And precipitable water:



I haven't been able to find references which show how H2O radiative forcing changes with increases in humidity - anyone have any hints? I'd like to at least ballpark how much additional heat is being trapped


Perhaps here, from Pierrehumbert 1995:

https://scienceofdoom.com/2012/12/23/clouds-water-vapor-part-five-back-of-the-envelope-calcs-from-pierrehumbert/

Or here:

http://journals.ametsoc.org/doi/pdf/10.1175/JCLI3611.1
ftp://texmex.mit.edu/pub/emanuel/water/annrev00.pdf

And so to continue with radiative flux, downward IRs at surface for 2016:



The normal:



2012:



En 2003 -high water vapor content also according to the reanalysis-:


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