Sea Surface Temperature And Sea Ice Trends

[Glacier Point]

:lol:

I would like to see the SSTA for autumn 1995 and compare it to now

if someone can show me to where it is?

This in in view of how the winter turned out (reasonaly cold) and following a hot summer not unlike this one.

Tamara

1995:

2005:

2006:

I'm struck by the similarity with last year really. Imagine how that would have turned out without the strongly -ve QBO and la Nina ?

[Dawlish]

The Bartlett could arise from all the hot air from Dawlish & WIB :lol: :lol:

Thank you Eye. I'll remember your excellent contribution sometime this winter, I'm sure. For the time being I'm far too depressed after watching England :lol:

[summer blizzard]

The Atlantic may be similar this year however the Pacific certainly is not, with massive differences.

[Stratos Ferric]

What do you mean if both both anomolies are positive, warm anomolies over cold anomolies favour a southern trough as is the situation now, i am not denying that the surface air will be modified, but either we are talking about two different things, or you do not understand sea surface temperature couplets, a strong Sub-Tropical Jet Stream in itself, would encourage a more southerly tracking Jet Stream.

The current setup in the Pacific is highly conducive to a split Jet Stream, with a strong sub-Tropical Jet Stream.

SB, with the exception of a small puddle of cool water off the Bahamas, and a cold drift, presumably of meltwater, off Greenland the anomaly in the Atlantic is universally positive. Yes, the anomaly in the S Atlantic is lower than the anomaly in the North Atlantic, but the point is that all areas the anomaly is a POSITIVE one.

Not sure I'd agree with your assessment that the picture in the Pacific c.f last year is massively different; broadly speaking the dispersal of warm and cold is similar to last year save for off Japan and just south of Alaska.

In the attached graphic I've captured the comparative SSTs for October 2006, 2005 and 1985. I've also shown Feb 1986. Bearing in mind how cold that month was, it does rather bear out me earlier point about cold SSTs favouring colder weather. It really is very difficult to get sustained cold with an anomalously warm Atlantic. Comparing Oct 1985 with the present the increased warming of the ocean surface around the globe is clear, save for the fringes of Antarctica.

The Feb 86 picture also shows how helpful a cold pool in the Atlantic is. I agree with SB's point about the tie up between SSTs and mean jet location, just that we seem to read the runes rather different ways.

SB, you might want to clarify your earlier point about southerly tracking PFJ and strong STJ; not sure what the logic is there.

[Stu_London]

SSTs are driven by by atmospheric conditions at our latitude whereas the reverse is true at tropical latitudes

Therefore it follows that cold anolomies will occur when the prevailing synoptics deliver cold weather (Feb 86 and Mar 06)

As for the mid altantic cold anomoly - that cuts little ice with me - it has been present in several of the last few autumns and early winters and it has been predominately mild

[BLAST FROM THE PAST]

SF

Looking at Oct 06 and 85 I can't see how your argument holds out. Also Feb 86 chart didn't cause the Feb 86 coldmonth for the UK

BFTP

[Stratos Ferric]

I must admit recent posts bear out my own confusion over SF's posts.

We had prevalent cold water anomalies over wide areas of water in the late Spring this year - using the warm=warm and cold=cold arguement, there should have been a cold summer :blink:

...

Tamara

Not really. The oceanic influence is much more important in winter than it is in summer. In winter the PFJ moves equatorward as the thermal equator moves south. Variations in the track of the jet away from long term mean (some of which are influenced by SSTs) determine whether we are in cold or warm air (one side of the PF or the other).

In summer the whole system is much further north and with climbing temperatures the gradient at the PF falls, making for slower average flows across the gradient and much reduced storm genesis at our latitudes (and generally). In addition re radiation is higher from the land in the hemispheric summer, and the ocean becomes less dominant as an engine. In summer, therefore, SST variations are less significant drivers in our weather, and in any case we are too far removed from the action for any impact - generally - to be felt significantly.

I vaguely recall from research I did for my thesis that one indicator of a cold winter in NW Europe is actually a cold pool in the N Pacific. As a driver generally the Pacific is more important than the Atlantic anyway, though the Atlantic obviously moderates our surface and can serve to reinforce alignment of the jet. A cold N Pacific will push the PFJ well south across the US and should be supportive of a cold pool building off the NE of the US, which points towards a Greenland High.

[The Enforcer]

I vaguely recall from research I did for my thesis that one indicator of a cold winter in NW Europe is actually a cold pool in the N Pacific. As a driver generally the Pacific is more important than the Atlantic anyway, though the Atlantic obviously moderates our surface and can serve to reinforce alignment of the jet. A cold N Pacific will push the PFJ well south across the US and should be supportive of a cold pool building off the NE of the US, which points towards a Greenland High.

I'm glad you said that. I've come to the same conclusion. Very shortly I'm going to be comparing SSTA charts, like this time last year. However, on this occasion I shall be focusing on the North Pacific.

Edited October 11, 2006 by The Enforcer

[AtlanticFlamethrower]

I vaguely recall from research I did for my thesis that one indicator of a cold winter in NW Europe is actually a cold pool in the N Pacific. As a driver generally the Pacific is more important than the Atlantic anyway, though the Atlantic obviously moderates our surface and can serve to reinforce alignment of the jet. A cold N Pacific will push the PFJ well south across the US and should be supportive of a cold pool building off the NE of the US, which points towards a Greenland High.

Stratos Ferric that is interesting research. Where in the North Pacific should the cold pool be/ how large must it be? I presume you mean the North East Pacific.

Huge cold pool off California but that is central Pacific.

Edit to add:

How does your research about a Pacific driver match up to this map of SSTAs and mean wind direction? Does it match?

ATMOSPHERIC GCM RESPONSE TO EXTRATROPICAL SST ANOMALIES:

SYNTHESIS AND EVALUATION (Peng et al) The patterns of wintertime (December-March), anomalous SST, ocean-to-atmosphere turbulent heat flux (latent plus sensible), and surface wind vectors, associated (via linear regression) with the leading principal component of SST variability in the North Atlantic (a and c) and North Pacific (b and d). Panels a and b are for observations from 1949 to 1999 (data for from NCEPNCAR CDAS-1, Reanalysis). Panels c and d are for the mean of a 10-member ensemble GCM integrations forced with global, time-varying SST anomalies from 1950 to 1999 ECHAM 3.5 GCM data provided by Lisa Goddard, IRI). Heat fluxes are in Wm-2 with positive/negative values in solid/dashed contours every 3 and a thick zero contour. Arrows depict the wind vectors in ms-1 with scales shown in lower left (panel a, c) and upper right (Panel b, d). The SST anomaly values, in °C, are denoted in colors according to scale (note that scale is kept at the –0.5 to 0.5 °C range for overall clarity, however, values in eastern equatorial Pacific extend up to 1.2 °C).

Warm anomalies also tend to move north west with time so looking at current SST anomalies we should expect to see High pressure over greenland and low pressure in the central Atlantic which with time should equate to Icelandic or Scandinavian high by winter time. In between and we might expect an increasingly stormy time. This is all theory and the response to SST anomalies is notorious for changing during mid winter and I can not help feeling high pressure and easterly winds are likely to be too far north.

If the Pacific was always the driver of our winters why do we have a measurable pattern of East to West flow develop over warm anomalies in the Atlantic over a period of many years? Surely no pattern would develop as Atlantic anomalies won't make a jot of difference. You can claim the Pacific and Atlantic anomalies are connected; when the North Pacific is warm, the North Atlantic is cold. That seems a silly thing to argue as obviously it would raise the question how the anomalies are connected! Also it should be fairly easy to prove or disprove whether a warm North Pacific results in majority West-East (Atlantic) flow over Europe.

Isn't it an interesting observation that warm SST amonalies at Northern lattitudes have been shown to result in flow from the East out-measuring that from the West? Surely that should impact our winter forcasts as the North Atlantic SSTs are generally very warm so we might expect an Easterly dominated winter.

Edited October 12, 2006 by AtlanticFlamethrower

[Stratos Ferric]

AFF,

Can't honestly say I understand what those four charts are trying to show: they need more narrative. They certainly don't demonstrate mean conditions over fifty years. What leading variant of SST, and in which winters? Winters with specific anomalies, or all anomalies (all winters have anomalies), and are the airflows the mean airflows only in those specific conditions?

I'd have to go back and check my college papers to confirm the Pacific link, though I'm fairly sure it was NE, so the anomaly would match up with the diagrams at :blink: and d). Even then the link was not strong though. It's certainly not the case that the Atlantic doesn't matter, just that the Pacific matters too. Given that the PFJ tends towards a mean wavelength of around 90 degrees it becomes possible to see why, when NA is exceptionally cold relative to norm for a season, Europe TENDS not to be, and v.v. A jet well S over the US will tend to be approaching the meridian from the NW, meaning surface flows tend to trail back W, with secondary systems developing (similar to recent winters); a jet further north will tend to approach the UK from the W/SW, similar to the sort of alignment we had in 1978 and 79, with incoming surface depressions often drawing in easterlies ahead of them. All of these are seasonal patterns though, and within this the jet will periodically destabilise, allowing blocks to develop; they may be cold or warm in nature of course, depending where they sit relative to each surface location.

SSTs are driven by by atmospheric conditions at our latitude whereas the reverse is true at tropical latitudes

Therefore it follows that cold anolomies will occur when the prevailing synoptics deliver cold weather (Feb 86 and Mar 06)

As for the mid altantic cold anomoly - that cuts little ice with me - it has been present in several of the last few autumns and early winters and it has been predominately mild

Stu, that's patently not the case, and you might need to clarify slightly. The thermal capacity of the oceans is huge in comparison to the air above (water being several orders of magnitude denser than air); in winter air is modified by the ocean far more than v.v. The main determinant of SSTs is the flow of water, particularly deep flows, in the oceans. El Nino / La Nina demonstrates this, and the weather lags the ocean current NOT v.v.

There is feedback of course, and the wind direction and strength across the ocean surface is important in driving surface currents and supporting upwellings, but the inertia in the oceans is huge and would continue for many years even if the earth suddenly stoppped spinning; the same is less true for air, which would flux, but would do so purely thermally (i.e. basically polewards aloft and equatorwards at the surface). Those wishing for cold weather would be best served, here in the UK, by hoping for the earth to stop spinning therefore.

[The Enforcer]

Ok, here's the first stage of the SSTA analysis. A comparison of the charts for the second week of October over the past seven years and the CET's for the winters that followed:

2000: Winter CET = 4.22

2001: Winter CET = 5.05

2002: Winter CET = 4.48

2003: Winter CET = 4.90

2004: Winter CET = 5.04

2005: Winter CET = 4.01

2006: Winter CET = ?.??

Not really enough data to draw a truly enlightening comparison as it would be nice to have a chart from, say, October 1995 or an October in the run up to an early 90's or 80's cold winter.

The one conclusion I can draw here is that at this stage in the autumn, the North Pacific contained the most extensive positive anomaly at Central Europe lattitude in both October 2000 and 2005 - the coldest UK winters of this series. Although, it has to be noted that otherwise there are a lot of differences between the two charts, notably, the western coast of South America (El Nino/La Nina) and the Northernmost sectors of the North Atlantic. Curiously, in October 2000, alongside the aforementioned positive anomaly, there was the most substantial negative anomaly of all of the charts at European lattitude in the North Pacific, which was not a feature in October 2005.

IF a warm anomaly in this area at this time of year is a good factor in producing a colder UK winter, then this October has some work to do, as the anomaly is way short of the mark.

I'm now going to move on to look at the charts from the winter months, which will arguably have more direct bearing on winter weather patterns, but I won't have the benefit of being able to draw comparison with this year. As the charts are updated on a weekly basis I shall return to the current period to see how 2006 is progressing.

Edited October 12, 2006 by The Enforcer

[BrickFielder]

AFF,

Can't honestly say I understand what those four charts are trying to show: they need more narrative. They certainly don't demonstrate mean conditions over fifty years. What leading variant of SST, and in which winters? Winters with specific anomalies, or all anomalies (all winters have anomalies), and are the airflows the mean airflows only in those specific conditions?

The diagram is taken from 'ATMOSPHERIC GCM RESPONSE TO EXTRATROPICAL SST ANOMALIES:

SYNTHESIS AND EVALUATION' by Yochanan Kushnir at Lamont Doherty Earth Observatory

The patterns of wintertime (December-March), anomalous SST, ocean-to-atmosphere

turbulent heat flux (latent plus sensible), and surface wind vectors, associated (via linear regression)

with the leading principal component of SST variability in the North Atlantic (a and c) and North

Pacific (b and d). Panels a and b are for observations from 1949 to 1999 (data for from NCEPNCAR

CDAS-1, Reanalysis). Panels c and d are for the mean of a 10-member ensemble GCM

integrations forced with global, time-varying SST anomalies from 1950 to 1999 (ECHAM 3.5 GCM

data provided by Lisa Goddard, IRI). Heat fluxes are in Wm-2 with positive/negative values in

solid/dashed contours every 3 and a thick zero contour. Arrows depict the wind vectors in ms-1 with

scales shown in lower left (panel a, c) and upper right (Panel b, d). The SST anomaly values, in °C,

are denoted in colors according to scale (note that scale is kept at the –0.5 to 0.5 °C range for overall

clarity, however, values in eastern equatorial Pacific extend up to 1.2 °C).

I would agree that Pacific conditions can largely override Atlantic ones.

Edited October 12, 2006 by BrickFielder

[Anti-Mild]

There's no real simliarities between 2006 and any of the other years shown, the obvious difference is the warm anomaly around equatorial Ecuador (try saying that quickly 10 times after a bottle of wine ).

Apart from that, last year seems to be the most similar.

The closer we get to December, the more I am becoming convinced that this Winter will be very similar to last year with a mild start and a cold end. That said, it looks like the PFJ will be more Southerly this time out and hopefully the Pacific Jet wont throw a spanner in our works.

AM

[The Enforcer]

I have now edited in my own crude analysis underneath the charts.

[Glacier Point]

Does a positive orientated SSTA couplet in the Atlantic have the same impact as a more clear cut positive - negative one ? This is essentially the debate at present regarding those warm anomalies to the north Atlantic.

Most contemporary research has concluded that extra-topical SSTAs vary in their influences between latitude, orientation and season with summer-time infleunces less so (but still significant) in the northern hemishpere.

What has not been successfully demonstrated yet is the response (particulalry in terms of the NAO signal) of warm anomalies over less warm anomalies. This is due to this being quiet a recent phenomenon, witnessed over the last 15 years:

compare 1980s to 1990s+ SSTAs

Now this may or may not be related to the lack of wintry weather experienced by western Europe (the timing certainly fits), but this could be attributed to other factors, not least decadal trends in the oceans.

Last year provided a really good test of the thoery that warm waters around 55 degrees north over less warmer waters in the Atlantic below 45 degrees north would bring about a -ve NAO and colder winter conditions. It didn't bring about a negative NAO, but it did bring to a juddering halt the long run of above average months and very mild winters. I would speculate that the NAO was heavily influenced and often over-riden last year by the strong easterly phase Pacific Jet and a developing La Nina.

By taking the NAO as a measurement of Atlantic SSTAs, for winters with all three months in a -ve NAO leading mode, the SSTA composite looks like this:

with warm waters to the north and cold anomalies to the SW Atlantic, and some hint of positive anomalies over the Pole.

The CDC (following Barnston and Livezey 1987) calculation of the NAO and therefore the impact of SSTAs on lower tropospheric height variability would appear to suggest that a warm and less warm scenario in the Atlantic will still result in a -ve NAO:

http://www.cdc.noaa.gov/map/wx/indices.shtml

My assessment of this is that warm waters in the north Atlantic and neutral or even marginally warm waters southwards will still inherently infleunce a -ve NAO pattern (allowing for the AO in its leading mode).

This year the SSTAs in the Atlantic are pretty similar to last:

and we will once again test this theory, particularly so as the weak El Nino will, if persistent, promote -ve mean height anomalies in the SW Atlantic where cooler anomalies (cold anomalies = winter time low pressure) are required.

In so far as 1985/6 is concerned SF, that is a poor example of how cold water anomalies are required for cold - a winter with the NAO values +.0.22, +1.11 and -1 despite some strong loading from a -ve AO throughout and a La Nina infleunced pattern to boot.

..no surprises that the SSTA for the preceeding 4 months in 1985 period looked like this...

GP

[Ross B]

Continued here