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AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #50 on: February 19, 2014, 05:44:08 PM »
The linked reference provides a valuable discussion of the relationship between ENSO and SAM and their associated predictability:


Lim, Eun-Pa, Harry H. Hendon, Harun Rashid, 2013: Seasonal Predictability of the Southern Annular Mode due to Its Association with ENSO. J. Climate, 26, 8037–8054. doi: http://dx.doi.org/10.1175/JCLI-D-13-00006.1

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00006.1


Abstract for the paper: "Predictability of the southern annular mode (SAM) for lead times beyond 1–2 weeks has traditionally been considered to be low because the SAM is regarded as an internal mode of variability with a typical decorrelation time of about 10 days. However, the association of the SAM with El Niño–Southern Oscillation (ENSO) suggests the potential for making seasonal predictions of the SAM. In this study the authors explore seasonal predictability and the predictive skill of SAM using observations and retrospective forecasts (hindcasts) from the Australian Bureau of Meteorology dynamical seasonal forecast system [the Predictive Ocean and Atmosphere Model for Australia, version 2 (POAMA2)].
Based on the observed seasonal relationships of the SAM with tropical sea surface temperatures, two distinctive periods of high seasonal predictability are suggested: austral late autumn to winter and late spring to early summer. Predictability of the SAM in the austral cold seasons stems from the association of the SAM with warm-pool (or Modoki/central Pacific) ENSO, whereas predictability in the austral warm seasons stems from the association of the SAM with cold-tongue (or eastern Pacific) ENSO.
Using seasonal hindcasts for 1980–2010 from POAMA2, it is shown that the observed relationship between SAM and ENSO is faithfully depicted and SST variations associated with ENSO are skillfully predicted. Consequently, POAMA2 can skillfully predict the phase and amplitude of seasonal anomalies of the SAM in early summer and early winter for at least one season in advance. Zero-lead monthly forecasts of the SAM are furthermore shown to be highly skillful in almost all months, which is ascribed to predictability stemming from observed atmospheric initial conditions."


The following website has a link to a pdf of the PowerPoint presentation for this paper at the AMS conference:

https://ams.confex.com/ams/94Annual/webprogram/Paper242257.html


Abstract for the presentation: "The Southern Annular Mode (SAM) is the dominant mode of variability of the extratropical atmospheric circulation in the Southern Hemisphere (SH) throughout different time-scales, ranging from weeks to decades. The positive index of SAM is characterised by lower than average pressure over the high latitudes and higher than average pressure over the mid latitudes, and its variability explains ~30% of the total variance of the circulation over the SH extratropics. SAM is driven by internal atmospheric dynamics as evidenced by its typical decorrelation time scale of ~10 days. Nevertheless, in the current study we demonstrate that seasonal variability of SAM can be predicted with good skill (proportion correct > 60%, correlation > 0.4) at lead times of up to 3 months by the Australian Bureau of Meteorology's dynamical seasonal forecast system, POAMA.
The predictability of seasonal SAM stems from its relationship with tropical sea surface temperatures associated with ENSO. Our study shows two distinctive periods of high predictability: the SH late autumn to winter and the SH late spring to early summer. Predictability of the SAM in austral winter stems from the association of the SAM with warm-pool (or Modoki/central Pacific) El Niño/La Niña, whereas predictability in austral early summer stems from the association of the SAM with cold-tongue (or eastern Pacific) ENSO. As POAMA is capable of predicting ENSO with high skill and simulating the SAM and ENSO relationship, it demonstrates good skill in predicting the phase and amplitude of seasonal anomalies of the SAM beyond a season in advance for austral early summer and late autumn."
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Andreas T

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Re: Antarctic Weather and Meteorology
« Reply #51 on: March 08, 2014, 02:21:07 PM »
I've been keeping an eye on temperature anomalies in Antarctica on the sea ice graphs page. The difference in baseline period for operational (1day) and reanalysis data is more significant in the Antarctic compared to the arctic and has to kept in mind when looking over the graphs I find.
What is striking is that after a consistently warmer SH winter we had a consistently colder SH summer and now as soon as the sun gets low, anomalies are turning positive again. That makes me want to see information about cloudiness, any suggestions where I should look?

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #52 on: March 08, 2014, 05:52:25 PM »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #53 on: March 14, 2014, 06:40:48 PM »
The following linked reference discusses the interaction between the Southern Hemisphere Atmospheric Circulation and the extratropical baroclinicity, the wave fluxes of heat, and radiative damping.   This behavior can influence ice mass loss from Antarctica:

David W. J. Thompson, Elizabeth A. Barnes, (2014), "Periodic Variability in the Large-Scale Southern Hemisphere Atmospheric Circulation" Science, Vol. 343 no. 6171 pp. 641-645, DOI: 10.1126/science.1247660


http://www.sciencemag.org/content/343/6171/641

Abstract:  "Periodic behavior in the climate system has important implications not only for weather prediction but also for understanding and interpreting the physical processes that drive climate variability. Here we demonstrate that the large-scale Southern Hemisphere atmospheric circulation exhibits marked periodicity on time scales of approximately 20 to 30 days. The periodicity is tied to the Southern Hemisphere baroclinic annular mode and emerges in hemispheric-scale averages of the eddy fluxes of heat, the eddy kinetic energy, and precipitation. Observational and theoretical analyses suggest that the oscillation results from feedbacks between the extratropical baroclinicity, the wave fluxes of heat, and radiative damping. The oscillation plays a potentially profound role in driving large-scale climate variability throughout much of the mid-latitude Southern Hemisphere."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #54 on: May 14, 2014, 12:29:52 AM »
The following link leads to an interesting NASA video describing the findings of new research related to teleconnections through the atmosphere between the Arctic and Antarctic and their impacts on NLCs:

http://www.livescience.com/45138-teleconnections-link-north-and-south-poles.html
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

LRC1962

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Re: Antarctic Weather and Meteorology
« Reply #55 on: May 20, 2014, 04:25:49 AM »
If the ENSO were to flip POD (see:http://climatecrocks.com/2014/05/12/kevin-trenberth-on-el-nino-part-2/ ), how would that change weather for the next decade or so?
Also as far as winds are, granted these are very high altitude winds I find it interesting to compare NP to SP
http://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=total_precipitable_water/azimuthal_equidistant=10.12,91.37,364
http://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=total_precipitable_water/azimuthal_equidistant=11.25,-82.83,207
would the far higher wind speed have partly to do with geography, or almost exclusively to do with the Ozone hole?
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AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #56 on: May 20, 2014, 04:09:30 PM »
LRC1962,

I am not a meteorologist, but I assume that Trenberth means that as both the El Nino and the positive phase of the PDO (Pacific Decadal Oscillation) both suppress the Pacific trade winds, that if a strong El Nino suppresses the trade winds sufficient then the weaker (but longer) PDO signal can keep the trade winds suppressed, even when the El Nino condition has gone away.

As to the difference in the upper atmosphere wind speeds between the Arctic and the Antarctic regions (again I am not a meteorologist) is primarily due to the fact that the Arctic region is an ocean surrounded by land masses, while the Antarctic region is a land mass surrounded by a continuous ocean.  I believe that the ozone hole is a secondary influence added on top of this primary factor.

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #57 on: July 14, 2014, 03:07:29 AM »
It is commonly assumed that the Antarctic ozone hole has been the main contributor to the positive summer trend in the SAM over recent decades (and this is likely true); however, the linked research indicates this positive trend may be opposed by future changes in the tropical Pacific.  This is significant because a more positive SAM tends to push the ABSL eastward away from the ASE in the austral summer; therefore, an opposing effect from the tropical Pacific increases the probability that the ABSL will direct more warm CDW into the ASE in the future, which will accelerate ice mass loss:

Nerilie J. Abram, Robert Mulvaney, Françoise Vimeux, Steven J. Phipps, John Turner and Matthew H. England, (2014), "Evolution of the Southern Annular Mode during the past millennium", Nature Clim. Change (2014); doi:10.1038/nclimate2235

http://www.nature.com/nclimate/journal/v4/n7/full/nclimate2235.html

Abstract: "The Southern Annular Mode (SAM) is the primary pattern of climate variability in the Southern Hemisphere, influencing latitudinal rainfall distribution and temperatures from the subtropics to Antarctica. The positive summer trend in the SAM over recent decades is widely attributed to stratospheric ozone depletion; however, the brevity of observational records from Antarctica1—one of the core zones that defines SAM variability—limits our understanding of long-term SAM behaviour. Here we reconstruct annual mean changes in the SAM since AD 1000 using, for the first time, proxy records that encompass the full mid-latitude to polar domain across the Drake Passage sector. We find that the SAM has undergone a progressive shift towards its positive phase since the 15th century, causing cooling of the main Antarctic continent at the same time that the Antarctic Peninsula has warmed. The positive trend in the SAM since ~AD 1940 is reproduced by multimodel climate simulations forced with rising greenhouse gas levels and later ozone depletion, and the long-term average SAM index is now at its highest level for at least the past 1,000 years. Reconstructed SAM trends before the 20th century are more prominent than those in radiative-forcing climate experiments and may be associated with a teleconnected response to tropical Pacific climate. Our findings imply that predictions of further greenhouse-driven increases in the SAM over the coming century also need to account for the possibility of opposing effects from tropical Pacific climate changes."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #58 on: October 29, 2015, 02:53:44 PM »
The linked articles indicates that because of the current strong El Nino, the weather in Antarctica this austral spring has been stormy:

http://antarcticsun.usap.gov/science/contenthandler.cfm?id=4185

Extract: "“It has been a stormy spring,” said Mike Carmody, the Antarctic Program’s Meteorological Operations Manager. “Any strong El Niño season you’ll have a stormy spring.”

...

“El Niño events tend to change the local wind direction along the Amundsen Sea coast of Antarctica,” Steig said. “This happens to push the ocean in a particular way so that you got more of the warm deep ocean water coming up under the ice shelves.”"
« Last Edit: October 29, 2015, 03:01:57 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #59 on: October 29, 2015, 11:40:09 PM »
The linked article indicates that there was a record-sized hole this month in the Antarctic ozone layer, but that we should not worry yet as the WMO has not changed their forecast that the hole will begin healing itself.  Note that the ozone-hole is helping to drive the circumpolar winds that together with the coriolis forcing is helping to advect warm CDW to the grounding lines of key Antarctic marine glaciers:

http://www.cbc.ca/news/technology/ozone-hole-1.3294004

Extract: ""This shows us that the ozone hole problem is still with us and we need to remain vigilant. But there is no reason for undue alarm," WMO Atmospheric and Environment Research Division senior scientist Geir Braathen said in a statement."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #60 on: January 04, 2016, 07:10:55 PM »
The attached Nullschool Earth 1000-hPa Wind and Temperature forecast for January 8 2016, indicates the possibility of widespread surface ice melting in West Antarctica and the Antarctic Peninsula, as the green color means above freezing surface temperatures.  It is conceivable that such surface meltwater might (or might not) contribute to local hydrofracturing calving events.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

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Re: Antarctic Weather and Meteorology
« Reply #61 on: January 04, 2016, 09:53:47 PM »
"Note that the ozone-hole is helping to drive the circumpolar winds that together with the coriolis forcing is helping to advect warm CDW to the grounding lines of key Antarctic marine glaciers"

I asked Prof Steig at realclimate about this idea, but he disagreed. In his view, CDW influx cannot be attributed to either the ozone hole or the increased surface temperature. This contrasts with Mercer who thought it would be the latter, specifically the location of the 0C isotherm.

sidd

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #62 on: January 04, 2016, 10:45:04 PM »
"Note that the ozone-hole is helping to drive the circumpolar winds that together with the coriolis forcing is helping to advect warm CDW to the grounding lines of key Antarctic marine glaciers"

I asked Prof Steig at realclimate about this idea, but he disagreed. In his view, CDW influx cannot be attributed to either the ozone hole or the increased surface temperature. This contrasts with Mercer who thought it would be the latter, specifically the location of the 0C isotherm.

sidd

I note that Prof Steig is scientifically conservative (ESLD), and as climate models do a particularly poor job of modeling the Southern Ocean, I can see that there is room for doubt.  Hopefully, AR6 will include the findings of advance ESMs like ACME.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

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Re: Antarctic Weather and Meteorology
« Reply #63 on: January 05, 2016, 01:13:39 AM »
I misrepresented Mercer: CDW did not figure in his articles. He viewed the 0C isotherm as the thing to watch, and stated that the breakup of ice shelves would be the canary. As for mechanisks of breakup, he was of the view that surface melt would play a role. But he said nothing about other mechanism such as CDW influx. I do not think he ever specified anything as a "main" driver except perhaps the Weertman instability.

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #64 on: January 06, 2016, 01:24:42 AM »
The attached image shows that for the five-day period beginning Jan 5 2016, almost all of West Antarctica will be anomalously warm for this time of year (probably due to the Super El Nino):
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #65 on: January 11, 2016, 06:28:43 PM »
The first three images show the Earth 1000-hPa & Temperature forecasts for West Antarctica for Jan 11, 12 and 15, respectively.  They all show surface ice melting along the coastal areas (note green is above freezing).  The fourth image shows that 1000-hPa atmospheric pressure corresponds to an Altitude (elevation) of 364 ft (111 m) above sea level, or right near the tops of the ice shelves in this area (note the ASE).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #66 on: January 14, 2016, 12:36:24 AM »
I believe that I have missed the peak, but the attached ClimateReanalyzer 5-day Maximum Temperature (at 2m) forecast from Jan 13 to 17, 2016, shows considerable areas of surface ice melting, including in the ASE
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Antarctic Weather and Meteorology
« Reply #67 on: January 14, 2016, 06:25:15 PM »
As a follow-up to my last post, the attached ClimateReanalyzer 5-day Maximum Temperature (2m) forecast from Jan 14 to 18 2016, show high risk of ice surface melting for Larsen C, PIIS, and Thwaites, all key WAIS ice features, that are susceptible to local hydrofracturing.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson