Skip to content

Australia Drought, The Indian Ocean Dipole & Sudden Stratospheric Warming

January 5, 2020

By Paul Homewood

 

 

One factor that seems to have received no attention at all in the media’s reporting of the Australian fires is the role of the Indian Ocean Dipole, or IOD.

The IOD is, in very simplistic terms, a similar phenomenon to ENSO. When it is in positive mode, the Indian Ocean is warmer than normal to the west, and cooler in the east.

This effect is driven by easterly winds, as we also see during La Ninas. In both cases, these winds drive the warm surface waters to the west, allowing cold, upwelling water to replace it.

This is how the Australian BOM describe it:

 image

http://www.bom.gov.au/climate/enso/history/ln-2010-12/IOD-what.shtml

 

But what is important about the IOD is that, during positive phases, rainfall is reduced over southern Australia. As the winds cool the east and warm the west, the pattern of tropical convection changes. Tropical convection favours warmer waters, so we see lower pressure, more rain and storms in the west , where we have warmer waters. And we see the opposite in the east parts, where we have higher pressure, less rain and storms and drier conditions across the region over Indonesia and Australia.

But not only is Australia affected, as the same phenomenon brings greater rainfall to India and East Africa.

Although the IOD has not been monitored for long, scientists agree that it is a naturally reoccurring event, with strong events occurring roughly every ten years.

 

So far, so good.

It won’t come as any surprise then that this years Australian drought has coincided with just such a strong positive IOD. In fact, arguable one of the strongest on record:

 

ENSO Monitoring Graph

http://www.bom.gov.au/climate/enso/indices.shtml?bookmark=iod 

 

Indian researchers have looked at the IOD closely as well, given its importance to the Indian monsoon. Quite obviously the latest positive IOD is far more powerful than anything else on record, at least since 1999:

 

mon_dmi-5dac27ba

http://enformtk.u-aizu.ac.jp/blog/2019/09/03/how-strong-is-the-2019-iod/

 

Indian climatologist, Saji N. Hameed, saw this coming months ago:

“The strength of this IOD is enormous. We were anticipating it to exceed the 2006 event, based on the DMI comparisons at http://enformtk.u-aizu.ac.jp/blog/2019/09/03/how-strong-is-the-2019-iod/

But, this seems destined to break some records. Look at the wind and OLR anomalies. They are well matched with SST anomalies and will further cool the SST at the eastern Indian Ocean, pushing the IOD to greater strength by the end of October. Perhaps, this IOD is similar to the 1961 event as my good friend Prof. Ashok Karumuri pointed out a few days ago.”

 http://enformtk.u-aizu.ac.jp/blog/2019/10/07/a-monster-of-an-iod/

And as we know, India has a very wet monsoon last summer.

He also stated in an interview in September:

“The dry spells over Indonesia, Australia and Singapore are strongly tied to the ongoing IOD. In fact, the Australian weather agency has been alerting Australians to adverse climate associated with IOD since early spring of this year”

https://weather.com/en-IN/india/monsoon/news/2019-09-16-2019-to-be-one-of-strongest-iod-years-on-record-expert

As Hameed states, the IOD is a naturally occurring event, which has nothing to do with climate change. Inevitably attempts have been made to link the strength of this event with global warming, but there is simply is not enough data to make such a deduction. What we do know is that Australia has been wetter since 1970 than it was before, which would suggest otherwise.

 

But there is one other factor to plug into the mix – a sudden stratospheric warming over the Antarctic. This is what the BOM were flagging up last September:

 image

Record warm temperatures above Antarctica over the coming weeks are likely to bring above-average spring temperatures and below-average rainfall across large parts of New South Wales and southern Queensland.

The warming began in the last week of August, when temperatures in the stratosphere high above the South Pole began rapidly heating in a phenomenon called "sudden stratospheric warming".

In the coming weeks the warming is forecast to intensify, and its effects will extend downward to Earth’s surface, affecting much of eastern Australia over the coming months.

The Bureau of Meteorology is predicting the strongest Antarctic warming on record, likely to exceed the previous record of September 2002.

(Left) Observation of September 2002 stratospheric warming compared to (right) 2019 forecast for September. The forecast for 2019 was provided by the Australian Bureau of Meteorology and was initialised on August 30, 2019.

What’s going on?

Every winter, westerly winds – often up to 200 km per hour – develop in the stratosphere high above the South Pole and circle the polar region. The winds develop as a result of the difference in temperature over the pole (where there is no sunlight) and the Southern Ocean (where the sun still shines).

As the sun shifts southward during spring, the polar region starts to warm. This warming causes the stratospheric vortex and associated westerly winds to gradually weaken over the period of a few months.

However, in some years this breakdown can happen faster than usual. Waves of air from the lower atmosphere (from large weather systems or flow over mountains) warm the stratosphere above the South Pole, and weaken or "mix" the high-speed westerly winds.

Very rarely, if the waves are strong enough they can rapidly break down the polar vortex, actually reversing the direction of the winds so they become easterly. This is the technical definition of "sudden stratospheric warming."

Although we have seen plenty of weak or moderate variations in the polar vortex over the past 60 years, the only other true sudden stratospheric warming event in the Southern Hemisphere was in September 2002.

In contrast, their northern counterpart occurs every other year or so during late winter of the Northern Hemisphere because of stronger and more variable tropospheric wave activity.

What can Australia expect?

Impacts from this stratospheric warming are likely to reach Earth’s surface in the next month and possibly extend through to January.

Apart from warming the Antarctic region, the most notable effect will be a shift of the Southern Ocean westerly winds towards the Equator.

For regions directly in the path of the strongest westerlies, which includes western Tasmania, New Zealand’s South Island, and Patagonia in South America, this generally results in more storminess and rainfall, and colder temperatures.

But for subtropical Australia, which largely sits north of the main belt of westerlies, the shift results in reduced rainfall, clearer skies, and warmer temperatures.

Past stratospheric warming events and associated wind changes have had their strongest effects in NSW and southern Queensland, where springtime temperatures increased, rainfall decreased and heatwaves and fire risk rose.

The influence of the stratospheric warming has been captured by the Bureau’s climate outlooks, along with the influence of other major climate drivers such as the current positive Indian Ocean Dipole, leading to a hot and dry outlook for spring.

Anomalous Australian climate conditions during the nine most significant polar vortex weakening years (1979, 1988, 2000, 2002, 2004, 2005, 2012, 2013, 2016) on both maximum and minimum temperatures, and rainfall for October–November, as compared to all other years between 1979–2016. Bureau of Meteorology.

http://www.bom.gov.au/climate/updates/articles/a035.shtml 

 

So, given the conjunction of an unusually strong IOD with an SSW event, is it at all surprising that large areas of Australia have just gone through one of the severest droughts on record?

30 Comments
  1. January 5, 2020 12:40 pm

    Interesting that there have been no cries of ‘massive bleaching’ on the GBR, particularly as this warming spell seems much hotter and drier than the average el Nino?

  2. January 5, 2020 1:04 pm

    Reblogged this on Climate- Science.press.

  3. Broadlands permalink
    January 5, 2020 1:59 pm

    It is noteworthy that the current ENSO is in neutral (El-Nada) territory and has been so for months. The threat of an El-Nino (or a La-Nina) is small. All of this is natural and there is no correlation with CO2.

  4. Joe Public permalink
    January 5, 2020 2:09 pm

    Hopefully, Aunty will soon have a vacancy for a competent & knowledgeable ‘Energy and Environment Analyst’.

    It involves travel to locations worldwide, and attendance at conferences in exotic locations. (Naturally, a generous tax-free expense account is offered, fully reimbursed courtesy of Telly-Tax payers)

    Would you consider accepting?

    • January 6, 2020 10:43 am

      Sorry no, it would ruin my carbon footprint 😆

  5. Dave Ward permalink
    January 5, 2020 3:19 pm

    “With strong events occurring roughly every ten years”

    Since sunspots have an average 11 year cycle. is there any correlation between the two?

    • Nancy & John Hultquist permalink
      January 5, 2020 4:51 pm

      In contrast, their northern counterpart occurs every other year or so during late winter of the Northern Hemisphere because of stronger and more variable tropospheric wave activity.

      Not a correlation there. So one needs to explain the SH and the NH differently.

  6. Vanessa Smith permalink
    January 5, 2020 4:18 pm

    There is a good interview on YouTube with an Aborigine farmer in Australia. He says they have burned the brush etc. every year but they need to do it carefully and with the long-known knowledge of HOW to do it properly. He says the knowledge is no longer known or is being ignored. Interesting ?

    • Graeme No.3 permalink
      January 5, 2020 9:56 pm

      Vanessa:
      There have been numerous Commissions and Inquiries over (at least) the last 80 years all recommending burn-offs in the appropriate time yearly. They have been ignored, indeed penalised if farmers or others do so. And the pressure from the Greenies …
      https://www.geco.org.au (December 23).

      • Graeme No.3 permalink
        January 5, 2020 10:29 pm

        Lest there be some confusion the cartoon is from the volunteerfirefighters.org.au
        GECO is for the Greenies

  7. A C Osborn permalink
    January 5, 2020 6:01 pm

    Could the IOD and the SSW be linked, all that energy going in to the atmosphere above the Indian ocean.

  8. Harry Passfield permalink
    January 5, 2020 8:06 pm

    Another factor that seems to have been ignored is how many fires have been deliberately set by arsonists. I would not put it pasty the likes of XR to see an opportunity for advancing their creed.

  9. January 6, 2020 1:11 am

    I discussed the role of the Indian Ocean Dipole and Southern Annular Mode in the Australian bushfires in my interview on BBC World News TV on Thursday 2nd Jan

    • January 6, 2020 10:38 am

      Thanks Richard.

      Perhaps you could spread this message wider throughout the media

  10. January 6, 2020 1:16 am

    • January 6, 2020 7:02 am

      There is no evidence that “climate change has made hot conditions hotter”. That is propaganda for the BBC. Presumably by climate change, you mean man-made global warming rather than the natural warming as the earth has recovered from the Little Ice Age.

    • calnorth permalink
      January 6, 2020 10:31 am

      Firestarters…the physical act(s). Answer please. Its no good repeatedly hanging out old washing on the topic of which the BBC and similar organisations excel. Australia has been seriously damaged by bad forestry management.

      I’ve been involved in Forest fires in N. Germany and where management had been limited to wide fire breaks. The fires I fought for 2 weeks at a time were from ignition of the low growth and top level soil mix layers on open ground, moving to the surrounding forest via wind. Ultimately extinguished by rainfall. Thats in 1963

      Ignition was by 25lb practice bombs off target on a bombing range.

    • January 7, 2020 9:54 am

      Richard – it seems your comments are being used to negate the climate change background. There is no explanation in this article that addresses the clear length of the drought that the AUS area has been undergoing – and this far surpasses the cycles and phases being highlighted in this article. I don’t doubt the climate pattern being addressed but your point that a hot/dry phase is exacerbated is being laughed at by deniers and excusers who are happy to relate all of the angst being experienced to single pattern cycles and arsonists.

  11. January 6, 2020 1:26 am

    Good post. Good information. Thank you.

  12. January 6, 2020 6:04 am

    A southwest Indian Ocean Blob has been identified.

  13. calnorth permalink
    January 6, 2020 10:45 am

    Lord Monckton on the topic:

    https://wattsupwiththat.com/2020/01/05/bush-bull/

  14. Paul H permalink
    January 6, 2020 11:58 am

    Paul. Please delete my earlier post on this thread, I’ve incorrectly tried to post some great historical data and made a pigs ear of it. Will try to re-post as the stuff I’m on about is pretty good. Regards & thanks. Paul H

    • Paul Holyoak permalink
      January 7, 2020 3:52 pm

      Paul, delete my post at 9-59 please as requested. Paul Holyoak

  15. January 7, 2020 4:44 am

    Hopefully these comments are not too late as in the last week, due to bush fires in the vicinity, have been away three nights, or no power or no internet.

    The interest in the IOD is comparatively recent, although aware that rain-bearing system form off NW Australia, dropping it across the continent to the south east corner.

    In the past, 30 or more years ago, the main generator of rain over the north and eastern states was regarded as the result of a positive Southern Oscillation Index (SOI), being fed by the trade winds westward across the Pacific Ocean. When negative for a prolong period we have dry spells or are in drought. Also when positive, warm water is seen in the west tropical Pacific region, and when negative, warm water is found in the east tropical region, displacing the cold water which comes up along the west coast of South America or up-whelmed from lower sea strata – an El Nino or ENSO event.

    Such events are periodic, without any regular repetition. So the question was what caused the SOI to change so much as to have such a major effect on the Australian weather systems? What would vary the trade winds? After looking at a number of possibilities in the late 1980s, what stood out was volcanic activity in certain regions, of sufficient and prolonged intensity, and in particular when an eruption penetrates the tropopause, spreading gases, dust and debris in the stratosphere, when droughts at their worst.

    There was sufficient data on the history of droughts in Eastern Australia and of volcanic activity back to early settlement times, giving a valid statistical relationship. The paper was published in the Newsletter of Australian Meteorological & Oceanographic Society in 1990. A so-called experts rubbished it and was forgotten. This work was done before I had access to the internet, but had a personal computer to prepare the paper and access to our CSIRO library facilities.

    Since then there have been evidence of similar events. Over the last twelve months the SOI has been consistently negative, with now a severe drought. There has been continuing volcanic activity in the Central America region and Indonesia over this time, the latter probably influencing the IOD.

    About three months ago a few items appeared on the Space Weather web page about colourful sunsets due to two volcanoes this year sending gas and particulate matter into the stratosphere. The two were Raikoke, Kuril Islands (NW pacific) in June and Ulawun, New Britain, in August. This alerted me to the fact that these eruptions again could be the reason for the severe intensity of the drought. [ See https://spaceweather.com/ selecting the date 19 September 2019 ] Part of the item: [Quote:]

    “PERSISTENT PURPLE SUNSETS: How long does volcanic gas linger in the stratosphere? Sky watchers around the world are seeing for themselves. Three months after the Raikoke volcano spewed a plume of sulfurous gas into the stratosphere, sunsets are still turning purple. Here’s the latest plum-colored sunset from Lavallette, New Jersey:
    … [Photo snipped] …

    “The purple color became prominent about 20 minutes after sunset,” says Joseph Golebieski, who took the picture on Sept. 18th. “I used a Nikon D500 digital camera set at ISO 200 for a 1/5s exposure.”

    Why purple? Fine volcanic aerosols in the stratosphere scatter blue light which, when mixed with ordinary sunset red, produces a violet hue. The stratosphere is laced with emissions not only from Raikoke in the Kirul islands, but also from the Ulawun volcano in New Guinea. Plumes from both punched through to the stratosphere during NH summer 2019.

    Research shows that sulfurous gas in the stratosphere can linger for as much as 3 years. Sulfur dioxide in the stratosphere combines with water to form sulfuric acid aerosols. Eventually, the droplets grow large enough to fall to Earth–but the process is slow. This means purple sunsets could continue for some time to come.

    “The stratosphere is laced with emissions not only from Raikoke in the Kirul islands, but also from the Ulawun volcano in New Guinea. Plumes from both punched through to the stratosphere during summer 2019.” [End of quote.]
    **********************************
    This was enough to remind me that my paper of nearly 30 years ago needed to be brought out again and dusted off. [Volcanism, ENSO, Australian Droughts – Linking Effects with Causes, Newsletter of AMOS Vol 5, No 3, Sep. 1990] The observation of unusually coloured sunsets were as described in a 1970 paper by H. H. Lamb, which was useful for my study and referenced in the paper.

    Although I have had no support for the hypothesis, nobody has explain why it could not be so! This reinforces the claim that droughts have no connection with CC caused by CO2. The climate is forever changing. The big eruptions do cause cooling, but this year a real El Nino has not developed, just negative SOI and lack of rain and severe drought. The cyclone whic has formed and moved over the WA coast brought 8 mm of rain yesterday via the jet stream to us here in North Narooma, NSW.

  16. January 7, 2020 9:02 am

    Reblogged this on WeatherAction News and commented:
    A very strong case for a completely natural weather pattern that, along with fuel load mismanagement and the arson, primed Australia for such devastating fires.

  17. January 9, 2020 9:26 pm

    Reblogged this on Climate Collections.

Comments are closed.

%d bloggers like this: