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Antarctica 2019

Re: Antarctica 2019

Unread postby clif » Sat 20 Jul 2019, 13:06:43

OK...who is the "denier" here?


To answer your question,

consult your closest mirror ....
How cathartic it is to give voice to your fury, to wallow in self-righteousness, in helplessness, in self-serving self-pity.
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Re: Antarctica 2019

Unread postby Azothius » Fri 13 Sep 2019, 11:27:20

Sudden warming over Antarctica to prolong Australia drought


https://www.yahoo.com/news/sudden-warmi ... 20967.html


A rare phenomenon causing "the strongest Antarctic warming on record" is set to deliver more pain to dought-stricken Australia, scientists said Friday.

The unusual event, known as "sudden stratospheric warming", started in the last week of August when the atmosphere above Antarctica began heating rapidly, scientists at Australia's Bureau of Meteorology said in a report.

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

The upper atmosphere above the South Pole has heated up from close to minus 70 to about minus 25 degrees Celsius, bureau climatologist Andrew Watkins told AFP.

"It has leapt up more than 40 degrees warmer than normal in the course of three weeks," he said.

Watkins said the uncommon occurrence was not believed to be linked to global warming.

The occurrence is triggered by a mix of "disturbances" in weather patterns closer to the ground, he added.

Sudden stratospheric warming is common in the northern hemisphere but has only been recorded on one other occasion, in 2002, in the southern hemisphere.

But is it amplified by global warming? Perhaps something to watch for, if it's frequency of occurrence increase?


How this affects Australia:
The rapid warming slows down westerly winds spinning in the upper atmosphere above the South Pole until they move to the surface.

The winds track northwards until they are over Australia, blowing eastwards across the dry centre to New South Wales and Queensland states, which are currently struggling through one of the driest periods on record.

"You start getting more winds from central Australia, from the desert and less winds from the ocean, so they tend to have drier, warmer conditions in New South Wales and Southern Queensland," Watkins said.

The impacts of the Antarctic event in Australia will start to arrive in the coming weeks, and be particularly felt in October before the weather pattern is expected to break down in December or January.

The east of Australia has been battling hundreds of bushfires in recent weeks, in an unusually early start to the season.
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Re: Antarctica 2019

Unread postby dissident » Fri 13 Sep 2019, 19:26:01

The claim that an SSW will control an Australian drought is downright BS. The SSW occurs well above 100 hPa where there is less than 10% of the atmospheric mass. Wind changes in the stratosphere do not just move on down to the surface and preserve their intensity. Any wind anomaly originating in the the stratosphere experiences exponential attenuation as it descends. But that is not all. The dynamical regimes of the troposphere and stratosphere are distinct. The tropospheric weather is dominated by baroclinic instability which includes blocking events. Thanks to the exponential decrease of air density with height, we have the troposphere dog waving the stratosphere tail. Events in the stratosphere are induced by tropospheric dynamics such as as quasi-stationary planetary wave fluxes originating from the land-sea pressure contrasts and wave-wave interactions for Rossby waves and baroclinic eddies.

The impact of dynamical processes in the stratosphere on the troposhere are subtle. There is a small annular surface pressure anomaly the interacts with tropospheric storm tracks and impacts the so called annular modes like the "Southern Oscillation". This process is normally not active in the southern hemisphere because the stratospheric polar vortex is too strong and stable to be disturbed by SSW events or wave-mean flow interaction in general to produce a significant surface pressure oscillation. While SSWs can influence storm track dynamics to some extent, if you are going to talk about droughts, then you have to deal with blocking dynamics. Blocks are a type of stalled baroclinic instability resonance mode. Instead of the subtropical jet spewing more eddies (low pressure systems) as is common when the baroclinicity is increased by global warming via the Hadley circulation (that induces and maintains the subtropical zonal jets), it can instead undergo a strong deviation from zonality, slow down and produce a large meridional excursion. This axially asymmetric state requires heat energy to be maintained so blocking does get worse thanks to global warming. But such blocks are not induced and maintained by any stratospheric dynamical process instead it is tropospheric wave-wave and wave-mean flow interactions that prime them. Stratospheric dynamics acts like more noise in the whole system which can randomly kick a weather state into gear. But it is silly to claim that any SSW will produce tropospheric weather. The occurence of SSWs in the southern hemisphere is just a sign that climate change is real of which there was never any doubt.
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