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#1151779 - 22/12/2012 15:54 If there was no great dividing range??
gleno71 Offline
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Registered: 09/11/2007
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Loc: Australia
How would the climate be different if the eastern part of Australia was dead flat and no great dividing range??

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#1151796 - 22/12/2012 17:15 Re: If there was no great dividing range?? [Re: gleno71]
kgb007 Offline
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Registered: 09/12/2010
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Alot drier thats for sure!

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#1151836 - 22/12/2012 21:13 Re: If there was no great dividing range?? [Re: kgb007]
Mezo Offline
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Registered: 01/12/2011
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Loc: Under the Meso (or Springfield...
It's an interesting question and hopefully someone with more technical knowledge will chime in. But, so many storm days have been confided to the ranges or only come to fruition because they're there to help trigger things off.
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#1151840 - 22/12/2012 21:50 Re: If there was no great dividing range?? [Re: Mezo]
Surly Bond Offline
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Loc: Manilla, near Tamworth NSW
gleno
Many years ago, Professor Cliff Ollier made the point that "the great dividing range" of eastern Australia scarcely exists. In places you can drive across it without seeing any range at all. The GREAT ESCARPMENT of eastern Australia, however, is a feature of global importance. It is thousands of kilometres long and nearly a kilometre high. The weather changes dramatically at the escarpment. Much of the humid maritime air cannot climb over it.
Early compilations of satellite images of cloud showed that, in summer, cloud blankets the area east of the escarpment, while the area inland from it is cloud-free. This is perhaps the most striking cloud boundary in the world.
When the rivers of Australia were first cutting their present valleys, Australia extended hundreds of kilometres further east than it does now. Rivers extended to similar distances east and west of the "great divide" . Then, 80 million years ago, a large slice of continent broke off, drifted away and sank. Rivers flowing east became much steeper, and cut down and cut back into the land, forming the escarpment. Many developed waterfalls that still exist, above which their valley are hardly any steeper than in rivers flowing west.
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#1151871 - 23/12/2012 00:35 Re: If there was no great dividing range?? [Re: kgb007]
Homer Offline
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Registered: 16/06/2007
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Originally Posted By: kgb007
Alot drier thats for sure!


Not in late winter.

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#1151876 - 23/12/2012 00:49 Re: If there was no great dividing range?? [Re: gleno71]
boomer Offline
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Registered: 21/11/2010
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Loc: Cairns
Originally Posted By: gleno71
How would the climate be different if the eastern part of Australia was dead flat and no great dividing range??

Ask Western Australia. I imagine Cairns north would be dry to the Cape... no Islands north. Torres Strait underwater.


Edited by boomer (23/12/2012 00:54)
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#1151901 - 23/12/2012 06:26 Re: If there was no great dividing range?? [Re: boomer]
Cloudz Offline
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Registered: 16/10/2010
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Loc: Southport QLD
We might actually get some of the storms that come across from the west as they all seem to disintergrate when they hit the ranges.

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#1151921 - 23/12/2012 08:04 Re: If there was no great dividing range?? [Re: kgb007]
Sandfly Offline
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Registered: 18/10/2010
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Loc: Rockhampton
Originally Posted By: kgb007
Alot drier thats for sure!


Can't get much drier than Rockhampton, and were east of the Great Divide.
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#1151982 - 23/12/2012 11:36 Re: If there was no great dividing range?? [Re: Sandfly]
ColdsnapIII Offline
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Registered: 19/01/2007
Posts: 6500
Loc: Mount Macedon, VIC
No ranges equals no uplift other than what naturally occurs along cold fronts, troughs or low pressure convergence. In Australia, the great dividing range is by no means the only area with significant topography. There are many smaller hills and ranges that are not associated with the Great Dividing range and are responsible for some of the wetter places in the country, eg. Otway Ranges, Strzelecki ranges, Wilsons Promontory, Adelaide hills, the hills east and southeast of Perth and in the far SW corner of Western Aus etc.

If there were no GDR, it would simply mean that the drier inland areas would extend right down to the coast except for where the other ranges occur like the ones I mentioned above.

The main effect of the GDR is to act as an extra lifting mechanism for moist air. This occurs from both sides, i.e. west/north and south/east. In winter, areas on the northern and western slopes of the GDR are significantly wetter than the southern/eastern slopes. In Summer the reverse is true. Also in summer, average temperatures are several degrees warmer on the northern and western sides of the divide than on the eastern side, often in as little distance as 20km or so. The GDR tends to act as a barrier between the coastal climatic influence and the continental influence, especially in the warmer months.


Edited by ColdsnapIII (23/12/2012 11:39)

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#1151987 - 23/12/2012 11:48 Re: If there was no great dividing range?? [Re: Surly Bond]
ColdsnapIII Offline
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Originally Posted By: Surly Bond
gleno
Many years ago, Professor Cliff Ollier made the point that "the great dividing range" of eastern Australia scarcely exists. In places you can drive across it without seeing any range at all. The GREAT ESCARPMENT of eastern Australia, however, is a feature of global importance.


This statement is a bit 'NSW/QLD centric' if you ask me. I'm not sure if you have travelled around Victoria but the GDR is very prominent, it contains a decent section of the Australian alps, some of the highest mountains in the country and many significant steep sided mountain ranges. There are also sharp changes in climate demarcated by the GDR in Victoria.

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#1151989 - 23/12/2012 11:49 Re: If there was no great dividing range?? [Re: ColdsnapIII]
HumphreyBear Offline
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For Sydney it would mean more continental influence (hotter summers, cooler winters) and probably less rainfall. Seabreezes would still be there of course, moderating our summer heat, but the westerlies would probably push it out quite often.

If you took away the oceanic influence as well, Sydney would be a very hot and arid place.

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#1151994 - 23/12/2012 12:18 Re: If there was no great dividing range?? [Re: HumphreyBear]
Andrew Miskelly Offline
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Registered: 15/11/2001
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Loc: Mittagong, NSW
There would be no such thing as a southerly bu[r]ster. As I understand it the ranges, and indeed their form and the angle at which they turn the corner at the NSW/Vic border are crucial to that bubble of dense air originating in the Bight surging up the NSW coast - occasionally at 40-50 knots.

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#1151995 - 23/12/2012 12:21 Re: If there was no great dividing range?? [Re: HumphreyBear]
Tom1234 Offline
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Registered: 08/04/2011
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Loc: Port Stephens
Could it go the other way though like much of the American midwest ? They have moisture pour in from the gulf coast which creates some great farming land/conditions. Summer easterlies could interact with troughs and provide more rainfall inland.


I wonder if the scud would clear out quicker too as it currently gets trapped on the coastal fringe.

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#1152031 - 23/12/2012 14:33 Re: If there was no great dividing range?? [Re: Tom1234]
HumphreyBear Offline
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Loc: Southern Sydney
True, there would be nothing to stop westerly moisture impacting Sydney (both from cold fronts and NW cloudbands), so there might be a little more rain from those sources but also more heat as the range tends to guard Sydney from many hot westerlies. Easterly troughs which are the main source of rainfall on the coast wouldn't be as active without the forcing provided by the ranges, so I reckon there would still be a net rainfall deficit (but perhaps more rain days)?

Your point about the southerlies is also valid Andrew- didn't think about that. There'd still be southerlies in some shape or form but probably more subtle.

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#1152116 - 23/12/2012 18:33 Re: If there was no great dividing range?? [Re: Tom1234]
MC Thomas Offline
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Registered: 06/12/2004
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Loc: Melbourne
Originally Posted By: Enrique
Could it go the other way though like much of the American midwest ? They have moisture pour in from the gulf coast which creates some great farming land/conditions. Summer easterlies could interact with troughs and provide more rainfall inland.


I think there is probably some truth to this. I believe the GDR probably limits the number of major synoptic-scale storm outbreaks (by blocking the transport of moisture inland). Here is an old one but I found it amusing-



Should just get rid of the GDR all together I think.

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#1152189 - 23/12/2012 22:58 Re: If there was no great dividing range?? [Re: MC Thomas]
Steve777 Offline
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Registered: 20/10/2011
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Loc: Artarmon (Sydney North Shore)
I think that it is also interesting to consider the opposite scenario - if the Great Dividing Range, instead of cresting at 700 to 1,000 metres in most places was 2,500 to 3,000 metres with a peaks over 4,000 metres. Permanent snowfields and glaciers in the SE and lots of snowmelt each Spring. Maybe the Murray and the Darling would be, if not the Mississippi and Missouri, then possibly the Tigris and the Euphrates. There would be huge implications for settlement and population. In fact, the Aborigines may have invented irrigation and agriculture long before Europeans arrived. Who knows? Maybe there would be analogues of Mildura, Wagga and Albury in this world with populations in the millions by now.

There would be less moisture penetrating inland from the East, but systems like East Coast lows seem to have little impact West of the Divide now. But any moisture that came in from the North and West would be triggered on the Western side. Southern Ocean cold fronts would have been depositing heavy Winter rains and snows on the Western side of the range south of about 30 degrees, although if they failed, as they seem to be doing now, it would still be bad news for the inland. The East would be reliably watered in Summer from the East and South as it is now, but would get little rain from Winter Cold fronts.

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#1152245 - 24/12/2012 07:32 Re: If there was no great dividing range?? [Re: Steve777]
GrizzlyBear Offline
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Registered: 23/06/2011
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Loc: Yetholme [1180m] Central Table...
That is interesting Steve777, could well be right. I also always imagine what it would be like if Australia was 10deg further south, would have a similar effect.

Originally Posted By: Southerly_Buster
For Sydney it would mean more continental influence (hotter summers, cooler winters) and probably less rainfall. Seabreezes would still be there of course, moderating our summer heat, but the westerlies would probably push it out quite often.

If you took away the oceanic influence as well, Sydney would be a very hot and arid place.


I quite agree with SB that the climate would be generally drier. I think it would be drier in all seasons on the coast and inland. Australia would be more like a semi desert island with the moist east coast almost missing.

Another interesting scenario would be to reverse Australia left/right so GRD was on the west coast. No doubt the Snowies would also get much more snow that way.

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#1152256 - 24/12/2012 08:13 Re: If there was no great dividing range?? [Re: GrizzlyBear]
Noname Offline
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Registered: 28/01/2011
Posts: 2104
Good topic.

I studied geology and climate science as well my environmental disasters and sustainability degree. There was a hot topic in climate science subject was talking about if the GDR does not exist.

So, if the land is flat from the plains to the coast in this case with Snowy Mountains to its' south. Easternlies will dominate at seasonal influence. Moist winds should able to reach as far as inland bringing showers with it. I'm certain without GDR for moisty easternlies will make it wetter at seasonal influence. However, no topography to cause orographical uplift of thunderstorms. Should see lesser thunder days, and of course lesser severe storms or supercells in this influence.

Dry westernlies as winter seasonal influence, the east coast should be more drier than today. But this will bring better snow influence in the Snowy Mountains.

So here is an example of Sydney climate averages:


Note the difference in change of min and max temperatures, and the rainfall influence. Wetter and humid summers should occur by dominating easternlies and lack of southerly change influence which you require the need of the ranges to support this. Winters should be a lot drier and much a lot colder. Since lack of southerly influence, showery weather wouldn't be around at all, so the SWlies winds will dominate into Spring where days become a lot hotter than today and night remains cold. As the westernlies turns off before heading into summer, easterly winds should shift.

So I believe this would become more of Mediterrean type of climate.
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#1481421 - 17/12/2018 15:28 Re: If there was no great dividing range?? [Re: gleno71]
niinjaniin Offline
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Registered: 02/04/2017
Posts: 33

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#1481429 - 17/12/2018 17:27 Re: If there was no great dividing range?? [Re: gleno71]
niinjaniin Offline
Cloud Gazer

Registered: 02/04/2017
Posts: 33
BTW, why is everybody saying here that Australia is gonna become drier? People elsewhere say that if this were to happen, moist ocean air will actually get into the inland parts of Australia. (Just randomly remembered to use my old account because I was looking for this question and wound up here.)


Edited by niinjaniin (17/12/2018 17:30)

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