https://www.abc.net.au/science/articles/2007/09/20/2038604.htm


Published 20 September 2007



The bane of sailors since Cook first circumnavigated Antarctica, these mighty winds influence everything from delicate native rainforest rodents to parrots and penguins.

By Heather Catchpole





If you've spent time on the west coast of Tasmania you'll know that the prevailing wind is westerly. And how. Stretching from latitudes 40-44 degrees South, Tasmania lies smack bang in the path of the roaring forties - westerly winds that rip around the Earth in latitudes between 40 and 50 degrees.

While similar wind patterns exist in the northern hemisphere, the lack of land in the south means there's little to stop or slow these gusty winds as they complete their circumpolar race.

"Because Tasmania dangles down from Australia it's more exposed to the westerlies. All of southern Australia experiences them, but more often than not Tasmania is within those westerlies," says Ian Barnes-Keoghan from the Bureau of Meteorology's Tasmania and Antarctica Regional Office.
When hot air meets a spinning Earth

Global wind currents like the roaring forties are influenced by the Earth's shape and spin, and by basic thermodynamics: hot air rises.

In the southern hemisphere, warm air rises at the equator and moves south, while cooler air moves north to replace it. You might expect that this elevated warm air would continue to travel straight to the South Pole, where having cooled it would sink. But our atmosphere is too thin and the distance too great to sustain a single convection cell like that. Instead, the warm air that rises south of the equator sinks again at around 30 degrees south - (think Coffs Harbour in the east and Kalgoorlie in the west). From here the air travels along the surface of the Earth until latitude 60 south, after which it rises again as it moves towards Antarctica. In simple terms, it's like a double figure 8 conveyor belt of air stretching from the Equator to the South Pole.

But if convection were the only factor affecting the movement of air we wouldn't have global wind systems like the roaring forties or trade winds. At the same time as this air is moving from the Earth's surface up into the atmosphere and back down again, the spin of the Earth forces air that's moving south along the surface (in particular the air between latitudes 30 and 60) to slide below overlying air. This creates a flow of air from west to east - the westerly roaring forties.

The great speed of the roaring forties is produced because of the relative change in rotational speed of the land at the Earth's surface. Because it's a sphere spinning on its axis, the surface of the Earth is traveling at different speeds depending on latitude. The equator - with a circumference of 40,000km - zips around the Earth at speeds of about 1500 km/hr, while Coffs Harbour is only moving through space at 260 km/hr. So as air moves from the equator to the South Pole, it does so over land that is rotating more slowly. To someone on land, this air has sped up, making these westerly winds seem furious in their speed and constancy.

While the roaring forties influence the entire island of Tasmania and southern parts of South Australia, Western Australia and Victoria, it's the mountainous western half of Tassie that feels the full brunt of the winds. Gusts of up to 200 km/hr - as fierce as a strong cyclone - have been measured.

Jasin wrote on Feb 5^th, 2024 at 9:21am:



The radioactive fallout from nuclear tests is everywhere on the planet -
even in the ice of Antarctica.

Jasin wrote on Feb 5^th, 2024 at 3:45pm:



I think most of that nuclear waste has dissipated and been diluted by now
but even a nanogram can cause cancer when ingested.

Jasin wrote on Feb 5^th, 2024 at 4:05pm:



This topic is more about living in the roaring 40s or sailing on a ship in the roaring 40s.
There is someone on this forum who lives at 43 degrees South.
It must be windy and cold in winter there.
It would be great right now in summer though.

How cold is too cold for a walk? Here’s how to tell

Published: May 31, 2022



If your dog has a single coat, you might need to think a bit more carefully about the cold.
Breeds in this category include maltese, cavaliers, greyhounds, whippets, and staffies.

Letting your dog choose

In Australia, a cold day is generally easier to manage for dogs than a hot day.

So yes, you could have an Italian greyhound as a pet in southern Tasmania, as long as you add layers when needed and maybe accept they are going to sleep in bed with you under the covers.

I like to let dogs choose, as much as possible, what they need to manage their core temperature.

For example, you might provide a bed with a cover, or extra bedding and blankets on a cold day, so they can use what they need and move away from it when they have warmed up enough.

Once I put a jacket on my dog, she is unable to take it off herself, so I am relying on being able to tell somehow that she doesn’t want it on anymore.

Jasin wrote on Feb 6^th, 2024 at 8:46pm:



We waste most of the rain water that hits the tropics here.
It just goes out to sea.

Bobby. wrote on Feb 5^th, 2024 at 2:25pm:


Radioactive fallout is dangerous for the first few days after detonation. It is still bad a week after detonation. It is safe in the region about a month later. Radiation may well make it to the Antarctic from test sites like Mururoa Atoll. But the significance would be mild and barely something that stays around.