Solution to bushfires in Australia

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dirtyharry
dirtyharry
WA
444 posts
WA, 444 posts
12 Jan 2013 8:59am
Carantoc said...
Whilst trying hard not to encourage this crap and more random crazy stupidity I would point out to the ignorant that most of Australia is a desert.

And that the definition of a desert being that evaporation exceeds rainfall.

Hence any dam in any desert will be, on average, dry.


A dam typically has a catchment area much bigger than the surface area of the dam itself. There's heaps of urban and agricultural areas where evap > rainfall and which aren't deserts and which have very well functioning dams.
Scotty88
Scotty88
4214 posts
4214 posts
12 Jan 2013 12:40pm
Carantoc said...
Whilst trying hard not to encourage this crap and more random crazy stupidity I would point out to the ignorant that most of Australia is a desert.

And that the definition of a desert being that evaporation exceeds rainfall.




A desert is defined by a annual rainfall (or lack of)is has nothing to do with evaporation once it hits the surface. I'm assuming around 100-150mm per year or less defines a desert. There are deserts in Siberia where it's farkin freezing so don't think there is much evaporation over there.
dinsdale
dinsdale
WA
1227 posts
WA, 1227 posts
12 Jan 2013 4:12pm
Scotty88 said...
A desert is defined by a annual rainfall (or lack of)is has nothing to do with evaporation once it hits the surface. I'm assuming around 100-150mm per year or less defines a desert. There are deserts in Siberia where it's farkin freezing so don't think there is much evaporation over there.

It used to <10" per year. Like everything else though that's probably changed to something the average Joe Bloggs can't quite understand.

Once the air temp is <0deg there can't be any evaporation, as the air can't hold any moisture.

southace
southace
SA
4798 posts
SA, 4798 posts
12 Jan 2013 7:18pm
I got a great solution lets all move back to the U.k where we came from and give all the land back to the indigionos ......the only fires then would be the locals cooking there tucker!
dinsdale
dinsdale
WA
1227 posts
WA, 1227 posts
12 Jan 2013 6:03pm
southace said...
I got a great solution lets all move back to the U.k where we came from and give all the land back to the indigionos ......the only fires then would be the locals cooking there tucker!


What planet did you just arrive from?

1. I'm 5th generation white Ozzie. I didn't come from the UK!
2. Our poor underprivileged black brothers and sisters systematically burnt out huge tracts of Oz for thousands of years. How else do you think they transformed what was mainly rain forest into desert?
Mr Milk
Mr Milk
NSW
3137 posts
NSW, 3137 posts
12 Jan 2013 11:25pm
dinsdale said...
southace said...
I got a great solution lets all move back to the U.k where we came from and give all the land back to the indigionos ......the only fires then would be the locals cooking there tucker!


What planet did you just arrive from?

1. I'm 5th generation white Ozzie. I didn't come from the UK!
2. Our poor underprivileged black brothers and sisters systematically burnt out huge tracts of Oz for thousands of years. How else do you think they transformed what was mainly rain forest into desert?


You quite sure about that? I had absorbed the idea that the rainforest and savannah disappeared with the climate change at the end of the last Ice Age. Which was the same change that dried out the western escarpment of the Arabian peninsula, giving rise to the idea that God threw Adam and Eve out of the garden of Eden.
And that burning makes fresh shoots available to the various mammalian protein factories which fed the locals because it gets rid of the twigs that otherwise would stick up their noses as they grazed
dinsdale
dinsdale
WA
1227 posts
WA, 1227 posts
12 Jan 2013 9:41pm
dinsdale said...
1. I'm 5th generation white Ozzie. I didn't come from the UK!
2. Our poor underprivileged black brothers and sisters systematically burnt out huge tracts of Oz for thousands of years

I'm absolutely sure about that much.

Harrow
Harrow
NSW
4521 posts
NSW, 4521 posts
13 Jan 2013 12:53am
dinsdale said...Once the air temp is <0deg there can't be any evaporation, as the air can't hold any moisture.



Why do you say this? Yes, there is evaporation, but you don't have water evaporating, instead you have ice evaporating directly to water vapour. Cold air holds less moisture, but it does not suddenly hold none at 0 deg C.

If you want a simple practical example, look what happens to your ice cube tray in the freezer if you don't use it. The ice actually evaporates over time. Over a few weeks the difference is very noticable, and that is at -18 deg C.

dinsdale
dinsdale
WA
1227 posts
WA, 1227 posts
13 Jan 2013 1:33am
Harrow said...
dinsdale said...Once the air temp is <0deg there can't be any evaporation, as the air can't hold any moisture.

Why do you say this? Yes, there is evaporation, but you don't have water evaporating, instead you have ice evaporating directly to water vapour. Cold air holds less moisture, but it does not suddenly hold none at 0 deg C.

Oh yes it does! At <0 deg C the relative humidity is a big fat ZERO. Any moisture in the air at that temp will be held as ice crystals, which are solid, NOT gaseous. They're held there mechanically, until they drop.
Harrow said...
If you want a simple practical example, look what happens to your ice cube tray in the freezer if you don't use it. The ice actually evaporates over time. Over a few weeks the difference is very noticable, and that is at -18 deg C.

Your particular freezer in this example is obviously a "frost free" freezer. It has a mechanisms built into it to remove frost: viz, a fan and a heater element. Go back to the old days before frost free and what had to done periodically? You had to defrost your fridge and freezer. Why? because every time you opened the door you allowed warm moist air in. As it cooled ALL the moisture condensed out of the air and formed as solid ice.

I'm sure just a couple of minutes Googling would fill you in with a more technical explanation. I used to be able to give you all the tech gen, but alas I'd have to Google it myself now.
cisco
cisco
QLD
12365 posts
QLD, 12365 posts
13 Jan 2013 4:11am
dinsdale said...
dinsdale said...
1. I'm 5th generation white Ozzie. I didn't come from the UK!
2. Our poor underprivileged black brothers and sisters systematically burnt out huge tracts of Oz for thousands of years

I'm absolutely sure about that much.




That is the way it is/was. That is a glaring example of human influenced climate change.
Ian K
Ian K
WA
4169 posts
WA, 4169 posts
13 Jan 2013 6:25am
dinsdale said...
Harrow said...
dinsdale said...Once the air temp is <0deg there can't be any evaporation, as the air can't hold any moisture.

Why do you say this? Yes, there is evaporation, but you don't have water evaporating, instead you have ice evaporating directly to water vapour. Cold air holds less moisture, but it does not suddenly hold none at 0 deg C.

Oh yes it does! At <0 deg C the relative humidity is a big fat ZERO. Any moisture in the air at that temp will be held as ice crystals, which are solid, NOT gaseous. They're held there mechanically, until they drop.
Harrow said...
If you want a simple practical example, look what happens to your ice cube tray in the freezer if you don't use it. The ice actually evaporates over time. Over a few weeks the difference is very noticable, and that is at -18 deg C.

Your particular freezer in this example is obviously a "frost free" freezer. It has a mechanisms built into it to remove frost: viz, a fan and a heater element. Go back to the old days before frost free and what had to done periodically? You had to defrost your fridge and freezer. Why? because every time you opened the door you allowed warm moist air in. As it cooled ALL the moisture condensed out of the air and formed as solid ice.

I'm sure just a couple of minutes Googling would fill you in with a more technical explanation. I used to be able to give you all the tech gen, but alas I'd have to Google it myself now.


Google "Vapour pressure over ice" or words to that effect" At 0 degrees the vapour pressure is
6.1115 millibars, at -20 it's dropped to about 1 millibar. Water at 2 degrees is 7.06 millibar, nothing special happens to the vapour pressure as the water turns to ice.
beerdead
beerdead
NSW
433 posts
NSW, 433 posts
13 Jan 2013 10:03pm
Recently read Bill Gammages book, (The Largest Estate on Earth, I think) about how the aborigines managed virtually the entirety of Australia with fire. Much more complex than I would have imagined.

The result of 60,000 years of learning and practice resulted in what the earlier explorers and settlers described as 'parkland', gentlemens parks', etc, virtually everywhere. Interestingly he claims that there were less trees in Australia in 1788, than after the invasion of Europeans, but that even in drought the countryside was green and lush grassland, with widely spaced trees.

The advantages of this kind of management was to promote various foods for different seasons and conditions. It also prevented wildfires, which kills much of the flora that was valuable.

In the words of a NT woman, "you Europeans work too hard. We just go and get it." They knew where to get what they wanted because they had already prepared the ground before hand, with fire.

In Bills terms "they farmed but were not farmers", the difference being management of the land for food production, but not being sedentary in terms of mobility. They didn't need to stay close to their crops and harvests as there were virtually no raiding or war. There were boundaries for each tribe, clan and family group, which were governed by totems and beliefs which were attached to the land (the dreaming), which required management based on spiritual attachment, and allocation to, specific areas . (This latter makes a joke of 'Terra Nullius'). In times of surplus, it was virtually mandatory that others tribes were permitted to travel into the area to partake.

I very interesting book, if a bit like swimming through molasses at times.

Feel like sparking up the reserve out the back now
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