You need to understand the geography and climate of SW W.A.
The wheatbelt is the area in the SW where the
rainfall is high enough to grow wheat. Check out
any satellite photos of the area. The rabbit
proof fence is the limit of that area pretty
much. I had a pal in physics at UWA in the late
1960s who came from a farm just west of the
fence. If they were lucky they got a crop 2 out
of 5 years and then the bastard emus would be
looking hungrily at it from the other side of the fence.
So the fence location isn't exactly independent
of the surface vegetation/rainfall characteristics.
The rain is mostly in winter apart from the odd
summer thunderstorm and comes from the showers
following passage of cold fronts. Much of the
rain falls on the coastal plain and Darling range
(what there is of it - Perth is built on a
coastal desert) and what is left goes to the wheatbelt.
After the harvest in December the wheatbelt is
nearly bone dry. Great outlanding country - tell
me about it. Your biggest problem, if you didn't
figure out where the fences/roads/houses were
while still airborne is figuring out where to
walk to after landing. If you fly there in summer
you'll get good at flying in blue thermals except
for the odd spectacular trough day which will
have very high based cu and high convection. I've
been to 16500 feet in blue thermals there. Much
like South Australia but without a large river
for irrigation fed by the Great Divide.
The dry ground and only a little bit of dry
stubble left means there sure as heck isn't a lot
of evaporation (latent heat flux) as there isn't
any water in the vegetation. In the scrub the
stunted poor excuses for trees will however still
evapo-transpire so in summer there will be more
latent heat flux there. In August the rains are
still happening in the crop growing areas with
higher rainfall so that's where the latent heat
flux is greater than in the scrub.
Nothing all that surprising in that paper.
What isn't obvious is the salinity problem. Lots
of salt lakes and salt coming to the surface as a
result of tree clearing. This has been addressed
since the mid 1970s with replanting and other mitigation methods.
Mike
At 06:49 PM 9/06/2014, you wrote:
Thanks Robert,
Just to clarify for me.Â
"The latent heat flux is the movement of heat
energy from the surface to altitude associated
with the evaporation of water at the surface and
its condensation at altitude in clouds."
 I take it that, Latent heat flux is one of the
effects which generates thermals. The other is
sensible heat ie ground gets hot, transfers heat
to near surface air by conduction. Air then rises (convection).
Do you have any thoughts on why the natural
vegetation (we used to call it scrub) has a
strong bias to Latent Heat Flux in December but not in August?
On Sun, Jun 8, 2014 at 11:17 AM, Robert Hart
<<mailto:[email protected]>[email protected]> wrote:
On 08-Jun-14 08:44, Peter Champness wrote:
That seems right. They should have asked glider pilots.
I note that the paper shows that the latent
heat flux is strongly skewed to the native
vegetation areas in Dec (soaring season). In
August it is the other way, higher over the agricultural areas.
I assume latent heat flux means avapoeration.
Latent heat is the heat absorbed or released
during a phase change (ie solid/liquid/gas
phases). In water, there is very significant
latent heat involved in evaporating water which
is then released when the water vapour
recondenses to liquid water (droplets) in clouds.
The latent heat flux is the movement of heat
energy from the surface to altitude associated
with the evaporation of water at the surface and
its condensation at altitude in clouds.
As flatland glider pilots, we ride this flux in
the form of thermals generated by a number of effects.
--
Note: I am changing my email address - please
only use my gmail address from now on!
Robert Hart                  Â
       <mailto:[email protected]>[email protected]
+61 438 385 533
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