As a horticulturalist and a glider pilot, perhaps the answer is that the
moist ground acts as more of a heat sink into the ground, up until it
achieves a full heat load and then dissipates this in the afternoon, more so
than the surrounding dry ground. Vegetation on a west facing slope is a
great source in the afternoons out our way.

I have found lift in moister areas, but much more so in the afternoons,
mainly when lower in the convection zone and certainly not in the mornings.
Try walking around a wet area at 10am and 6pm and compare the relative heat
to dry areas.

The other issue that could be occurring is the bubble of cool air over the
moist ground could be acting as a trigger point, for the drifting heated air
from the surrounding dry areas. We all know of the tremendously small things
that can act as a trigger.

As to lapse rates the air is not saturated till cloud base, unless of course
a fog is present (mornings) which is a different case than trying to get a
thermal.

Robert P
Nimbus 2C

"Mike Rapoport" wrote in message
hlink.net...

"Andrew Sarangan" wrote in message
om...
(Kirk Stant) wrote in message
. com...
"K.P. Termaat" wrote in message
...
My experience is that it works, especially on days with very low
humidity,
but no boomers and only low.


"Mike Rapoport" schreef in bericht
ink.net...

You will find less lift over water of any kind, even if it is
contained in
vegetation. The best lift is always over the highest, dryest,
darkest
surface around. The water vapor idea is...well...it is hard to
find
a
place
to start...but it won't work

Mike
MU-2


Have to disagree with you, Mike - out here in Arizona, in the desert
areas that are not irrigated, we often find good lift directly over
small cattle "tanks" - small shallow ponds that are scattered around.
A lot of us have noticed this and compared notes, and it works; if too
low to get to high, dark ground, I'll head for the nearest pond and it
will usually turn up a nice thermal. We think it may be due to the
fact that the ponds are in a natural low spot, and coupled with the
little bit of moisture, could be the necessary trigger for a thermal.

Now obviously, large irrigated farm fields or river basins are death
to thermals - but a local lake (reservoir) seems to have little effect
on thermal activity - could it be all the drunk boaters?

What's the old saying about never saying never?

Kirk
LS6-b


The adiabatic rate of moist air is about 1.5C/1000ft. For dry air it
is 3C/1000ft. Therefore, assuming that the water temperature is the
same as the surrounding ground (which would be true if the water is
shallow), I could see how one will experience greater lift above
water.

Not for unsaturated air it isn't. The moist rate only applies to saturated
air (ie in clouds)

Mike
MU-2