Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Tuesday, December 01, 2009

Cloud Farm views (of Knights Hill)

My friends Steve and Celeste live on Mount Murray at a property poetically named "Cloud Farm". From their hilltop one can look south towards Knights Hill, where the telecommunications towers for the Illawarra region are located.

Afternoon light shining on Knights Hill.
This was taken on the Winter Solstice.
The ocean is just visible in the background,
but it blends into the line of clouds out to sea.
The clifflines of the Illawarra Escarpment are highlighted
by the afternoon light.
Several weeks ago I went and had dinner at their house, after a big day out Orchid hunting with ANOS. Anyway, in a state of near-exhaustion I stayed over at their house, after dinner.

Next morning I woke just on sunrise - because they get so much light into their house.

I stumbled out of bed and looked outside and found them out and about already - rejoicing in the wonderful cloud and light effects of fog on the plateau near Carrington Falls and just topping Knights Hill.
This image was taken from the same place as the first image.
Its hard to imagine.
Check the trees on the left and foreground.
The TV towers are clearly visible protruding from the seemingly "flat" cloud of fog. In fact this hill is quite high, over the Illawarra Escarpment to the east (left) and it also drops away quite sharply (but nothing like as as severely) to the west (right) onto a sandstone plateau around Carrington Falls. One cannot see any of these details below the thick fog.

This image appears to me as something from Antarctica.
Two separate TV Towers (not quite in line - from this direction).
They are probably about 1 km apart, on top of Knights Hill.
Taken with the 300mm lens.
More interesting, to me, was the way in which the fog was behaving at the eastern edge of the escarpment.

The cloud was behaving as a glacier does, only with far greater fluidity. You can see the cloud breaking down (disintegrating), after it tumbles down off the cliffline.
Click to enlarge to see the full effect.

At the end of the plateau/cliff line, the cool mountain air was falling down over the edge, as the air on the coastal escarpment started to rise.

The circumstances created an almost circular pattern of air movement (the hot air rising, sucking the cold air (above it) down to fill the pressure imbalance thus created).

As the sun rose higher in the sky, it created this lovely effect of lighty behind the large Brown Barrel Eucalypt.
You will all be pleased to know that I then went back to bed for another hour, to "wake" at a more civilised hour. That comment is just for "Mick's" benefit, as she is always up and about early - looking for waders at "Sandy Straits and beyond". She knows that I am a night person. We often nearly cross over with our comments - me before I go to bed, and she as she starts the day.

Thanks to Mosura of Nature of Tasmania for a comment, in which he provided the technical name of the cloud behavour I was reporting.
Orographic Clouds
I knew there was a specific name for these louds, but could not remember it. The following extract - in red - describes the cloud movement I was able to witness.
"Orographic clouds develop in response to the forced lifting of air by the earth's topography (mountains for example).
"Air passing over a mountain oscillates up and down as it moves downstream. If the air lifts upward and cools through expansion as it rises to its saturation temperature during this process, the water vapour within condenses and becomes visible as a cloud.
"Upon reaching the mountain top, the air is heavier than the environment and will sink down the other side, warming as it descends. Once the air returns to its original height, it has the same buoyancy as the surrounding air. However, the air does not stop immediately because it still has momentum carrying it downward. With continued descent, the air becomes warmer than the surroundings and begins to accelerate back upward towards its original height. It is during the upper-most ascent phase of this cycle that clouds develop. In regions where air is descending, skies are clear."
Source: Cloud Structures: "Orographic Clouds"


mick said...

The fog and clouds over the plateau and spilling down into the valley below is fascinating. Your photos have captured it beautifully. Now I had a whole series of comments to make about how one misses such sites unless one wakes early enough - then I read your last paragraph! Nothing more to say!!

Denis Wilson said...

Hi Mick
Nicely done - the comment you make when not making a comment.
Don't worry, my friend Jim, a pilot, to whom I showed these images yesterday already said it all - and more - about the benefits of early morning rises.

mick said...

But - unfortunately - you obviously weren't convinced!

Denis Wilson said...

What can I say?
Not entirely convinced, but in Robbo the birds tend to wake slowly on cloudy mornings anyway.
Whipbirds are calling outside my study window at 11:00am. That's civilized.
I do rise early for some things - for example when out birding in the central west of NSW - I photographed a sunrise, if you recall!

Mosura said...

Beautiful orographic clouds. Might have to get up early more often myself :-)

celeste said...

Hi all,

They are beautiful pics.
Glad I dragged you out to see them.


Denis Wilson said...

Hi Mosura
Glad you knew the technical name for those clouds.
You deserve credit for letting me know about the clouds.
But credit for making the Clouds goes to the Great Spirit of the Universe - by whichever name you know her.

Denis Wilson said...

Dear all
I have had an inquiry to buy a copy of one of the images - from a couple of friend who live on Knights Hill - underneath those clouds.
That's flattering.

Lynn S said...

Fantastic photos etc Denis. Let me know if you would be happy to sell a photo!!

Denis Wilson said...

Hi Lynn
I am sure we can work out something.
They are really special photos, and I am glad people like them.