## Wednesday, April 18, 2007

### RealClimate » Learning from a simple model

RealClimate » Learning from a simple model:
"A lot of what gets discussed here in relation to the greenhouse effect is relatively simple, and yet can be confusing to the lay reader. A useful way of demonstrating that simplicity is to use a stripped down mathematical model that is complex enough to include some interesting physics, but simple enough so that you can just write down the answer. This is the staple of most textbooks on the subject, but there are questions that arise in discussions here that don't ever get addressed in most textbooks. Yet simple models can be useful there too.

I'll try and cover a few 'greenhouse' issues that come up in multiple contexts in the climate debate. Why does 'radiative forcing' work as method for comparing different physical impacts on the climate, and why you can't calculate climate sensitivity just by looking at the surface energy budget. There will be mathematics, but hopefully it won't be too painful.

So how simple can you make a model that contains the basic greenhouse physics? Pretty simple actually. You need to account for the solar radiation coming in (including the impact of albedo), the longwave radiation coming from the surface (which depends on the temperature) and some absorption/radiation (the 'emissivity') of longwave radiation in the atmosphere (the basic greenhouse effect). Optionally, you can increase the realism by adding feedbacks (allowing the absorption or albedo to depend on temperature), and other processes - like convection - that link the surface and atmosphere more closely than radiation does. You can skip directly to the bottom-line points if you don't want to see the gory details."

### Mathematician suggests extra dimensions are time-like

Mathematician suggests extra dimensions are time-like:
"In a recent study, mathematician George Sparling of the University of Pittsburgh examines a fundamental question pondered since the time of Pythagoras, and still vexing scientists today: what is the nature of space and time? After analyzing different perspectives, Sparling offers an alternative idea: space-time may have six dimensions, with the extra two being time-like."

“In my case, I am led to the conclusion that the ordinary four dimensional space-time extends naturally into six dimensions: the four dimensional space is hyperbolic as usual, but in the surrounding space there are equal numbers (3 each) of space and time dimensions, so the formula for s2 reads something like s2 = x2 + y2 + z2 - t2 - u2 - v2, where u and v represent the new time variables. I call this structure a (3, 3)-structure (mathematicians call it ultra-hyperbolic).”

## Tuesday, April 17, 2007

### Explosion video, shockwave

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100 tonnes of explosives go up at once.

It's the shockwave and the interesting fluid dynamics that interest me, not the enormeous xplosions

## Monday, April 16, 2007

### Dark Roasted Blend: Mammatus, Lenticular & Other Extreme Clouds

Dark Roasted Blend: Mammatus, Lenticular & Other Extreme Clouds:

"Mammatus Clouds, or 'breast-clouds', are fascinating formations in the sky, made mostly from the cumulus cloud base. Although they are not a sign that a tornado is about to form, they often accompany tornado-producing storms, or even may be direct byproduct of tornado activity - an aftermath of severe thunderstorms."
The exact processes that lead to the formation of mamatus clouds is unknown.
"[Lenticular] clouds are often formed by so-called "mountain waves" of air created by strong winds forced over high mountains. Then they hang over the mountains like alien "motherships"... Mount Rainier in Washington produces some of the most spectacular lenticulars."

Although the clouds are virtually stationary, the air within is usually moving very rapidly, with water condensing as it enters the cloud zone and evaporating as the air leaves.

## Tuesday, April 10, 2007

### Video - Running on "Water"

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