Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: bob4866 on 08/05/2005 13:31:07

Title: Atmospheric Temperatre drop
Post by: bob4866 on 08/05/2005 13:31:07

In text books it is noted that the atmospheric temperature drops by approx. 6.5 degrees per kilometer.  At 11 km the temperature holds constant for a time (in the tropopause), then increases.  What is the reason the temperature holds constant and not continue dropping please?

Title: Re: Atmospheric Temperatre drop
Post by: gsmollin on 09/05/2005 01:05:36

Ah, an atmospheric thermodynamics question. I am going out on a limb with an answer here, since this is a verry complicated field.

In the lower atmosphere, the air is heated by convection currents from the ground, so the temperature is highest near the ground. In the stratosphere and above, the air can be heated directly from the sun. The amount of energy in the air in the stratosphere and ionosphere is much less than in the troposphere, because there is much less air, but the temperature can rise to rather high values, because the air cannot cool itself with convection currents like the dense air in the troposphere. The air in the stratosphere blocks ultraviolet radiation (B-C band) from the sun, and this can heat it. In the ionosphere, the temperature is high enough to ionize the air, but the air density is a minute fraction of sea level. The air in the ionosphere absorbs energy from the solar wind. An energetic sun can heat the ionosphere so much it expands and rises to higher altitudes. This happened during the Sky Lab's mission, and contributed to its early re-entry into the atmosphere.

You have asked a very complicated question, and physicists have spent their careers on the study of energy transfer in the upper atmosphere. It is a worthy study, and I encourage you to research it further.

Title: Re: Atmospheric Temperatre drop
Post by: chimera on 10/05/2005 13:52:41

Behind this simple question lurks one of the great unknowns, it seems. Is it convection only? Or is there maybe something even stranger going on, in the sense of some kind of harmonics in the earth's magnetic field, that causes the particles to react differently to sunlight than at other heights? Maybe Mr. Bernouilli would have found it interesting, too if he had known a bit about particles and quantum mechanics...

Actually, the asteroid belt came to mind when this bubbled up from nowhere... even though that's gravity, of course. But maybe similar principles hold.

The living are the dead on holiday.  -- Maurice de Maeterlinck (1862-1949)