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HailMan06

Adiabatic Lapse Rate vs. Second Law of Thermodynamics

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I know in the troposphere as you descend the temperature roughly increases by 3.56F/1000ft, depending on the atmospheric conditions at the time.

However, I have trouble in understanding why the atmosphere maintains an adiabatic lapse rate since the second law of thermodynamics suggests the heat in the lower atmosphere would eventually equal the temperature of the upper troposhere/stratosphere.

To visualize this, imagine using the old addage of a hand-operated tire pump to fill a tire. We all know the tire pump warms adiabaticlly because of the increase in pressure. Now let's say you keep the pressure constant inside the pump, second law of thermodynamics would cause the pump to enventually cool down to the surrounding temperature, even though the pump is still pressurized. Why doesn't this same principle work in the atmosphere?

Thanks

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I know in the troposphere as you descend the temperature roughly increases by 3.56F/1000ft, depending on the atmospheric conditions at the time.

However, I have trouble in understanding why the atmosphere maintains an adiabatic lapse rate since the second law of thermodynamics suggests the heat in the lower atmosphere would eventually equal the temperature of the upper troposhere/stratosphere.

To visualize this, imagine using the old addage of a hand-operated tire pump to fill a tire. We all know the tire pump warms adiabaticlly because of the increase in pressure. Now let's say you keep the pressure constant inside the pump, second law of thermodynamics would cause the pump to enventually cool down to the surrounding temperature, even though the pump is still pressurized. Why doesn't this same principle work in the atmosphere?

Thanks

The volume isn't fixed in the atmosphere. Gases are allowed to expand and contract relative to surrounding gases, which still allows for cooling and heating in specific areas, yet still follows the 2nd law of thermo. The dry and moist adiabatic lapse rates are an idealized parcel following constrict refines of the 2nd law...the actual atmosphere follows different curves as it cools and heats...therefore relative areas of instability/stability can be inferred.

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I know in the troposphere as you descend the temperature roughly increases by 3.56F/1000ft, depending on the atmospheric conditions at the time.

However, I have trouble in understanding why the atmosphere maintains an adiabatic lapse rate since the second law of thermodynamics suggests the heat in the lower atmosphere would eventually equal the temperature of the upper troposhere/stratosphere.

To visualize this, imagine using the old addage of a hand-operated tire pump to fill a tire. We all know the tire pump warms adiabaticlly because of the increase in pressure. Now let's say you keep the pressure constant inside the pump, second law of thermodynamics would cause the pump to enventually cool down to the surrounding temperature, even though the pump is still pressurized. Why doesn't this same principle work in the atmosphere?

Thanks

You can't compare a tire to the Atmosphere.

1.The atmosphere is not a closed system. heat enters and leaves via radiation. The upper atmosphere constantly radiates and cools while the lower atmosphere is heated by the sun.

2. Heat in a tire is spread via conduction. However a tire is 2ft tall, the troposphere is 35,000 ft tall, conduction is not the dominant force. This is the same reason the earths surface is 55F while the earths core 9,800 F. The heat flux from conduction just doesn't balance out the radiation.

I hope that explains it. But #2 probably just puzzled you even more.

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