#### Mavmb

##### Well-Known Member
It's 3 degrees per 1000 feet. Now, just for personal knowledge, why is this important at all? I don't understand what adiabatic really means and how it causes weather or how it is significant to clouds or turbulence. Any takers on that question?

I think it just gives you a very rough method of approximating temperature.

Plus, there needs to be a standard temperature deviation from sea level/59F/15C at various altitudes.

But that's just off the top of my head.

Adiabatic means that the temp in the raising air changes withot adding or taking away heat from outside the parcel of air [ air rises, press decreases ,temp decreases] if air sinks it will be compressed by increassing pressure ,temp will rise

[in my best Samuel L. Jackson voice...] : Check out the big brain on Jetman!!!

It also serves as a way to determine the stability of an airmass. If the lapse rate of the airmass in question is higher than the average lapse rate it will be an unstable mass. If it's lower than the average the airmass will tend to be stable. I may have that backwards but I'm pretty sure that's correct. I'll go check around ...

Be careful about that though...there is a dry lapse rate and a moist lapse rate. I believe the moist lapse rate is less because water doesn not cool as quickly as air

I've used it to get a rough in-air estimate of where the freezing level might be. Granted, that's pretty high up in Florida....

Adiabatic lapse rate is not the same as environmental lapse rate (actual lapse rate).

I dunno how much knowing the adiabatic lapse rate helps in practice since there isn't really a way to figure it out that I know of. It's 3 for dry air and around 1.5 for moist air...

But the environmental lapse rate is important because it gives a rough measure of air stability; i.e. &gt;2/1000'=unstable and &lt;2/1000'=stable.

Think of an inversion, there's a negative lapse rate and very stable air. When figuring out freezing levels, etc. use 2/1000' because that's the standard lapse rate.

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Be careful about that though...there is a dry lapse rate and a moist lapse rate. I believe the moist lapse rate is less because water doesn not cool as quickly as air

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Water doesn't cool as quickly as air. Thanks. Than that makes sense why the dry lapse rate is 3 degrees per 1000 feet. The standard is 2 degrees celsius per 1000 feet. There's an examiner that asks about the adiabatic lapse rate (3 per 1000) and I just wondered what the adiabatic rate affects. Maybe it's just one of those examiner questions. Me thinks we need a meteorologist here.

I hope mtsu doesn't ridicule me for this one: HA

Adiabatic is really important when it comes down to undestanding meterology. Adiabatic spefically means the NO heat is exchanged with the surrounds of the gas or liquid. Yes, air cools as it rises but this is due to the amount of expansion or compression that parcel of air is allowed in that gain in altitude. Always think in terms of that and it will help; if a gas expands, it cools. Conversely, if it compresses it is heated. All this is due to how tightly knit the molecules are.

If you were to take a parcel of air and lift it will expand at nearly the same rate the atmosphere expands. If you were to measure the temperture along the way you would get its lapse rate. I won't go further unless it is warranted, andI am about to be late for the muuvvvie.

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I hope mtsu doesn't ridicule me for this one: HA

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I just took out my trusty balloon and squeeeeeezed it really hard. It got warm!

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I just took out my trusty balloon and squeeeeeezed it really hard. It got warm!

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Don't pop it....

To add to this super interesting discussion
....

The moist lapse rate is less because as the water vapour condenses, it is releasing latent heat. This release of heat, which always occurs with condensation, causes the moist lapse rate to be slightly less. Meteorologists use the dry lapse rate when the parcel has yet to condense. Once clouds begin to form, the parcel is cooling at the moist rate.

You're forcing me to strain my already impared memory, but I think this the the model I used back in my IFR checkride days.

Air with a low lapse rate will cool of slowly as it rises (i.e. stays warmer at altitude). Because it is warmer than the surrounding air, it will continue to rise.

Rising air means less stable air.

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