azaviator08
New Member
What would you use as a good rule of thumb for how much temperature decreases with altitude?
standard temperature decrease
- Thread starter azaviator08
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CoffeeIcePapers
Well-Hung Member
2*C/1000 is the standard lapse rate, but that is just a standard.
Ayork62493
GBR
I use standard, however it very rarely is standard.(Where I am anyways)
elmetal
Ain't nobody got time for that
on a XC of mine I ended up in El Paso and my god, it is weird out there. Coming in at 8 thousand it was nice and -4, we land I look down and it's positive 5
talk about inversion
elmetal
Ain't nobody got time for that
wait, it was backwards, we were at 4 positive land and it's -5.
A150K
Well-Known Member
I was going to say, not much of an inversion there.lol
elmetal
Ain't nobody got time for that
lol after i wrote it I was like what the heck it was a normal day! Then I remembered it was colder on the ground.
Ayork62493
GBR
Best thing to do is, before you do all the performance figures and all that good stuff just get a DUAT's report. Weather baloons don't lie. (For the most part)
CoffeeIcePapers
Well-Hung Member
Also, for the FAA written, they have a problem where you need to calculate the cloud base and for some reason they use Fahrenheit. Just use 4.4*/1000 for F.
Just a different way, convert to C:
(degrees F - 32) / 1.8 = degrees C
I always forget this formula, but for some reason I have no problem remembering the that it is + or - 32 and * or / by 1.8. So I just check myself with: 212 F (boiling point) - 32 = 180 / 1.8 = 100 C.
born2aviate
Well-Known Member
Not sure if this is correct but it has been explained to me that temperature decreases at 3 degree per 1,000 feet but dewpoint decreases 1 degree per thousand feet thus averaging it out to 2 degrees per thousand feet. Or something to that affect...I don't remember exactly but if anyone knows what I'm talking about feel free to correct me.
CoffeeIcePapers
Well-Hung Member
You are somewhat correct. The air expands as you climb, so the temperature cools, this is adiabatic, meaning there is no heat exchange. This rate is different for dry air and saturated air. Dry air's adiabatic lapse rate is 3*C/1000 and fully saturated air cools at 1*C/1000. Page 51 in the old "Aviation Weather" book by the FAA explains it.
OldTownPilot
Well-Known Member
Just to clarify, its 3C/1000ft dry adiabatic lapse and 1F/1000ft dew point lapse. so the base of the cumulus clouds is 4.4F/1000 ft or 2.4C/1000ft
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Don't confuse, and definately dont mix Celcius and Farenheit.
Dexter23
"An Optimist is just a pessimist with experience"
you had me confused until i read the correction
KSCessnaDriver
Well-Known Member
It so much easier to use Celsius and kilometers, but that doesn't do a lot of good for flying. If you really want to know the environmental lapse rate, take a look at a Skew-T/Log-P chart.