Atmospheric Pressure & Pressure Systems Flashcards
Define: air pressure.
The mass of air above the earth’s surface.
How does atmospheric pressure vary with altitude?
It decreases with increasing altitude.
State the relationship between bars, milibars, and hectopascals.
1 bar = 1,000 mbar = 1,000 hPa
Define: barometer.
An instrument that measures pressure.
What is the average sea level pressure?
1,013 hPa.
Define: Pascal.
1 Pa = 1 N / 1 m2
Define: bar.
1 bar = 100,000 N / 1 m2
1 bar ≈ 1 atm
State the MSL (standard) pressure value in:
(a) hPa
(b) in Hg
(c) mm Hg
(a) 1,013
(b) 760
(c) 29.92
In different units, express the amount of force exerted by air on each square metre at MSL.
1,013 mbar = 1 bar (≈ 1 atmosphere) = 100,000 N = 10,000 kg = 10 t
Define: aneroid.
Partially evacuated air chamber.
Generally speaking, what weather is associated with what pressure?
High pressure = good weather.
Low pressure = bad weather.
Define: ideal gas law.
P · V = n · R · T
Does temperature affect how quickly the pressure decreases with increasing altitude?
Yes, pressure decreases more rapidly in cold air than in warm air.
How does true altitude vary from indicated altitude as a function of ISA deviation?
Colder than ISA = True < Indicated.
Warmer than iSA = True > Indicated.
Define: isobar.
A line joining points of equal pressure.
