Mountain Waves Flashcards
(20 cards)
Define mountain waves
Waves or ripples which form in the atmosphere caused by air encountering an obstruction or barrier at the surface of the earth
List the 4 factors that affect the evolution of mountain waves
Obstruction
Stable layer
Strong wind
Weak directional shear
The wavelength and strength of the vertical currents are affected by:
The width of the obstruction
The amplitude and strength of the vertical currents are affected by:
the lee side fall (sudden drop)
The waves immediately following the obstruction are the __________
strongest and get progressively weaker
A stable layer must be present just ______ the barrier
above
The minimum speed at which wind will create a mountain wave i:
25kts
An angle of incidence of ____ degrees each side of the barrier is the maximum allowable deviance
30
List the 3 cloud types associated with mountain waves:
Cap
Rotor
Lenticular
What type of lift creates cap clouds and what dissipates them on the other side?
Orographic lift
Adiabatic heating
Rotor clouds form past the obstruction as a result of __________. they appear as ___________
Turbulent mixing
long line of stratocumulus
Wave crests may be marked with:
Lenticular clouds
lenticular clouds at mid levels are called
ACSL Altocumulus standing lenticular
What are the most dangerous element of mountain waves?
Rotor Clouds
List the 5 hazards to aviation associated with mountain waves
Wind shear Obscured terrain Turbulence Up/downdrafts Changes in pressure
Downdrafts are most severe:
near a mountain and at about the same height as the top
Increased wind speed in the wave crests cause a:
lowering of the pressure (bernouilli)
the most turbulent area of in a mountain wave system is:
the rotor
Strong vertical wind shears are often concentrated ____________ the jet stream
Just above and below
Mountain waves are more pronounced on the __________ side of the jet stream
warm
