Mountain Waves Flashcards
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
