Turbulence Flashcards
List the 4 types of Turbulence
Shear
Mechanical
Convective
Wake
Define Turbulence
The irregular motion of the air resulting from the formation of eddies and/or vertical currents of air.
What is the difference between turbulence and LLWS
Turbulence is related to erratic changes in altitude/attitude, while LLWS is a rapid gain or loss of air speed
what is mechanical turbulence caused by?
Interaction between low level winds and the ground
What is shear turbulence caused by?
A drastic change in wind speed and/or direction with distance in the horizontal or vertical. It is the result of opposing air currents
What is shear turbulence that is produced in the absence of clouds called?
Clear air turbulence (CAT)
What is convective turbulence called?
Unequal heating of the earth’s surface
Wake turbulence is caused by: (5)
Wing tip vorticies Rotor tip vorticies Jet Blast Prop wash Rotor downwash
what 3 factors control the evolution of mechanical turbulence?
Roughness of the terrain
Stability of the air
Strength of the winds
Shear turbulence is determined by (3):
Degree in difference between opposing wind direction/speed
- Sudden increases/decreases in wind direction/speed
- Location of frontal boundries, mountainous terrain, location of upper features
What are the 4 factors that control the evolution of convective turbulence?
Stability of the air
Degree of difference in unequal heating
Time of day/year
Degree of difference associated with cold air advection.
Mountains and hills disturbing the flow of air over them is referred to as:
Orographic Turbulence
What are the 3 intensities of turbulence
Light, Moderate and Severe
What are the key words associated with light turbulence?
small and slightly
What are the key words associated with moderate turbulence?
larger, forced, positive control
What are the key words associated with severe turbulence?
Very large, not in positive control, violently forced
What types of turbulence can occur as a result of wind in the PBL and in the free atmosphere?
PBL: Shear, mechanical turbulence
Free Atmosphere: Shear, convective
What types of turbulence can occur as a result of clouds?
Shear, Convective, mechanical
What types of turbulence can occur in the absence of clouds
Convective, Shear
Define low level wind shear
A variation in wind speed/direction over a short distance in the low levels of the troposphere.
We can quantify the effects of wind associated with turbulence in the PBL with the following values
Non existant less than 10kts
LGT 10-12 knots
MDT wind or gust > 15 kts
SEV wind or gust > 20 kts
List the 3 vertical shear criteria and intensities in the free atmosphere
LGT <5 kts/1000ft
MDT 5-9 kts/1000ft
SEV 10kts or more/1000ft
