Turbulence(oxford)

Question 1

Turbulence occurs(3):

Answer 1

1. in the friction layer
2. in clouds
3. in clear air

Question 2

Define the friction layer:

Answer 2

The friction layer is the lower part of the atmosphere extending from the surface to a height of 2000 ft to 3000 ft above the surface.

Question 3

The friction layer depth depends on:

Answer 3

1. roughness of the terrain
2. wind speed
3. the stability of the layer(stable conditions will resist vertical movement and hench limit the depth)

Question 4

Within the friction layer there are 2 sources of turbulence:

Answer 4

• Convection from thermal currents

* Frictional or mechanical turbulence

Question 5

Explain thermal turbulence:

The time when thermal turbulence is greatest?

Answer 5

During the day, some areas on the earth’s surface heat up faster than others due to the short wave radiation from the sun, this will cause stronger convection currents in certain areas. The end effect being variable vertical speed currents.

15:00

Question 6

Explain mechanical turbulence:

Answer 6

Physical obstructions to the normal flow of air such as hills, mountains, coasts, trees and building.

Question 7

mountain waves may also be referred to as standing waves or lee waves. These occur when the following conditions exist:

• The wind direction is perpendicular to the mountain range (+/-30°) without significant change in direction as altitude increases
• The wind speed at the summits is at least __ kt with speed increasing as altitude increases
• A marked layer of _____ around the altitude of the ______, e.g. an _______ layer or ______, with less ____ air ____ and ____

Answer 7

• The wind direction is perpendicular to the mountain range (+/-30°) without significant change in direction as altitude increases
• The wind speed at the summits is at least 15 kt with speed increasing as altitude increases
• A marked layer of stability around the altitude of the summits, e.g. an isothermal layer or inversion, with less stable air above and below