14 Turbulence

Where is standing wave maximum turbulence most likely to exist?

• two wavelengths downwind from the crest and just above its surface.

• approximately one wavelength down wind of, and approximately level with, the top of the ridge

• Just below the tropopause above the ridge

• Down the lee side of the ridge and along the surface

During the formation of a mountain wave, what characteristic should be within the wind that is above the level of the ridge over which it is being generated?

• Decrease or even reverse direction.

• Increase initially then decrease.

• increase with little change in direction.

• Increase and then reverse in direction.

Which of the following is probably the most dangerous practice, when flying in IMC in a region close to a range of hills 2000 ft high AMSL, in stable air and with wind direction at right angles to the axis of the range of hills?

• Flying towards the hills, into the wind, at altitude 6500 ft AMSL

• Flying parallel to the hills on the downwind side at altitude 4000 ft AMSL

• Flying towards the hills downwind at altitude 5500 ft AMSL

• Flying parallel to the hills in the upwind side at altitude 4000 ft AMSL

Which of the following statements referring to Jet Streams is correct?

• CAT associated with Jet Streams is probably associated with the rapid wind shear in the vicinity of the jet.

• The maximum windspeed in a Jet Stream increases with increase of height up to the tropopause and remains constant thereafter.

• The core of a Jet Stream is usually located just below the tropopause in the colder air mass.

• The rate of change of windspeed at any given level is usually greatest on the warmer side of the jet.

What can be determined from the observation of the existence of lenticular clouds?

• There may be mountain waves present and there will be severe turbulence.

• There are mountain waves present but they may not give severe turbulence.

• A Fohn wind can be expected with no turbulence.

• A Katabatic wind is present which may lead to fog in the valleys

For standing waves to form, the wind direction must be near perpendicular to a ridge or range of mountains and the speed must:

• Decrease with height within a stable layer above the hill.

• increase with height within an unstable layer above the hill.

• Decrease with height within an unstable layer above the hill.

• increase with height within a stable layer above the hill.

A mountain range, height 10,000 ft AMSL is producing marked mountain waves. Where will the greatest potential danger exist for an aircraft?

• on the windward side of the ridge

• at FL 350 over and parallel to the ridge

• towards the ridge from the lee side at 14000 ft AMSL

• above a line of clouds parallel to the ridge on the lee side at 2500 ft AMSL

Clear air turbulence, in association with a polar front jet stream in the Northern Hemisphere, is

• Underneath the jet core

• In the centre of the jet core

• Looking downstrearn on the right hand side

• Looking downstream on the left hand side

Mountain waves can occur ...

• Up to a maximum of 5000 ft above the mountains and 50 nm to 100 nm downwind.

• Up to mountain height only and 50 nm to 100 nm downwind.

• Above the mountain and downwind up to a maximum height at the tropopause and 50 nm to 100 nm downwind.

• In the stratosphere.

What intensity of turbulence should be reported if crew and passengers feel a definite strain against their seat or shoulder straps, food service and walking is difficult and loose objects become dislodged?

• Light

• Extreme

• Severe

• Moderate