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Flashcards in Upper Level Meteorology Deck (51)
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1

What happens to atmospheric pressure as there is an increase in altitude?

It decreases

2

What is the ISA atmospheric pressure?

1012.25 HPA at mean sea level

3

What is the atmospheric pressure at each altitude?
5,000ft
10,000ft
FL185
FL235
FL300
FL340
FL385
FL445

5,000ft- 850 HPA
10,000ft- 700 HPA
FL185- 500 HPA
FL235- 400 HPA
FL300- 300 HPA
FL340- 250 HPA
FL385- 200 HPA
FL445- 150 HPA

4

Rate of pressure decrease with altitude gain?

1HPA / 30ft up to 5,000ft AMSL

Not linear above 5,000ft

5

If a column of air is colder than ISA it will be...

Denser and therefore heavier and pressure will be reduced

6

If a column of air is warmer than ISA it will be..

Less dense, lighter and have an increased pressure

7

If pressure is warmer or cooler than ISA will the altimeter be accurate?

No, altimeters are calibrated for the vertical pressure distribution and rate of change in ISA, if it is not iSA they will not read correctly.

8

What will the altimeter error be if it is colder than ISA?

Senses the lower pressure and consequently indicate a higher altitude than the aircraft actually is

(Overread)

9

What will the altimeter error be if it is warmer than ISA?

Altimeter will sense the higher pressures and indicate a lower altitude than the aircraft actually is

(Underread)

10

How to calculate altimeter error caused by temperature variation on flight computer?

Set current OAT at a particular pressure height in the window and then read true altitude on the outside of the wheel against the calibrated or indicated altitude (what altimeter reads) on inside

11

Altimeter temperature error rule of thumb?

Altimeter error is approx. 4% of the indicated height per 10 degrees of variation from ISA

12

When aircraft are operating on local QNH for an airport, the altimeter error due to ISA is only applicable to...

Height of aircraft above the airport (AGL Error Only)

- Local QNH cancels out any error up to the level of the airport

13

What is the ELR?

1.98 rounded to 2 degrees per 1,000ft from a value of 15 degrees at mean sea level to -56 degrees at the tropopause at a height of 36,090ft

14

After the Tropopause what happens to the temperature until 66,000ft?

It remains constant at -56.5 degrees

15

What is tropopause defined as?

An abrupt and definite change from a steady environmental lapse rate where the temperature is steadily decreasing with increasing altitude to a situation where temperature remains virtually constant or isothermal (slightly increasing) with increasing altitude

16

Because of the greater depth of atmosphere in the tropics, the change in lapse rate occurs?

At an altitude above 36,090ft, often as high as 60,000ft

17

Around the poles where does the tropopause exist?

Often below 36,000ft

18

Over the tropics, the tropopause has a much ... temperature than ISA

Colder
Often as cold as -70 degrees

19

Where are jet streams often found?

At the breaks in the tropopause

20

What is a jet stream?

A strong narrow current of air concentrated along a horizontal axis in the upper troposphere or in the stratosphere

21

What are jet streams characterised by?

Strong horizontal and vertical wind shear and wind speeds in excess of 60kts

22

How far can jet streams extend horizontally?

Thousands of miles
Usually less than 100nm wide and only several thousand feet deep

23

What wind speed must be reached to be considered a jet stream?

60kt

24

Max jet stream speed?

200kt

25

In each hemisphere the dominant jet streams are...

Westerly and occur at the level of the tropopause

26

Why are jet streams often associated with Clear air turbulence?

Because of the strong wind shears encountered around them

27

Where is Clear Air Turbulence considered to be most severe?

On the polar side of the jet stream below the level of core

28

Is clear ice turbulence usually more severe in winter or summer?

Winter when the jet streams are stronger and when the jet stream is over land and curved

29

Why do jet streams form?

As a result of upper-level pressure distribution in much the same way as surface winds

30

How is a thermal wind formed?

Result of the temperature differential between two columns