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ATPL Meteorology > Upper Level Meteorology > Flashcards

Upper Level Meteorology Flashcards

1
Q

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

A

It decreases

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2
Q

What is the ISA atmospheric pressure?

A

1012.25 HPA at mean sea level

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3
Q 
What is the atmospheric pressure at each altitude?
5,000ft
10,000ft
FL185
FL235
FL300
FL340
FL385
FL445
A 
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
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4
Q

Rate of pressure decrease with altitude gain?

A

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

Not linear above 5,000ft

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5
Q

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

A

Denser and therefore heavier and pressure will be reduced

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6
Q

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

A

Less dense, lighter and have an increased pressure

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7
Q

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

A

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.

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8
Q

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

A

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

(Overread)

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9
Q

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

A

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

(Underread)

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10
Q

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

A

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

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11
Q

Altimeter temperature error rule of thumb?

A

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

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12
Q

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

A

Height of aircraft above the airport (AGL Error Only)

  • Local QNH cancels out any error up to the level of the airport
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13
Q

What is the ELR?

A

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

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14
Q

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

A

It remains constant at -56.5 degrees

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15
Q

What is tropopause defined as?

A

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

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16
Q

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

A

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

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17
Q

Around the poles where does the tropopause exist?

A

Often below 36,000ft

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18
Q

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

A

Colder

Often as cold as -70 degrees

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19
Q

Where are jet streams often found?

A

At the breaks in the tropopause

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20
Q

What is a jet stream?

A

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

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21
Q

What are jet streams characterised by?

A

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

22
Q

How far can jet streams extend horizontally?

A

Thousands of miles

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

23
Q

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

A

60kt

24
Q

Max jet stream speed?

A

200kt

25
Q

In each hemisphere the dominant jet streams are…

A

Westerly and occur at the level of the tropopause

26
Q

Why are jet streams often associated with Clear air turbulence?

A

Because of the strong wind shears encountered around them

27
Q

Where is Clear Air Turbulence considered to be most severe?

A

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

28
Q

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

A

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

29
Q

Why do jet streams form?

A

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

30
Q

How is a thermal wind formed?

A

Result of the temperature differential between two columns

31
Q

What is an Isotach?

A

Joins points of equal wind speed

32
Q

In the lower tropopause in the polar regions, the temperature stops lapsing earlier and the temperature is relatively warmer above the polar tropopause than above the equatorial tropopause. Above the tropopause, a warm column is over the pole and cold over the equator. This causes….

A

Reversal of thermal wind and creates a tendency for the wind to blow north. This northerly wind is deflected by Coriolis to the left in the southerly hemisphere resulting in and Easterly wind above the tropopause which opposes the westerly flow

33
Q

High above the tropopause what winds prevail?

A

Easterly

34
Q

What are the two main jet streams?

A

Subtropical jet and Polar front jet

35
Q

Where is the Sub Tropical Jet found?

A

The altitude of around 200 HPA (FL385) at 30 degrees latitude

36
Q

Where is the Polar Front Jet found?

A

Just below the level of the tropopause above the 500 HPA position of the polar front

37
Q

In the southern hemisphere summer, the patterns move south and so the subtropical jet stream moves….

A

A little further south in summer and north in winter

38
Q

Is the Subtropical jet stream or Polar Front Jet stream stronger?

A

Generally Subtropical

39
Q

If the OAT drops when flying South in the Southern hemisphere where are you in relation to the jet stream?

A

Still below the tropopause and therefore likely to be flying under the jet stream

40
Q

If the OAT rises when flying South in the Southern hemisphere where are you in relation to the jet stream?

A

ABove level of the tropopause and therefore likely to be flying above the jet stream

41
Q

If the OAT remains the same when flying South in the Southern hemisphere where are you in relation to the jet stream?

A

You are likely in the jet stream core

42
Q

Most common upper-level forecasts?

A

Route Sector Winds and Temperatures (RSWT)

GridPoint Winds and Temperatures (GPWT)

Significant Weather Prognosis (SIGWX PROG)

43
Q

Where are forecasts provided in relation to RSWT?

A

Frequently used air routes

44
Q

Levels of RDWT…

A 
FL445 150HPA 
FL385 200 HPA
FL340 250 HPA
FL300 300 HPA 
FL235 400 HPA 
FL185 500 HPA
45
Q

How is RSWT formatted?

A

DDSSSTT

DD- 2 numbers indicating wind direction to nearest 10 degrees

SSS- 3 numbers indicating wind speed to nearest 5kt

TT- 2 numbers indicating mean temperature in degrees Celcius without the negative sign

ISA temp also next to flight level

46
Q

What is the difference between GPWT and RSWT?

A

GPWT forecast for the midpoint of 5x5 degree square of latitude and longitude while data in RSWT forecast refers to average weather along a particular route

47
Q

What is the validity period of GPWT?

A

3 hours on either side of the stated validity time

48
Q

What does SIGWX PROG depict?

A

Expected occurrence of significant weather in the airspace from FL185 to FL445

49
Q

What is the validity period of SIGWX PROG?

A

3 hours on either side of the stated validity time

50
Q

Where in the AIP can you find the approved symbols and abbreviations for SIGWX PROG?

A

AIP GEN 3.5/ 22

51
Q

Key features of SIGWX PROG?

A
  • Predicted location
  • Level
  • Maximum jet stream speed
  • Height of tropopause
  • Location and of expected significant weather areas above FL185

ATPL Meteorology (12 decks)

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