Aviation weather

Question 1

What is CCN

Answer 1

Cloud condensation Nuclei - Solids, dust, volcanic ash, sands pollutants needed to encourage clouds to form.

Question 2

How many feet does it take for a pressure change of 1hpa (below 20,000ft)

Answer 2

30 feet.

Question 2

Standard pressure setting

Answer 2

1013.2

Question 3

Explain the dew point

Answer 3

Where the air is holding as much water as possible, it is saturated. If temp and dew point are close together you get a low cloud base.

Question 4

Explain what happens with high humidity

Answer 4

Air is less dense and therefore has less lift as oxygen molecules are replaced with H2O.

Question 5

DALR & SALR

Answer 5

DALR - 3c per 1000ft
SALR - 1.5c per 1000ft

Question 6

What direction does wind flow around high pressure and low pressure

Answer 6

High pressure - Clockwise
Low pressure - Anticlockwise

Question 7

Backing and veering winds

Answer 7

Winds backed at surface due to surface friction, can be expected up to 2000ft.

Question 8

Stable and unstable air

Answer 8

Stable - Warm air cooled from below
Unstable - Cool air heated from below

Question 9

Pressure systems
Low pressure =
High pressure =

Answer 9

Low pressure - rising air, encourages weather formation.
High pressure - sinking air, suppresses weather.

Question 10

Isobaric chart - Lows

Answer 10

Anti-clockwise direction
Referred to as depression or cyclone
Expect more poor weather

Question 11

Isobaric chart - high

Answer 11

Clockwise direction
Isobars more widely spread (light wind)
sinking air, suppresses weather

Question 12

Isobaric chart - Trough

Answer 12

‘T’ or bold black line
Extension of low pressure
Poor weather

Question 13

Name the four kinds of icing

Answer 13

Run-back ice
Rime ice
Clear ice
Hoar frost

Question 14

Define run-back ice

Answer 14

Clear
Flows back from heated surface
Back of wing

Question 15

Define rime ice

Answer 15

Opaque - air pockets
Light
Brittle

Question 16

Define clear ice

Answer 16

Clear
Dense
Adhesive
(Most dangerous, hard to see, hard to clear)

Question 17

Define hoar frost

Answer 17

White
Brittle

Question 18

METAR and when issued

Answer 18

Meteorological aerodrome report - H:20 & H:50

Question 19

TAF and when issued

Answer 19

Terminal aerodrome forecast - Every three hours at military airfield, nine hour forecast.

Question 20

When a trend is added to a METAR how long is it valid for?

Answer 20

2 hours

Question 21

The QNH is always rounded…

Answer 21

down

Question 22

What does it mean if cloud is coloured green on a cross section

Answer 22

Temp in cloud is above freezing

Question 23

Height of the tropopause

Answer 23

36090ft