Met 4 (Visibility and precipitation)

Question 1

What is super cooling?

Answer 1

Where water droplets cool to below freezing but due to the severe curvature of their shape they do not freeze. They instead freeze on impact with surfaces.

Question 2

What is the Bergeron process?

Answer 2

In clouds with very low temperatures water vapour can freeze into rapidly growing ice crystals.

Question 3

What are the 5 precipitation symbols?

Answer 3

(-) Light
(  ) Moderate
(+) Heavy
(VC) In vicinity
(SH) Showers

Question 4

What are the 8 different types of precipitation?

Answer 4

• Rain RA
• Drizzle DZ
• Snow SN
• Snow grains SG
• Ice pellets PL
• Ice crystals IC
• Hail +5mm GR
• Hail -5mm GS

Question 5

What are the 8 solids in the atmosphere?

Answer 5

• Sand SA
• Dust DU
• Haze HZ
• Smoke FU
• Volcanic ash VA
• Dust/sand swirls PO
• Dust storm DS
• Sand storm SS

Question 6

What’s RVR?

Answer 6

Indicates the range over which the pilot on the centre line of a runway can expect to see the runway surface markings.

Question 7

What is IRVR?

Answer 7

Instrumented runway visual range. Automatic, continuous display of RVR values.

Question 8

At what 3 points is IRVR measured?

Answer 8

Touchdown, Mid-point and Stop-end.

Question 9

Where is all the Met data displayed to a controller?

Answer 9

ADIS

Question 10

What increments is visibility reported in?

Answer 10

• 50m up to 800m
• 100m up to 5000m
• 1000m up to 9km
• 9999 when 10km+

Question 11

What is CAVOK?

Answer 11

Cloud and visibility okay

Question 12

When can CAVOK be used?

Answer 12

When visibility is 10km+, no cloud below 5000ft or Cb, TCu. No weather significant to aviation.

Question 13

Define fog (FG)

Answer 13

A suspension of small water droplets reducing visibility below 1000m.

Question 14

Define mist (BR)

Answer 14

The same as fog except visibility is not less than 1000m.

Question 15

Define haze (HZ)

Answer 15

A suspension of solid particles of smoke or dust reducing visibility to not less than 1000m where the RH is less than 95%.

Question 16

What are the 6 fog Met codes?

Answer 16

• Fog FG
• Mist BR
• Shallow fog MIFG
• Fog patches BCFG
• Fog covering part of the aerodrome PRFG
• Fog in the vicinity of aerodrome VCFG

Question 17

What are the two types of fog?

Answer 17

• Radiation fog

- Advection fog

Question 18

What are the 5 conditions for the formation of radiation fog?

Answer 18

• Clear sky
• Land surface
• Moist air
• Light wind
• Long night

Question 19

What 3 ways does radiation fog cleared?

Answer 19

• Solar heating
• Cloud cover
• Increasing wind

Question 20

What 2 ways dies advection fog formed?

Answer 20

• When warm, moist air is transferred by advection currents to a cold land or sea area.
• The warm air loses heat to the cold surface and fog forms if the cooling is sufficient to saturate the air.

Question 21

What 4 ways is advection fog dispersed?

Answer 21

• Change of air mass to drier air

- Insulation heating ground above the dew point of air mass.

Question 22

What is freezing fog?

Answer 22

Fog with a temperature below 0 degrees. Rime ice is deposited on surfaces.

Question 23

What is shallow fog?

Answer 23

Less than 2m in height over land. Less than 10m in height over sea. More than 1000m visibility over the fog layer.