Meteorology Flashcards
How does pressure change with height in the lowest layers of the troposphere?
Decreases by 1hPa per 30ft.
Where is the tropopause the highest?
Near the equator
Deposition refers to…
A change in state from gas to a solid.
What is the height of the tropopause in the ISA?
36.090ft
In ascending order, what are the layers of the atmosphere?
Troposphere, stratosphere, mesosphere, thermosphere.
What does 05/05 mean in a METAR?
Temp 5 degrees, dew point 5 degrees, RH 100%.
What is an inversion?
A layer where temperature increases with height.
What is a layer where temp is constant with height?
Isothermal Layer
What is the DALR?
Dry Adiabatic Lapse Rate - 3C per 1000ft
What is the SALR?
Saturated Adiabatic Lapse Rate - 1.5C per 1000ft.
If the ELR was 2C per 1000ft, what would stability be?
Conditionally unstable (inbetween the DALR and SALR)
If warm air is cooled from below, what happens to the stability?
It becomes more stable.
Which way does Coriolis act in the Southern Hemisphere?
Left
If low pressure is on your left in the northern hemisphere, where will the wind be?
Behind you
If cool air is warmed from below, what will happen to stability?
The air will become unstable.
How do surface winds compare to winds at 2000ft?
Directions are backed and speeds reduced (backed and slacked).
Picture a wind arrow pointing down and to the right, with a flag and small line at the end. What does this indicate?
South-Easterly at 55kts.
What does 09010KT indicate in a METAR or TAF?
Wind from 090 degrees at 10 knots.
What is an effect of the Fohn effect to the Lee of high ground?
Higher cloud bases
Which of the following is likely to cause turbulence?
- Foehn Effect
- Coriolis Effect
- Thermals
- Mass Descent
Thermals
What does SCT200 stand for in a METAR or TAF?
3-4 Oktas at 20000ft
Name the trigger actions (to create cloud)
Convergence, Convection, Mass Ascent, Orographic uplift
List these clouds in ascending order: AS, CC, ST, SC
ST, SC, AS, CC
What are the mechanisms for cloud dispersal?
- Changing the airmass
- mixing (increasing the wind speed)
- warming the air
- increasing precipitation
What conditions would you expect in NW Scotland in a polar maritime airmass in winter?
Unstable, SCT/BKN CU TCU CB, SHRA, TSRA
A tropical maritime air mass is likely to affect to the UK when…
There is a low pressure over the Atlantic
Buys ballots law states: when you stand with your back to the wind…
Low pressure is always on your left in the northern hemisphere
What hazard is usually associated with an orographic low?
Turbulence
Low pressure found to the Lee side of high ground.
What happens to air in a high pressure system?
It sinks and diverges, dissipating cloud.
Anti-cyclone (high pressure) is often associated with good weather. Haze is possible at the surface.
What weather is associated with a low pressure system?
Poor weather, clouds, rain etc.
A cold front has passed over your station. What type of weather would you expect after the front has cleared?
Showers
Polar maritime airmass (unstable) usually follows a cold front
At what temperature is icing most likely to occur?
Zero to MS20.
Icing usually relies on supercooled water droplets, which are generally present in the temperature range described above.
Ice crystals are present below MS20, which aren’t conducive to aircraft icing.
Which type of icing occurs in cloud and has a white, opaque appearance?
Rime Ice
What type of ice is white and forms in clear skies?
Hoar frost
What does the following symbol show?
‘U’ with 3 vertical lines in the middle.
Severe Icing
Symbol that looks like a ‘mountain with a hat’
Turbulence - moderate is just a ‘hill’. Severe is a ‘hill with a hat’
If visibility is 1200M and the RH is 98%, what weather would be reported?
Mist
If visibility is 1200M, which an RH of 94%, what is present?
Haze
When is the min vis reported at a military airfield?
When it changed the colour state.
What is likely to clear radiation fog?
- an increase in wind speed (mixing)
- increase in air temperature
What does ‘W’ stand for in the mnemonic ‘WHISTLE’?
Weather
What is the correct sequence of cloud development prior to a thunderstorm?
CU to TCU to CB
In TAFs, what does the change group BECMG indicate?
A gradual but permanent change in one or more elements of the forecast, during the time period shown.
TAF EGYD 070445Z 0706/0715 22010KT 2000 BR BKN005 TEMPO 0706/0709 1000 FG OVC001 BECMG 0709/0712 5000 SCT020 TEMPO 0713/0715 8000 SCT025=
Based on the above TAF, at what time will cranwell be green colour state or better?
12 Z
Know the boundary of the green colour state - vertical cloud base and horizontal visibility
What are the Green colour state parameters?
3700-5000M visibility
700-1500FT clouds
How long is a METAR trend valid for?
2 hours
What are the white colour state parameters?
5000M-8km visibility
1500-2500ft clouds
What are the blue colour state parameters?
8km+ vis
2500ft+ clouds
What are the requirements for CAVOK to be reported?
Vis greater than 10000ft, no cloud below 5000ft
Where is the ITCZ?
Inter Tropical Convergence Zone - In the tropics
Only directly over the equator in the spring and summer equinox.
(Area in-between the two Hadley cells)
What are the names of the 3 atmospheric circulation cells?
- Polar (near poles)
- Ferrel (sub-tropics)
- Hadley (near equator)
What direction are the trade winds in the northern hemisphere?
North-Easterly
Trade winds are underneath the Hadley cell
Which direction are the trade winds in the Southern Hemisphere?
South-Easterly
High pressure at thermal equator, low pressure further south.
What are the requirements for tropical storm formation?
- Sea Temps greater than 26C
- Light Winds
- 5-15 deg from equator
Can’t form at the equator due to no Coriolis effect
The QNH is always rounded…
Down (knock decimal off)
Makes you potentially think you’re lower than you are (meaning you’ll be too high - not unsafe)
What does it mean if cloud is coloured green on a cross section?
Temperature in cloud is above freezing.
Red clouds are at / below the isotherm and present risk of icing.
