Meteorology Flashcards
Minus graphing
Name the 5 atmosphere layers
Troposphere
Tropopause
Stratosphere
Mesosphere
Thermosphere
What height is ISA temperature fixed after ?
36’090ft (11Km)
What is the ISA fixed temperature after 36’090 ?
-56.6 C
Rate of temperature change in the troposphere ?
-1.98 C Per 1000ft (until 36’090 is reached)
Or -0.65 C Per 100m
-2 in calculations.
What Is ISA sea level temperature ?
+15 C
Composition of the atmosphere
78% Nitrogen
21% Oxygen
1% Other gasses
What gasses make up the 1%
Argon
Carbon dioxide
Hydrogen
Ozone (O3)
Carbon monoxide
1/2 Of water vapour is found below what ?
1.5 Km
Amount of water vapour depends on what ?
Temperature (Heat)
Warm air can hold more vapour than cold air.
Cold air has lower carrying capacity.
Height of tropopause depends on ?
Temperature of the air in the troposphere near the earths surface
Heights and Temperature of polar and equatorial tropopause
Polar 8-10 Km (-40)-(-50) C
Equatorial 16-18 Km (-70)-(-90) C
Why is the stratosphere a good or bad place to fly ?
Cloud formation is rare
Above hazards of troposphere (Eg CB)
Greater engine efficiency
Turbulence is still possible
What height is temperature constant to in the stratosphere, until the Ozone layer starts ?
Approx 20 Km (65’000ft)
What does Ozone layer do ?
Absorb short wave radiation (UV)
Ozone relationship with Stratosphere
Ozone layer in 90% within.
Ozone is responsible for the temperature increase within the stratosphere.
Negatives of ozone
Extremely corrosive gas
Can impact cabin air quality at very high altitudes, possible respiratory problems.
InHg and mmHg meaning ?
Inches/Millimeters of mercury
Relationship with altitude of pressure and density ?
Pressure and density decrease with altitude.
(pressure due to less air res)
ISA Temperature Calculation (ft)
ISA Temp = 15-2 x altitude (ft) / 1000
ISA Temperature Calculation (Km)
ISA Temp = 15-6.5 x altitude (Km)
As temperature increases density … ?
Decreases
ISA deviation is ?
ISA temp compared to actual conditions.
If it’s warmer than ISA conditions, deviation is positive (+)
If it’s colder than ISA conditions, deviation is negative (-)
What is the ISA static pressure (hPa)
1013.25
1013 in calculations
ISA Density comparison from AMSL to 22’000ft and 40’000 ft
22’000 is approx 50% compared
40’000 is approx 25% compared
World Area Forecast Centre…
(WAFC)
Issue significant weather charts every 6-9 hours.
They report:
~Upper winds/temp/humidity
~Tropopause Height/Temp
~Areas of significant weather- (CB, Icing, turbulence)
Located in London and Washington.
Meteorological offices
(MO)
Issue a Terminal Area Forecast (TAF) every 3-6 hours.
(rumour/projected report)
UK office is in Exeter
Is a low level area forecast every 6 hours (GAMET)
Meterological stations
(MS)
Issue METARS every 30-60 mins
(True report)
Issue SPECIs- interim METAR due to significant change.
Issue landing forecasts valid for 2 hours.
Issue SNOWTAM, warning of snow/ icy condition valid for up to 2 hours.
Issue Aerodrome warnings
Meteorological watch office
(MWO)
Issue weather warnings
SIGMET, upper level warning that is valid for 4-6 hours.
AIRMET, low level warning below FL100/150 valid for 4 hours.
ASHTAM, volcanic activity and ash clouds valid for up to 24 hours.
7 SIGMET info issues
Thunderstorms (TS)
Tropical cyclone
Severe turbulence
Severe icing
Severe mountain waves
Heavy sand and dust storms
Volcanic ash and Radioactive cloud
SIGMET process
Pilot encounters bad conditions, Reports to air traffic, air traffic inform higher power if required and then pass the report to the MWO who then issues the SIGMET.
Reliability of TAF and METAR
TAF is said to be more of a rumour.
METAR is said to be the truth.
CAVOK conditions
Visibility is 10km+
No CB, TCU
No significant weather phenomena
No cloud below 5000ft or Minimum sector altitude (Highest altitude + 1000ft) whichever is greater.
VOLMET
Weather reports and forecasts in flight, HF in oceanic, and VHF in Europe.
Can provide TAF, SIGMET and METAR
VHF VOLMET is normally broadcast in a continuous loop.
HF VOLMET normally published schedule with five min allocated to each station.
ATIS
Wind direction is magnetic
Takeoff and landing report by ATC
weather and operational info
change is indicated with the next letter of the alphabet
What is an aerodrome warning ?
+ Examples
Warning issued for condition that could adversely affect aircraft on the ground and pedestrians.
Fog (VIS)
Sandstorm (SS)
Freezing conditions (FZ)
Foreign objects
Birds
AIRMET + GAMET
AIRMET - En-Route weather phenomena which may affect safety at low level. (less severe than a SIGMET)
GAMET - Area forecast for low level local flights.
What is a ridge ?
Gentle extension of a high pressure system
What is a trough ?
Extension of a low pressure system
What is a line trough
Shows deep surface convection currents. It brings extreme weather (CB etc) and should be avoided.
Usually in a low pressure zone but high in summer.
What is the cut off value for high and low pressure charts ?
1013, above is high, below is low pressure.
OKTA level abbreviations ?
SKC - Sky Clear
1-2 - FEW
3-4 - SCT (Scattered)
5-7 - BKN (Broken)
8 - OVC (Overcast)
Lack of visible weather in the stratosphere is due to ?
The isothermic or inversion conditions in the stratosphere create a physical barrier to further vertical Development of cloud.
Isothermal definition
Constant temperature
ISA Density
1.225 kg/m3
Airborne Radar coverage ?
70/90º either side from heading of aircraft
How is incoming radiation distributed ?
15% is absorbed or refelcted by the earths atmosphere.
85% is felt at the ground.
Name of dark area on a weather radar ?
Shadow effect (biggest limitation)
Airborne radar controls
On/Off/Standby
Gain (sensitivity- hearing)
Tilt
Mode switch
Range (40-320)
Can go 70/90º either side of nose
Geo stationary Satellite characteristics ?
Orbit type
Type of detector
Geo stationary satellite Detector types ?
Infrared
Visible
Distance From earths surface of geo stationary satellite ?
35786 Km
POES orbit distance + P&Ns ?
850 Km
Flexible orbit
Better resolution
Picks up small details
Not good at tracking storm movements
50% sea level pressure is at what height ?
18’000 ft
Half and a quarter of sea level density is at what height ?
Half is 22’000 ft
1/4 is 40’000 ft
QNH is ?
Sea level pressure (distance above sea level)
QFE is ?
Pressure at a point above ground level (height)
(On the ground it reads 0)
Elevation is ?
Ground height above mean sea level
Weather conditions in a trough (low pressure) ?
Showers of Rain/Hail etc
Visibility is good outside of showers (Key info)
Strong winds
Thunderstorms
Air instability
Weather conditions in a ridge (High pressure)
Clear skies/ Few clouds (stratiform - layered cloud)
Hazy (Poor vis due to inversion)
Gentle winds
Light turbulence
An inversion is ?
Layer of Temperature increase with height
Types of inversion ?
Surface inversion
Aloft inversion
Vally inversion
Frontal inversion
Friction layer
Dinural Variation is ?
(+Impacting factors)
The change in surface temperature over a 24 hour period.
Cloud, wind and being over water reduces dinural variation
What are the three ways stopping 15% of solar radiation reaching the surface ?
Absorbance- ozone layer + water vapour
Reflection- Top of clouds
Scattering- various particles in the sky
What is earths average albedo ?
31%
Relative tilt of the earth is ?
23.5º
Equinox Dates ?
23rd of September
21st of March
Solstice dates ?
21st of June
22nd of December
Aphelion and perihelion dates and distance ?
Aphelion- 4th of July 152M km
Perihelion - 4th of January 147M km
Radiosonde (Balloon) general info ?
Rise to 115’000 ft (35 km)
Collects data on
-humidity
-temperature
-pressure
(every 1.3 seconds)
Stevenson screen general info ?
1.2m clear of the ground (avoiding ground radiance)
measures surface temperature and humidity
What is shadow effect on a weather radar ?
Its when the radar can’t see behind the initial cloud so what’s there is unknown
Primary atmosphere heat source ?
Terrestrial radiation from earth to the air
Conduction is ?
Energy transfer by contact
Convection is ?
Energy transfer by vertical air movement
(Unstable)
Advection is ?
Energy transfer by horizontal air movement
Density relationship with temperature and pressure ?
Density is inversely proportional to temperature
Density id proportional to pressure
Moist air is …. dense than dry air ?
less
Convergence
Divergence
Advection
Subsidising
Moving towards
Moving away
Rising
Falling
Cyclonic rotation direction
NH = Anti-clockwise
SH = Clockwise
Anti-cyclonic airflow rotation
NH = Clockwise
SH = Anti-clockwise
Warm and cold Anti-cyclone examples ?
Siberia- Cold
Azores- Warm
Areas of low pressure are found at ?
The equator and in the region of 60º latitude
Areas of high pressure are found at ?
The poles and in the region of 30º altitude
Saturated air is when ?
humidity is 100%
Which processes absorb latent heat ?
Evaporation and melting (S-L-G)
Which processes release latent heat ?
Condensation + freezing (G>S)
Deposition is ?
Gas directly changing state to solid
Sublimation is ?
Solid directly changing to a gas
Size of Raindrop formation parts ?
Condensation nuclei - 2µ Diameter
Moisture droplets - 20µ Diameter
Typical raindrop - 2000µ Diameter
SCWD is ?
Supercooled water droplets.
Water droplets that freeze well-after 0º.
Found in CB’s, causes clear ice which freezes on the leading edge
Which air temperature has the higher capacity for water vapour ?
Warm air due to higher energy, so it can accept more from its surrounding.
Absolute humidity values at 0 and 10º
0º= 3.8g/ per kg of air
10º= 7.6/ per kg of air
Dew point is ?
The temperature to which the air must cool for it to become completely saturated with water.(vaour becomes droplets)
When temp and DP are close together low cloud or fog is more likely to form.
Relative Humidity calculation ?
RH % = 100- (5x (ambient temperature -dew point))
Stable, Neutral, Unstable
Stable- Parcel of air returns
Neutral- No tendency to return to original position
Unstable- Parcel of air continues to rise
ELR in ISA conditions is ?
ELR in non ISA conditions ?
2ºC / 1000ft
Ranges 0.6ºC > 4.0ºC / 1000ft
How is ELR measured ?
Radiosonde
Dry adiabatic lapse rate (DALR) is ?
Rate at which air cools in a dry air parcel
3ºC / 1000ft or 1ºC/ 100m
Saturated adiabatic lapse rate (SALR) is ?
Rate at which air cools after the condensation level/ dew point
1.8ºC/ 1000ft or 0.6ºC/ 100m
Adiabatic rise triggers ?
Convection
Orographic wind
Convergence
Frontal lift
Atmosphere is absolutely stable when…. ?
(+ Clouds)
The ELR is less than the DALR
Stratus (low level)
Nimbostratus (Rain bearing, layered)
Altostratus (mid level)
Atmosphere is absolutely unstable when…. ?
(+Clouds)
The ELR is greater than the DALR
Cumulus
Towering cumulus
Cumulonimbus
Tephigram display of stability ?
If plotted left of DALR and SALR is absolutely unstable
If plotted right of both its absolutely stable
If plotted in-between its conditionally stable
Temperature error calculation (TEC)
(Height/1000) x 4 x ISA deviation
When isa deviation is warmer ?
(TEC)
Add TEC to indicated altitude to get true.
Minus TEC from true to get indicated
(opposite for colder)
Where is TEC considered ?
between the ground and the aircraft- Height above the ground station
METAR cloud ceiling ?
has to be greater than half the sky so BKN or OVC, it is the base of the cloud.
Impact of side winds in NH ?
If you apply Buys Ballot Law by turning your back to the wind, you will find the low pressure to your left in the northern hemisphere. Therefore, your aircraft is flying towards higher pressure.
What happens when flying from low to high pressure ?
When you go from low pressure to a high pressure without changing the altimeter subscale, it will under
read. In other words, you will be higher than you think you are.
If QFE is bigger than QNH ?
You are below sea level
Visibility is ?
The greatest at which a black object of suitable dimensions can be seen and recognised when observed against a bright background/horizon
Minimum VMC conditions in class B,C,D,E, F,G airspace when flying on IFR
1.5Km horizontal distance from cloud
1000 ft cloud clearance
Vis below 10000ft > 5Km
Vis above 10000 > 8Km
Slight change for G and F over mountains
Non atmospheric low vis causes
Glare from the sun
Contaminated windscreen
Scratched windscreen
UV damaged (acrylic windscreens)
Atmospheric low vis causes
Water droplets
Ice crystals
Smoke
Chemical pollutants
Volcanic ash
Conditions when vis is between 1000-5000m
Mist
Haze
Smoke
Widespread dust
Sand
Conditions when vis is less than 1000m
Fog
Ideal conditions for radiation fog formation ?
Relatively high humidity
Light winds
Clear skies, long nights
It has a max height of 500ft
Radiation fog dispersal ?
Often clears early morning when temperature increases above the dew point.
Wind mixes dry and saturated air, may lift into a low stratus or stratocumulus
Advection fog ?
Warmer air moving over a cold surface cooling the air from below, condensing it and causing fog.
Associated with cool sea areas and adjacent coasts in the summer.
In winter it may occur over land if the surface is very cold.
Steam/Arctic fog or sea smoke ?
Caused by very cold dry air moving over warmer moist surface.
As soon as water evaporates from surface it condenses and forms fog
Frontal fog ?
Found on a warm front
Up to 200nm ahead of the front, super saturated area exists, the moisture falls and condenses air to cause fog
Orographic/hill fog ?
Forms when a stable airmass is forced over the top of a mountain, it appears as cloud from below but got when level.
Freezing fog ?
Fog at a temperature below freezing, it will normally remain in liquid from, supercooled droplets.
Freezing fog droplets readily freeze on impact with cold surface.
How is diamond dust formed ?
Freezing/ice fog below -35ºC
Shallow Mist and fog ABVs
Shallow fog = MIFG
Shallow mist = MIBR
Visibility relationship with moisture ?
Visibility reduces where there is more moisture present, more moisture is close to the ground so worse vis
What is haze ?
Suspension of very small dust particles in the air but sufficiently numerous to give opalescent appearance
What Is smoke ?
A suspension of small particles produced by combustion
What is dust haze ?
Suspension of very small dust particles
Sand and dust storms wind requirements and vis impacts ?
Require strong winds above 15kts
Heavy dust storm vis is less than 200m
Moderate dust storm vis is 200-600m
When is RVR reported at most airports ?
When vis is less than 1500m
What is usually better RVR or Meteorological visibility ?
RVR
Distance of RVR is measured in ?
Meters or Feet depending on state
RVR is passed to pilots by ?
Datalink connection
Aeronautical broadcasts
(U) (N) (D) meanings in RVR setting ?
If significant upward(U) or downward(D) or neutral(N)
trend is viewed within 10 mins prior.
How is wind speed and direction normally measured ?
Cup anemometer and direction with a weather vane located 10m above the ground to avoid interference, reported in kts
Where is m/s used to report wind speed ?
Russia and china
Wind strengths ?
Calm - 1 Kts or less
Gale force - 34 - 47 kts
Storm force - 48 - 63 kts
Hurricane force ≥ 64 kts
What is a gust ?
Sudden increase of 10kts or more lasting less then 1 minute
What is a squall ?
Same as a gust but last longer than a minute
what is a lull ?
A sudden drop on wind speed
