Meteorology Flashcards
What is the rough Composition of the Atmosphere?
79% Nitrogen
21% Oxygen
1% Argon
0.05% Other Gases
What is the Temperature Trends in the different divisions of the Atmosphere?
Troposphere - Down
Stratosphere - Up
Mesosphere - Down
Thermosphere - Up
Where does most weather in the atmosphere occur?
Troposphere
What is the height of the Troposphere over the poles vs the equator?
28,000’ over the poles
54,000’ over the equator
What is the ICAO Standard Atmosphere in terms of Mean Sea Level Pressure, Mean Sea Level Temperature, & Lapse Rate?
29.92” Hg
15°C
1.98°C/1000’
What are the 3 Principle Properties of the Atmosphere?
Expansion
Compression
Mobility
As moisture goes from Ice to Water is heat absorbed or released?
Absorbed
What is the Definition of Dewpoint?
Temperature, at a given pressure, to which air must be cooled to cause saturation
What is the Definition of Relative Humidity?
Compares amount of water vapour in the air to amount if could hold if it were saturated, expressed as a percentage
What is denser Cold Air or Warm Air?
Cold Air
What kind of radiation is Terrestrial Radiation?
Infrared
What are the 6 Atmospheric Heating Processes?
- Conduction - Heating through contact
- Convection - Warm air is less dense and tends to rise
- Turbulent Mixing - Friction causes eddies to form as air moves over surfaces
Advection - Horizontal movement of air masses
Compression - Descending air increasing in pressure, in turn increasing in temp
Release of Latent Heat - Changing state down an energy level
Which way does air flow around a High Pressure Centre?
Clockwise
Which way does air flow around a Low Pressure Centre?
Counter-Clockwise
Does air aloft converge or diverge around a High Pressure System?
Converge
What are the 6 Adiabatic Atmospheric Cooling Processes?
- Expansion Cooling - Rising air expands, cools according to lapse rate
- Orographic & Upslope Lift - Result of air flowing over features that cause air to rise
- Frontal Lift - Occurs when warm air forced up along a frontal surface
- Mechanical Turbulence - Same mechanism as warming
- Convection - Rising air cools according to lapse rate
- Convergence - Air at centre of low rises, causes cooling
What is the Dry Adiabatic Lapse Rate and the Saturated Adiabatic Lapse Rate?
DALR: 3°/1000’ (< 100% relative humidity)
SALR: 1.5°/1000’ (100% relative humidity)
What displaces what - cold air or warm air?
Cold Air displaces Warm Air
What are 2 other Cooling Processes?
- Radiation Cooling - Surface temps below air temps, surface emits heat into colder upper atmosphere
- Non-Expansional Cooling - Advection - air moving older colder surface. Evaporation - heat absorbed
Describe Stable, Unstable and Neutral Air?
Stable - Will return to original state
Unstable - Will move further way from original state
Neutral - Will remain at disturbed state
What determines Atmospheric Stability?
Temperature Difference between rising air parcel and surrounding air
What is an Isothermal Layer?
Temperature doesn’t change with change in altitude, very stable
What is an Inversion?
Temperature increases with height, extremely stable
What kind kind of Cloud is formed in Stable vs Unstable Air?
Layered (Stratiform) - Stable
Heaped (Cumuliform) - Unstable
How do you calculate Cloud Base?
(Spread/2.5)*1000’ = Height AGL
How do you calculate Freezing Level?
(Dewpoint/2.5)*1000’ = Height Above Cloud Base
What height separates the different Cloud Classifications?
High - >20,000’ ASL
Middle - 6,500 - 20,000’ ASL
Low - < 6,500’ ASL
What are the prefixes associated with the different heights of clouds?
Cirro - High
Alto - Middle
Strato - Low
What are thunderstorm clouds called?
Cumulonimbus (CB)
When does a thunderstorm reach its mature stage?
When precipitation hits the ground
What is Fog?
Stratus cloud at ground level
What are 3 Requirements for Fog to form?
- High Relative Humidity
- Abundance of Condensation Nuclei
- Mixing Action
What are the 5 different types of Fog?
- Radiation Fog - Cool, clear nights with high relative humidity - found in low lying areas
- Advection Fog - Coastal areas when warm, moist air moves over a cold surface, doesn’t burn off needs change in wind direction
- Steam Fog - When cold air moves over warm water surfaces - found over rivers and small lakes, evaporation saturates air
- Frontal Fog - During passage of warm front
- Ice Fog - Very cold days, very small ice crystals, associated with hoar frost
What is the difference between Fog and Mist?
Visibility
Fog < 1/2 SM
Mist > 1/2 SM
What is Pressure?
Weight of an imaginary column of air
What are 2 forms of Pressure Measurement?
- Mercury Barometer
- Aneroid Barometer
What is Station Pressure?
Weight of column of air lying above an airport
What is Mean Sea Level Pressure?
Station Pressure + Weight of column of air between ground and sea level - using average temp from last 12 hrs
What is Altimeter Setting?
Station Pressure + Weight of column of air between ground and sea level - calculated using ICAO standard atmosphere
What is a Low Pressure System called?
Cyclone
What is a High Pressure System called?
Anti-Cyclone
What is an Isobar?
Lines joining places of equal pressure
What is Buy-Ballot’s Law?
If you stand with your back to the wind in the Northern Hemisphere, the low pressure will be on your left
What determines the intensity of a Pressure Gradient Force (PGF)?
Spacing between isobars
What is the Coriolis Effect?
The atmosphere doesn’t rotate at the same speed as the surface so air will rotate
What is the Friction Effect?
Topographical features effect movement of air, reducing wind speeds at low level
What is the difference between Veer and Back?
Veer - Clockwise change in wind direction (during climbs - veers and increases - less surface friction)
Back - Counter-clockwise change in wind direction (descents - backs and decreases)
What is the difference between Land and Sea Breeze?
Sea Breeze - During day - land warms up more quickly than water (sea -> land)
Land Breeze - At night - land cools more quickly than water (land -> sea)
What is the difference between Anabatic and Katabatic Wind?
Anabatic - Occurs during day, sun warms side of mountain, air less dense rises up mountain
Katabatic - Occurs at night, air cools, air becomes more dense and falls down mountain
What is Wind Shear?
Sudden change in wind speed/direction
What is an Air Mass?
Large section of troposphere with uniform properties of temperature & moisture in the horizontal
What Moisture Content can an Air Mass have and what Temperature Content can an Air Mass have?
Moisture: Maritime or Continental
Temperature: Arctic, Polar, Tropical
When a Cold Front overtakes a Warm Front what determines the weather?
Moisture content & stability of warm air mass
What are common characteristics of cold front passage?
Decrease in temp, wind shift (veer & increase), pressure increases followed by clearing skies
When a Warm Front is overtakes a Cold Front what determines the weather?
Moisture content & stability of warm air mass
What is an Upper Front?
Narrow transition zone between two air masses where no temp difference at surface - front doesn’t come all the way down
What are thunderstorms called when formed by a steep cold front?
Frontal Thunderstorms - Squall Line
What are thunderstorms called when formed by daytime heating/unstable air mass?
Air Mass Thunderstorms - not as organized
What is the difference between the Cumulus and Dissipating stage of a Thunderstorm?
Cumulus - Mainly updrafts
Dissipating - Mainly downdrafts
What are the 2 requirements for Icing?
- Visible moisture
- Below freezing temps
What is Clear, Rime and Mixed Icing?
Clear - Slow Freezing, Smooth
Rime - Rapid Freezing, Bumpy
Mixed - Combination
How does icing effect lift and drag?
Decreases Lift by 30%
Increases Drag by 40%
What are the different types of Icing in Layer, Vertical, and Towering Cumulus Cloud?
Layer - Freezing Level - -5°C (Rime)
Vertical - Freezing Level - -15°C (Clear)
Towering Cumulus - Up to -25°C
What is Frost?
Sublimation of water vapour directly onto A/C
What are the 2 requirements for for Frost?
- Cold, clear night
- Rapid descent in below freezing temp (hoar frost)
What is Turbulence?
Unpredictable & irregular motion of air
How is the wind reported in a METAR?
2 min mean wind direction and speed
Gusts need to be 5 kts or more than steady speed
Variations - preceding 10 mins varies between 60°-180°, and speed greater than 3kts
What does MI, BC, SG, GR, GS, FU, +FC mean in a METAR?
Shallow
Patches
Snow Grains
Hail
Snow Pellets
Smoke
Tornado
When in wind shear reported in a METAR?
Up to 1600’ when pilot reported
What altitude does a GFA go up to?
24,000’
Does each new set of GFA charts replace the preceding ones?
Yes
What is altitude measured in in a GFA?
Hundreds of Feet ASL
What are the requirements to be considered IFR, MVFR, and VFR?
IFR: < 1000’ AGL or < 3 SM
MVFR: 1000’ - 3000’ AGL or 3 - 5 SM
VFR: > 3000’ AGL and > 5 SM
What interval are isobars shown in?
4 mb intervals
When is motion shown for synoptic features?
When it moving greater than 5 kts
When are scalloped borders used to enclose cloud cover?
When it is BKN or OVC
What does a dashed green line in an area, and a solid green line in an area represent?
Dashed Green Line - Showery Precipitation
Solid Green Line - Continuous Precipitation
What are the abbreviations used for Convective Cloud and Showers?
ISOL - < 25%
SCT - 25 - 50%
NMRS - > 50%
What are the abbreviations used for Non-Convective Cloud and Showers?
LCL - < 25%
PTCHY - 25 - 50%
XTNSV - > 50%
When is speed and direction of surface winds shown on a GFA?
When there is a sustained speed equal to or greater than 20 kts
What interval are freezing level lines indicated at on a GFA?
2,500’ Intervals
What area are TAFs applicable in?
5 NM surrounding aerodrome
What is the maximum number of significant weather groups that can be reported at one time in a TAF?
3
What does FM represent in a TAF?
Permanent change group (rapid), all conditions before are superseded
What does BECMG represent in a TAF?
Permanent change group (gradual), occurs in 2 or less weather elements, if deteriorating apply at beginning, if improving apply at end
What does TEMPO represent in a TAF?
Transitory change group, temporary fluctuation during specific period
When is the 3000’ level of an FD eliminated?
When ground elevation >1,500’
What is the process for reporting FDs when the wind speed is from 100-199 kts?
Add 50 to direction
Subtract 100 from speed
What is the process for reporting FDs when the wind speed is above 199 kts?
Will be reported as 99
What is a PIREP?
Observations of actual conditions taken by pilots during flight
What is a SIGMET?
Highlights significant weather - broadcast on 126.7 in affected areas
What is an AIRMET?
Highlights conditions that have changed from a GFA, but don’t require a SIGMET
When is a Surface Analysis Map issued?
4 times a day at 6 hour intervals
How far up does a Surface Analysis Map represent the weather?
3000’ AGL
When is an Upper Air Analysis issued?
Twice a day 0000z and 1200z
What altitude does the 750 mb chart of an Upper Air Analysis represent?
10,000’
What is the difference between Satellite and Radar?
Satellite shows cloud cover
Radar shows precipitation or cloud tops
