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134 Cards in this Set
- Front
- Back
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What effect does water vapour in the atmosphere have on air density?
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Lowers density
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What is the chemical composition of the atmosphere?
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Nitrogen (N) - 78%
Oxygen (O) - 21% Other - 1% |
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Describe the troposphere?
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Temperature reduces with altitude
Contains nearly all water vapour in the atmosphere Most weather occurs here |
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Describe the stratosphere?
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Temperature constant, or increases slightly
Ozone occurs here when UVC causes bonding of Oxygen molecules |
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What is the boundary between the troposphere and stratosphere called?
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Tropopause
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ISA - Temperature?
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+15 degrees at AMSL
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ISA - QNH?
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1013.25 HPa
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ISA - Air Density?
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1.225 kg/m3
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ISA - Environmental lapse rate
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1.98 (2) degrees Celsius per 1,000 ft until 36,090 ft where it remains at -56.5 degrees Celsius
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ISA - Pressure lapse rate
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1 HPa per 30 ft
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Under ISA what assumption is made about the air?
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It is dry
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What are the transition phases between Ice and Water Vapour?
(indicate whether latent heat or cooling occurs) |
Ice to Vapour - Sublimation (cool)
Vapour to Ice - Deposition (heat) |
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What are the transition phases between Water Vapour and Water?
(indicate whether latent heating or cooling occurs) |
Vapour to Water - Condensation (heat)
Water to Vapour - Evaporation (cool) |
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What are the transition phases between Water and Ice?
(indicate whether latent heating or cooling occurs) |
Water to Ice - Freezing (heat)
Ice to Water - Melting (cool) |
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When a parcel of air can no longer hold anymore water, what does it become?
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Saturated
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When air of a constant pressure is cooled at what point will it become saturated?
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Dewpoint
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What process describes a temperature change which occurs as a result of pressure change, even though heat energy is neither added or removed?
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Adiabatic Process
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Clouds are formed when moist air rises. Name 4 ways that this can occur?
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1. Convection
2. Orographic lifting (mountains) 3. Turbulence & Mixing 4. Widespread ascension of air mass |
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Name the 3 cloud forms?
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Stratiform
Cumuliform Cirroform |
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What are the heights for Low, Medium & High cloud?
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Low - 5000 ft
Med - 5000 to 15000 ft High - above 15000 ft |
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Where are cloud levels measured?
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The base of the cloud
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Describe high level clouds, include type and code?
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Composed entirely of ice crystals
CI - Cirrus CS - Cirrostratus CC - Cirrocumulus |
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Describe medium level clouds, include type & code?
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Greyish or bluish
Composed predominantly of supercooled water vapour AS - Altostratus AC - Altocumulus NS - Nimbostratus Lenticular (form of AS) |
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Describe low level clouds, include type & code?
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Composed of water, supercooled water or ice
ST - Stratus SC - Stratocumulus CU - Cumulus CB - Cumulonimbus TCU - Towering Cumulus Mammatus |
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List the 7 precipitation types?
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1. Rain / Showers (liquid water drops)
2. Drizzle (fine water droplets) 3. Freezing Rain / Drizzle (freeze on contact with cold surfaces) 4. Snow (ice crystals) 5. Hail (ice) 6. Dew / Frost (deposition of moisture on a surface) 7. Virga (precipitation falling) |
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How is precipitation intensity displayed?
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Light (-)
Moderate (no modifier) Heavy (+) |
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Which type of pressure system has cyclonic airflow and divergence?
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Low pressure
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Which type of pressure system has anti-cyclonic airflow and convergence?
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High pressure
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What is the Dry Adiabatic Lapse Rate (DALR)?
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3 degrees Celsius per 1000 ft
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What is the Saturated Adiabatic Lapse Rate (SALR)?
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1.5 degrees Celsius per 1000 ft
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Why is the SALR lower than the DALR?
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The latent heat generated by the condensation as clouds are formed
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How is Environmental Lapse Rate (ELR) measured?
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Radiosonde attached to a weather balloon
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Describe the air when ELR > DALR?
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Unstable in all circumstances
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Describe the air when ELR = DALR?
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Conditional Instability
Neutral if unsaturated, Unstable if saturated |
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Describe the air when DALR > ELR >= SALR?
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Conditional Instability
Stable if unsaturated, Unstable if saturated |
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Describe the air when SALR > ELR or when ELR is negative?
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Stable in all circumstances
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What clouds form in unstable air?
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CU, CB
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What clouds form in stable air?
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AS, ST, NS
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Which clouds are indicative of conditional instability?
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AC, SC
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At what percentage of saturation does dry air become saturated air?
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100%
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What are the 3 types of cloud dissipation?
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1. Subsidence
2. Precipitation 3. Mixing |
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What are the 4 types of heat transfer?
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1. Conduction
2. Convection 3. Radiation 4. Advection |
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Typically, what are the coolest and warmest times of day?
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Coolest - 1 hour after sunrise
Warmest - approx 15:30 |
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Describe wind?
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Horizontal movement of air
Caused by pressure differences Moves from high pressure to low pressure |
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How is wind measured?
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Anemometer for speed
Wind vane for direction |
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What is the general rule regarding wind direction heading?
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Spoken - Magnetic heading (ATIS etc)
Written - True heading |
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What words are used to describe the wind changing clockwise and anti-clockwise?
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CW - veering
ACW - backing |
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A sudden increase in average windspeed by at least 16 knots to at least 22 knots for at least 1 minute is known as what?
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Squall
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What is term to describe a small duration speed increase in the wind from average?
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Gust
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Define the term lull?
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A decrease in windspeed from the mean
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What affects the direction of the wind?
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Pressure gradient force acting at right angles from the centre of the pressure system
Coriolis Force |
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"That in the southern hemisphere, if you stand with your back to the wind, the area of low pressure will be to your right"
Whose law is this? |
Buys Ballot's Law
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Describe a Katabatic Wind?
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Occurs at night
Cold air descends a mountain slope Can produce strong winds near river mouths and in valleys Can cause valley fog to occur |
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Describe an Anabatic Wind?
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Occurs during the day
Warm air rises up a mountain slope More likely on westward facing slopes in summer May combine with sea breeze and increase wind |
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Describe the Fohn Wind?
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Air travelling over a mountain range cools and forms clouds
Dry warm air occurs on the lower slopes of the other side of the mountains |
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Describe low level jetstreams?
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Occur within friction layer (0 - 2000 ft)
Convergence of the flow due to mountain barrier Increase in windspeed causes Coriolis deflection |
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Weather descriptor - BC
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Patches
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Weather descriptor - BL
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Blowing
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Weather descriptor - DR
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Drifting
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Weather descriptor - FZ
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Freezing
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Weather descriptor - MI
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Shallow
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Weather descriptor - SH
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Showers
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Weather descriptor - TS
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Thunderstorms
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Weather descriptor - PR
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Aerodrome partially covered (FG only)
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Weather phenomena - BR
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Mist
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Weather phenomena - DU
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Dust
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Weather phenomena - DS
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Dust Storm
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Weather phenomena - DZ
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Drizzle
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Weather phenomena - FC
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Funnel cloud
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Weather phenomena - FG
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Fog
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Weather phenomena - FU
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Smoke
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Weather phenomena - GR
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Hail
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Weather phenomena - GS
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Small hail pellets
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Weather phenomena - HZ
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Haze
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Weather phenomena - IC
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Ice crystals
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Weather phenomena - PL
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Ice pellets
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Weather phenomena - PO
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Dust devils
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Weather phenomena - RA
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Rain
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Weather phenomena - SA
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Sand
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Weather phenomena - SG
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Snow grains
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Weather phenomena - SN
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Snow
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Weather phenomena - SQ
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Squalls
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Weather phenomena - SS
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Sand storm
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Weather phenomena - UP
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Unknown precipitation type
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Weather phenomena - VA
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Volcanic ash
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Name the 6 types of inversion?
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1. Surface (radiation) inversions
2. Turbulence inversions 3. Subsidence inversions 4. Frontal inversions 5. Sea-breeze inversions 6. Tropopause inversions |
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Name the 5 causes of turbulence?
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1. Inversion
2. Mechanical 3. Thermal 4. Frontal 5. Mountain waves |
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Describe windshear?
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Change in wind direction or speed over a small distance
Can be vertical or horizontal The stronger the change or shorter the distance, the stronger the windshear |
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Describe wake turbulence?
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Caused by wing generating lift
Not a meteorological phenomena Light crosswind (< 5kts) may hold rotor on the rwy |
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A warm front is steeper than a cold front. TRUE or FALSE?
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FALSE
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A ________ front is depicted by a line with barbs?
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Cold
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A ________ front is depicted by a line with hemispheres?
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Warm
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Cold fronts travel faster than warm fronts, if they combine the result is known as?
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Occlusion / Occluded front
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A front that does not move, or moves along its length
Usually has high pressure systems on either side Not likely to have significant weather due to little interaction What is this? |
Quasi-stationary front
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On a weather chart, what is the difference between a developing front and a decaying front?
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Both are broken lines, developing front line is inter-spaced with squares, whereas a decaying front is inter-spaced with plus signs
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What are the 3 phases of a thunderstorm?
What defines each stage? |
1. Cumulus / Developing stage (strong up-draughts)
2. Mature (commencement of down draughts) 3. Dissipating (only down-draughts) |
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What is the typical lifespan of a thunderstorm?
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30-60 minutes
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What additional descriptors can be applied to thunderstorms?
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ISOL - isolated
OCNL - occasional FREQ - frequent EMBD - embedded |
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What are the conditions when icing can occur?
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Visible moisture
Temperature +10 to -40 degrees Celsius Airframe must be < 0 degrees Celsius |
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Snow and ice crystals in-flight do not normally adhere to an aircraft. TRUE or FALSE?
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TRUE
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What are the worst conditions for icing?
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Near the freezing level
Heavily stratified clouds ST, NS CU or CB clouds with strong up-draughts In freezing rain beneath NS |
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What are the 4 types of airframe ice?
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1. Clear
2. Rime 3. Mixed clear and rime 4. Frost |
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What is the most dangerous form of icing? Why?
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Clear ice
Hard to see Insidious Heavy Smooth Can flow back over the wing |
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In what part of CU is icing the most likely to occur?
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Where the temperature is between 0 to -15 degrees Celsius
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What is the difference between temperature and dewpoint known as?
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Dewpoint depression
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What is the definition of visibility?
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In meteorological observations and forecasts visibility is the greatest distance that a person with normal sight can identify objects
Visibility is a measure of how transparent the atmosphere is to the human eye |
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How is visibility measured?
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In metres horizontally, in feet vertically
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What does a transmissometer measure?
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Runway Visual Range (RVR)
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Humidity is higher in fog than it is in mist. TRUE or FALSE
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TRUE
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What does a hydrometeor measure?
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Fog, Mist, Spray, Haze (moisture)
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What does a lithometor measure?
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Sand, Dust, Pollen / Bacteria, Smoke
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What conditions need to occur for fog?
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Temperature equals dewpoint and light winds
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What are the 4 categories of effects that volcanic ash has on aircraft?
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1. Abrasion
2. Obstruction 3. Electrical interference 4. Chemical |
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What met products can contain information regarding volcanic ash?
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VAA (Volcanic Ash Advisory), SIGMET, SIGWX, METAR / SPECI, TAF, TTF, ARFOR, Aerodrome warning, Volcanic Activity Report, Special Air Report
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What aviation colour codes are there to indicate volcanic activity?
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Green Yellow Orange Red
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What was the name of the volcano in Iceland that disrupted air traffic in Europe during 2010?
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Eyjafjallajokull - This is sure to come up in the exam...
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What are the 4 ingredients for tropical cyclone formation?
Where do they most typically occur? |
1. Warm sea-surface temperatures, greater than 27 degrees Celsius
2. Deep moisture at low levels 3. Light winds throughout the troposphere 4. Need convergence as a trigger Occur typically in the ITCZ (Inter Tropical Convergence Zone) |
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What are the 3 cells that make up general circulation?
Which way do they circulate? |
Polar cell - air moves down over the pole
Hadley cell - air moves up over the equator Ferrule cell - located between Polar and Hadley. air moves in the same direction as its neighbour |
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What are the 4 stages of a tropical cyclone?
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1. Formative stage
2. Immature stage 3. Mature stage 4. Decaying stage |
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Where do the strongest winds occur in a tropical cyclone?
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The forward left quadrant
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What factors can inhibit cyclone formation?
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Cool sea surface temperatures
Drier air at low levels Strong trade wind inversion Strong upper level winds |
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What is the difference between a cyclone and a hurricane?
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Nada, Zip, Bugger-all, etc, etc
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Which MET report provides the following?
Forecast for low-level route operations Met situation, winds and temps Areas of turbulence Critical localities |
ARFOR
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How are the plots of soundings from radiosondes displayed?
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On aerological diagrams
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Area QNH must not differ from an adjoining area QNH by more than?
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5 HPa
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Abbreviations - NCD
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No cloud detected
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Abbreviations - NSC
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Nil significant cloud
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Abbreviations - NSW
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Nil significant weather
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To what weather phenomena can intensity (+/-) be appended?
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DU, DS, DZ, GR, GS, RA, SA, SG, SN, SS
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The change in conditions indicated by an INTER will last longer than a change in conditions indicated by an TEMPO? TRUE or FALSE
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FALSE
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What are the conditions for reporting RVR on an ATIS?
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May report when RVR < 1500m
Must report when RVR < 800m |
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What weather phenomena will require the issue of a SIGMET?
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Thunderstorms (OBSC, EMBD, FRQ, SQL)
Tropical cyclones Hail Severe turbulence Severe icing Severe mountain waves Widespread sandstorms / duststorms Volcanic ash cloud Radioactive cloud |
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What are the 4 categories of windshear intensity?
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Light - minor excursions...
Medium - significant effect... Strong - control difficulty... Severe - hazardous effects... |
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What is a VOLMET?
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5 minute broadcast on HF at pre-determined times
Contains METAR / SPECI or TTF Advice regarding availability of SIGMET |
