Meteorology Flashcards
What is the chemical composition of the earth’s atmosphere?
78% nitrogen
21% oxygen
1% CO2, inert gases
Water vapour
Impurities
Describe the different atmospheric layers in terms of altitude and temperature
What are the vital characteristics of the atmopshere?
Mobility, capacity for expansion, capacity for compression
List the characteristics of the ICAO standard atmosphere
15°C at sea level
Lapse rate of 1.98 degrees / 1000’
29.92” mercury
No humidity
Describe the atmospheric mass below certain altutides
What are two sources of temperature change?
Diurnal and seasonal
Where is the atmosphere heated from?
from below
Describe air in terms of conductivity and ability to absorb radiation
Air is a very poor conductor yet will readily absorb radiated heat
What is advection?
The horizontal transport of an atmospheric variable (like heat) due to mass motion by the wind
How does temperature affect the density of air?
Air expands when it is cool, and compresses when it is warm
List and describe three different ways humidity can be quantified
Relative humidity - how much water vapor is in the air, compared to how much it could hold at that temperature
Absolute humidity - measure of water vapor in the air, regardless of temperature
Temperature/dewpoint spread - the number of degrees of difference between the air temperature and the dew point
What is the dew point?
the temperature (in degrees) to which air must be cooled in order to be saturated with water vapor already in the air
Describe the state changes of water
At what humidity do clouds form? How can a parcel of air reach this humidity?
100% humidity
A parcel of air can become 100% humid by adding water and decreasing temperature
What are the following lapse rates:
Environmental
Dry adiabatic
Saturated Adiabatic
Environmental: 1.98°C/1000’
Dry adiabatic: 3°C/1000’
Saturated adiabatic: 1.5°C/1000’
List the altitude ranges for high, medium, and low clouds
High: 20,000’ - 40,000’
Medium: 6500’ - 20,000’
Low: ground - 6500’
Categorize the following clouds into low, middle, and high clouds. Which ones have vertical development?
altocrumulus, altostratus, cirrocumulus, cirrostratus, stratus, stratocumulus, nimbostratus, cumulonimbus, cirrus, cumulus
What kind of cloud is this?
Cirrus
What kind of cloud is this?
Cirrostratus
What kind of cloud is this?
Cirrocumulus
What kind of cloud is this?
Altostratus
What kind of cloud is this?
Altocumulus
What kind of cloud is this?
Cumulus
What kind of cloud is this?
Cumulonimbus
What kind of cloud is this?
Lens clouds
What kind of cloud is this?
Cap cloud
Describe orographic lifting. Where do clouds and precipitation form?
Describe how convective lifting forms a cumulus cloud
Describe how fronts form clouds
Describe the turbulence lifting agent
Air blowing on uneven surfaces causes uneven heating, which allows vertical currents to occur. Air moves upward, expands, and cools
Describe the convergence lifting agent
Air piles up over a region of low pressure. Excess air is forced to rise, expand, and cool
Describe cloud cover in oktas
Clear - no clouds
Few - 2 oktas
Scattered - 3 to 4 oktas
Broken - 5 to 7 oktas
Overcast - 8 oktas
How much does atmospheric pressure decrease with every 1000’?
one inch of mercury
How much in error will your altimeter be if you park the plane overnight and the pressure drops .10” of mercury?
100”
Define the following:
Indicated altitude, true altitude, absolute altitude, pressure altitude, density altitude
Indicated altitude: what the dial says
True altitude: actual height above sea level
Absolute altitude: actual height above ground
Pressure altitude: what your altimeter would read if set to 29.92”
Density altitude: a theoretical concept
You are at 10 000’ and your altimeter setting is 29.62”. What is your pressure altitude?
10,300’
You are at the ocean side; atmospheric pressure is 29.92” and temperature is 10°C. What is your density altitude?
3600 feet
Describe how the Koch chart is used
What is Fennel’s law?
Wind in the northern hemisphere is always deflected to the right
What is the coriolis force?
The force which pulls an object to the right (clockwise) in the northern hemisphere and to the left (anticlockwise) in the southern hemisphere
An aircraft is flying in a straight line through space. Due to the coriolis effect, in which direction does the aircraft appear to be veering?
Right in the northern hemisphere or left in the southern hemisphere
What is surface friction?
Friction between the surfaceon the earth and the atmosphere that will slow the movement of air
What is the relationship between surface friction and air’s ability to flow into a low?
The greater the surface friction, the more directly air flows into a low
What is the relative windspeed around a high and a low?
Wind speed is higher around a high and lower around a low
What is Buy Ballot’s law?
Standing with your back to the wind, the low is on your left and the high is on your right
Explain the movement of air in high and low pressure areas in terms of convergence and divergence
Explain how the land and sea breeze cycles
Explain the difference between katabatic and anabatic winds
Explain the movement of wind as it comes in contact with a mountain range
When stable air goes over a ridge, is the flow laminant or turbulent?
Laminar if the ridge is smooth, turbulent if the ridge is sharp
Describe the formation of chinook winds. What is a key characteristic of chinook winds?
Large differences in temperature in a relatively small area
What is glacier wind?
A kind of katabatic wind that forms under extreme cooling conditions
Describe how and where jet streams form
Describe the four classifications of turbulence
Light - slight changes in altitude/attitude or slight bumpiness
Moderate - may feel a strain against safety belt and unsecured objects dislodged
Severe - large and abrupt changes in altitude/attitude and large variations in indicated air speed
Extreme - aircraft impossible to control
Define wind shear
A sudden change of horizontal or vertical wind velocity and/or direction
What are some causes of wind shear?
Frontal wind shear
Temperature inversions
Surface obstructions
Low level wind shear associated with Cb
What is the difference between gusts and squalls?
Main difference is the duration of the peak speed. Squalls last longer than gusts
What is the difference between veering and backing wind?
Veering wind: wind that turns clockwise with height
Backing wind: wind that turns counter clockwise with height
Describe the effect of altitude and temperature on stability
What is an inversion?
Normally, air temperature decreases with an increase in altitude. During an inversion, warmer air is held above cooler air
What are the air masses affecting Canada?
What does the weather inside an air mass depend on?
The stability of the air and the moisture content
Explain how an the properties of an air mass may be modified as it travels from its source region
What is the difference between a cold front and a warm front?
Cold front: cold air mass is advancing
Warm front: cold air mass is retreating
What are three large scale Canadian fronts?
Continental Arctic Front, Maritime Artctic Front, Maritime Polar Front
How does a frontal depression form?
The boundary between two air masses is distorted by warmer air bulging into the colder air, with the bulge moving along like a wave. The cold front usually moves across the surface faster than the warm front. The pressure near the top of the wave falls sharply and a depression forms
What is an occlusion?
The front formed by a cold front overtaking a warm front and lifting the warm air above the earth’s surface. An occlusion (or frontal occlusion) forms when an air mass is trapped between two colder air masses and is forced to higher and higher levels
What is a quasi-stationary front(QS)?
A front where neither air mass is advancing into the other at a speed exceeding 5 knots
Define frontogenesis and frontolysis
Frontogenesis: formation of a front
Frontolysis: dissipation of a front
Define TWOWAL
TROugh of Warm Air ALoft. Areas of intense lift and frontogenesis are commonly associated with TROWAL
Describe the different frontal shapes
Describe cold front weather
Wind veers
Temperature drops
Pressure increases
Usually active weather but then cleared out
Showery precipitation
Turbulence yet good visibility
What are the factors affecting frontal weather?
Speed of the front, slope of the front, temperature diference between the air masses, moisture content and stability of the air
Describe warm front weather
Wind veers with passage though not abruptly
Slow rise in temperature
Low ceilings or fog, steady precipitation
Visible weather depends on moisture content and stability of air
What are the dangers of winter warm fronts?
Warmer air rising over a layer of sub-freezing air may result in the formation of freezing rain. As you approach the front, the cloud layers build quickly and the clear air between layers rapidly disappears
Define the following types of precipitation:
DZ, FZDZ, RA, FZRA, GR, SN, SG, GS, PL, IC
DZ: very small water drops, appear to float
FZDZ: temps at or below freezing level, drizzle will freeze on impact with object
RA: large droplets of water
FZRA: super cooled water droplets
GR: hard outer layer of ice, white core
SN: water vapour sublimated into ice crystals then agglomerates together
SG: snow crystals with rime coating
GS: soft white ice, (hail with no hard ice)
PL: frozen raindrops
IC: tiny crystals, very low temp
Describe the cumulus stage of thunderstorm development
Describe the mature stage of thunderstorm development
Describe the dissipating stage of thunderstorm development
List the dangers of a thunderstorm
Downburst (micro and macroburst), tornados, wind shear, hail, heavy rain, turbulence, freezing rain, lighting
How should a pilot deal with a thunderstorm?
Avoid it
Go around it by 20nm, to the right if possible
Do not go through or under it
Do not fly between thunderstorms
Do not land near a thunderstorm
What should a pilot do if caught in a Cb?
Go straight through
Reduce airspeed
Don’t try to maintain altitude
Turn on cabin lights
Descend below freezing level
Describe the formation of ice pellets in terms of freezing levels
Describe how airfoil shape, aircraft speed, and droplet size affects the rate of catch
What are three types of icing?
Rime, clear, mixed
What are the four levels of icing?
Trace, light, moderate, severe
What should you do if icing forms during flight?
Turn around or climb/descend to warm air
What two factors can affect slant range and horizontal visibility?
Aircraft altitude and height of cloud base
Under what conditions does radiation fog form?
Still, cold night
Valleys
Clear skies
What causes advection fog? Where is most common?
Warm, moist air moves over cold surface. Most common in coastal regions
How long can advection fog last and why?
Can last for days over water since water does not heat up much in the daytime
How and where does steam fog form?
Forms over rivers and lakes in the morning when still, cold air moves over warm water
When does frontal fog form?
When precipitation falls from warm into cold air and saturates it
What is the visibility distance due to haze?
6sm or less
Define the following:
Flight visibility
Slant range visibility
Ground visibility
RVR
Flight visibility: air to air
Slant range visibility: air to ground
Ground visibility: as reported by an accredited observer
RVR: runway visual range
How often are the following prepared:
METAR, SPECI, TAF,FD
METAR, SPECI: 24 hours at international airports
TAF: 4 times daily at aerodromes, valid for 30 hours
FD: Twice daily (00Z, 12Z)
At what times are GFA charts issued daily? At what time are they valid?
Issued at 2330, 0530, 1130, 1730 UTC
Valid half hour after being issued
What is included in a GFA chart?
Clouds and weather, icing and turbulence, IFR outlook for an additional 12 hour period in the final clouds and weather chart
What are the 7 GFA areas in Canada?
What are the units of measurement in a GFA?
Speed: knots
Height: in 100 of feet
Horizontal distance: statute miles
Time: UTC
What criteria is IFR outlook based on?
AIRMET is a short term weather advisory intended for airborne aircraft under what conditions?
IMC conditions < 3 SM or 1000 AGL
Freezing precipitation
MDT icing
MDT turbulence
CB isolated not area or line
Valid upon receipt
Coded A1, B1
Decode the following AIRMET reports:
What hazardous weather phenomenon is SIGMET intended for?
Area or Lines CB
Hail
Severe thunderstorm
Icing
Mountain wave
Hurricanes
Sand dust storms
Volcanic ash
Low level shear wind
Decode the following SIGMET reports:
What are the following abbreviations:
Describe turbulence reporting duration
Occasional - less than 1/3 of the time
Intermittent - 1/3 to 2/3 of the time
Continuous - more than 2/3 of the time
Describe turbulence reporting (intensity, aircraft reaction, reaction inside aircraft)
The TAF is intended for flight operations within __ of the center of runway complex
5nm
Decode the section in red
TAF = Aerodrome Forecast
CYXE = Saskatoon
281139Z = 28th Day Issued at 1139Z
Decode the section in red
2812/2912 = Date Time Group
TAF Is Valid From the 28th at 1139Z until The 29th At 1200Z
Therefore this is a 24 Hour Forecast
Decode the section in red
24010G25KT = Wind Group
Wind Out Of 240 Degrees True at 10 Knots Gusting To 25 Knots
Decode the section in red
Wind Shear From Surface to 1100 AGL With The Wind At The Shear Height of 270 Degrees
True at 50 Knots
Prevailing visibility 3 SM in Light Snow, First Cloud Layer Broken at 1000 Feet And Overcast at 4000 feet. (First Broken Layer Is the Ceiling = 1000 Feet)
Decode the section in red
TEMPO = Temporary Change is a Transitory Change Group, the following conditions apply to a TEMPO Change: Expected to last less than 1 hour and will not recur for more than 1.2 the period
The TEMPO period above is expected to start on The 28th at 1800Z and recur until the 29th at 0100Z
During the TEMPO period the visibility will decrease to 1 ½ SM in light snow and Blowing Snow With A Broken Cloud Layer (Ceiling) 800 feet
Decode the section in red
During the PROB30 (probability group) period, from the 28th at 2000Z until the 28th at 2200Z the visibility will decrease to 1/2SM in snow with a vertical visibility of 500 feet AGL
Decode the section in red
Following the FM which will occur on the 29th day at 0130Z the wind will be 280 degrees True at 10Knots, visibility 5SM in –SN with a broken cloud layer at 2000 feet AGL
Decode the section in red
The becoming period commences on the 29th day at 0600Z to the 29th day at 0800Z; during this time period the weather will change to: wind calm, visibility greater than 6SM, sky clear. The next forecast will be issued on the 28th day by 1800Z
In a FD, what is the code group if the wind speed is less than 5 knots?
9900
Decode the following FD report
What are the various weather codes for descriptors, precipitation, obscuration, and other?
Describe the condition, explanation, and parameters of sky conditions in METAR
Describe the ceiling, visibility, CB, preciptiation, and wind conditions conditions that could trigger a SPECI report
When are SPECI reports published?
When one of the following elements changes between transmission times:
Wind shift direction
Wind velocity doubles or exceeds 30 knots
Temp increases by 5°C when previous was 20°C+; or decreases to reported value of 2°C or lower
Layer aloft <1000 AGL or below highest minimum IFR altitude
