Meteorology Flashcards
The primary source of all weather is the
Sun
Areas of . . . . . pressure flow towards areas of . . . . . pressure. This movement of flowing air is known as . . . . .
High, low, wind
Wind does not flow directly towards a low pressure system because of the
Coriolis force
The primary cause of all changes in Earth’s weather is
a.changes in air pressure over the surface.
b.variation of solar energy at the surface.
c.movement of air masses from moist areas to dry areas.
d.none of the above.
B
What is the atmosphere made up of?
78% nitrogen
21% oxygen
1% other gas, argon, water vapour and carbon dioxide
What are the major layers of the atmosphere?
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere
Average height of troposphere?
Approximate height at poles and equator?
36,000 feet,
25,000 feet at poles
54,000 feet at equator
What is ISA
15 c
29.92 in Hg
1013.25 mb
Standard atmosphere at sea level
What does ISA +6 mean?
Temperature is 6 degrees warmer than standard temp
The ozone layer is located in the
Stratosphere
During cruise at FL200 the OAT is -35°C. The air mass therefore has an average temperature which is
a.5°C warmer than ISA.
b.20°C colder than ISA.
c.5°C colder than ISA.
d.10°C colder than ISA.
D
Standard temperature is 15°C at sea level.
Therefore with a lapse rate of approx 2°C /1 000 feet
20 x 2° = 40°
15° - 40° = -25°
Standard temp at FL200 would be -25°
The feature that is associated with the Tropopause is
a.the absolute upper limit of cloud formation.
b.the abrupt change of lapse rate.
c.the absence of wind and turbulence.
d.none of the above.
B
What is boyle’s law?
At a given pressure, warm air will take up a greater volume than cold air
How far apart are standard isobars?
4 hectopascals
How often are altimeter setting measurements taken?
What about msl measurements?
1 hour
12 hours
Accuracy of altimeter setting varies with ___ from the station, especially if there is a strong ____ ____
Distance
Pressure gradient
From hot to cold, you are being bold. What does this mean?
When flying from higher temperature to colder than standard temperature, the aircraft will be lower than indicated, causing possible terrain impact amongst other hazards
The steeper the pressure gradient the ____ the wind.
Stronger
High pressure areas are areas where the air is ____ (sinking/rising)
Is the temp higher or lower?
What is the general air movement?
Another name for high pressure system?
Type of weather associated with a high?
Does it move fast or slow
Sinking
Lower
Clockwise, outwards (diverging, descending)
Anticyclone
Fair weather, fewer clouds, good visibility, light winds, can remain for days and produce early morning fog
Typically slower moving systems
Low pressure areas the air is ____ (rising/sinking)
Temp high or low?
General air movement?
Another name for low pressure system?
Type of weather expected with low?
Does it move fast or slow
Rising
High
Counterclockwise and inward (converging and ascending)
Cyclone
Cloudy weather, precipitation. Expect thunderstorms, rain, hail, snow, if there is a steep pressure gradient expect strong winds
Typically fast moving, summer 500 miles a day, winter 700 miles
What is a trough?
What does it bring with it?
An elongated area of low pressure
Usually brings clouds, showers and wind shift
What is a ridge?
What does it bring?
Area of elongated high pressure with low pressure on each side.
Usually brings fair weather
What is a col?
What usually occurs within the area for weather?
Neutral region between two highs and two lows.
Usually unsettled weather, fog in winter and showers/thunderstorms in summer
According to standard atmosphere the station pressure as measured by two stations in the same region but at different altitudes will be
a. the same.
b. higher as measured by the lower station.
c. higher as measured by the higher station.
d. 29.92 in Hg.
B
Flying over mountains with a temperature of 24ºC and the altimeter setting of 30.22 in Hg received from a nearby airfield. The terrain below the aircraft rises to 4 000 feet ASL, the true altitude when reaching 6 000 feet ASL will be
a.6 075 feet.
b.5 925 feet.
c.6 145 feet.
d.5 784 feet.
C
Pressure Altitude = 5 700 feet (29.92 - 30.22 = - 0.3 x 1 000 = - 300 + 6 000 feet =)
Temperature is 24ºC
Using the E6B correct altitude of 2 000 feet AGL (= IALT 6 000 - Elev 4 000), will get 2 145 feet and add to 4 000 feet ASL
What are the two main ways the atmosphere is heated?
Radiation, conduction
What is radiation heating?
The suns rays absorb into the earth and re-radiated creating infrared (terrestrial) radiation (longer wavelengths)
Water Vapor and carbon dioxide are very effective at absorption and heating surrounding atmosphere. remember atmosphere is always heated from below
What is conduction heating?
The layers of air that are in immediate contact with the surface are conduction heated. Air is a poor conductor thus conduction is only responsible for heating the layers closest to the surface
What is a diurnal variation?
What does the wind do in the day?
In the night?
As the sun rises vertical currents begin, and causes mixing between upper and lower air masses.
Winds usually increase and veer and become gusty.
At night winds decrease and back
What is a seasonal variation in regards to heating?
It has to do with the axial tilt of the earth, a shallow lighting angle gives less heating (winter) and more direct lighting angle gives more heating (summer)
What is convection?
Air near a warm surface is heated and due to its buoyancy it rises.
Summer afternoons produce the greatest convection.
Also forms in winter when cold air moves over open water.
What is advection?
Is a process that moves heat laterally. Cold air is carried to a warm area and heated from below
What is latent heat?
Heat energy that is hidden in water vapour. Water takes away heat from surrounding area, rises, condenses, which will release heat that it absorbed near surface and heat the surrounding air
What is compression heat?
When a parcel of air sinks or subsides it is compressed by increasing air pressure of lower atmosphere, resulting in air warming up.
What is radiation cooling?
When sun sets the surface continues to radiate heat, causing ground to eventually cool and cool the surrounding air as well. Usually only affects the first few thousand feet altitude.
What is advection cooling?
Carries air from a warm area to over a cooler area.
What are the adiabatic cooling rates?
Same as lapse rate, 3 degrees dry 1.5 wet 2 standard
What is a temperature inversion?
Temp of atmosphere increases with an increase in altitude. Air is stable.
With a strong inversion you can expect wind shear
What is an isotherm?
Line of area with same temperature
What is melting?
When a solid become a liquid
What is evaporation?
When a liquid becomes a gas
What is condensation?
When a gas becomes a liquid
What is freezing?
When a liquid becomes a solid
What is deposition?
When a gas becomes a solid
What is sublimation?
When a solid becomes a gas
What is the dew point?
The temperature at a given pressure that the air must be cooled to in order to become 100% saturated.
What is relative humidity?
the amount of water vapour present in the air compared to the amount which the air could hold when saturated, given as a percentage.
Heating ____ the relative humidity.
Cooling ____ the relative humidity.
(Increases/decreases)
Heating decreases
Cooling increases
the amount of water vapour that an air mass can hold depends entirely upon its _____.
Temperature
The Environmental Lapse Rate is a theoretical measured change in temperature with increased height above the ground.
True or false?
False, it is the actual measured change
What is the standard adiabatic lapse rate?
1.98 degree change per 1,000 feet of elevation
What is the dry adiabatic lapse rate?
3 degrees per 1,000 feet
What is the saturated adiabatic lapse rate?
1.5 degrees per 1,000 feet
What is precipitation?
when the water droplets grow sufficiently in size and weight to overcome lifting agents such as fronts and updrafts.
Droplet size is often related to the strength of an updraft.
True or false?
True
What are the three main types of rainfall?
• Convergent and Cyclonic Rainfall
• Orographic or Relief Rainfall
• Convectional Rainfall
Where is Convergent and Cyclonic Rainfall found?
Warm front causes what type of rain?
Cold front causes what type of rain?
This form of rain is caused by the convergence of two air masses (fronts).
• Warm front rainfall tends to be steady.
• Cold front rainfall tends to be showery.
How is Orographic or Relief Rainfall formed?
• When warm moist air is forced to rise over an obstacle (mountain range) it cools.
• This cooling allows condensation to take place forming clouds and precipitation.
Rainfall totals will increase where mountains are parallel to the coast.
True or false?
True
What is a rain shadow?
an area of reduced rainfall on the leeward side of the mountains.
How is Convectional Rainfall formed?
When the ground surface is locally heated and the adjacent air expands and rises, convectional rainfall occurs. Ie cumulonimbus
How does snow form? This change of state is known as _____.
Snow forms under the same conditions as rain except that the dew point temperature is below freezing so the vapour goes straight to a solid
Deposition
When freezing rain freezes in the air it becomes?
Ice pellets
How do ice pellets form?
Occurs when there is a shallow layer aloft with above-freezing (2 to 4°C) temperatures and with a deep layer of below-freezing air based at the surface.
• As snow falls into the shallow warm layer, the snowflakes partially melt.
• If the depth of the warm air is great enough, then this can also melt further and turn into freezing rain.
• If there is a second layer of cold air below the warm air, (near the surface) then the partially melted snow or freezing rain can refreeze into ice pellets.
What type of precipitation is above ice pellets?
Freezing rain
How does freezing rain form?
Where is it commonly found?
What temperatures can large droplets freeze at?
Begins as rain and/or snow, but becomes all rain in the warm layer.
• The rain falls back into below-freezing air, but since the depth is shallow, the rain does not have time to freeze into ice pellets.
• This occurs when there is a deep layer aloft with above-freezing temperatures and with a shallow layer of below-freezing air at the surface.
- commonly found along a warm front, where a warm air mass overruns a cold air mass.
- large droplets can freeze at temps slightly below zero
-very tiny droplets can remain liquid up to -40c
Hail is ice which is larger than __ mm in diameter.
5mm
How does dew or frost occur?
The ground cools the air and this causes the moisture present to condense.
> If the dew point is above freezing then dew will form.
> If the dew point is below freezing then frost will form through deposition.
• Dew or frost usually form within 20 feet of the ground.
The best indication of relative humidity is
a.the amount of moisture in the air as a ratio of water vapour to air.
b.the temperature and dew point spread.
c.the dew point alone.
d.none of the above.
B
Given: Surface temperature 20°C
Dew point 5°C
Elevation 1 000 feet ASL
The expected cloud base is
a.5 000 feet ASL.
b.6 000 feet ASL.
c.10 000 feet ASL.
d.11 000 feet ASL.
B
Calculate Spread: Temp 20°C - Dew Point 5°C = 15°C / 3°C = 5 x 1 000 feet = 5 000 feet Cloud Base AGL
Cloud Base 5 000 feet + Elevation 1 000 feet = 6 000 feet Cloud Base ASL
Given: Surface temperature 18°C
Dew point 3°C
Elevation 523 feet ASL
The freezing level is at
a.2 000 feet AGL.
b.7 000 feet AGL.
c.2 523 feet AGL.
d.7 523 feet AGL.
B
Temp 18°C - DP 3°C = 15°C / 3°C = 5 x 1 000 = 5 000 feet AGL cloud base
Dew point 3°C / 1.5°C = 2 x 1 000 - 2 000 feet above cloud base + cloud base 5 000 = 7 000 feet AGL
What are some characteristics of stable air?
• Smooth flying
• Poor visibility
• Steady precipitation
• Layer cloud (Stratus)
• Ultimate - Fog
• Shallow lapse rate
• Inversion
• Warm air moving over cold air
What are some characteristics of unstable air?
• Bumpy flying
• Good visibility
• Showery precipitation
• Cumulus cloud (heap)
• Ultimate - Thunderstorm
• Steep lapse rate
• High temperature / dew point
How can unstable air form?
-Radiation heating during the day
-warm air moving into a region
-surface based cold advection
These will be enhanced if there is moist air near the ground and dry air aloft and the unstable air extends into higher levels
What are the 4 types of lapse rates?
• Steep Lapse Rate
• Shallow Lapse Rate
• Inversion
• Isothermal Layer
What is a steep lapse rate?
Stable or unstable?
Temperature decreases rapidly with altitude.
* A steep lapse rate is one that leads to instability.
What is an inversion?
Stable or unstable?
• The temperature increases with altitude.
• In this case the air is stable.
What is an isothermal layer?
Stable or unstable?
• The temperature does not change with altitude.
• In this case the air is stable.
What are the 4 methods of surface heating?
Radiation
Conduction
Advection
Convection
Explain how each of the 4 surface heating elements work.
Radiation- reflection of the earths rays
Conduction- warm air contacting cold air
Advection- horizontal movement of air
Convection- unequal surface heating
Explain briefly the following lifting processes:
Convection
Convergence
Mechanical turbulence
Orographic lift
Frontal lift
Convection- unequal surface heating
Convergence- excess air rises as pressure systems meet
Mech turbulence- surface friction
Orographic lift- air moving up hills (anabatic)
Frontal lift- advancing air being pushed up by cold air on the bottom
The ____ the dew point, the greater the amount of moisture the air contains.
(Higher/lower)
Higher
What is subsidence?
Subsidence is when air sinks, this results in compression and warming the air.
Not a source of unstable air conditions is
a.moist air near the ground is lifted by convection.
b.advection of warm air over the ground.
c.large scale rising of the air.
d.radiation cooling during the night.
D
After the passage of a cold front there is a nice VFR flying day with excellent visibility and a fair amount of cumulus clouds. Expected conditions are
a.very little convection due to a small spread between the temperature and dew point.
b.increased stability of the atmosphere since the front is already passed.
c.unknown as not enough information is given.
d.bumpy and turbulent flying conditions due to instability of the atmosphere with possible development of thunderstorms.
D
Heat can be transferred into the atmosphere by
a.radiation, conduction, advection, and convection.
b.rotation, consumption, invention, and convention.
c.radiation, precipitation, wind, and fronts.
d.none of the above.
A
Dissipation of clouds is related to
a.convection.
b.an increase pressure.
c.subsidence.
d.a decrease in temperature.
C
After an initial rise, a saturated parcel of air continues to rise but an unsaturated parcel of air remains cooler than the surrounding atmosphere. This is known as
a.conditional stability.
b.potential instability.
c.absolute stability.
d.absolute instability.
A
If the Sun was to burn out it would take us on Earth . . . . . to know about it.
8 minutes
The Sun’s visible layers from outer to inner are the
a.Corona, Chromosphere and Photosphere.
b.Chromosphere, Photosphere and Corona.
c.Photosphere, Corona and Chromosphere.
d.Photosphere, Chromosphere and Corona.
A
The Sun’s energy output operates on a . . . . . year cycle.
11
The Earth’s axis is tilted at an angle of . . . . . with respect to the orbital motion.
23.5 degrees
When looking at Earth from the top of the north Pole, it rotates which direction?
Counterclockwise
The time of year when day or night is the longest is the
a.Solstice, occurring approximately June 21st and December 20th.
b.Equinox, occurring approximately June 21st and December 20th.
c.Solstice, occurring approximately March 21st and September 21st.
d.Equinox, occurring approximately March 21st and September 21st.
A
Identify the following as well as okta coverage.
What is SKC?
FEW
SCT
BKN
OVC
SKC- clear sky
FEW- 1-2/8 sky coverage
SCT - 3-4/8 sky coverage
BKN- 5/8 to less than 8/8 coverage
OVC- overcast, 8/8 coverage
VFR pilots are NOT permitted to fly above a ____ or ____ layer unless they have a ____ ____ rating
BKN or OVC
VFR OTT
Clouds are classified into four families based on their _____ and _____ ______.
Height, vertical development
What are the 4 cloud classes?
• High Clouds
• Middle Clouds
• Low Clouds
• Clouds with Vertical
Development
Low clouds, height level?
Some types?
Surface to 6500 ft agl
Stratus
Nimbostratus
Stratocumulus
Cumulus fractus
Status fractus
Middle level clouds height?
Some types?
6500-20,000 ft agl
Altostratus
Altocumulus
Altocumulus castellanus (turbulence)
High level cloud height?
Some types?
20-40,000 ft agl
Cirrus
Cirrostratus
Cirrocumulus
A ragged windswept appearance of the Cirrus Clouds is always an indication of very strong winds or jet streams.
True or false?
True