1
Q
every day clouds form and dissolve in the
A
troposphere
2
Q
All of these clouds, in one way or another and to varying degrees,
A
affect aviation
3
Q
Describe the two main types of clouds
A
Stratiform (Stratus-Type) Clouds
* Horizontal layers
* Very small vertical motions
* Can cover a large area
Cumuliform (Cumulus-Type) Clouds
* Prominent vertical formation
* Usually cover a small area
* Result of rising air currents
* Significant up/downdrafts
* Of particular interest due to impact on flying conditions: precipitation, icing, high wind, turbulence, poor visibility, runway contamination
4
Q
List the four basic clouds of vertical development
A
Cumulus (CU)
Towering Cumulus (TCU) or Cumulus Congestus
Cumulonimbus (CB)
Altocumulus Castellanus (ACC)
5
Q
CU is what kind of cloud? Describe it
A
Cumulus
* Develop vertically in the form of rising mounds, domes, or towers
* Have a bulging upper part
* Appear detached from other clouds
* Generally dense with sharp or ragged outlines
* Mostly brilliant white at the top with relatively dark and nearly horizontal bases
6
Q
TCU is what kind of cloud? Describe it
A
Towering Cumulus (Cumulus Congestus)
* Made up of a rapidly growing cumulus or individual dome-shaped cloud
* Height exceeds width
* Distinctive cauliflower top often means showers below
7
Q
CB is what kind of cloud? Describe it
A
Cumulonimbus
* Thunderclouds containing thunderstorm activity
* Appear heavy and dense with a considerable vertical extent in the form of a mountain or huge tower
* At least part of the upper portion is smooth, fibrous, or striated and nearly always flattened - this part often spreads out in the shape of an avail or a vast plume
* Low ragged clouds frequently occur under the base and may or may not merge with the base
8
Q
ACC is what kind of cloud? Describe it
A
Altocumulus Castellanus
* White, grey or both
* Contain patches, sheets, or layers of cloud, generally with shading
* Composed of laminae, rounded masses and rolls, which are sometimes partly fibrous or diffuse and which may or may not be merged
* Most of the regularly arranged small elements have an apparent width of between one and five degrees
* Display vertical growth
* Are the result of mid-level instability, the up and down movement of air in the middle levels of atmosphere
9
Q
Which type of clouds get progressively larger and potentially more severe as the vertical updrafts and downdrafts grow?
A
- Cumulus (CU)
- Towering Cumulus (TCU) (Cumulus Congestus)
- Cumulonimbus (CB)
10
Q
CB clouds can attain heights of more than ___ ft, but most in Canada average about ___
A
70 000 ft,
39 000 ft
11
Q
What type of cloud results in significant icing and turbulence, and is often a factor in weather-related accidents?
A
CB clouds
12
Q
What kind of cloud is often a telltale sign of impending thunderstorm development?
A
ACC
13
Q
What kind of cloud is this?
A
Stratiform
14
Q
What kind of cloud is this?
A
Cumuliform
15
Q
What kind of cloud is this?
A
ACC
16
Q
What kind of cloud is this?
A
ACC
17
Q
What kind of cloud is this?
A
CB
18
Q
What kind of cloud is this?
A
CB
19
Q
What kind of cloud is this?
A
CU
20
Q
What kind of cloud is this?
A
CU
21
Q
What kind of cloud is this?
A
TCU
22
Q
What kind of cloud is this?
A
TCU
23
Q
Describe high-pressure areas
A
- A region where the atmospheric pressure is greater than its surroundings
- a high or anticyclone
- generally associated with nice weather
- pressure values increase towards centre
- Air circulates clockwise around the centre
- Diameter from hundreds to thousands of kilometres
- Labelled BLUE H on surface weather maps
:)
24
Q
Describe low-pressure areas
A
- A region where the atmospheric pressure is lower than its surroundings
- a low, cyclone, or depression
- Generally associated with cloudy, rainy, snowy weather
- Pressure values decrease towards centre
- Air circulates counter-
clockwise around the centre - Diameter from tens to hundreds of kilometres
- Labelled RED L on surface weather maps
:(
25
What are ridges vs. troughs?
Ridges
* An elongated region of relatively high atmospheric pressure
* Tend to bring warmer, drier weather (since air is often sinking)
Troughs
* An elongated region of relatively low atmospheric pressure, often associated with fronts
* Tend to bring clouds, showers, wind shift (esp after passage)
26
What are isobars?
curved lines that connect points of equal pressure and show variations in pressure at any given time. Isobars join lines of equal mean sea level pressure (MSL) and form pressure patterns that outline or enclose high- and low-pressure areas.
* Measured in hectopascals (hPa)
* Analyzed on meteorological charts
* Used to identify high, low-pressure systems
* Spaced every 4 hPa above/below 1000hPa
27
Pressure gradient is
the rate of change of pressure with horizontal distance measured in kilometres
28
The speed of wind is \_\_\_ proportional to the pressure gradient
directly
(the faster the pressure changes, the stronger the wind will be)
29
The difference in pressure between isobars is always \_\_\_, while the horizontal spacing or the distance in kilometres between the isobars \_\_\_, so the rate of pressure change with horizontal distance (pressure gradient) will also vary.
4 hPa
varies from location to location
30
Pressure gradient is always calculated as
4 hPa in “X” km, where X is the distance between two consecutive isobars
31
What is it called when isobars are widely spaced? What are lows and highs called?
Weak Pressure Gradient
* Pressure change occurs over a relatively long distance
A low is termed “shallow”
A high is termed “weak”
32
What is it called when isobars are closely spaced? What are lows and highs called?
Steep Pressure Gradient
* Pressure change occurs over a relatively long distance
A low is termed “deep”
A high is termed “strong”
33
Wind circulation is a result of
many forces acting on each other
Different forces will affect the presence of wind, its direction and its speed.
34
Air moves from \_\_\_-pressure areas towards \_\_\_-pressure areas, but \_\_\_
high, low
not directly
35
Wind flows roughly parallel to
isobars
36
What is the Coriolis Force?
* Caused by the Earth’s rotation
* **Northern Hemisphere**: As air moves from a high-pressure area to a low-pressure area, the **Coriolis force deflects the moving air to the right** because the Earth rotates counter-clockwise if you are in the northern hemisphere
* **Southern Hemisphere**: As air moves from a high-pressure area to a low-pressure area, the **Coriolis force deflect the moving air to the left** because the Earth rotates clockwise if you are in the southern hemisphere
## Footnote
RIGHT hemisphere (NH), air moves RIGHT
37
Does the Coriolis Force cause wind?
No, just affects the direction of the air movement.
38
If the Earth didn’t rotate, the wind would
flow directly from a high- to a low-pressure area
39
What is Buys Ballot's Law?
**Northern hemisphere**, Pressure gradient force + Coriolis force combine to cause the air to flow parallel to the isobars, **clockwise around a high and counter-clockwise around a low**.
The opposite exists in the southern hemisphere.
**With the wind at your back in the northern hemisphere, the area of lower pressure lies to your left**
## Footnote
NH: Lower pressure on Left
40
Pressure patterns are constantly moving and changing in intensity, so the wind
frequently changes direction
41
Veering is when the wind
makes a **clockwise** change in direction
e.g. from South (180 degrees) to West (270 degrees)
42
Backing is when the wind
makes a **counter-clockwise** change in direction
e.g. from South (180 degrees) to East (90 degrees)
## Footnote
(like a clock BACKING up)
43
Friction at the surface and up to about \_\_\_ ft causes the wind to:
3000 ft
* Slow down +
* Flow into a low-pressure area +
* Flow out of a high-pressure area
44
Friction diminishes with ____; therefore, the wind
height
veers and the speed increases
45
\_\_\_ are used to represent wind information on surface maps. They are always plotted to indicate the direction the wind is blowing \_\_\_.
Arrows
FROM
46
What do the barbs on arrows indicate on surface maps?
Wind speed:
* Each full barb = 10 knots
* Each half barb = 5 knots
47
A lifting agent is
Air must be lifted so that it can \________________ for \____________ to occur.
a force that pushes air upwards.
it can cool and condense
for clouds and precipitation to occur
48
What 2 factors determine the types of clouds that form?
Lifting agents and the relative stability of the air
49
List and describe the 5 atmospheric lifting agents
**Convection**
Air is heated from below by contact with the Earth’s surface. Rising columns of air (thermals) are usually separated by areas of sinking air (subsidence).
**Orographic Lift**
Air is forced up sloping terrain by the wind. The type of cloud that results depends on the stability of the lifted air.
**Frontal Lift**
Air is forced to rise by a wedge of colder and denser air.
**Mechanical Turbulence**
Friction between the air and ground causes the air to be stirred up into a series of areas of swirling motion known as eddies.
Depends on the strength of the wind and the roughness of the terrain.
**Convergence**
The air converges at the centre of low-pressure systems and is forced to rise, resulting in cloud and precipitation.
50
What are thermals? What is subsidence?
Thermals: rising columns of warm air
Subsidence: Sinking cold air
51
A cold front is defined as
the transition zone between advancing cold air and the warm air it undercuts
52
A warm front is defined as
the transition zone between retrating cold air the hot air it gives way to (which is less dense and slides over the cold air)
53
An air mass is
a large section of the troposphere with relatively uniform properties of temperature and moisture in the horizontal
54
Air masses can be
several thousand kilometres across
55
The pressure within any given air mass
can vary considerably
56
An air mass takes on its original properties from
the surface over which it has formed (e.g. one that forms over the Arctic is dry and cold, one that forms over the Caribbean is very warm and very moist)
57
All air masses are described by both:
**Humidity**
(humid or dry)
**Temperature**
(cold, temperate, warm)
58
There are 2 types of air masses (based on humidity):
**Maritime** air masses form over large bodies of water and are humid
**Continental** air masses form over large land areas and are dry
each can be cold, temperate, or warm
59
Temperatures of Air Masses in North America
* **Arctic** air masses are cold and form in the Arctic or at high latitudes
* **Polar** air masses are temperate. Despite their name, polar air masses actually form in the temperate zones (permafrost line to 30 deg N) by the heating of an Arctic air mass or the cooling of a tropical air mass.
* **Tropical** air masses are warm and form in the tropics or lower latitudes (between 30 deg N and the equator)
## Footnote
APT, APT
60
What are the 4 common air masses in North America?
* Continental Arctic (cA) - **winter only**
* Maritime Arctic (mA)
* Maritime Polar (mP)
* Maritime Tropical (mT)
Continent Polar (cP) and Continental Tropical (cT) can occur, but seldom appear in North america
61
A front is
the transition zone between two air masses
62
Fronts are often areas of
intense weather significant to aviation
63
Since North America has 4 air mass structures (cA, mA, mP, mT), there are
3 frontal boundaries
64
List and desribe the 3 front types
* Cold Front - Transition zone between advancing cold air and warm air
* Warm Front - Transition zone between warm air and retreating cold air
* Stationary Front - Transition zone between two air masses that are not moving
65
How are stationary, warm, and cold fronts identified on weather maps?
* Stationary: alternating arrowheads and half-circles
* Warm: Half-circle (on side of cold air)
* Cold: arrowhead (on side of warm air)
66
What kind of front is this?
Stationary
67
What kind of front is this?
Warm
68
What kind of front is this?
Cold
69
What is?
Convection
70
What is?
Orographic Lift
71
frontal lift
72
mechanical turbulence
73
convergence
74
Buys Ballot's Law
75
Coriolis Force
76
The Polar Front Theory states that
the Earth is covered by polar (cold) air in polar regions and tropical (warm) air in the equatorial regions. They are separated by the polar front. It is a two-air mass, one-front model.
77
We rarely experience three rapid frontal passages. When it does occur, it often takes \_\_\_ to go from cA to mT or vice versa. However...
months
However, because a frontal boundary is not a straight line, we often alternate from one air mass to another over short periods.
78
Think of a summer that is hot and humid, then a cold front (drier and warm) arrives and is later replaced by the hot and muggy conditions again. These conditions would indicate the sequential passage of:
* mT air
* cold front passage to mP air
* and warm front passage back to mT
79
At a front, the colder air acts as an inclined plane that forces the warmer air to rise. This lift creates
cooling, which often produces clouds,precipitation
80
The severity of the weather created by a front depends on:
* The slope of the frontal surface
* The speed of frontal movement
* The temperature of the lifted air mass
* The moisture content of the lifted air mass
* The stability of the lifted air mass
81
The wind ahead of a \_\_\_ front is typically out of the south-south-west and will shift to the west-northwest once the front passes through
cold
82
The wind ahead of a \_\_\_ front is typically out of the east and will shift to the south-southwest once the front passes through
warm
83
The passage of a warm front will result in
an increase in temperature that may begin before the front reaches the station. This is due to the proximity of the warm air to the surface as the depth of cold air over the station decreases.
84
Re: temperature, the arrival of a cold front will generally result in
a sudden decrease in surface temperature. The temperature change usually begins when the front reaches the station.
You should remember that the front is really a zone, often of considerable width. **The first part of the cold air mass will have been warmed in the lower levels as a result of its passage over a warmer surface.** Consequently, it may be many hours after the frontal passage before temperatures drop to the true value of the cold air mass.
85
Re: temperature, with the passage of a cold front, it is possible to see
a small temperature increase for a short period of time after front passage, especially if there is no cloud cover to prevent the sun from heating the ground.
The slight increase of temperature accompanying the passage of a cold front occurs only near the surface where the ground has been heated. We can therefore expect low-level convection to occur since the ground is heated unevenly.
86
As temperatures change with the passage of fronts, we can also expect a change in the moisture content of the air.
Dew point temperatures generally
**increase with a warm frontal passage and decrease with a cold frontal passage**
As you may remember, air temperature determines the amount of moisture that air can hold, and **dew point temperatures can never be higher than air temperatures**
87
Fronts are generally associated with areas of \_\_\_ pressure
low
88
As the warm front approaches, the pressure will generally \_\_\_ .
After the warm front passes...
fall
the fall in pressure is more gradual or there is a slight increase in pressure.
89
Once the cold font has passed a location, the pressure will begin to
rise (because cold air is denser than warm air). This rise is sometimes quite steep.
90
(Frontal) Turbulence is more commonly associated with
cold fronts, but may also be present to a lesser degree in a warm front
91
Frontal turbulence is caused by
It is strongest when
The most severe cases are generally associated with
* lifting of warm air by a frontal surface leading to instability, or
* abrupt shifts in wind direction and speed between the warm and cold air masses near the frontal surface
Strongest when the lifted warm air is moist and unstable
fast-moving cold fronts. In these cases, the mixture of two air masses, as well as the difference in the windspeed and/or direction (wind shear) add to the intensity of the turbulence
92
Describe the effect of a warm front on visibility
* Because of the shallow slope and the generally large band of cloud and precipitation, **visibility can be reduced well in advance of warm fronts**.
* Precipitation may begin as virga (precipitation that does not reach the ground) and gradually increase in intensity
* The passage of the front may bring little immediate change in visibility with potentially more severe weather typical just ahead of the front due to low clouds, fog, and precipitation
93
Describe the effect of a cold front on visibility
Ahead:
Nearby:
After:
* Ahead of cold fronts, visibility is generally good.
* Close to the front, visibility may be reduced due to precipitation and mist.
* After the passage of the front, there will usually be a marked improvement in visibility. The air behind the front is usually unstable, and the vertical currents will carry suspended particles aloft.
Any part of an air mass that is stable and has recently passed over an industrial regions will be loaded with pollutants (haze, dust, smoke) and have poorer visibility than usual
94
# Surface Wind
Before a warm front arrives:
Once the front passes through:
The wind ahead of the front in the cooler air mass is typical from the east
The wind usually shifts (veers) around to the south-southwest (in the warmer air mass)
95
# Surface Wind
Before a cold front arrives:
Once the front passes through:
The wind ahead of the front (in the warmer air mass) is typically out of the south-southwest.
The wind will usually shift (veer) around to the west-northwest (in the colder air mass).
96
A sudden change in wind direction is common with
the passage of a front. On the ground, the wind shift usually occurs at the front.
97
Air moves nearly parallel to the isobars, but crosses the isobars inwards around a low because of
surface friction
98
The wind shift occurs at the frontal surface and is most significant in
the lower levels.
99
The wind shift associated with flight through a front is more \_\_\_ at a cold front than a warm front.
abrupt
100
3 factors determine the type of cloud and precipitation in a warm front:
* The moisture content of the overrunning warm air
* The stability of the overrunning warm air
* The degree of overrunning (the pressure gradient in the warm air and angle of warm air motion relative to the frontal surface)
101
3 factors determine the type of cloud and precipitation in a cold front:
* The moisture content of the lifted warm air
* The stability of the lifted warm air
* The degree of lift (the slope of the frontal surface and the speed of the front)
102
The arrival/passing of a front, whether warm or cold, has an effect on:
* Temperature
* Dew Point
* Pressure
* (Frontal) Turbulence
* Visibility
* Surface Wind
* Precipitation
1. ABC (Aviation Basics Course)
flashcards
Decks in class (22)
# Cards
-
Foundations of Decision-Making in ATS13
-
Airport Layout, Traffic Organization, and Lighting40
-
ATS Services & Positions34
-
Regulations Around VFR Flights47
-
Classification of Canadian Airspace39
-
Routes, Airways, and Charts90
-
Regulations19
-
From Ground to Flight56
-
Synoptic Features102
-
Thunderstorms77
-
Turbulence84
-
Icing67
-
Aviation Weather Reports279
-
Aircraft Performance94
-
Wake Turbulence54
-
Airborne Collision Avoidance Systems63
-
ATS Coding277
-
ATS Communication81
-
Surveillance, Systems and Equipment52
-
Practice Your ATS Decision-Making19
-
LO Chart Legend104
-
VNC Legend96
