Met General Flashcards
1
Q
What gases make up the atmosphere?
A
78% nitrogen, 21% oxygen, 1% argon. Small portions of helium, neon, ozone and carbon dioxide
2
Q
What are the layers of the atmosphere?
A
Troposphere, stratosphere, mesosphere, thermosphere.
3
Q
What layer of the atmosphere is most weather found in?
A
Troposphere
4
Q
The temperature of the tropopause is general colder over the poles or the equator?
A
The equator
5
Q
Where is the trop highest?
A
Equator - density of air is less and therefore higher
6
Q
Most ultraviolet radiation is absorbed by what gas?
A
Ozone
7
Q
The earths surface is heated by?
A
Short wave solar radiation (UV)
8
Q
The lower atmosphere is heated by?
A
Conduction and long wave solar radiation (infrared)
9
Q
Conduction definition
A
If two bodies are touching heat will flow from the warmer to the cooler one
10
Q
Coriolis is caused by what?
A
Rotation of the earth
11
Q
Where is coriolis strongest?
A
The poles
12
Q
A process that will lead to rising air is known as:
A
Convection
13
Q
Diurnal (day to night) range in temperatures are least where?
A
Water or maritime areas
14
Q
Convergence refers to air that is:
A
Flowing from high pressure into and converging at an area of low pressure
15
Q
Overrunning refers to:
A
How fast warm air rises vertically as it flows up along the frontal surface over the retreating cold air
16
Q
Term used to describe process whereby a rising, expanding parcel of air does not undergo any heat transfer in or out of the parcel as it ascends
A
Adiabatic
17
Q
Subsiding air, even if it is initially saturated will warm at which lapse rate?
A
Dry adiabatic lapse rate
18
Q
When air subsides, what normally decreases?
A
Relative humidity
19
Q
T/F - during the condensation process, latent heat is released to the surrounding air.
A
True
20
Q
When condensation occurs in an unstable air mass, the stability of the air tends to become…
A
More unstable as heat is released to the surrounding air.
21
Q
When discussing stability/instability of the atmosphere, we are referring to:
A
Property of the atmosphere that suppressed or promotes vertical motion
22
Q
Surface highs and lows develop as a result of:
A
Upper level convergence and divergence forcing air to sink or rise respectively
23
Q
A trough is
A
An elongated area of relatively low atmospheric pressure
24
Q
A neutral area, where light winds are blowing and weather is changing slowly between two high and two low pressure systems is
A
A Col
25
MSL pressure is
Station pressure reduced to msl using the average surface temperature for the last 12 hrs
26
Altimeter setting is
Station level pressure reduced to MSL assuming ISA conditions
27
Drizzle forms through the
Condensation and coalescence processes in stratus cloud
28
Snow falling from a layer of stratocumulus cloud would indicate
The liquid water content in the cloud is decreasing
29
Snow grains implies that what type of precipitation is aloft
Freezing drizzle
30
A large area of land or ocean of relatively uniform characteristics and above which an air mass can form is a
Source region
31
T/F air masses are classified according to their moisture content
True
32
Fronts are named according to
Colder air mass and direction of movement
33
T/F Within an anticyclone there is a general increase in relative humidity
False
34
T/F the calculation of the density altitude at a given aerodrome consists of correcting the existing pressure altitude with the ISA temperature for that level
False
35
What cold fronts are likely to be found in Canada during summer months?
Maritime arctic and maritime polar
36
Does the wind back or veer when passing through a front?
Veers regardless of type of front or direction of travel
37
Winds that occur as a result of daytime heating on mountains. They flow in which direction: up/down
Anabatic. Up
38
Winds that occur as a result of cooling on mountain slopes in the evening, and flow in which direction?
Katabatic. down
39
The area on the earth where solar radiation is at its strongest is known as
The intertropical convergence zone
40
Why does the ITCZ move south during the winter?
The northern hemisphere tilts away from the sun moving the point of maximum solar radiation striking the earth south
41
The relationship between the amount of water vapour actually present in the air and the maximum possible amount of water vapour that could be held by the air at that temp and pressure is
Relative humidity.
42
Height of a cloud base is most dependent upon the
Moisture content of the air
43
Clouds and precip are common in areas of:
Ascending air
44
Cloud order flying towards a warm front:
CI, CS, AS, NS (embedded CB’s if warm air moist and unstable)
45
A combination of cold and warm front weather conditions would most likely be associated with what two types of fronts:
Occluded, trowal.
46
In the northern hemisphere the future movement of a mature frontal depression and its associated frontal wave will tend to be parallel to:
The warm sector isobars.
47
At a stationary front, the cold air moves:
Parallel to the front
48
The transition zone between two different air masses where there is a sudden change in temp and moisture content is called:
A front
49
Besides a snow covered surface, what adds to a whiteout illusion?
Uniform overcast sky
50
Advection fog forms how and where
when a warm, moist air mass moves over a cold surface or water
51
3 factors that lead to formation of fog:
High relative humidity, condensation nuclei, a process to cause the temp/dew point spread to reduce to zero (cooling atmosphere or adding moisture to raise the dew point)
52
Type of fog that follows a warm front
Advection fog
53
What are the types of fog that form as a result of raising the dew point (adding moisture) up to the outside air temperature
Steam fog, arctic sea smoke, frontal fog
54
Adiabatic cooling cause which type of fog to form
Upslope fog
55
______ is the physical process involved in the formation of ice fog
Sublimation
56
Moderate to severe icing in a TCU or CB can occur down to what temp?
-25 and light icing down to -40
57
What rate of catch and droplet size is likely for rime ice
Low and small
58
What part of a cloud would freezing drizzle be at its worst?
Near the base of the cloud
59
Water droplets instead of ice crystals exist at temps down to -10 due to:
Absence of Ice nuclei until below -10
60
How do snow pellets form?
When ice crystals and supercooled water droplets collide (known as riming)
61
The growth of snowflakes as they collide together is known as:
Aggregation
62
When making a quick fuel stop with light wet snow falling, when and how should you check for surface contamination?
Tactile feel just prior to closing the cabin as you will be unable to determine visually if the melted snow has refrozen or not
63
How many degrees could the wind be across the isobars over rough terrain?
40 degrees
64
A rapidly moving cold front with a steep frontal surface that does not produce extensive areas of convective cloud would indicate what with respect to relative humidity?
The warm air mass has a low relative humidity
65
What two warm fronts would be likely in Canada during winter?
Continental arctic and maritime arctic
66
Can you take off with frost on the underside of the wing?
Yes, as long as it doesn’t exceed aircraft manufacturers recommendation
67
T/F - An airspeed of at least 500kts is required to ensure no ice will collect
True
68
As well as a lifting force or triggering action, other conditions necessary for the formation of a well developed thunderstorm are:
An abundant supply of moisture and a steep lapse rate
69
Dissipating stage of a storm cell is characterized by:
Downdrafts encompassing the entire cell horizontally
70
Flight beneath an anvil cloud should be avoided due to:
Hail
71
What stage of development of a TS would the most serious icing problem be?
Just before the cell enters the mature stage as this is when the most amount of moisture would be in the cloud. (Rain marks the beginning of the mature stage)
72
Mammatus clouds are frequently associated with:
Violent thunderstorms and tornadoes
73
T/F - Conditions of very low humidity and the absence of vorticity in the air favour the formation of funnel clouds
False
74
A distinct hook on a weather radar could be:
A tornado
75
Distances to avoid TS by:
5 below freezing level, 10 above freezing level, 20 if severe
76
Where to scan a TS with radar?
Start in mid levels and then below
77
The shaft of a microburst is normally how wide
2.2nm or less
78
Characteristics of low level nocturnal jets
1. Occur mostly in summer
2. Generally form over flat terrain during presence of southwest winds
3. Usually associated with temp inversions
79
Location of a low level frontal jet
Parallel to the cold front in the warm sector of the frontal wave
80
Where is the CAT associated with the LLJ located?
1-3hrs prior to the passage of the cold front
81
T/f - dry microbursts usually occur in areas where the air is very humid
False
82
Microburst downdrafts could be as strong as:
6000ft/minute
83
Where are lens clouds located in a mountain wave?
At the wave crests
84
The most powerful rotor associated with the presence of a mountain wave is located:
In the proximity of the first wave crest
85
Severe turbulence at high alt is likely to be associated with a mountain wave system when:
There’s a jet stream aloft that is oriented perpendicular to the axis of the mountain range
86
T/F - altimeter readings are likely to over-read when flying through the crest of a mountain wave
True
87
The trop can be identified in a climb by:
An abrupt change in the temp lapse rate
88
There is an abrupt change in the height of the trop over each:
Frontal surface
89
ISA height and temp of the trop
36,089ft and -56.5 degrees
90
What causes jet streams?
1. Strong px gradient drives from a strong temp contrast on the earths surface that upsets the height of px levels
2. Hadley cell of circulation in the subtropics undergoes long and slow acceleration as coriolis deflects air right in the northern hemisphere
91
T/F - jet streams occur on the warm side of the frontal surface with their cores positioned just beneath the trop
True
92
You would expect a North-
south jet flow when:
The air beneath the jet is colder to the east then to the west
93
Why do jets suddenly accelerate and decelerate?
Centrifugal forces around sharp ridges and troughs
94
How are jets named in Canada?
3 of them after their under lying front and the 4th is the subtropical jet which is due to the circulation within the Hadley cell located in the subtropics
95
T/F - the polar jet stream moves south during the winter and generally has higher core speeds then in the summer
True
96
Flying across a jet stream in North America and encounter CAT, with a temp rise. To quickly escape you should:
Climb
97
Flying near a jet in a crosswind situation and encountering CAT, the OAT remains constant, to escape the cat you should
Climb or descend
98
CAT is also related to vertical wind shear, so when the shear is greater then ___kts/1000ft turbulence is likely.
5
99
Jets having speeds above _______kts at the core will have areas of significant turbulence near them in the sloping trop above the core, in the jet stream front below the core and on the cold air side of the core
110kts
100
Rotor clouds found during mountain wave activity are located:
Located at ridge top heights with their bases often extending below, and beneath the wave crests within the mountain wave
101
When the properties of two air masses along a front are becoming increasing different in temp and moisture, it is referred to as what?
Frontogenesis
102
A pressure of 200hPa is closest to which level in ICAO?
FL390
103
FL450 is associated with which px level in ICAO?
150 hPa
104
Cold fronts wx is determined by:
Stability of the warm air mass, moisture content of the warm air mass, and speed of the front and steepness of its frontal surface
105
Lapse rates: avg, dry, saturated
2°(1.98), 3°, 1.5°
106
Condensation definition
When the rate of attachment of water vapour molecules is equal to or greater then the rate of detachment, a small water droplet will begin to form
107
Evaporation definition
When the rate of detachment is greater then the rate of attachment, the water droplet gets smaller
108
Collision-Coalescence definition
Larger water droplets bang into smaller water droplets (collision) and join together (coalescence)
109
Tropopause, stratopause, mesopause are what type of layers?
Isothermal. Constant temp with height
110
Latent heat definition
When moisture in the air changes into another state, energy is released or absorbed. This energy is latent heat
111
Terrestrial radiation
The amount of energy re-radiated back into the atmosphere
112
Deposition definition
Vapour (cloud/fog) to a solid (ice)
113
Evaporation theory
Air absorbing latent heat. When evaporation happens the air gets cooler as heat is absorbed.
114
Diurnal effects cause the air to move what direction first?
Vertically and then horizontally. (Sea breeze - earth heats up in the day time, air moves vertically making room for cooler air from the ocean to come in)
115
Stability vs instability with regards to lapse rates
If the ELR is greater then the DALR, that air is unstable. If the ELR is less then the SALR, the air is stable. Conditional means dependent on if in dry or saturated air.
116
Trop is from approx what altitudes?
ISA - 36,089 to 65,000
117
Does MSL change when it becomes warmer then standard but the station pressure remains the same?
Warmer temp - lower pressure
Lower temp - Higher pressure
118
How to find a px at a specific isobar
1000hPa has to be on the chart. Start at 1000 and work up or down to whatever the L/H pressure is.
119
How does surface friction affect wind?
Backs wind, regardless or H/L, and decreases. More so over land. Can actually increase over water.
120
How does upper level convergence make a surface H?
Air converges and has no where to go but down, forcing the air down to the ground where it then diverges which creates a high
121
What forces act on the wind?
-PX GRADIENT - isobars close/far apart
-CORIOLIS - stronger the winds, stronger effects of coriolis. Stronger near poles aswell
-FRICTION - wind backs and decrease
-thermal wind gradient - warm to cold
-centrifugal force
122
For the same pressure gradient, would wind speed around a surface low be greater or less then a surface high?
Less then the high as air around a high is pushed outwards by centrifugal force.
123
Difference between cold/warm front passage
Cold:
-winds veer and increase
-px increases
-temp change (can take 2-3hrs)
Warm
-winds veer and increase
-px decreases
-temp change (can take 2-3 hrs)
124
An approaching cold front that initially has a shallow frontal surface, steepens some distance behind the surface front. You experience a wind shift and a drop in temperature, when would you expect clouds and precipitation to occur?
Will occur later. (Upper cold front)
125
What would happen to the OAT as you fly through a trowal?
It would rise then drop
126
Visibility in a metar is prevailing vis which is measured from?
Tower
127
Fog forms over the Pacific Ocean but not over land, why?
Air is cold and dry with a land breeze.
128
There is a shallow fog over the touchdown zone, what is true about the visibility?
Prevailing vis may be better then RVR due to tower being above layer
129
What is the difference between a low level nocturnal jet and a frontal jet?
Mainly speed, and alt. Nocturnal <45kts and 200-2000agl. frontal is up to 100kts, up to 5000’.
130
Explain Bergeron process.
When ice nuclei are introduced, SC water will freeze in its entirety (once started, will continue until everything is frozen). So if you see ice crystals in cloud, it’s only a matter of time until the whole cloud is ice crystals and no more icing. Larger SC water droplets tend to freeze first as they have more impurities.
131
What temp can you expect icing on layer type cloud?
0 to -15°. SC water near top of cloud.
132
When can you expect icing in cumulus cloud?
Moderate from 0 to -10°
133
When would you expect mixed icing?
Large and small SC droplets with relatively high catch rates.
134
How are rotor clouds and lens clouds described from an auto station?
Rotor - below wave crests
Lens - at wave crests
135
Jet streams are defined as how many kts?
60kts
136
Which is the strongest jet stream?
Polar, largest contrast between temps creates a strong rotation. (Warm air moves to cold air)
137
What is the difference between a roll cloud and a shelf cloud?
A roll cloud is detached from the TS. Both are on the leading edge, and where the updrafts meet the downdrafts.
138
How far can shear effects from downdrafts reach?
10nm from storm centre.
139
How does evaporation effect virga?
It accelerates the downdrafts as it absorbs heat and cools the surrounding air.
140
What is a tornado and where are they found?
It is a horizontal vortex which is pulled vertically into the TS on the edge of the TS (wall cloud)
