Exam revision Flashcards
1
Q
What is the atmosphere broken into?
A
78% Nitrogen
21% Oxygen
1% Other Gases (argon etc)
2
Q
What layers is the atmosphere?
A
Troposphere Tropopause Stratosphere Stratopause Mesosphere Mesopause
3
Q
What percentage of the air is water in the troposphere?
A
0 to 5%
4
Q
What is the lowest portion of the atmosphere?
A
Troposphere
5
Q
What happens with temperature in troposphere?
A
Decreases with increase in height
6
Q
Where is the majority of water vapour, clouds and weather found?
A
Troposphere
7
Q
What is the boundary where temperature no longer decreases with height?
A
Tropopause
8
Q
What altitude is tropopause at pole and equator?
A
Approx 26500km at temp of -40 over poles
Approx 59500km at temp of -70 at equator
9
Q
In the lower portions of the stratosphere, what is the temperature? Increasing, decreasing or constant?
A
Constant (aka isothermal layer)
10
Q
What is the temperature in the upper stratosphere like? Increasing, decreasing or constant?
A
Increases with height due to ozone
11
Q
What is an inversion?
A
Temperature increases with height
12
Q
When can an inversion occur in the troposphere?
A
When the lapse rate is negative
13
Q
What is the ISA ELR?
A
Decrease of temp of 2 degrees (1.98) per 1000 feet
14
Q
What height is the ISA ELR for?
A
0 to 36090ft AMSL
15
Q
What is the ISA Mean sea level temp?
A
15 degrees
16
Q
What is the ISA tropopause temp?
A
-56 degrees
17
Q
What are the three ways heat can be transferred
A
Radiation
Conduction
Convection
18
Q
What are isotherms?
A
Lines on weather map joining places having same temperature at particular time
19
Q
Normally the diural range of temperature is greatest where?
A
An inland location
20
Q
What is the primary cause of weather?
A
Temperature differential
21
Q
Radiant energy arriving from the sun is termed?
A
Insolation
22
Q
What is an isobar?
A
Joins places having same surface pressure at a particular time
23
Q
What happens to atmospheric pressure with increase in altitude?
A
Decreases
24
Q
At low level, what does pressure reduce at?
A
1Hpa per 30 ft
25
What does air density depend on?
Pressure
Temperature
Humidity
26
What does a decrease in pressure do to density?
Decreases density
27
What does an increase in temperature do to density?
Decreases density
28
What does increase in humidity do to density?
Decreases density
29
What is semidiurnal variation?
Rhythmic variation in pressure over 12 hours
30
What causes semidiurnal variation?
Expansion and contraction of atmosphere as it heats and cools
31
When is the semidiurnal variation greatest?
In the tropics
32
What is local QNH?
Set sea level pressure for location
33
What will setting airfield elevation on main scale do with regards to local QNH
Provide approximate QNH
34
What is area QNH?
Predicted average sea level pressure for 3 hour period
35
When would you use area QNH?
Within 100nm when cruising at or below 10000ft
36
What separates aircraft on standard pressure and on QNH?
Transition layer
37
What is QFE?
Station level pressure
38
With QFE on the subscale of altimeter, what will the mainscale indicate?
Height above/below the reference pressure point
39
How can you obtain the QFE for a point?
Set zero ft on mainscale
40
What is QFF?
Meterological mean sea level
41
What are isobars?
Lines on synoptic chart joining places of equal pressure
42
An altimeter in an aircraft flying towards a low pressure without adjusting the QNH, what will the altimeter do?
Over read
43
What is a col?
Neutral area between two highs and two lows
44
What is a trough?
Elongated area of low pressure
45
What is a ridge?
Elongated area of high pressure
46
What is pressure gradient?
Change in pressure with horizontal distance
47
How is pressure gradient measured?
High to low at right angles to the isobars
48
What does close isobar spacing indicate?
Strong gradient and strong winds
49
What does wide isobar spacing indicate?
Weak or shallow gradient and light winds
50
Pressure may be defined as:
Force per unit area
51
What effect does density have on aircraft performance?
Good performance when density is high
52
If altimeter subscale is set at 1013 what will the altimeter read?
Pressure height
53
While in level flight with correct area QNH set, what will the altimeter read?
Approx height AMSL
54
What is QFE?
Aeredrome level pressure
55
What is latent heat?
Heat which must be added to change substance to higher state
56
What is humidity?
Amount of water vapour contained in air sample
57
What is relative humidity?
Ratio of amount of water present in air sample compared to max amount that could be contained at that temp and pressure
58
What is saturated air?
When air sample cannot hold any extra water vapour without condensation occuring
59
When a sample of air is saturated , what is the relative humidity?
100%
60
What happens to humidity with increase in temperature?
Humidity is decreased
61
What happens to the volume, pressure and temp of a parcel of air as it rises?
Pressure reduces
Volume of parcel increases
Temperature decreases
62
How will air cool as it rises?
By expansion
63
What is adiabatic?
Change in temperature due to change in pressure without change in total heat energy of air sample
64
What is ALR?
Rate at which air sample cools as it rises
| Depends on whether it is dry or saturated
65
What is DALR?
Air cools at 3 degrees per 1000 feet
66
What is SALR?
Air cools at 1.5 degrees per 1000 feet
67
What is dew point lapse rate?
0.6 degrees per 1000ft
68
What is a stable atmosphere?
Air parcel returns to original level after being forced vertically.
69
What is an unstable atmosphere?
Air parcel continues to rise on its own forced vertically
70
If the temperature of the air parcel being forced vertically remains greater than the environment, what is the atmosphere said to be?
Unstable
71
If the temperature of the air parcel being forced vertically becomes less than the environment, what is the atmosphere said to be?
Stable
72
What happens when ELR is less than SALR?
Stable conditions
73
What happens when ELR is greater than DALR?
Unstable conditions
74
What is a surface inversion?
Air close to the surface is cooled at night by conduction.
75
When is surface inversion the greatest?
Just before dawn when surface temp is the lowest
76
What is turbulence inversion?
Moderate winds at low levels cause adibatic expansion and cooling in lower layers due to mixing. If lower layer becomes cooler, inversion forms
77
What is a frontal inversion?
Boundary of two masses of different temperatures as warm air slides up over cooler air
78
What is a subsidence inversion?
Column of air subsides the top of the column undergoes greater compression and heating than the bottom. The top becomes warmer forming an inversion
79
What conditions, stable or unstable, are associated with inversions?
Stable
80
What are conditions like beneath the inversion?
Poor visibility and turbulent
81
What are conditions like above the inversion?
Good visibility and clear
82
What is a fohn wind?
Hot dry breeze blowing down the lee side of the moutain
83
With regards to the fohn wind, where is the cloud higher?
Higher on the windward slope due to precipitation and change in dew point
84
When a parcel of air becomes saturated and condensation occurs, what happens to latent heat?
Latent heat is released
85
What is relative humidity?
Percentage degree of saturation
86
How do we get dew point temperature?
Moist air cooled at constant pressure for it to become saturated
87
What happens to latent heat when water droplets in liquid state freeze?
Latent heat released
88
How is relative humidity measured?
Psychrometer
89
What height is wind measured and at what average?
Height of 10m over open terrain as average over 10 mins
90
What is a gust?
Sudden increase in wind lasting short time and dying suddenly
91
What is a squall?
Sudden increase in wind by 16 knots or more lasting at least 1 min and reaching top speed of 22 knots
92
What is veer?
Wind change clockwise?
93
What is back?
Wind change anticlockwise
94
How does wind flow in pressure areas?
From high to low pressure, across isobars
95
Where is the strength of the gradient force measured?
Perpendicular to isobars
96
Due to the earths rotation, which direction is the air deflected and what is this known as?
To the left in the southern hemisphere
| Coriolis effect
97
The stronger the winds, what happens to the coriolis effect?
It is also stronger
98
Which direction does wind flow in low pressure?
Clockwise
99
Which direction does wind flow in high pressure?
Anti clockwise
100
What is the pressure like in the equatorial trough?
Long belt of low pressure
101
As air cools in the ITCZ, what happens?
Descends in sub tropical regions and creates sub tropical ridge of high pressure
102
What is the pressure like at the poles and why?
Cold and dense air creates polar high pressure
103
What is the sub polar low?
Air moving out of polar high at surface converges with air flowing out of sub tropical ridge and is forced up forming low pressure belt
104
During summer in the souther hemisphere, what happens to equatorial trough?
Moves south to lie across norther Australia
105
What does equatorial trough moving south in summer in southern hemisphere do to weather?
Draws warm, moist air and therefore rain (northwest monsoon)
106
What is the difference between the movement of the equatorial trough in the southern and norther hemisphere in summer?
Moves further north from the equator in summer due to greater area of land in northern hemisphere
107
What are the winds over norther australia like in winter?
South eastly due to south east trades
108
What does winter weather like in northern australia? What about east coast
Dry except over east coast where trade winds contain abundant moisture
109
What is the South east trade wind?
Wind from the sub tropical ridge towards the equatorial trough
110
What is the roaring 40s?
40 degrees south.
Air flows from sub tropical ridge towards sub polar low.
In Southern hemisphere, north westerly
111
When coriolis matches gradient force, which direction does gradient wind flow?
Gradient wind flows parallel to curved isobars
112
What is the friction layer?
Lower 3000 ft of atmosphere
113
What happens to wind in friction layer over land and sea?
Over land speed reduced by 2/3
| Over sea speed reduced by 1/3
114
What happens to wind and coriolis force in friction layer?
Reduced coriolis force
| Wind reduces and veers
115
What happens to wind above friction layer?
Wind flows parallel to isobars
116
Surface wind around a low pressure in southern hemisphere blows what direction?
Clockwise and inward
117
What are the high level clouds and what are the cloud bases above?
Cirrus
Cirrostratus
Cirrocumulus
Bases above 20000ft
118
What are cirrus clouds like?
White Fibrous or Threadlike Appearance.
Little turbulence unless associated with a jet stream.
Nil Icing.
119
What are cirrostratus clouds like?
White, Sheet or Layer. Halo Phenomena.
Turbulence may be felt on entering cloud, usually only light.
Usually too high for significant icing
120
What are cirrocumulus clouds like?
Global form of cloud indicates presence of turbulence.
| Too high for significant icing. Cloud usually dissipates rapidly.
121
What are thin altostratus clouds like?
Medium level.
Bluish sheet or layer.
Virga may be encountered.
Little turbulence in cloud. Distinct bumps felt on entering or leaving cloud.
Some icing risk. Usually light rime ice, as cloud particles are small and temperature is
usually low
122
What are thick altostratus clouds like?
Bluish sheet or layer. Sun appears as through glass at thinner portions.
Light to moderate rain or snow.
Generally light turbulence in cloud; may be moderate to severe at fronts, over highlands.
Bumps on entering or leaving.
Definite icing risk. Moderate rime. Clear ice possible in lower levels of clouds.
123
What are altocumulus clouds like?
Middle level cloud. White to grey.
Usually light turbulence.
Nil Icing
124
What are altocumulus lenticularis clouds like?
Lens or almond shaped.
Form of cloud indicates waves, which form in the atmosphere with consequent
turbulence, usually not severe.
May be light rime ice
125
What are altocumulus castellanus clouds like?
Turret or castle shaped protuberances on common base.
Possible rain showers.
Moderate to severe Turbulence.
May be light rime ice.
126
What are cumulus clouds like?
Low level, Cellular, Flat base, Small vertical extent, Cauliflower shaped.
Light to Moderate turbulence.
Little icing risk. Freezing level usually above cloud.
127
What are large cumulus clouds like?
Low level, Cellular, Flat base, Large vertical extent, Cauliflower like.
Showers of rain
Moderate/severe turbulence in and below cloud. Violent on entering or leaving.
Definite icing risk. Clear ice just above freezing height.
128
What are cumulonimbus clouds like?
Cellular, Very large vertical extent. Tops fibrous or striated, may be in shape of anvil.
Thunderstorms, lightening, showers of rain, snow or hail.
Severe turbulence both in and below cloud. Very violent on entering or leaving.
Definite icing risk. Dangerous clear ice possible.
129
What are stratocumulus clouds like?
Mostly grey.
May be drizzle
Light to moderate turbulence beneath and in cloud, bumpiness passing through inversion
at cloud top, smooth above.
Occasional Rime ice if freezing level is low enough
130
What are stratus clouds like?
Greyish, generally thin sheet or layer. May be ragged.
May be drizzle
Light turbulence. May be inversion as with Sc (Cloud limited due inversion)
Usually nil icing.
131
What is fog?
Cloud on the ground
Visibility below 1000 metres. Obliterates view of ground.
Nil turbulence.
Nil Icing
132
What is orographic uplift? And what happens in stable and unstable conditions with it?
Air forced up mountain
Air cools adiabatically
If stable, stratiform or nimbostratus clouds form, if unstable cumliform cloud
133
What are mountain waves?
```
Orographic uplift at right angles to the range with speed increasing to at least 25kts at top of range AND
Stable layer (inversion) above range
```
134
What is a passage of a cold front marked by?
Barbs pointing direction cold front is moving
135
What temp, wind and pressure happens in cold front?
Fall of temp
Back of wind
Rise in pressure
136
What temp, wind and pressure happens in warm front?
Rise in temp
Back of wind
Fall in pressure
137
A cold front usually lies along?
Trough of low pressure
138
A cold air mass is characterised by?
Unstable conditions and cumuloform clouds
139
Defined boundary between two air masses is called?
Front
140
Warm air masses are characterised by?
Stable but hazy conditions
141
What happens to warm and cold air at cold front?
Cold air is dissipating warm air at the surface
142
What happens to warm and cold air at warm front?
Warm air slides over cold air at surface
143
What weather scenario follows passage of warm front?
Nil significant weather
144
Where do cyclones form?
Between 5 and 15 degrees north or south of equator
145
Where does cyclone get its energy?
Heat stored in tropical waters. And from latent heat released during condensation and cloud formation
146
What is the life cycle of a cyclone?
Formative
Immature
Mature
Decaying
147
What happens in formative stage of cyclone?
Existing depression deepens
Winds reach gale force (greater than 34 knots)
Eye develops
148
What happens in the immature stage of cyclone?
Pressure falls below 1000HPa
Winds reach hurricane force (greater than 64 knots)
Spiral bands form
Storm radius 30-50km
149
What happens in the mature stage of cyclone?
Pressure steady
Area of storm expands
Hurricane force winds can expand up to 300 km away
150
In the southern hemisphere, where is the most destructive part of cyclone?
Front left quadrant
151
What happens in the decaying stage of cyclone?
Pressure begins to rise
Storm contracts
If land is encountered, cyclone turns into rain depression
152
When is cyclone season in Australia?
November to April
153
How does fog form?
Air cooled below dew point temperature
154
What is fog?
Cloud at ground with visibility less than 1000m with relative humidity near 100%
155
What is mist?
Visibility greater than 1000m
| Relative humidity less than 100%
156
How is fog formed by radiation? What conditions?
Air close to ground cooled
| Clear night with moist air, inversion and light wind (6kts)
157
When is radiation fog most intense?
Dawn when surface temperatures are the lowest
158
How is fog formed by advection? What conditions?
Warm moist air cools as it flows over cool surface
159
When does fog disipate?
Air temperature raises above dew point
| Wind mixes dry air
160
What conditions must exist for thunderstorm?
```
Unstable conditions (steep ELR)
Abundant supply of water (high humidity)
Lifting mechanism to trigger (heat, front terrain, convergence)
```
161
What happens in the cumulus (developing) stage of a thunderstorm?
Updraughts as cloud builds.
| Cloud is warmer than the environment so vertical development continues
162
What happens in the mature stage of a thunderstorm?
Cumulonimbus Cloud with anvil shaped top
Rain falls
Strong down and up draughts
Drop in temp ahead of storm
163
What happens in the dissipating stage of a thunderstorm?
Only down draughts
Rain decreases
Cloud breaks up
164
How long does a storm last?
Approx 60 mins
165
What is a frontal thunderstorm?
Formed by instability at boundary between two air masses.
| Closely spaced and fast moving
166
What is cold stream thunderstorm?
Cold air over warm surface
167
What are the hazards of thunderstorm?
Severe turbulence
Heavy rain, hail
Lightning
168
What are jet streams?
Fast moving narrow current of air
169
Where are jet streams found?
Near the tropopause
170
What characterised jet stream?
Strong horizontal wind shear
171
Surface wind compared to gradient wind does what with regard to backing/veering and speed?
Surface wind veers to the right and is slower
172
Over land, what does surface wind do?
Veers by 30 degrees and slowed by 2/3
173
Anticyclonic wind flows about what?
High in southern hemisphere
174
What does a Fohn wind do to humidity at mountains?
Lower humidity on lee side of mountain at low level
175
What does surface friction do to coriolis effect?
Decreases it
176
When is conditional stability said to occur?
SALR is unstable
| DALR is stable
177
What cloud produces virga?
Thin altostratus
178
What is a low level jet?
Fast moving stream at low level
179
How is a low level jet formed?
Air circulating around a high hit mountain range and accelerated into narrow stream along the range
180
What must be present for a low level jet?
Surface inversion
181
When are max speeds of low level jet ?
Early morning
182
What conditions will result in considerable lee side turbulence?
Stable conditions
183
What is a sign of turbulence near mountains?
Lenticular clouds with rotor cloud under
184
What is the common temp for rime ice to form?
-10 to -20
185
What cloud types can you get rime ice in?
Stratiform clouds
186
How does rime ice form?
Small super cooled droplets freezing on impact with aircraft surface
187
What is the common temp for clear ice?
0 to -15
188
When can clear ice be encountered?
Cumuliform clouds above freezing level
189
What icing is there in altostratus?
Light rime
| Clear ice if very thick
190
Meteorological visibility refers to what?
The greatest visibility prevailing over half or more of the horizon
191
What does INTER on forecast mean?
Phenomena expected to last for less than 30 mins
192
What does TEMPO mean on the forecast?
Phenomena expected to last for less than 60 mins but more than 30mins
193
If conditions are colder than ISA what does the altimeter do?
Sense lower pressure and OVERREAD
| pilot believe they are higher then they are
194
If conditions are warmer than ISA what does the altimeter do?
Sense higher pressure and UNDERREAD
195
What is the rule of thumb for operating at higher altitudes and ISA temp/pressure deviation
4% of indicated height per 10 degrees of variation from ISA
196
Where are jet streams often found?
Breaks in the tropopause
197
What are jet streams like?
Strong horizontal and vertical wind shears and speed in excess of 60knots
198
What direction are jet streams?
Westerly
199
Where is CAT considered most severe?
On the polar side of the jet stream below the level of the core.
Also in winter
200
What is an isotach?
Join points of equal wind speed showing the max wind speed in the jet core
201
Where are strong down draughts close to the ground, air mass or frontal thunderstorms?
Strong down draughts close to the ground are more likely beneath frontal
202
What conditions are more favourable for formation of low level jet across souther QLD?
Early morning
Clear sky
HIGH centred to the west of GDR
203
What conditions are required for dust storm of Adelaide?
Approaching cold front
| High pressure area to the East
204
What would there be with a fast moving cold front?
Broken cumliform clouds
| Rain showers
205
What conditions are required for a dust storm?
Land surface dry and dusty
Wind at least moderate
Unstable atmosphere
206
What is the most likely cause of turbulence over land on a hot day?
Thermal convection
207
What type of cloud is associated with unstable air over a mountain?
Cloud with extensive vertical development
208
What happens to the wind, temp and pressure with the passage of a cold front?
Wind backs
Temp falls
Pressure rises
