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ATPL Meteorology > Atmosphere > Flashcards

Atmosphere Flashcards

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1
Q

Approx composition of dry air by volume

A

Nitrogen 78%

Oxygen 21%

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2
Q

What % of atmosphere can be made up of water

A

Up to 4 %

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3
Q

In order, the different layers of the atmosphere (low to high)

A 
Troposphere 
Tropopause 
Stratosphere 
Stratopause 
Mesosphere
Mesopause 
Thermosphere
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4
Q

What is the lapse rate in the Troposphere

A

Lapse rate 2°c / 1000ft (1.98°c)

Or

0.65°c / 100m

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5
Q

What % of the earths gasses are in the troposphere

A

75%

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6
Q

How high does the troposphere extend

A

11km average or 36,000 feet

Equator 16-18 km

Poles 8-10km

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7
Q

What causes tropopause folds

A

Large surface temperature changes over a short distance cause abrupt changes in height of the tropopause

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8
Q

Tropopause temperature

A

Isothermal = -56.5°c = ISA

Over equator can be -75°c
Over poles can be -40/-50°c

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9
Q

Stratosphere height range

A

From tropopause to around 50km

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10
Q

Stratosphere temperature

A

At tropopause remains constant until 20 km

Then increases at 0.3°c/ 1000ft

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11
Q

Mesosphere height range

A

50km - 80km

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12
Q

Mesosphere characteristics

A

Coldest layer of the atmosphere at around -90°c

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13
Q

Thermosphere characteristics

A

Ever increasing temperature

Boundary for space occurs around 120km

Temp can vary as high as 2000°c depending on solar activity

The ionosphere is found here

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14
Q

ISA temperature

A

+15°c

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15
Q

ISA pressure

A

1013.25Hpa

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16
Q

ISA density

A

1.225kg/m^3

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17
Q

Pressure lapse rates

A

0-10,000 = 1hpa / 27 feet

10,000 - 18,000 = 1hpa/ 37 feet

18,000 > = 1 hpa / 50 feet

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18
Q

Density at 10,000feet

A

0.903 kg/m^2 (75% of msl)

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19
Q

Density at 22,000 feet

A

0.609 kg/m^3 (50% of msl)

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20
Q

Density at 40,000 feet

A

0.302 kg/m^3 (25% of msl)

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21
Q

Freezing temperature in Fahrenheit

A

32°F

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22
Q

Boiling temperature in Fahrenheit

A

212°c

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23
Q

How to get air temperature accurately

A

Stevenson screen placed 4feet (1-2m) off the ground away from ground heat radiation

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24
Q

How is the temperature high up measured

A

Radiosonde

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25
What is insolation
Hearing of the earth from suns rays
26
What is terrestrial radiation
Radiation let off by the earths surface due to suns heating
27
What is conduction
Heating of the air next to the ground by contact with the warmer ground
28
What is convection
The vertical transfer of heat
29
What is advection
The horizontal transfer of heat
30
What is latent heat
The heat released or absorbed without changing temperature
31
Hottest time of day is...
2/3 hours after local mid day
32
Coldest time of day is..
30 mins after sunrise
33
Latitudinal variations
The sun rays striking the ground at different angles Heat equator = straight on Poles = at angles
34
What effect does the sea have on diurnal variations
Hotter nights and colder days
35
Effect of wind on diurnal temperature variations
Colder during day, hotter during night
36
How does cloud affect diurnal temperature variations
Cloud = colder days Hotter nights No cloud = hotter days Colder nights
37
What is a isothermal layer
No change in temperature with vertical distance
38
What is a nocturnal surface inversion
When the air in the atmosphere has cooled slightly but the air next to land has cooled more meaning the air above is warmer
39
How does a aneroid barometer work
As static pressure decreases the pressure inside the capsule stays the same and expands the capsule which is manually or electively connected to a needle
40
What is a valley inversion
When air in a valley cools quicker than air above the valley
41
What is a frontal inversion
When cold air in the front is more dense than warm air so is pushes the warm air up
42
What is a high pressure inversion
When the air is heated as it defends, when the air is heated more above than it is below it can’t descend any further (as hot air is less dense) there for inversion is created
43
What is a col
Area of not much slack in the isobars between 2 high and 2 low pressures
44
What weather does a col bring
Thunderstorms in summer Fog in winter
45
Is the pressure change higher or lower in cold or warm weather
Higher in warm air pressure Lower in cold air pressure
46
Isohypes
Lines of equal pressure above the surface Like isobars except for vertical distance
47
How does temperature affect transition level
Cold air = lower | Warm air = higher
48
How much does altitude differ for ever 1°c deviation from ISA
120 feet
49
What % do you apply to the indicated altitude for 10°c deviation from the ISA
4%
50
Bernoulli effect on altitude reading
Increased airflow causes a reduction in static pressure = dynamic pressure up Therefore altimeter over reads
51
Why do thermal lows occur over water in winter
Because air over water is warmer than surrounding air = rises = low
52
What is a orographic low
Where air flows round a mountain and leaves an area of less air at the downwind side of the mountain
53
What does a blocking anticyclone do
Blocks polar fronts by diverting them
54
What is a temporary cold anticyclone
Only exists between 2 polar low pressures
55
What is the heat equator
Equatorial low pressure belt
56
What needs to be present for condensation to occur
A nuclei for the water vapour to form around
57
What is absolute humidity
The amount of water vapour in a given unit of air (g/m^3)
58
what is specific humidity
The mass of water vapour compared to the mass of air Kg/kg
59
What is relative humidity
The amount of water vapour present compared to the amount of water that could be present if the air was saturated given as a %
60
How much water vapour is there at -20°c
0.8g
61
How much water vapour is there at -10°c
1.8g
62
How much water vapour is there at 0°c
3.8g
63
How much water vapour is there at 10°c
7.8g
64
How much water vapour is there at 20°c
15g
65
How much water vapour is there at 30°c
28g
66
When is relative humidity at its highest
In the morning 30 mins after sunrise
67
What is adiabatic cooling
Where air rises and cools, when the air expands due to a less pressure there for the molecules have more room to spread out reducing the temperature
68
What is adiabatic warming
Where a parcel of air sinks it is in a higher pressure environment there for occupies less space, in turn this means the particles hit off each other more frequently causing a rise in temperature
69
What is the dry adiabatic lapse rate (DALR)
1°c / 100m 3°c / 1000ft Only applies when air is anything less than 100% relative humidity
70
What is the saturated adiabatic lapse rate (SALR)
0. 6°c / 100m 1. 8°c /1000 f Only when relative humidity is 100%
71
What is absolute stability
When a parcel of air is risen from its equilibrium... once the original lifting force is removed it returns to its equilibrium This happens when the ELR is less than the DALR and the SALR
72
How stable do inversions and isotherms tend to be
Very stable
73
What does the weather in absolutely stable conditions tend to be like
``` Clouds = very flat Precipitation = fairly light Visibility = haze, for, mist (due to lack of vertical air movement) Turbulence = usually little or non ```
74
What is absolute instability
When the ELR is greater than the DALR and the SALR This means once a parcel of air is displaced from its equilibrium it will keep rising
75
When might you find air that is absolutely unstable
Summer afternoon Because air next to surface is hot Air further up is considerably cooler Therefor High ELR
76
Weather in unstable conditions
Clouds = clouds of considerable vertical extent Precipitation = intense Visibility = good Turbulence = moderate to severe
77
What is conditional instability
This depends on weather the air is dry or saturated for it to be stable or unstable DALR will be stable SALR will be unstable
78
What is neutral stability
When the either the DALR or the SALR are the same as the ELR so when the air is displaced it is the same temp as the outer environmental air therefor stays at the same height
79
In cloud form what does cumulus mean
Vertically developed (unstable air)
80
Water vapour that isn’t attached to a nuclei and is below freezing is said to be what
Super cooled
81
Water vapour from 0°c > - 10°c is said to be what
Almost entirely super cooled water
82
Water vapour between -10°c and -40°c is said to be what
A mixture of supercooled water droplets and ice particles
83
Water vapour less than -40°c is said to be what
Almost entirely ice particles
84
What height is low level cloud
Surface - 6500ft
85
What height is middle level cloud
6500-23000
86
What heigh is high level cloud
16500-45000
87
What are High level cloud made up off
Ice crystals
88
What are medium level clouds made up of
Mixture of ice and water droplets
89
What are low level clouds made from
Mainly water droplets
90
What is 0 oktas of cloud cover
Sky clear
91
What is 1-2 oktas of cloud cover
Few
92
What is 3-4 oktas of cloud cover
Scattered
93
What is 5-7 oktas of cloud cover
Broken
94
What is 8 oktas of cloud cover
Overcast
95
What is the name of the laser used to measure cloud base
Ceilometer
96
What is the cloud ceiling
Lowest layer of cloud that covers more than half the sky (5 oktas or more)
97
What defines at cirrus cloud
Ci High whispy Ice crystals
98
What defines a cirrostratus cloud
Cs Thin veil of high level cloud Smooth appearance Halo phenomenon
99
What defines a cirrocumulus cloud
Cc High level Lumpy Round appearance Ripples
100
What defines a altostratus cloud
As Layer cloud Medium level Can just see the sun Can contain burga Can be high icing risk
101
What defines a altocumulus cloud
Ac Medium level Lumpy Shady Boulders Rounded appearance
102
What defines a stratus cloud
St Grey Ragged Sun can be seen in bits but no blue sky Flat layer
103
What defines a strato cumulus cloud
Sc Low patchy Dark Thick Rounded Slightly layered
104
What defines a nimbostratus cloud
Low - medium level High water content Dark Thick
105
What defines a cumulus cloud
Cu Low level Vertically formed Rounded Fluffy
106
What defines a cumulonimbus cloud
Cb Heavy Dense Towering Up to tropopause Heavy rain or hail
107
What defines a cumulus humilis
Cu hum Low level Below 10,000 Fair weather Shallow
108
What defines a cumulus mediocris cloud
Cu med Low level Medium vertical extent Max 10,000 feet
109
What defines a cumulus congestus
Cu con Towering cumulus Up to 25,000 Low / medium level base
110
What defines a cumulonimbus calvus
Cb calv Up to 45,000 Sharp outlines
111
Cumulonimbus capillatus
Cb cap Flat top at tropopause
112
What defines a fractus cloud
St/cu Broken cumulus (fractured)
113
What defines a castellanus cloud
Acc Middle level Castle like Instability Cirrus Cirrocumulus Alto cumulus
114
What defines a mamatus cloud
Downward hanging cloud shape Thunderstorm
115
What defines a lenticularis cloud
Cc / Ac / Sc Lens shape Like flying saucers
116
What is the cloud descriptor ISOL
Isolated (individual)
117
What is the cloud descriptor OCNL
Occasional (well- separated)
118
What is the weather descriptor FRQ
Frequent (little or no separation)
119
What is the cloud descriptor EMBO
Embedded
120
What is the cloud descriptor WDSPD
Widespread
121
What is the wegener-Bergeron- findeisen process
Ice crystals grow Water attaches to ice crystals causing them to grow more Once weight overcomes any updrafts then they fall to earth
122
What is the coalescence theory
All precipitation starts at temperatures above 0°c (water droplets) Water droplets combine and make larger droplets These fall out the clouds
123
What is the size of a cloud droplet
0.02mm
124
What is the size speed and code of drizzle
DZ 0.5mm 4m/s Shallow cloud (stratiform)
125
What is the size speed and code for rain
RA 0.5-5.5mm 9m/s Almost all clouds
126
What is the code for ice crystals
IC
127
What is the temp range and code for snow
SN -5°c > 4°c Biggest firmed at 0°c
128
What is the size and code of snow grains
SG <1mm Stratiform clouds
129
What is the size of snow pellets / soft hail
2-5mm Breaks on impact with the ground
130
What is the size and code of ice pellets
PL up to 5mm Nimbostratus
131
What’s the size and weight and code of hail
GR >5mm 1kg From CB frozen droplets tossed up and down repeatedly in cb
132
What is the code and size of small hail
GS <5mm From CB
133
What causes freezing rain
An inversion under a warm front underneath a nimbostratus
134
What are the prerequisites for continuous precipitation
60 mins with no breaks As Ns
135
What is intermittent precipitation
Continuous with breaks As Sc
136
What clouds are showers from
Cumuliformed clouds
137
What is the scale of intensity for rain
Slight Moderate Heavy Violent
138
What is the visibility in drizzle
Often <500m
139
What is the visibility in heavy rain
<1000m
140
What is the visibility in moderate rain
3-10km
141
What is the visibility in heavy snow
<50m
142
What is the visibility in moderate snow
1000m
143
What is the visibility in blowing surface snow
Greatly reduced (can be white out)
144
What types of precipitation takes place in stratocumulus
Rain Freezing rain Snow Snow pellets
145
What precipitation occurs in nimbostratus clouds
Rain Freezing rain Snow Ice pellets
146
What precipitation occurs in altostratus clouds
Rain Freezing rain Snow Ice pellets
147
What precipitation occurs in cumulus clouds
Rain | Snow
148
What precipitation occurs In cumulonimbus clouds
Rain Snow Snow pellets Hail
149
What precipitation occurs in stratus clouds
Drizzle Freezing drizzle Snow grains Ice crystals
150
What pressure setting are isobars taken from
QFF
151
What are the 3 conditions for a thunderstorm
Unstable air through at least 10,000ft above the freeing layer Lots of moisture Trigger for up lift (low pressure, convection, weather fronts)
152
What is a heat thermal thunderstorm
Land heats up (clear skies) This heats up the air next to land (typically late afternoon) Causing a high ELR Therefore ELR > DALR
153
What is a air mass thunderstorm
Cold air moves over warm surface (cold sea to warm land / warm sea to cold land) Warm moist air rises through cold air Rapidly rises
154
What is a frontal thunderstorm
Cold air cuts under warm air Warm air forced up Creates thunderstorm
155
What is a squall line
Frontal thunderstorms along a cold front Can be 100’s miles long
156
What is a orographic thunderstorm
Can happen day or night Where air is forced up by the land
157
What speed do thunderstorms move at
Usually the wing speed at 10,000ft (only a rough guid)
158
What is the first stage of a thunderstorm
Initial / cumulative phase
159
What speed can air rise at in the cumulative / building stage of a thunderstorm
>60kts
160
How long does the building stage of a thunderstorm last
15-30 mins
161
What is the second stage of a thunderstorm called
Mature stage
162
How long does the mature stage of a thunderstorm last usually
20 mins
163
What are the characteristics of the mature stage of a thunderstorm
``` Rising air Precipitation Downdraughs Wind sheer / gusting conditions 20miles ahead Very turbulent 6,000ft up or down Microbursts 4/5km upto 5 mins ```
164
How is a “roll” created in a thunderstorm
As downdraught hits ground and bounces back up it creates a roll infront of the storm
165
What is a shelf cloud
Warmer air infront of thunderstorm gets sucked into storm
166
When does a microburst turn into a macroburst
When it lasts longer than 5 mins
167
What causes and anvil formation on top of a thunderstorm
Caused by updraughs pushing air up to tropopause creating a thunderstorm “hat”
168
What is stage 3 of a thunderstorm
The dissipating stage
169
How long does the dissipating stage of a thunderstorm last
1-2 hours
170
What happens in the dissipating stage of s thunderstorm
Downdraughs only Precipitation reducing Cloud base rising Still chance of hail
171
What is a supercell thunderstorm
Forms the same as a single cell thunderstorm except lasts longer Upper winds cause cell to “tilt” = downdraughs are not going through updraughs = doesn’t cancel them out
172
What is the radius / region of a microburst
3nm (5km) usually
173
What is the radius / region of a macroburst
3-5 miles across
174
Does an anvil have precipitation
No but hail can be found in the armpit of the anvil
175
How could you summarise the 3 stages of a thunderstorm
1) updraughs only 2) up and downdraughs 3) downdraughs only
176
What are the hazards of thunderstorms
Structural damage ``` Hail (can fire out top of storm) Turbulence Lightning Tornados Debris Icing ```
177
What dangers can hail cause to engines
Ingestion can cause too much water into engine causing a flame out
178
What is st Elmo’s fire
Static building up outside aircraft
179
What is thunder and lightning
Lighting = electrostatic discharge Thunder = rapid expansion of air due to heating from lightning
180
What is the main risk from lightning
Instrument = unreliable
181
What instrument errors can occur in a thunderstorm
Pressure sensors, rising and falling air can cause them to give unreliable readings Magnetic from lightning
182
How does virga cause icing
Rain falling Rain evaporating Latent heat lost in surrounding air Temperature falls
183
What is the first stage of windshear
Lift, IAS increase
184
What is the second stage of windshear
Downdraughs
185
What is the third stage of windshear
Tail wind
186
When does a tornado become a tornado
When the funnel of spinning air (funnel cloud) only becomes a tornado when it touches the ground
187
What is the time duration of a tornado
30 mins max
188
What is the average diameter of a tornado
100-150m
189
Where and when are tornados most frequent
Mid west USA Late spring early summer
190
What can the wind speeds of a tornado be
120-150kts (can exceed 200)
191
What is the ground speed of a tornado
20-40kts
192
How do you measure the intensity of a tornado
Fujita scale (mph)
193
What is a tornado over water called
A water spout
194
What is a dust devil
Like a tornado but smaller (10-100ft wide) upto 600ft tall
195
What is common consequence of static electricity on the radios
Noise on high / medium frequency radio bands As static increases noise increases
196
What gives you weather radar returns
``` (Strongest to weakest) Wet hail Rain Hail Wet snow Dry hail Dry snow ```
197
What is the avoidance distance for thunderstorms >20,000ft
By 20 miles at least 5000ft above and below
198
What distance should thunderstorms be avoided by <20,000
10 miles at least 5,000ft up and down
199
What frequency band is highly sensitive to wet precipitation
8-12 ghz | 2.5 and 4 cm
200
For airfields below sea level in warm air the QFF is what compared to QNH
QFF is higher than QNH
201
For airfields below sea level in cold conditions the QFF is what compared to QNH
QFF lower than QNH
202
What are the regions affected by tropical revolving thunderstorms
America = hurricanes South east China = typhoons Everywhere else = cyclone
203
What % of hurricanes (TRS) occur in the North Atlantic
10-12%
204
How many cyclones (TRS) occur off North east Australian coast
10%
205
Where do most of the TRS occur
China sea
206
What is the speed requirement for a tropical depression
20-33 knots
207
What is the speed requirement for a tropical storm
34-63 knots
208
What is the speed requirement for a tropical revolving storm
Wind greater than 64 knots and rotating around a defined core
209
What is the Beaufort scale
Measures intensity of hurricanes (TRS)
210
What is a category 1 hurricanes
64-82 knots
211
Where do TRS occur
5°-25°N/S of equator
212
What sea temperature is required for a TRS
26.5°c
213
What is the minimum depth of ocean for a TRS to form
200-300 feet deep
214
Where are the worst conditions in a TRS
Eye wall Worst precipitation / wind speeds / turbulence
215
How quickly does a TRS travel across the ground
15-20 knots
216
What is the main objective of the tropical cyclone advisory centre (TCAC)
A meteorological centre designated by regional air navigation agreement to provide advisory information
217
What is the conditions in the eye of the TRS like
Calm and clear skies
218
Where are the highest winds found in a TRS in the northern hemisphere
Just to the right of track
219
What is the size of the eye of a TRS
20-50 km
220
When is the peak period for TRS
June - October in norther Hemisphere Deferment - April in Southern Hemisphere
221
What cloud is the highest risk of icing
Medium level (alto) Due to mix of super cooled water droplets + water droplets + ice crystals
222
What type of moisture consists in cloud between 0 to -20°c
Both large and small super cooled water droplets
223
What moisture occurs in clouds between -20 and -40 °c
Small super cooled water droplets
224
What moisture is present in clouds below -40°c
Most droplets have frozen
225
How much of a SCWD freezes on impact for ever 1°c below 0°
1/80th
226
What is the most severe temperature for icing
Most severe ice forming temperature is 0 to -10°c due to large SCWD
227
What is the worst wing speed combination for icing
Thing high speed wing
228
Can anti/de-icing equipment sustain long periods of icing
No icing or anti icing equipment can cope with prolonged flight in severe icing conditions
229
What is hoar frost
Water vapour sublimated onto cold surface No cloud
230
What is rime ice
Caused by impact with small SCWD On leading edge of aircraft Builds forwards Trapped air creates opaque appearance Easy to remove Can be in FZFG -15°c / -40°c
231
What is clear ice (glaze ice)
Flows back over wing surface Increases weight Large SCWD Fraction freezes on impact rest flows back and freezes over wing Covers whole airframe rapidly Difficult to remove 0/-15°c Worst in CB
232
What is FZRA
Freezing rain Found ahead of warm front Clear ice Can be 100’s miles line 500’s miles wide
233
What is mixed ice
Mix of small and large SCWD Clear and rime ice -20 / -10 °c Horned rough appearance
234
What is cloudy ice / packed snow
flying though air below freezing with wet wing Ice crystals attach to wing Snowflakes also attach
235
What risk is there if icing in CB
Clear ice / mod - sev
236
Stratiform icing risk
Light / mod risk <0°c small SCWD Drizzle
237
What risk of icing is there in High level cloud
Light risk
238
What icing risk is there in medium level cloud
Light to moderate
239
What icing risk is in stratiform (low) cloud
Light to mod
240
What icing risk is in nimbostratus/ cumuliform cloud
Mod / sev
241
What risk of icing if nimbostratus or cumulus is caused by orographic lifting
Severe Orographic intensification
242
What is a severe risk of icing
Accumulation is greater than rate you can get rid of it Immediate diversion needed
243
What is moderate icing
Icing equipment is able to cope
244
What is light icing
Accumulation might be a problem if in situation for over 1 hour Occasional use of icing equipment
245
What is trace icing
Not hazardous even without icing equipment
246
How to calculate the lowest usable flight level to give a min safe altitude
Lowest QNH Lowest temp
247
What icing severity is mandatory to report
Moderate | Severe
248
What is the pressure 10,000 ft
700hpa
249
What is the pressure at 20,000ft
500hpa
250
What is the pressure at 30,000ft
300hpa
251
What is the pressure at 40,000ft
200hpa
252
What is the definition of relative humidity
Relative humidity is the absolute humidity relative to the maximum for that temperature as a percentage
253
What is the pressure lapse rate
27 ft / hpa 8m / hpa
254
What are the geostrophic winds like on isobars
Isobars are straight lines with no surface friction
255
What does wind speed change by over water with decreasing height
Backs / slacks 10° / 75% of speed
256
When is the windspeed higher with straight isobars compared to curved isobars
Windspeed higher with curved anticyclone isobars if all other factors are constant
257
What height (in hpa) is a max wind speeds for a subtropical jet stream in summer
Around 200hpa Below tropopause
258
Low level cloud height
GL - 6500

ATPL Meteorology (8 decks)

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