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ATPL Meteorology > Atmosphere > Flashcards

Atmosphere Flashcards

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
Q

What is insolation

A

Hearing of the earth from suns rays

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26
Q

What is terrestrial radiation

A

Radiation let off by the earths surface due to suns heating

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27
Q

What is conduction

A

Heating of the air next to the ground by contact with the warmer ground

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28
Q

What is convection

A

The vertical transfer of heat

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29
Q

What is advection

A

The horizontal transfer of heat

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30
Q

What is latent heat

A

The heat released or absorbed without changing temperature

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31
Q

Hottest time of day is…

A

2/3 hours after local mid day

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32
Q

Coldest time of day is..

A

30 mins after sunrise

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33
Q

Latitudinal variations

A

The sun rays striking the ground at different angles

Heat equator = straight on

Poles = at angles

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34
Q

What effect does the sea have on diurnal variations

A

Hotter nights and colder days

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35
Q

Effect of wind on diurnal temperature variations

A

Colder during day, hotter during night

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36
Q

How does cloud affect diurnal temperature variations

A

Cloud = colder days
Hotter nights

No cloud = hotter days
Colder nights

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37
Q

What is a isothermal layer

A

No change in temperature with vertical distance

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38
Q

What is a nocturnal surface inversion

A

When the air in the atmosphere has cooled slightly but the air next to land has cooled more meaning the air above is warmer

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39
Q

How does a aneroid barometer work

A

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

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40
Q

What is a valley inversion

A

When air in a valley cools quicker than air above the valley

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41
Q

What is a frontal inversion

A

When cold air in the front is more dense than warm air so is pushes the warm air up

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42
Q

What is a high pressure inversion

A

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

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43
Q

What is a col

A

Area of not much slack in the isobars between 2 high and 2 low pressures

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44
Q

What weather does a col bring

A

Thunderstorms in summer

Fog in winter

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45
Q

Is the pressure change higher or lower in cold or warm weather

A

Higher in warm air pressure

Lower in cold air pressure

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46
Q

Isohypes

A

Lines of equal pressure above the surface

Like isobars except for vertical distance

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47
Q

How does temperature affect transition level

A

Cold air = lower

Warm air = higher

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48
Q

How much does altitude differ for ever 1°c deviation from ISA

A

120 feet

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49
Q

What % do you apply to the indicated altitude for 10°c deviation from the ISA

A

4%

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50
Q

Bernoulli effect on altitude reading

A

Increased airflow causes a reduction in static pressure = dynamic pressure up

Therefore altimeter over reads

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51
Q

Why do thermal lows occur over water in winter

A

Because air over water is warmer than surrounding air = rises = low

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52
Q

What is a orographic low

A

Where air flows round a mountain and leaves an area of less air at the downwind side of the mountain

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53
Q

What does a blocking anticyclone do

A

Blocks polar fronts by diverting them

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54
Q

What is a temporary cold anticyclone

A

Only exists between 2 polar low pressures

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55
Q

What is the heat equator

A

Equatorial low pressure belt

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56
Q

What needs to be present for condensation to occur

A

A nuclei for the water vapour to form around

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57
Q

What is absolute humidity

A

The amount of water vapour in a given unit of air (g/m^3)

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58
Q

what is specific humidity

A

The mass of water vapour compared to the mass of air

Kg/kg

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59
Q

What is relative humidity

A

The amount of water vapour present compared to the amount of water that could be present if the air was saturated given as a %

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60
Q

How much water vapour is there at -20°c

A

0.8g

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61
Q

How much water vapour is there at -10°c

A

1.8g

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62
Q

How much water vapour is there at 0°c

A

3.8g

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63
Q

How much water vapour is there at 10°c

A

7.8g

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64
Q

How much water vapour is there at 20°c

A

15g

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65
Q

How much water vapour is there at 30°c

A

28g

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66
Q

When is relative humidity at its highest

A

In the morning 30 mins after sunrise

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67
Q

What is adiabatic cooling

A

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

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68
Q

What is adiabatic warming

A

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

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69
Q

What is the dry adiabatic lapse rate (DALR)

A

1°c / 100m
3°c / 1000ft

Only applies when air is anything less than 100% relative humidity

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70
Q

What is the saturated adiabatic lapse rate (SALR)

A
  1. 6°c / 100m
  2. 8°c /1000 f

Only when relative humidity is 100%

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71
Q

What is absolute stability

A

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

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72
Q

How stable do inversions and isotherms tend to be

A

Very stable

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73
Q

What does the weather in absolutely stable conditions tend to be like

A 
Clouds = very flat 
Precipitation = fairly light
Visibility = haze, for, mist (due to lack of vertical air movement)
Turbulence = usually little or non
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74
Q

What is absolute instability

A

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

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75
Q

When might you find air that is absolutely unstable

A

Summer afternoon

Because air next to surface is hot
Air further up is considerably cooler

Therefor

High ELR

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76
Q

Weather in unstable conditions

A

Clouds = clouds of considerable vertical extent

Precipitation = intense

Visibility = good

Turbulence = moderate to severe

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77
Q

What is conditional instability

A

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

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78
Q

What is neutral stability

A

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

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79
Q

In cloud form what does cumulus mean

A

Vertically developed (unstable air)

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80
Q

Water vapour that isn’t attached to a nuclei and is below freezing is said to be what

A

Super cooled

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81
Q

Water vapour from 0°c > - 10°c is said to be what

A

Almost entirely super cooled water

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82
Q

Water vapour between -10°c and -40°c is said to be what

A

A mixture of supercooled water droplets and ice particles

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83
Q

Water vapour less than -40°c is said to be what

A

Almost entirely ice particles

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84
Q

What height is low level cloud

A

Surface - 6500ft

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85
Q

What height is middle level cloud

A

6500-23000

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86
Q

What heigh is high level cloud

A

16500-45000

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87
Q

What are High level cloud made up off

A

Ice crystals

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88
Q

What are medium level clouds made up of

A

Mixture of ice and water droplets

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89
Q

What are low level clouds made from

A

Mainly water droplets

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90
Q

What is 0 oktas of cloud cover

A

Sky clear

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91
Q

What is 1-2 oktas of cloud cover

A

Few

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92
Q

What is 3-4 oktas of cloud cover

A

Scattered

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93
Q

What is 5-7 oktas of cloud cover

A

Broken

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94
Q

What is 8 oktas of cloud cover

A

Overcast

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95
Q

What is the name of the laser used to measure cloud base

A

Ceilometer

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96
Q

What is the cloud ceiling

A

Lowest layer of cloud that covers more than half the sky (5 oktas or more)

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97
Q

What defines at cirrus cloud

A

Ci

High whispy

Ice crystals

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98
Q

What defines a cirrostratus cloud

A

Cs

Thin veil of high level cloud

Smooth appearance

Halo phenomenon

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99
Q

What defines a cirrocumulus cloud

A

Cc

High level

Lumpy

Round appearance

Ripples

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100
Q

What defines a altostratus cloud

A

As

Layer cloud

Medium level

Can just see the sun

Can contain burga

Can be high icing risk

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101
Q

What defines a altocumulus cloud

A

Ac

Medium level

Lumpy

Shady

Boulders

Rounded appearance

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102
Q

What defines a stratus cloud

A

St

Grey

Ragged

Sun can be seen in bits but no blue sky

Flat layer

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103
Q

What defines a strato cumulus cloud

A

Sc

Low patchy

Dark

Thick

Rounded

Slightly layered

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104
Q

What defines a nimbostratus cloud

A

Low - medium level

High water content

Dark

Thick

105
Q

What defines a cumulus cloud

A

Cu

Low level

Vertically formed

Rounded

Fluffy

106
Q

What defines a cumulonimbus cloud

A

Cb

Heavy

Dense

Towering

Up to tropopause

Heavy rain or hail

107
Q

What defines a cumulus humilis

A

Cu hum

Low level

Below 10,000

Fair weather

Shallow

108
Q

What defines a cumulus mediocris cloud

A

Cu med

Low level

Medium vertical extent

Max 10,000 feet

109
Q

What defines a cumulus congestus

A

Cu con

Towering cumulus

Up to 25,000

Low / medium level base

110
Q

What defines a cumulonimbus calvus

A

Cb calv

Up to 45,000

Sharp outlines

111
Q

Cumulonimbus capillatus

A

Cb cap

Flat top at tropopause

112
Q

What defines a fractus cloud

A

St/cu

Broken cumulus (fractured)

113
Q

What defines a castellanus cloud

A

Acc

Middle level

Castle like

Instability

Cirrus

Cirrocumulus

Alto cumulus

114
Q

What defines a mamatus cloud

A

Downward hanging cloud shape

Thunderstorm

115
Q

What defines a lenticularis cloud

A

Cc / Ac / Sc

Lens shape

Like flying saucers

116
Q

What is the cloud descriptor ISOL

A

Isolated (individual)

117
Q

What is the cloud descriptor OCNL

A

Occasional (well- separated)

118
Q

What is the weather descriptor FRQ

A

Frequent (little or no separation)

119
Q

What is the cloud descriptor EMBO

A

Embedded

120
Q

What is the cloud descriptor WDSPD

A

Widespread

121
Q

What is the wegener-Bergeron- findeisen process

A

Ice crystals grow

Water attaches to ice crystals causing them to grow more

Once weight overcomes any updrafts then they fall to earth

122
Q

What is the coalescence theory

A

All precipitation starts at temperatures above 0°c (water droplets)

Water droplets combine and make larger droplets

These fall out the clouds

123
Q

What is the size of a cloud droplet

A

0.02mm

124
Q

What is the size speed and code of drizzle

A

DZ 0.5mm 4m/s

Shallow cloud (stratiform)

125
Q

What is the size speed and code for rain

A

RA 0.5-5.5mm 9m/s

Almost all clouds

126
Q

What is the code for ice crystals

A

IC

127
Q

What is the temp range and code for snow

A

SN -5°c > 4°c

Biggest firmed at 0°c

128
Q

What is the size and code of snow grains

A

SG <1mm

Stratiform clouds

129
Q

What is the size of snow pellets / soft hail

A

2-5mm

Breaks on impact with the ground

130
Q

What is the size and code of ice pellets

A

PL up to 5mm

Nimbostratus

131
Q

What’s the size and weight and code of hail

A

GR >5mm 1kg

From CB frozen droplets tossed up and down repeatedly in cb

132
Q

What is the code and size of small hail

A

GS <5mm

From CB

133
Q

What causes freezing rain

A

An inversion under a warm front underneath a nimbostratus

134
Q

What are the prerequisites for continuous precipitation

A

60 mins with no breaks

As Ns

135
Q

What is intermittent precipitation

A

Continuous with breaks

As Sc

136
Q

What clouds are showers from

A

Cumuliformed clouds

137
Q

What is the scale of intensity for rain

A

Slight
Moderate
Heavy
Violent

138
Q

What is the visibility in drizzle

A

Often <500m

139
Q

What is the visibility in heavy rain

A

<1000m

140
Q

What is the visibility in moderate rain

A

3-10km

141
Q

What is the visibility in heavy snow

A

<50m

142
Q

What is the visibility in moderate snow

A

1000m

143
Q

What is the visibility in blowing surface snow

A

Greatly reduced (can be white out)

144
Q

What types of precipitation takes place in stratocumulus

A

Rain
Freezing rain
Snow
Snow pellets

145
Q

What precipitation occurs in nimbostratus clouds

A

Rain
Freezing rain
Snow
Ice pellets

146
Q

What precipitation occurs in altostratus clouds

A

Rain
Freezing rain
Snow
Ice pellets

147
Q

What precipitation occurs in cumulus clouds

A

Rain

Snow

148
Q

What precipitation occurs In cumulonimbus clouds

A

Rain
Snow
Snow pellets
Hail

149
Q

What precipitation occurs in stratus clouds

A

Drizzle
Freezing drizzle
Snow grains
Ice crystals

150
Q

What pressure setting are isobars taken from

A

QFF

151
Q

What are the 3 conditions for a thunderstorm

A

Unstable air through at least 10,000ft above the freeing layer

Lots of moisture

Trigger for up lift (low pressure, convection, weather fronts)

152
Q

What is a heat thermal thunderstorm

A

Land heats up (clear skies)

This heats up the air next to land (typically late afternoon)

Causing a high ELR

Therefore ELR > DALR

153
Q

What is a air mass thunderstorm

A

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
Q

What is a frontal thunderstorm

A

Cold air cuts under warm air

Warm air forced up

Creates thunderstorm

155
Q

What is a squall line

A

Frontal thunderstorms along a cold front

Can be 100’s miles long

156
Q

What is a orographic thunderstorm

A

Can happen day or night

Where air is forced up by the land

157
Q

What speed do thunderstorms move at

A

Usually the wing speed at 10,000ft (only a rough guid)

158
Q

What is the first stage of a thunderstorm

A

Initial / cumulative phase

159
Q

What speed can air rise at in the cumulative / building stage of a thunderstorm

A

> 60kts

160
Q

How long does the building stage of a thunderstorm last

A

15-30 mins

161
Q

What is the second stage of a thunderstorm called

A

Mature stage

162
Q

How long does the mature stage of a thunderstorm last usually

A

20 mins

163
Q

What are the characteristics of the mature stage of a thunderstorm

A 
Rising air 
Precipitation 
Downdraughs 
Wind sheer / gusting conditions 20miles ahead
Very turbulent 6,000ft up or down 
Microbursts 4/5km upto 5 mins
164
Q

How is a “roll” created in a thunderstorm

A

As downdraught hits ground and bounces back up it creates a roll infront of the storm

165
Q

What is a shelf cloud

A

Warmer air infront of thunderstorm gets sucked into storm

166
Q

When does a microburst turn into a macroburst

A

When it lasts longer than 5 mins

167
Q

What causes and anvil formation on top of a thunderstorm

A

Caused by updraughs pushing air up to tropopause creating a thunderstorm “hat”

168
Q

What is stage 3 of a thunderstorm

A

The dissipating stage

169
Q

How long does the dissipating stage of a thunderstorm last

A

1-2 hours

170
Q

What happens in the dissipating stage of s thunderstorm

A

Downdraughs only

Precipitation reducing

Cloud base rising

Still chance of hail

171
Q

What is a supercell thunderstorm

A

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
Q

What is the radius / region of a microburst

A

3nm (5km) usually

173
Q

What is the radius / region of a macroburst

A

3-5 miles across

174
Q

Does an anvil have precipitation

A

No but hail can be found in the armpit of the anvil

175
Q

How could you summarise the 3 stages of a thunderstorm

A

1) updraughs only
2) up and downdraughs
3) downdraughs only

176
Q

What are the hazards of thunderstorms

A

Structural damage

Hail (can fire out top of storm)
Turbulence 
Lightning 
Tornados 
Debris 
Icing
177
Q

What dangers can hail cause to engines

A

Ingestion can cause too much water into engine causing a flame out

178
Q

What is st Elmo’s fire

A

Static building up outside aircraft

179
Q

What is thunder and lightning

A

Lighting = electrostatic discharge

Thunder = rapid expansion of air due to heating from lightning

180
Q

What is the main risk from lightning

A

Instrument = unreliable

181
Q

What instrument errors can occur in a thunderstorm

A

Pressure sensors, rising and falling air can cause them to give unreliable readings

Magnetic from lightning

182
Q

How does virga cause icing

A

Rain falling

Rain evaporating

Latent heat lost in surrounding air

Temperature falls

183
Q

What is the first stage of windshear

A

Lift, IAS increase

184
Q

What is the second stage of windshear

A

Downdraughs

185
Q

What is the third stage of windshear

A

Tail wind

186
Q

When does a tornado become a tornado

A

When the funnel of spinning air (funnel cloud) only becomes a tornado when it touches the ground

187
Q

What is the time duration of a tornado

A

30 mins max

188
Q

What is the average diameter of a tornado

A

100-150m

189
Q

Where and when are tornados most frequent

A

Mid west USA

Late spring early summer

190
Q

What can the wind speeds of a tornado be

A

120-150kts (can exceed 200)

191
Q

What is the ground speed of a tornado

A

20-40kts

192
Q

How do you measure the intensity of a tornado

A

Fujita scale (mph)

193
Q

What is a tornado over water called

A

A water spout

194
Q

What is a dust devil

A

Like a tornado but smaller (10-100ft wide) upto 600ft tall

195
Q

What is common consequence of static electricity on the radios

A

Noise on high / medium frequency radio bands

As static increases noise increases

196
Q

What gives you weather radar returns

A 
(Strongest to weakest)
Wet hail 
Rain 
Hail 
Wet snow 
Dry hail 
Dry snow
197
Q

What is the avoidance distance for thunderstorms >20,000ft

A

By 20 miles at least 5000ft above and below

198
Q

What distance should thunderstorms be avoided by <20,000

A

10 miles at least 5,000ft up and down

199
Q

What frequency band is highly sensitive to wet precipitation

A

8-12 ghz

2.5 and 4 cm

200
Q

For airfields below sea level in warm air the QFF is what compared to QNH

A

QFF is higher than QNH

201
Q

For airfields below sea level in cold conditions the QFF is what compared to QNH

A

QFF lower than QNH

202
Q

What are the regions affected by tropical revolving thunderstorms

A

America = hurricanes
South east China = typhoons
Everywhere else = cyclone

203
Q

What % of hurricanes (TRS) occur in the North Atlantic

A

10-12%

204
Q

How many cyclones (TRS) occur off North east Australian coast

A

10%

205
Q

Where do most of the TRS occur

A

China sea

206
Q

What is the speed requirement for a tropical depression

A

20-33 knots

207
Q

What is the speed requirement for a tropical storm

A

34-63 knots

208
Q

What is the speed requirement for a tropical revolving storm

A

Wind greater than 64 knots and rotating around a defined core

209
Q

What is the Beaufort scale

A

Measures intensity of hurricanes (TRS)

210
Q

What is a category 1 hurricanes

A

64-82 knots

211
Q

Where do TRS occur

A

5°-25°N/S of equator

212
Q

What sea temperature is required for a TRS

A

26.5°c

213
Q

What is the minimum depth of ocean for a TRS to form

A

200-300 feet deep

214
Q

Where are the worst conditions in a TRS

A

Eye wall

Worst precipitation / wind speeds / turbulence

215
Q

How quickly does a TRS travel across the ground

A

15-20 knots

216
Q

What is the main objective of the tropical cyclone advisory centre (TCAC)

A

A meteorological centre designated by regional air navigation agreement to provide advisory information

217
Q

What is the conditions in the eye of the TRS like

A

Calm and clear skies

218
Q

Where are the highest winds found in a TRS in the northern hemisphere

A

Just to the right of track

219
Q

What is the size of the eye of a TRS

A

20-50 km

220
Q

When is the peak period for TRS

A

June - October in norther Hemisphere

Deferment - April in Southern Hemisphere

221
Q

What cloud is the highest risk of icing

A

Medium level (alto)

Due to mix of super cooled water droplets + water droplets + ice crystals

222
Q

What type of moisture consists in cloud between 0 to -20°c

A

Both large and small super cooled water droplets

223
Q

What moisture occurs in clouds between -20 and -40 °c

A

Small super cooled water droplets

224
Q

What moisture is present in clouds below -40°c

A

Most droplets have frozen

225
Q

How much of a SCWD freezes on impact for ever 1°c below 0°

A

1/80th

226
Q

What is the most severe temperature for icing

A

Most severe ice forming temperature is 0 to -10°c due to large SCWD

227
Q

What is the worst wing speed combination for icing

A

Thing high speed wing

228
Q

Can anti/de-icing equipment sustain long periods of icing

A

No icing or anti icing equipment can cope with prolonged flight in severe icing conditions

229
Q

What is hoar frost

A

Water vapour sublimated onto cold surface

No cloud

230
Q

What is rime ice

A

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
Q

What is clear ice (glaze ice)

A

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
Q

What is FZRA

A

Freezing rain

Found ahead of warm front

Clear ice

Can be 100’s miles line 500’s miles wide

233
Q

What is mixed ice

A

Mix of small and large SCWD

Clear and rime ice

-20 / -10 °c

Horned rough appearance

234
Q

What is cloudy ice / packed snow

A

flying though air below freezing with wet wing

Ice crystals attach to wing

Snowflakes also attach

235
Q

What risk is there if icing in CB

A

Clear ice / mod - sev

236
Q

Stratiform icing risk

A

Light / mod risk

<0°c small SCWD

Drizzle

237
Q

What risk of icing is there in High level cloud

A

Light risk

238
Q

What icing risk is there in medium level cloud

A

Light to moderate

239
Q

What icing risk is in stratiform (low) cloud

A

Light to mod

240
Q

What icing risk is in nimbostratus/ cumuliform cloud

A

Mod / sev

241
Q

What risk of icing if nimbostratus or cumulus is caused by orographic lifting

A

Severe

Orographic intensification

242
Q

What is a severe risk of icing

A

Accumulation is greater than rate you can get rid of it

Immediate diversion needed

243
Q

What is moderate icing

A

Icing equipment is able to cope

244
Q

What is light icing

A

Accumulation might be a problem if in situation for over 1 hour

Occasional use of icing equipment

245
Q

What is trace icing

A

Not hazardous even without icing equipment

246
Q

How to calculate the lowest usable flight level to give a min safe altitude

A

Lowest QNH

Lowest temp

247
Q

What icing severity is mandatory to report

A

Moderate

Severe

248
Q

What is the pressure 10,000 ft

A

700hpa

249
Q

What is the pressure at 20,000ft

A

500hpa

250
Q

What is the pressure at 30,000ft

A

300hpa

251
Q

What is the pressure at 40,000ft

A

200hpa

252
Q

What is the definition of relative humidity

A

Relative humidity is the absolute humidity relative to the maximum for that temperature as a percentage

253
Q

What is the pressure lapse rate

A

27 ft / hpa

8m / hpa

254
Q

What are the geostrophic winds like on isobars

A

Isobars are straight lines with no surface friction

255
Q

What does wind speed change by over water with decreasing height

A

Backs / slacks

10° / 75% of speed

256
Q

When is the windspeed higher with straight isobars compared to curved isobars

A

Windspeed higher with curved anticyclone isobars if all other factors are constant

257
Q

What height (in hpa) is a max wind speeds for a subtropical jet stream in summer

A

Around 200hpa

Below tropopause

258
Q

Low level cloud height

A

GL - 6500

ATPL Meteorology (8 decks)

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