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ATPL > Meterology > Flashcards

Meterology Flashcards

1
Q

Where does troposphere go up to?

A

11 km or 36,090 ft

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2
Q

What is the lapse rate?

A

1.98 C per 1000 ft

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3
Q

What is the gas composition of the troposphere?

A

78% Nitrogen
21% Oxygen
1% Other Gases

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4
Q

How much water vapour can be in the atmosphere?

A

0-5%

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5
Q

ISA Mean sea level temp?

A

15 C

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6
Q

ISA average pressure?

A

1013.25 hPa

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7
Q

ISA average density?

A

1.225 kg/m^3

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8
Q

How much water vapour in troposphere?

A

90%

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9
Q

What is the boundary between the troposphere and stratosphere called?

A

Tropopause

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10
Q

What are the ‘pauses’?

A

Boundaries separating layers, layers are ‘Spheres’, i.e troposphere

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11
Q

What is a layer of constant temperature called?

A

Isotherm

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12
Q

What is the temperature of the tropopause?

A

-56.5 C

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13
Q

What is the height of the tropopause at the poles?

A

8 km

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14
Q

What is the temperature of the tropopause at the poles?

A

-45 C

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15
Q

Height of tropopause at equator?

A

16 km

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16
Q

Temp of tropopause at equator?

A

-75 C

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17
Q

What is a tropopause fold?

A

A break in the tropopause due to a division of differing air masses. Also large surface temp changes over a short distance can cause.

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18
Q

What equation can we use to work out ISA temp?

A

ISA Temp = 15 - (Alt/1000 * 2)

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19
Q

What is ISA Deviation?

A

Difference between ISA temperature and OAT (Ambient air temperature)

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20
Q

Which layer is after troposphere/tropopause?

A

Stratosphere

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21
Q

What altitudes does the stratosphere exist between?

A

11 km - 50 km

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22
Q

Where is the ozone layer within the stratosphere?

A

15-20 km

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23
Q

What does ozone do?

A

Absorb UV (shortwave) and causes heating in the stratosphere above 20 km.

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24
Q

What comes after the stratosphere?

A

Mesopause/Mesosphere

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25
Q

What do we see from the ozone layer?

A

Inversion (heating with height) due to Ozone heating between 20-50 km converting shortwave to longwave (IR) heating to the top of the stratosphere to 0c.

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26
Q

What is temperature increasing with height called?

A

Inversion

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27
Q

Where is there no turbulence but you can get clouds?

A

Stratosphere

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28
Q

What are the altitudes the mesosphere exists between?

A

from 50-90 km

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29
Q

How does lapse rate change in the mesosphere vs stratosphere?

A

Temperature now reducing with height again (no more inversion)

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30
Q

What is the important property of the mesosphere?

A

It is the coldest layer

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31
Q

What comes after the mesosphere?

A

The thermosphere?

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32
Q

What altitude does the thermosphere exist in?

A

90 km +

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33
Q

Which layer does the ionosphere exist in?

A

The thermosphere

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34
Q

Where does the ionosphere start?

A

85 km

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35
Q

What is important to know about the ionosphere?

A

Lots of positive ions and free electrons, it disturbs EM and radio comms.

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36
Q

Convert Kelvin to Celsius

A

K = C + 273

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37
Q

What is Fahrenheit?

A

32 + 1.8*C

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38
Q

How do we measure surface air temperature and humidity?

A

Stevenson screen

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39
Q

What does a radiosonde measure?

A

Pressure, humidity and temperature, can measure winspeed/direction with addition of GPS.

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40
Q

What is the amount of radiation per unit area that reaches the earth called?

A

Insolation

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41
Q

What direction does the Earth orbit the sun

A

Anticlockwise, like the rotation of the Earth

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42
Q

What plane does the Earth orbit the sun around?

A

Elliptical

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43
Q

What is the name of the closest distance to the sun and the month it occurs?

A

Perihelion - 91 Million miles

Winter - 4 Jan

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44
Q

What is the name of the farthest distance from the sun and the month is occurs?

A

Aphelion - 95 Million miles

Summer - 4 July

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45
Q

What is the tilt of the Earth’s rotational axis?

A

23.5 Degrees

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46
Q

What latitude is the summer solstice at?

A

Precisely equal to the tilt of the Earth - N23.5

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47
Q

What is the circle of latitude at the summer solstice called?

A

Tropic of Cancer

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48
Q

What latitude is the winter solstice at?

A

S23.5 - Equal to the tilt of the earth

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49
Q

What is the circle of latitude at the winter solstice called?

A

Tropic of Capricorn

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50
Q

Explain greenhouse effect

A

Sun emits shortwave radiation, earth emits longwave (terrestrial) radiation. Longwave radiation heats the air but greenhouse gases trap this terrestrial radiation, heating the atmosphere.

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51
Q

Explain surface heating

A

Sun emits shortwave radiation, earth emits longwave (terrestrial) radiation. Longwave radiation heats the air

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52
Q

Why does temp decrease with alt?

A

Atmosphere densest near surface, lots of air to heat from absorption of terrestrial radiation (surface heat), as you go higher, less dense and terrestrial radiation weaker combine to reduce temperature.

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53
Q

Where is the spring equinox?

A

0 Latitude, but when tending toward summer solstice (N23.5)

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54
Q

When is autumn equinox?

A

0 Latitude, but when tending toward Winter solstice (S23.5)

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55
Q

What is the name for less dense warm air rising?

A

Convection

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56
Q

What is the name for cooler more dense air falling?

A

Subsidence

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57
Q

What 4 things can convection be started by?

A

Surface heating
Converging air masses
Orographic uplift (Mountain - Windward forces air up)
Polar front depression (cold front moves faster than the warm front pushing warm air up)

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58
Q

What is advection?

A

Horizontal transfer of heat - movement of air current i.e wind

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59
Q

What is latent heat?

A

Heat released or absorbed by a body without a change in temperature.

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60
Q

When is no latent heat released?

A

From ice->water->vapour (Breaking bonds harder, energy required) energy absorption with no change in temperature

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61
Q

When is latent heat released?

A

From vapour->water->ice - Latent heat released heating air up!

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62
Q

What are nuclei and what are their purpose?

A

A Nuclei is a solid particle of impurity in the air, required for freezing/condensation and sublimation to occur.

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63
Q

What is sublimation?

A

A instant phase change from solid->gas or gas->solid.

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64
Q

What is Diurnal surface temperature variation?

A

A variation of surface temperature between the day and night. During the day, surface temp increases, during night, decreases.

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65
Q

When does the coldest time of day occur?

A

30 minutes after sunrise

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66
Q

When does the warmest time of day occur?

A

2-3 hours after midday

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67
Q

What 3 things affect the minimum and maximum diurnal temperatures?

A

Type of surface, Wind, Cloud cover

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68
Q

How does the wind affect diurnal temperatures?

A

Turbulent mixing occurs in the lower atmosphere. During the day, warmer surface temperatures mix with the cooler air at higher levels, creating a lower surface temperature.

During the night it mixes the warmer air above with the cooler air below causing increased temperatures.

Wind reduces the amount of diurnal variation in surface temperature.

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69
Q

How do clouds affect diurnal temperatures?

A

During the day, clouds refelect solar radiation, less insolation during the day and lower day temperatures.

During the night, clouds emit terrestrial (longwave) radiation from the absorbed during the day, resulting in increased night temperatures.

Cloud reduces the diurnal temperature variation.

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70
Q

What is ground inversion?

A

During the night surface temperatures decrease, we get warmer air above.

So we get a ground/radiation inversion as air is warming with altitude.

This only occurs at night!

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71
Q

What is a Valley inversion?

A

Cold dense air at night subsides down a valley, creating a ‘pool’ at the bottom.

The air in the centre is warm due to it being a bad conductor and so an inversion forms with cold air at the bottom ‘pool’ and warm air at the top.

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72
Q

What do we find under an inversion?

A 
Poor visibility (trapped pollen etc.)
Good performance (Cold, dense air)
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73
Q

What do we find above an inversion?

A 
Good visibility (particles move freely again)
Poor performance (Warm, less dense air)
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74
Q

What is a subsidence inversion?

A

As air falls, warms due to compression.
It could become warmer than the air at the surface.

High pressure system with subsiding air

The less dense air can’t get through the denser air

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75
Q

What is a frontal inversion?

A

Form at boundaries between warm and cold air.

Due to different densities, heavier colder air slides under warm lighter air.

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76
Q

What is a turbulence inversion?

A

Due to mixing, the cool air above is drawn down.

It can be mixed enough to produce warm air above.

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77
Q

What are the 3 hazards and weather associated with an inversion?

A

Warm air is usually rising, but inversions stop cloud growth.

We can have:
Wind shear
Low level jet streams
Poor visibility

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78
Q

Where does the pressure reduce more quickly?

A

Lower altitudes

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79
Q

What is the pressure at FL100 (10,000 ft)?

A

700 hPa

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80
Q

What is the pressure at FL180 (18,000 ft)?

A

500 hPa

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81
Q

What is the pressure at FL200 (20,000 ft)?

A

400 hPa

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82
Q

What is the pressure at FL300 (30,000 ft)?

A

300 hPa

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83
Q

What is the pressure at FL400 (40,000 ft)?

A

200 hPa

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84
Q

What is the pressure at FL500 (50,000 ft)?

A

100 hPa

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85
Q

What is the equation for distance for a pressure change? (Pressure lapse rate)

A

ft per hPa = (96 * Kelvin)/Pressure

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86
Q

What is an isobar?

A

Line of equal pressure on a surface pressure chart (horizontal pressure)

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87
Q

What are the names for a high pressure system?

A

Anticyclone / High

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88
Q

What causes/happens in a high pressure system? (4 Stages) (Page 123)

A

Air enters quickly at the tropopause, like venturi static pressure. (At high alt, rising air from surface cools and flows outward, cool air sinks causing localiser low pressure which air converges to).

Compression warms air as it falls (falling air - subsidence)

Pressure increases at the bottom

Friction from high pressure (traffic jam) slows air, makes air leave slower than it enters.

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89
Q

How is a high pressure system linked to subsidence inversion?

A

When subsiding air falls and is compressed it becomes warm, temperature rises.

Temp can get warmer than surface.

-> Inversion

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90
Q

Which pressure systems can clouds not form in?

A

High pressure system (subsiding, falling, dry air from tropopause)

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91
Q

What direction does a high pressure system (anticyclone) rotate in the Northern Hemisphere?

A

Clockwise

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92
Q

What direction does a high pressure system (anticyclone) rotate in the Souther Hemisphere?

A

Anticlockwise

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93
Q

What winds are high pressure systems associated with?

A

Lighter winds than low pressure systems (Diverging air, venturi effect, lower velocity).

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94
Q

What are the isobars like in high pressure vs low pressure?

A

More spread out

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95
Q

What are 2 other names for a low pressure system?

A

Cyclone

Depression

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96
Q

What 4 stages causes a low pressure system (Page 107)?

A

Small scale heat lows develop over the day (some areas of surface heat up more than others, depending on material)

Air in contact warms, less dense, convection occurs.

Venturi effect causes drop in static pressure

Draws in more air from relatively higher pressure zones in surrounding areas.

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97
Q

What pressure systems do clouds form in?

A

Low pressure systems (convecting air)

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98
Q

What direction does a low pressure system (cyclone/depression) rotate in the Northern Hemisphere?

A

Anticlockwise

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99
Q

What direction does a low pressure system (cyclone/depression) rotate in the Southern Hemisphere?

A

Clockwise

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100
Q

What winds are low pressure systems associated with?

A

High surface winds (Venturi effect for converging air, velocity increase)

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101
Q

What are isobars in a low pressure system like vs high pressure system?

A

More compact isobars

Pressure changes at greater rate over distance (faster windspeeds, higher pressure changes over surface associated with higher winds).

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102
Q

What is an isohype?

A

Isohypes show heights of a given pressure level.

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103
Q

What chart are isohypes in?

A

Constant pressure charts

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104
Q

What does a constant pressure chart show?

A

The height which we find given pressures.

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105
Q

What happens to the vertical pressure levels with higher temps?

A

They occur at higher altitudes (higher pressure due to temp)

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106
Q

What happens to the vertical pressure levels with lower temps?

A

They occur at lower altitudes (lower pressure due to temperature)

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107
Q

What is the spacing of an isobar on pressure charts?

A

4 hPa

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108
Q

How does a mercury barometer work?

A

Evacuated tube with mercury in reservoir, static pressure pushes on reservoir causing height of mercury to increase up tube.

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109
Q

How does aneroid barometer work?

A

Pressure compress/expand cell mechanically linked to needle.

How altimeter works

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110
Q

What is QFE (3 facts)?

A

Measured from pressure station

Reads 0 ft at station

Reads height - Vertical above ground

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111
Q

What is QNH (3 Facts)

A

QFE adjusted to mean sea level in ISA temp conditions

Reads altitude

Gives elevation above see level

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112
Q

What is a problem with QNH?

A

It is incorrect if ISA temperature conditions are not present.

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113
Q

How do we work QNH from QFE?

A

QNH = (Elevation/27 ft) +/- QFE (AMSL/BMSL)

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114
Q

What atmospheric report do we only get QNH in?

A

METAR

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115
Q

What atmospheric report can we find QNH or QFE in?

A

Local report

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116
Q

What is QFF and how does it differ from QNH?

A

QFF uses actual temperatures instead of ISA temperatures when calculating pressure for sea level.

If it could be used in flight it would read correct altitude.

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117
Q

Which pressure datum is used on surface pressure chart (Isobars)

A

Isobars use QFF on surface pressure charts.

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118
Q

What happens to QNH compared to QFF in warmer ISA conditions AMSL?

A

QNH>QFF

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119
Q

What happens to QNH compared to QFF in cooler ISA conditions AMSL?

A

QNH < QFF

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120
Q

What happens to QNH compared to QFF in warmer ISA conditions BMSL?

A

AMSL is: QNH > QFF

WE FLIP FOR BMSL: QNH < QFF

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121
Q

What happens to QNH compared to QFF in cooler ISA conditions BMSL?

A

AMSL is QNH < QFF

WE FLIP FOR BMSL: QNH > QFF

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122
Q

What can we say about QNH and QFF at MSL?

A

QNH = QFF = QFE

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123
Q

What is the standard pressure setting?

A

1013 hPa

Datum at sea level for ISA conditions

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124
Q

What do we read Standard pressure setting altitudes?

A

Flight level (FL) or Pressure altitudes

125
Q

What altitude do we change from QNH->SPS

A

Transition altitude

126
Q

What altitude do we change from SPS->QNH

A

Transition level (We are in SPS so altitudes are read as levels)

127
Q

What is the difference between the transition altitude and transition level called?

A

Transition layer

128
Q

If we reset our altitude subscale, what does adding pressure do?

A

Increase altitude (Higher pressure for zero point lower down)

129
Q

If we reset our altitude subscale, what does reducing pressure do?

A

Decrease altitude (Lower pressure as zero point gets higher)

130
Q

What happens to our true altitude if our pressure level is set higher than the actual?

A

Zero point is set artifically low (higher pressure)

Reads higher than we are (Indicated altitude)

Overreading so we take off difference (for true altitude)

131
Q

What happens to our true altitude if our pressure level is set lower than the actual?

A

Zero point is set artificially high (lower pressure)

Reads lower than we are (indicated altitude)

Under reading so we add difference. (for true altitude)

132
Q

What happens to your true altitude as you follow Indicated altitude and there is an increase in temperature above ISA?

A

True altitude increases as you follow Indicated altitude

133
Q

How does temperature affect pressure levels?

A

Spreads them further apart as the pressure lapse rate is lower at smaller temperatures.

134
Q

Why is temperature error particularly dangerous vs pressure error?

A

It can’t be dealt with by changing the pressure datum, manual adjustments have to be made

135
Q

What is the equation for the temperature error correction (TEC)?

A

TEC = (ISA Deviation/10)0.04Altitude

Where altitude is the altitude after pressure corrections have been applied.

If aerodrome elevation has been given in the question this has to be taken into account, we can only apply this formula to the altitude which contains air (from layer to ground).

136
Q

If we have a different ISA temperature and a pressure error on our altimeter, which do we consider first?

A

The pressure error

137
Q

What happens when we fly over a mountain to our true altitude?

A

Velocity increase due to venturi,

Pressure and temperature drop

True altitude drops

138
Q

Where do we get a band of low pressure systems?

A

Around the equator due to high surface temperature, these are known as the thermal lows.

139
Q

At N30/S30 what pressure systems form and what is their name?

A

High pressure systems, sub tropical highs

140
Q

At N60/S60 what pressure systems form and what are their names (4 names)?

A

Low pressure systems

Polar low/ Polar frontal depression / Westerly Waves/ Westerly situations

141
Q

At N90/S90 what pressure systems form and what is their name?

A

High pressure system

Polar highs

142
Q

How many pairs of cells are there and what are their names?

A

3 pairs of 2 cells

Polar
Ferrell
Hadley

143
Q

What is the inter-tropical convergence zone? (ITCZ)

A

A band of thermal lows following the hottest places around the world.

144
Q

What is the maximum location of the ITCZ during Summer (July) in the Northern Hemisphere?

A

N25

145
Q

What is the maximum location in the Souther Hemisphere of the ITCZ during winter (Jan)

A

S20

146
Q

How does the position of the ITCZ over oceans change over the year?

A

Hardly affected as water has higher specific heat capacity so temperature doesn’t vary as greatly as land.

147
Q

What is the position of the ITCZ over Dakar?

A

N5

148
Q

Name two cold high pressure systems in winter (Jan) over the Northern hemisphere?

A

Siberian high and Canadian high

149
Q

Name two warm high pressure systems in Winter (Jan) over the Northern hemisphere?

A

Azores high

Pacific high

150
Q

In the northern hemisphere name two cold polar lows?

A

Icelandic low

Aleutian low

151
Q

What happens to pressure systems in the souther hemisphere in Winter (Jan)?

A

Thermal lows where ITCZ is, otherwise sub tropical highs.

152
Q

Name two warm low pressure systems in the Northern hemisphere in Summer (July)

A 
Asian low (Was Siberian High)
North American low (Was Canadian High)
153
Q

What happens to the pacific high in Northern Hemisphere in summer (July)

A

Stays the same (over ocean)

154
Q

What happens to the Azores high in the Northern Hemisphere in Summer?

A

Goes to Bermuda high (Could refer to Azores in exam)

155
Q

What happens to the icelandic low in summer (Northern hemisphere)?

A

Splits into 3 covering Greenland, Iceland and the Baltics

156
Q

What happens in the Southern hemisphere to pressure systems in summer?

A

Sub tropical highs, warm

157
Q

What is the radius of a small scale low? (Cyclone)

A

1-20 Nautical miles

158
Q

What is the radius of a large scale low (Cyclone)?

A

300-1000 Nautical miles

159
Q

How does orographic depression form a small scale low?

A

As air travels toward the windward side of the mountain it is forced up convecting.

Sometimes air travels around the mountain rather than over it creating a lack of air and pressure on the lee side developing a small scale low.

160
Q

What clouds are associated with small scale lows?

A

Depression so rising air, cumuliform clouds are associated with these.

Cumulus
Towering cumulus
Cumulonimbus

161
Q

What type of rain is associated with small scale low pressure systems?

A

Showers (Fast onset and stopping of precipitation)

162
Q

What happens if a cold front passes over the ridge of a mountain (think small scale low)?

A

It will make conditions even worse in the orographic depression (small scale low)

163
Q

Two examples of large warm depressions? (large scale warm low pressure systems/lows)

A

North American low and Asian low

They often follow the ITCZ

164
Q

What happens to the pressure levels at SFC and altitude for a warm depression?

A

Lower pressure levels at SFC

Higher pressure levels at altitude (warmer air in centre)

165
Q

What is the temperature of the air inside a warm depression?

A

Relatively warmer

166
Q

What weather is associated with a warm depression and why?

A

We get loads of uplift so:

Lots of Cumuloform clouds
Showers and precipitation

167
Q

Where are warm depressions likely to form during winter and why?

A

Landlocked oceans in the winter are still warm (higher specific heat capacity) and the land is cooler.

We get a warm depression.

eg. Mediterranean low

168
Q

What happens to the pressure levels at SFC and altitude for a cold depression?

A

Lower pressure levels at the SFC

Lower pressure at altitude

169
Q

Another name for cold depressions?

A

Polar front depression (N/S 60)

170
Q

Why are fronts formed in cold depressions?

A

Cooler polar air mixes with warmer sub tropical air forming a front

The warmer air is forced to convect

171
Q

Weather we can expect in a cold depression?

A

Cold low pressure system so:

  • Cumuloform clouds
  • Rain precipitation
172
Q

Name two examples of cold depressions?

A

Icelandic / Aleutian low

173
Q

What is an extended area of low pressure called?

A

A trough where we see isobars extending away from low pressure system

174
Q

What weather can we expect in a trough for a low pressure system?

A

The wind changes direction very quickly so we get more convergence and convection activity and consequently more intense weather.

Stronger low pressure weather:

  • Cb clouds
  • Heavy showers
  • Strong wind
  • Hail
  • Gusts
175
Q

How do we identify a trough on a surface pressure chart?

A

A trough or convergence line is identified as a solid black line on a surface pressure chart.

176
Q

Weather for low pressure system? (4)

A

Good visibility
Significant cloud
Significant precipitation
Small diurnal variation of pressure

177
Q

Size of high pressure system?

A

Much larger - 1500 nm across

178
Q

What do high pressure systems look like in terms of isobars?

A

More spread out isobars

=> Slower windspeeds

179
Q

What happens to pressure levels at the surface and altitude in a warm high pressure system?

A

SFC pressure levels increase (high pressure due to compression)
Pressure levels at altitude increase (due to warm air in centre)

EASA might say increase in intensity with altitude! - Warm high pressure system

180
Q

Name two examples of warm high pressure systems?

A

Azores (Bermuda) high / Pacific high

Sub tropical highs N/S 30

181
Q

Over what land masses do we usually find warm high pressure systems?

A

Desserts

182
Q

What weather is associated with warm high pressure systems?

A

Hot, dry, clear skies, visibility rapidly reduce (subsidence inversion), haze

183
Q

What are pressures at the surface and altitude like for cold high pressure systems (anticyclones)

A

Pressure levels higher at surface (compression)

Pressure levels lower at altitude

184
Q

Two examples of cold high pressure systems ? (Anticyclones)?

A

Siberian high

Canadian high

185
Q

How can clouds form in high pressure systems?

A

If there is enough isolated/localised surface heating we can generate enough convection to form clouds.

These will be stratoform type clouds only.
As the inversion prevents cloud growth.

However, if there is enough surface heating we can generate Cb clouds but generally St types.

186
Q

Which clouds form in low pressure systems?

A

Cumuloform

187
Q

Which clouds form in high pressure systems?

A

Stratoform

188
Q

What is a blocking anticyclone?

A

Sub tropical highs (Azores high) massive and doesn’t move a great deal deflecting depressions (lows) Northwards as they move from West to East.

Quasi/Large stationary pressure systems occuring at N50-N70 which can stay for long periods of days/weeks.

189
Q

What is a ridge?

A

Extension of a high pressure system, protrudes outwards.

190
Q

What weather do we expect in a ridge?

Skies, clouds etc.

A

Clear skies, fog, haze, St clouds

191
Q

What is a col?

A

Is between 2 high pressure systems and 2 low pressure systems.

There will be a lack of isobars (little or no wind)

192
Q

What weather do we get in a col?

A

Summer - No moving air mass so thunderstorms

Winter - No air moving forms fog

193
Q

What is a flat pressure area?

A

An area with no isobars at all

194
Q

What is density altitude?

A

Density alt = 120 ft * ISA Deviation

Tells equivilent altitude aircraft will perform to.

195
Q

What is humidity mixing ratio?

A

Mass of water vapour to mass of dry air

Remains constant no matter what it’s doing

196
Q

What is humidity mixing ratio in mid latitude?

A

50g/kg

197
Q

What is humidity mixing ratio in polar vs tropical?

A

Lower in polar than tropical

198
Q

What is saturation mixing ratio?

A

Mass of water vapour per unit mass of saturated air

Maximum amount of water vapour we can get into air before it saturates

199
Q

Why is saturation mixing ratio affected by temperature?

A

Warmer air can hold more water vapour
So saturation mixing ratio increases with temp
Saturation ratio also increases with decreases in altitude (warmer air)

200
Q

How do we work out relative humidity from humidity mixing ratio and saturation mixing ratio?

A

RH = (HMR/SMR)*100

201
Q

How does temperature affect Relative humidity?

A

Increases saturation mixing ratio

So DECREASES RELATIVE HUMIDITY (HMR/SMR)*100

202
Q

When is Relative humidity greatest during the day?

A

30 minutes after sunrise (coolest temp so lower SMR in HMR/SMR) saturation mixing ratio

Cold air holds less moisture

203
Q

When is relative humidity lowest during the day?

A

2-3 hours after Midday
SMR is greatest - saturation mixing ratio
HMR/SMR is smallest

Warm air holds more moisture

204
Q

What is in a psychrometer?

A 
Normal thermometer (dry bulb)
Thermometer wrapped in wet cloth (wet bulb)
205
Q

What happens to the wet bulb in a psychrometer in dry humidity conditions?

A

More evaporation occurs absorbing latent heat causing a drop in temperature of the wet bulb vs dry bulb.

206
Q

What happens in saturated air to the psychrometers wet bulb?

A

No evaporation can take place so the temperature remains the same as the dry bulb.

207
Q

How does a hair hygrometer work?

A

Hair expands when wet showing higher humidity on a scale.

208
Q

What is the dew point?

A

The temperature the air must be cooled for it to become fully saturated.

209
Q

How are dew point and relative humidity related? (Give equation)

A

RH = 100-5*(T-Td)

T - Temp
Td - Dew point temp

210
Q

What does closer ambient temp to dew point mean?

A

More humid air

211
Q

On reports what are dew points rounded to?

A

Nearest warmest degree

212
Q

What is an adiabatic process?

A

A process of warming or cooling where no heat (energy) is transferred to or from the system.

i.e Parcel of air warming or cooling with no external heat source

213
Q

Adiabatic cooling example?

A

Air risises, expands, loss of pressure and drop in temperature.

Gas expansion

214
Q

Adiabatic warming example?

A

Air forced to descend compresses and warms

Gas compression

215
Q

What is the environmental lapse rate?

A

2C per 1000 ft

216
Q

What is the dry air lapse rate? (DALR)

A

3C per 1000 ft

217
Q

What is the saturated air lapse rate? (SALR)

A

1.8 C per 1000 ft

218
Q

Why is the SALR < DALR?

A

Because saturated air condenses as it rises releasing latent heat, warming surroundings and slowing down the cooling process

219
Q

Why does SALR go greater higher up?

A

Colder air can’t hold as much water vapour, less condensation occurs and less release of latent heat to warm surroundings.

220
Q

What is absolute stability?

A

When the ELR < Both DALR & SALR

Because as vapour/dry air rises, it wants to fall back down as it’s temperature is less than the environment surrounding it.

221
Q

What weather do we get with absolute stability?

A

ELR < Both DALR&SALR

Stratoform clouds (started to lift up and then fell again)
Smaller droplets, drizzle rather than rain. Continous or intermittent

Possibly fog/haze / low vis (high pressure system)

222
Q

What is absolute instability?

A

ELR > Both DALR & SALR

Environment cools more rapidly than dry air / saturated water vapour.

Vapour and air warmer so want to continue to rise further

Linked to low pressure system

223
Q

Weather associated with absolute instability?

A

Cumuloform clouds
Rain showers
Good visibility
Bad turbulence

Think low pressure system.

224
Q

What is conditional instability?

A

DALR > ELR > SALR

Saturated particles rise, dry fall
Weather similar to absolute instability (rising particles)

225
Q

What is indifferent stability?

A

ELR=DALR
or
ELR = SALR

226
Q

What does a tephigram measure?

A

Amount of energy - > Stability/instability

  • Pressure levels
  • Temperature
  • DALR
  • SALR
  • Dew point
227
Q

What is convective uplift?

A

Air at low levels warmed by surface and rises, it cools adiabatically and at the codensation level begins to form cloud.

228
Q

What cloud is formed first in convective uplift?

A

Fair weather cumulus

229
Q

What sort of stability occurs when warm air mass passes over a cold surface?

A

Stable as cold air mass cools warm one causes dropping of air parcels.

230
Q

What sort of stability occurs when cool air mass passes over warm?

A

Unstable as warm air mass warms cool one causing parcels to rise within it.

231
Q

What happens in convective uplift if we continue to feed moisture and convection?

A

Cumulonimbus

232
Q

What are blue thermals?

A

Where there are convective currents from insolation but not enough moisture to form clouds.

Also called clear air turbulence

233
Q

What conditions do we get with a warm front?

A

Stable conditions as a cooler air mass is below (polar in front of warm air mass and tropical air in between)

234
Q

What clouds do we get along a warm front?

A

Stable conditions so:

Stratoform type clouds

235
Q

What are the stratoform type clouds ? (5)

A 
St - Stratus
Ns - Nimbostratus
As - Altostratus
Cs - Cirrostratus
Ci - Cirrus
236
Q

Which is the only stratoform cloud associated with heavy rain?

A

Nimbostratus

237
Q

What is a cold nose?

A

The area near the surface of a cold front pertrudes out because cold front follows warm faster, colder air at the surface is affected by friction which slows it down relative to the rest

238
Q

What weather do we get along cold front?

A

Unstable conditions (cold nose so warmer air below cold in this region)

Cumuloform clouds

239
Q

Why should we be concerned at the cold front in terms of cloud formation?

A

We get embedded Cb clouds behind stratoform clouds.

240
Q

What happens in orographic uplift if we have unstable conditions?

A

Air will rise over the mountain and continue to rise forming Cumuloform type clouds

241
Q

What happens in orographic uplift in stable conditions?

A

Moist air forced to rise up mountain side, might cool enough and reach dew point forming cloud.

Cloud might become heavy enough for rain / precipitation

Now rising at SALR depositing more moisture.

When it gets to lee side it has deposited moisture so falls warming at DALR which is greater, we get much warmer air on the lee side of the mountain.

242
Q

What do we get on the windward side of a Fohn wind? (Stable orographic uplift)?

A

Cooler temps
Lower cloud base
Precipitation

243
Q

What do we get on the leeward side of a Fohn wind? (Stable orographic uplift)?

A

Warmer temps
Higher cloud base
No precipitation

244
Q

What type of clouds form for stable environments?

A

Stratoform

245
Q

In stable orographic uplift, what clouds do we get on top?

A

Drier - Cap clouds
or
Lenticular clouds which extend down and away from ridge

246
Q

What conditions clouds etc. in convergence uplift?

A

More unstable types

Cu clouds etc.

247
Q

What clouds will form from turbulent uplift and how high?

A

Can get uplift from turbulence forming stratocumulus clouds due to the friction layer of wind above the turbulence

form at 2000-3000 ft

248
Q

What is the cloud base?

A

Height at which we go from solid particles to water droplets/ice crystals above ground.

249
Q

What is cloud ceiling?

A

Lowest level of cloud that is

  • Measured below 20,000 ft
  • More than 4 Oktas (Broken or Overcast)
250
Q

What is an oktar?

A

Section of sky split into 8 pieces

251
Q

What are clouds classified into in cloud reports?

How many oktas do they require for their class?

A

Few - 1/8 - 2/8
Scattered - 3/8 - 4/8
Broken - 5/8 - 7/8
Overcast - 8/8

252
Q

What does NSC stand for in cloud report?

A

No significant cloud

253
Q

What are the conditions for CAVOK?

A

Visibility > 10 km
No clouds below 5000 ft or MSA (whicever is lower)
No TCU/CB/TS (Towering cumulus/ cumulonimbus/ thunderstorm)
No significant weather

254
Q

What are the 3 heights clouds are classified into?

A

Low - Strato - 0-6500 ft
Middle - Alto - 6500-23,000 ft
High - Cirro - 16,500 - 45,000 ft

255
Q

What appearance (genera) are clouds classified into? (4)?

A

Cumulus - Fluffy, heaped
Stratus - Flat, layered
Cirrus - Wispy, feathered
Nimbo - Rain bearing

256
Q

What is the average cloud droplet size?

A

0.02mm

257
Q

What cloud does drizzle form in?

A

Stratiform clouds

258
Q

What is drizzle drop’s diameter?

A

0.2-0.5 mm

259
Q

Drizzle’s terminal velocity?

A

4 m/s

260
Q

What clouds does rain form in?

A 
Convective clouds (Cumulus types)
Any cloud with prefix nimbo
261
Q

What is the diameter of a rain drop?

A

0.5mm to 6 mm in diameter

262
Q

What is the terminal velocity of rain?

A

9m/s

263
Q

Where does freezing rain usually form??

A

Ahead of warm fronts

Fall out of nimbostratus onto cooler polar air below warm front, form supercooled droplets. Ice risk!

264
Q

When does snow form?

A

Temps above -5C

265
Q

Heaviest snow occurs when?

A

Between 2 and -2 C

266
Q

Snowflake average diameter?

A

4mm

267
Q

What temp will snow melt and form sleet?

A

Above 2c

268
Q

Snow grains diameter?

A

< 1mm

269
Q

Snow grains temperature for formation?

A

0 and -10c

270
Q

Snow grains appearance?

A

Opaque, white in colour

Mace of ice, elongated in shape

271
Q

Diamond dust made of?

A

Tiny ice crystals 100 micrometers

272
Q

Diamond dust forms in temps?

A

< -10 C

273
Q

Snow pellets appearance?

A 
White and opaque in colour
Shape is conical
Mix of snowflake and ice
Brittle
Bounce on ground often break
274
Q

Snow pellets diameter?

A

up to 5mm

275
Q

Clouds snow pellets form in?

A

Cu or Cb

276
Q

Small hail diameter?

A

< 5mm

277
Q

Hail diameter?

A

> 5mm

278
Q

Hail formed in which clouds?

A

Cb

279
Q

What is a rain shower?

A

Shower is when precipitation stops and starts very suddenly

280
Q

What is intermittent and continous rain?

A

Comes from stratoform clouds

Continous when lasts for over an hour

281
Q

3 requirements for Thunderstorm formation?

A

Need instability over 10,000 ft
Need lots of moisture
Need uplift trigger

282
Q

Most common time for tornado to form?

A

5:00 PM

283
Q

Speed tornadoes travel over ground?

A

20-40 kts

284
Q

Tornado duration?

A

few mins up to 30 mins

285
Q

Tornado funnell speed?

A

200 kts

286
Q

Tornado average diameter?

A

100-150m

287
Q

VFR thunderstorm avoidance range?

A

10 NM

288
Q

IFR TS avoidance range?

A

<20,000 ft - 10nm

>= 20,000 ft - 20 nm

289
Q

Height you fly above a TS for avoidance?

A

5000 ft

290
Q

Earth-Ionosphere potential?

A

250-500 kv

291
Q

What ocean temps for tropical rotating storms?

A

26.5 C

292
Q

What latitudes to TRS form at?

A

N/S 10-20

293
Q

TRS Stage 2 - Tropical depression wind speed?

A

up to 33 kts

294
Q

TRS Stage 3 - Tropical storm wind speed?

A

34-63 kts

295
Q

TRS Stage 4 - Tropical revolving storm wind speed?

A

> 64 kts

296
Q

TRS Eye wall wind speeds?

A

175 kts

297
Q

TRS Eye wall vertical movement speed?

A

43 kts

298
Q

Which way do tropical storms move?

A

East to West

299
Q

Where do tropical storms turn in Northern Hemisphere?

A

North (Coriolis)

300
Q

Where do tropical storms turn in Southern Hemisphere?

A

South (Coriolis)

301
Q

Hurricane Season in America?

A

May to Nov

302
Q

Typhoon season in Japan/China?

A

April-Jan

303
Q

Cyclone season rest of world?

A

Oct-may Souther hemisphere

April-Dec Northern hemisphere

304
Q

When do easterly waves form?

A

Apr-Nov

N5-N15

305
Q

How many easterly waves become TRS?

A

1 in 5

306
Q

What percentage of all hurrianes start in Easterly Waves?

A

85%

307
Q

Diameter of eye of storm?

A

20-50 km

308
Q

TRS approximate diameter?

A

500-1000 km

309
Q

TRS average height?

A

12 km (Tropopause height)

ATPL (5 decks)

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