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BTC 5-24 > Meteorology > Flashcards

Meteorology Flashcards

1
Q

What are the 5 layers of the atmosphere?

A

Exosphere
Thermosphere
Mesosphere
Stratosphere
Troposphere

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2
Q

Troposphere height

A

7km

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3
Q

Stratosphere height

A

50km

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4
Q

Mesosphere height

A

85km

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5
Q

Thermosphere height

A

650

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6
Q

Exosphere height

A

10,000

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7
Q

Troposphere characteristics

A

fall of density, pressure and temperature with height
presence of virtually all atmospheric water vapour
marked variation in space and time in the vertical and horizontal motion

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8
Q

Stratosphere characteristics

A

biggest concentration of ozone
extremely dry air
water trapped below in troposhere
no precipitation

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9
Q

Mesosphere characteristics

A

no heat source
keeps temp decreasing down to minimum in atmosphere
-80 to -100 degrees Celsius

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10
Q

Thermosphere characteristics

A

very high temperature increase
1200 to 1700 degrees Celcius

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11
Q

What does the bombardment of high energy radiation from the sun cause in the atmosphere?

A

Many of the molecules and atoms to become ionised

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12
Q

Nitrogen%
Oxygen%
Argon, helium, hydrogen%

A

78% , 21% , 1%

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13
Q

The atmosphere is ____ ____ to sun’s radiation

A

relatively transparent

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14
Q

Where is most of the energy from the sun absorbed?

A

earth’s surface

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15
Q

What height does temperature decrease with height go up to?

A

36,000ft

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16
Q

What temperature decrease with height called?

A

Lapse rate

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17
Q

What is the average temperature lapse rate in the atmosphere?

A

1.98c/1000ft

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18
Q

Pressure =

A

Density x Depth

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19
Q

what do pressure readings vary according to?

A

density of the atmosphere above that point

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20
Q

What does density vary according to?

A

air temp & water content

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21
Q

What is MSL pressure?

A

1013.25 hPa

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22
Q

what are the rates of change of pressure with increasing height?

A

1 hPa = 30ft to MSL
1 hPa = 50ft at 20,000ft
1 hPa = 100ft at 40,000ft

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23
Q

What is density?

A

the mass in a unit of volume

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24
Q

What does air density affect?

A

ROC
Drag on an aircraft
Aerodynamic forces on propellers
Pressurisation

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25
Q

What are the tools used for met data? (8)

A

Thermometers
Radar systems
Barometers
Rain gauges
Wind vanes/ Anemometers
Transmissometers
Hygrometers
Satellites

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26
Q

Atmospheric pressure is measured in… ?

A

Inches of mercury (ins)
Millibars (mb)
Hectopascals (hPa)

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27
Q

What does a mercury barometer suffer from?

A

Index error
temperature error
gravity error

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28
Q

What does Aneroid mean?

A

Without liquid

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29
Q

How does an aneroid barometer work?

A

It uses a partially evacuated metal capsule that reacts to changes in air pressure by expanding or contracting.

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30
Q

What does the aneroid barometer suffer from?

A

Index error but is provided with a correction chart

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31
Q

ISA

A

International standard atmosphere

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32
Q

ISA at MSL
Temp
Pressure
Density

A

+15 degrees Celsius
1013.25 hPa
1.225 kg/m3

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33
Q

ISA lapse rate above MSL

A

1.98c/1000ft up to 11km
0c/1000ft from 11km to 20km

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34
Q

Precipitation can be reported as?

A

Present, significant or recent

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35
Q

Specific heat capacity

A

heat required to raise the temperature of 1kg of a substance by 1c

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36
Q

what is radiation?

A

transfer of heat between bodies that aren’t in contact

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37
Q

what is conduction?

A

transfer of heat between bodies that are in contact

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38
Q

What is convection?

A

transfer of heat by vertical movement

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39
Q

What is diurnal variation?

A

Change within the day

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40
Q

Diurnal variation- Surface

A

Variation is greater over land than sea

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41
Q

Diurnal variation- windspeed

A

wind causes turbulence that spreads cooling effect of the earth through a greater depth of air

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42
Q

Diurnal variation- clouds

A

reduces heat loss

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43
Q

what is inversion?

A

certain conditions may cause temperature to increase with height or remain the same in an isothermal layer

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44
Q

How do you measure temperature?

A

thermometer

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45
Q

Celcius to fahrenheit

A

9*c/5 + 32

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46
Q

Fahrenheit to celcius

A

5(F - 32) / 9

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47
Q

Kelvin scale -
Theoretical absolute zero-
Freezing point H2O
Boiling point H2O

A

0k (-273c)
273k
373*k

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48
Q

Fahrenheit-
Freezing point
boiling point

A

32f
212f

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49
Q

What happens water changes state?

A

Latent heat locks heat into, or gives heat back to the atmosphere

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50
Q

What happens when saturated air is cooled?

A

water vapour content will be too great and visible droplets will appear. (condensation)

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51
Q

What is sublimation?

A

process where ice and snow changes into water vapour without moving through the liquid stage

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52
Q

What does the amount of water vapour present in the atmosphere depend on?

A

temperature of the air

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53
Q

What is dew point?

A

the atmospheric temperature below which water droplets begin to condense and dew can form.

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54
Q

What are the 4 ways air may be cooled below dew point?

A

Conduction
Evaporation
Adiabatic cooling
Mixing

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55
Q

What is latent heat?

A

heat required to cause a change in state

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56
Q

What is relative humidity?

A

the measurement of the amount of water vapour present in the air, relative to how much would be require to cause saturation at the temperature

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57
Q

How do we measure humidity?

A

hygrometer

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57
Q

What are the 2 types of hygrometer?

A

Hair hygrometer
wet and dry hygrometer

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57
Q

Why is no heat transferred within the atmosphere during the adiabatic process?

A

air is a poor conductor of heat

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57
Q

How do we calculate dew point with a wet and dry hygrometer?

A

Finding the difference between the dry and wet bulb temperatures

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57
Q

What is the adiabatic process?

A

as the temp of air increases, so its density decreases and if its surrounded by colder, denser air, it will tend to rise.

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57
Q

Dry adiabatic lapse rate (DALR)

A

3c/1000ft
unsaturated air rising cools at this rate

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57
Q

What are the 3 lapse rates?

A

Dry adiabatic lapse rate
saturated adiabatic laps rate
environmental lapse rate

58
Q

Saturated adiabatic lapse rate (SALR)

A

1.5 - 2c/1000ft
saturated air rising whilst condensation is taking place.
saturation of air impacts rate

58
Q

unstable atmosphere

A

a small perturbation to an object encounter a force which will move the object farther from its original position

58
Q

Environmental lapse rate (ELR)

A

lapse rate at any given time or location

58
Q

Conditional instability

A

When the ELR lies between the DALR and SALR. A parcel of dry air will be cooler at height than the environment and will sink, but a parcel of saturated air will be warmer and will continue to rise

58
Q

neutral atmosphere

A

a perturbation to a body results in restoring or displacing force being applied, so that the body remains in its perturbed position.

58
Q

Stable atmosphere

A

any small perturbation to a body, or a body of air, will encounter a restoring force which tends to return it to its original position

58
Q

Absolutely stable atmosphere

A

When the ELR in a layer is less than the SALR

58
Q

Absolute instability

A

the ELR is grater than the SALR and DALR

58
Q

What are the 5 lifting processes?

A

frontal lifting
orographic lifting
convergence (depression)
convergence (thermal)
turbulence

59
Q

what is frontal lifting?

A

advancing cold air forcing warm air to rise and vice versa

60
Q

what is orographic lifting?

A

when mountains or other large geographical features force air to pass over them

61
Q

What is convergence (depression)?

A

where relatively low pressure exists at the surface of a depression, air will tend to move in from all directions to equalise the pressure. This causes vertical movement within the atmosphere

62
Q

Relatively high temperature implies…

A

low density

63
Q

High level clouds

A

cirrus
cirrocumulus
cirrostratus

64
Q

medium level clouds

A

altocumulus
altostratus
nimbostratus

65
Q

low level clouds

A

cumulus
stratus
cumulonimbus
stratocumulus

66
Q

What are the associated hazards from a
Cumulonimbus cloud?

A

Turbulence, hail, lightning, icing, static,
windshear

67
Q

What are the requirements to make a TS?

A

Moisture, instability, trigger

68
Q

How long does a TS last normally?

A

Growing stage 30 mins, mature stage 30
mins, dissipating stage can last 2 hours or
can regenerate.

69
Q

What does supercooled water do when it
hits an airframe?

A

If the airframe is below 0C it will freeze,
causes clear ice and RIME ice

70
Q

When does clear ice form on an aircraft?

A

Transparent or translucent ice formed by
large droplets that are only just
supercooled. A large percentage of each
drop flows backwards and gradually freezes
to produce a rapid build-up of heavy thick
ice

71
Q

When are we likely to get RIME Ice?

A

When flying through cold air and
approaching a warm front

72
Q

What are the significant factors for Ice?

A

Temperature, Drop size, Airframe shape,
Kinetic heating, Concentration

73
Q

Definition of Fog?

A

A suspension of small water droplets
reducing visibility below 1000m

74
Q

Definition of Mist?

A

The same as fog except visibility is not less
than 1000m

75
Q

Definition of Haze

A

A suspension of solid particles of smoke or
dust reducing visibility to not less than
1000m where the relative humidity is less
than 95%

76
Q

How is RVR measured?

A

Human observer method
Instrumented RVR

77
Q

What is the Human observer method?

A

An assessment is made counting the lights
or markers along the runway length and
calculating the distance from a calibrated
table

78
Q

What is Radiation Fog?

A

Forms over land. On a clear night the
ground radiates heat, its temperature drops
rapidly and if the air is sufficiently moist the
layer in contact with the ground will be
cooled below its dew point and
condensation will occur. Just before dawn is
the most likely time

79
Q

Requirements for Radiation Fog?

A

Clear sky, Land surface, Moist air, Light
wind, Long night

80
Q

How does the windspeed affect Radiation
fog?

A

No wind – settles on ground as dew
2-8kts – thin layer of fog
8kts+ - lifts fog to form stratus cloud

81
Q

How is hill fog formed?

A

Air moving up slopes and condensing at the
top, to form low cloud/hill fog

82
Q

How is advection fog formed?

A

Warm air with a relatively high humidity
may be cooled enough, by contact with a
cold surface, to cause condensation

83
Q

How is steam fog formed?

A

Caused by cold, dry air moving over
relatively warm moist water. Small
quantities of water evaporate into the air
and cause localised condensation that
resembles steam or a thin layer of thick fog
at the water’s surface

84
Q

What is windshear?

A

Wind shear is a rapid change of wind speed
and/or direction over a short distance
horizontally or vertically

85
Q

What is a microburst?

A

A microburst is a localized column of sinking
air (downdraft) within a thunderstorm and
is usually less than or equal to 2.5 miles in
diameter

86
Q

Cloud Okta scale?

A

FEW 1-2
SCT 3-4
BKN 5-7
OVC 8

87
Q

how is turbulence caused?

A

random fluctuations in the wind flow causing the wind to vary in speed and/or direction over a short distance

88
Q

when is turbulence called wind shear?

A

at lower levels or in the vicinity of an airfield

89
Q

Convection turbulence

A

caused by variations in convection currents affecting aircraft at low level and speed

90
Q

The degree of turbulence present in the friction
layer depends upon…

A

Strength of the surface wind
The stability of the wind
The nature of the surface.

91
Q

What is wind shear?

A

a rapid change of wind speed
and/or direction over a short distance
horizontally or vertically

92
Q

When is a pilot likely to encounter wind shear?

A

-Climbing or descending through an inversion.
-Climbing or descending through a warm front.
-In the lee of high ground or large buildings when
close to the ground.
-In the vicinity of standing waves.
-Flying near, and especially underneath, a
cumulonimbus

93
Q

What does low level wind shear cause?

A

changes of wind velocity along an
aircraft’s flight path that occur faster than it can
accelerate or decelerate to compensate for them.

94
Q

What is a microburst?

A

A microburst is a localized
column of sinking air within a
thunderstorm and is
usually less than or equal
to 2.5 miles in diameter

95
Q

(LLWSAS)

A

low level wind shear alert system

96
Q

What does LLWSAS consist of?

A

five anemometers situated around
the airfield perimeter and one centrally located

97
Q

What is a low level wind shear alert based on?

A

-Mean surface wind of at least 20kts.
-A difference between surface and 2000ft wind
speeds of at least 40kts.
-Thunderstorms or heavy showers within 5nm of
the airfield.
-Pilot reports of local wind shear conditions.

98
Q

Downdrafts (macrobursts)

A

4 km (2.5 miles) in diameter and can produce
winds as high as 60 metres per second, or 215 km
per hour (200 feet per second, or 135 miles per
hour)

99
Q

What is clear air turbulence?

A

turbulence that occurs without any cloud to
indicate its presence

100
Q

Where CAT normally present?

A

upper troposphere or lower stratosphere

101
Q

How can a pilot detect CAT?

A

observing the significant change in outside air temperature that will be experienced when flying through the frontal boundary between warm and cold air.

102
Q

What is an air mass?

A

An air mass is a volume of air with many uniform
characteristics extending over a large region.

103
Q

Equatorial masses are:

A

very warm

104
Q

Tropical and polar masses are:

A

Warm and cold respectively

105
Q

Arctic is reserved for:

A

VERY COLD air masses that originate
in the Arctic Ocean

106
Q

How are air masses classified?

A

based on their source region

107
Q

Arctic: Very cold and humid
Polar Maritime: Cold and humid
Polar Continental: Cold and dry
Tropical Maritime: Warm and humid
Tropical Continental: Warm and dry
Equatorial: Hot and humid

A
108
Q

Low pressure systems are known as:

A

depressions or cyclones

109
Q

high pressure systems are known as:

A

anticyclones

110
Q

Depressions are characterised by…

A

Strong winds and rising air

111
Q

Measurements of a depression

A

1000km-2000km across, extend up from surface to tropopause

112
Q

What direction anticyclones revolve?

A

clockwise

113
Q

Anticyclones are characterised by…

A

Light winds and subsiding air leading to clear
skies and fine weather with no precipitation.

114
Q

what is anticyclonic gloom?

A

A condition of low visibility associated with
anticyclones

115
Q

What is a trough?

A

An elongated area of relatively
low surface pressure

116
Q

What is a ridge?

A

an area of high pressure which
elongates to form a ridge of high pressure

117
Q

synoptic chart

A

shows pressure

118
Q

What is a front?

A

A boundary between 2 air masses

119
Q

WMO

A

World Meteorological Organisation

120
Q

WAFS

A

World area forecast system

121
Q

SADIS

A

satellite distribution system

122
Q

RAFC

A

Regional area forecast centre

123
Q

MWO

A

Meteorology watch organisation

124
Q

WAFC

A

World area forecast centre

125
Q

VAAC

A

Volcanic ash advisory centre

126
Q

Where is MET info derived from?

A

Surface Observations
Upper Air Observations
Observations from Aircraft in Flight
Observations from Satellite

127
Q

What reports are available at aerodromes?

A

Meteorological Aerodrome Report (METAR)
Special Report (SPECI)
Terminal Aerodrome Forecast (TAF)
Aerodrome Warnings
Wind Shear Warnings

128
Q

METAR

A

A report of actual weather conditions at a
particular aerodrome at a specified time.
For each hour or half hour

129
Q

SPECI

A

An amendment to a METAR that is designed
to draw attention to an improvement or
deterioration of a condition that might
significantly affect aircraft operations

130
Q

TAF

A

A concise statement of expected meteorological
conditions at an aerodrome during a specified
period

Issued in a code form.
Prepared every 3 hours for 9 hour period.
24 or 30 hour TAFS for long haul schedules are
issued at 6 hourly intervals.
Trends - for selected aerodromes are added to
METAR to indicate significant expected changes
over next 2 hours

131
Q

Aerodrome warnings

A

Issued to aerodromes by MWO by AMHS / phone.
They relate to the following phenomena having
occurred or expected:
Gales / Strong wind warning
Squalls
Thunderstorm
Hail
Fog
Frost / Snow
Freezing precipitation

132
Q

Wind Shear Reports

A

Windshear reports are based on recent pilot reports
of windshear on the approach or climb-out.
Pilots should give concise information concerning
wind shear conditions, whether by reference to speed
loss or gain or in terms of its effect on the aircraft.
Cancelled when aircraft reports indicate that
windshear no longer exists.
Pilot should report windshear even if already reported
or warned

133
Q

MARKED TEMPERATURE INVERSION

A

For specific aerodromes warnings of marked
temperature inversions are issued whenever a
difference of 10°c or more exists up to 1000ft aal.
This warning is broadcast on departure and arrival
ATIS at aerodromes so equipped

134
Q

SIGMET

A

Warn pilots of actual or anticipated weather conditions
that could affect the safety of aircraft operations.
They include the following for subsonic flight:
Active Thunderstorm Tropical Cyclone
Freezing Rain Heavy hail
Severe turbulence Severe icing
Severe mountain waves Volcanic ash cloud
Heavy dust/sandstorms

135
Q

SIGMET distribution

A

MET office prepares SIGMET info sends to ACC/FIC.
ACC/FIC pass SIGMET to aircraft in flight if up to
500nm ahead on route or 2 hours flying time.
Valid for 4 hours and reissued if necessary

136
Q

AIREP

A

AIRCRAFT OBSERVATIONS AND REPORTS
Severe turbulence or icing.
Severe Mountain wave.
Thunderstorms with or without Hail.
Volcanic ash or pre-eruption.
Any other phenomena that, in the opinion of
the pilot, may adversely affect the safety of
aircraft operations.

137
Q

ATIS

A

ATIS - AUTOMATIC TERMINAL INFORMATION SERVICE
A repetitive recording that is continuously transmitted
on a dedicated airfield VHF frequency. It transmits the
following information in plain language –
Aerodrome Status
Current weather
ATIS Information Code

138
Q

MET office duties

A

Prepare and obtain relevant information for all
flights with which it is concerned.
Supply other meteorological information to
aeronautical users.
Display available meteorological information.
Exchange information with other met offices.

139
Q

Information that is required by aerodrome and approach
control on a routine basis includes:

A

METAR with trend as appropriate every hour or half hour.
SPECIs as appropriate.
Aerodrome forecasts (TAF).
Aerodrome warnings.
SIGMET.
Additional information as agreed locally.

140
Q

ATC will only transmit what has been supplied
by the met office - the exceptions are:

A

Indicated wind speed & direction.
RVR observation.
Controller observation of sudden deterioration -
inform aircraft.
Aircraft reports of weather hazards.
Cloud echoes observed on radar.
Official met observation (certificated).
Unofficial met observation.

141
Q

Once a flight is airborne, pilots can obtain aerodrome
weather information from any of the following:

A

-VOLMET broadcasts.
(see GEN 3.5)
-Automatic Terminal Information Service (ATIS)
broadcasts.
-By request to an ATS Unit but whenever possible only if the information required is not available from a broadcast.

142
Q
A

BTC 5-24 (9 decks)

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