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Met Flashcards

1
Q

What are the 7 constituents of the atmosphere?

A

Thermosphere = Exosphere + Ionosphere

Mesopause

Mesosphere

Stratopause

Stratosphere

Tropopause

Troposphere

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2
Q

What are the temperatures of the isothermal layers in the atmosphere?

A

Mesospause = MS 90

Stratopause = 0

Tropopause= MS 56.5

MSL = PS 15

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3
Q

What are the heights of the layers of the atmosphere?

A

Mesosphere < 280,000ft

Stratosphere < 160,000ft

Troposphere < 36,090ft (ISA)

< 25,000 Poles, 36,000ft UK, 55,000 Equator

MSL 0ft

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4
Q

Describe the temperature characteristics of the troposphere and Stratosphere?

A

Troposphere air cools at ISA 1.98 degrees celcius per 1000ft

Stratosphere air warms due to ozone O3 forming

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5
Q

What is the significance of the Tropopause to aircrew?

(5 things occur)

A

The following occur at or below the Tropopause:

1) Clouds and weather (majority mass of water vapour in this layer)
2) Jet Streams occur just below (100-200kts UK)
3) Turbulence
4) Condensation trails
5) Turbo jet engines most efficient

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6
Q

What are the 3 heat transfer processes by which the Earth and Atmosphere lose and gain heat?

A

1) Conduction
2) Convection
3) Radiation

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7
Q

Radiation

(definition)

A

Flow of heat from one material to another without heating the intervening space.

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8
Q

Conduction

(definition)

A

Heat transfer from an area of high to low temperature without the transfer of the atmospheric constituents.

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9
Q

Convection

(definition)

A

Heat transfer from one place to another by the bodily transfer of air.

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10
Q

What is the effect of clouds on the way heat is gained and lost by the earth and atmosphere?

A

Clouds prevent heating - a lot of radiation reflected back into the upper atmosphere and a little absorbed and re radiated.

Clouds prevent cooling - some radiation reflected back down towards earth and a lot absorbed and re-radiated.

E.g. cloudy day less warm, cloudy night less cold.

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11
Q

What is the effect of wind on heat transfer?

A

In general the diurnal variation is greatest when the wind is calm.

E.g. for calm winds at night the min temps will be lower, in the day the max will be higher.

Strong winds have the opposite effect reducing the diurnal variation.

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12
Q

What is temperature inversion?

A

An increase of temperature with height.

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13
Q

Specific Heat

(definition)

A

Thermal capacity is the amount of heat required to raise the temperature of the substance by 1 degree celcius.

Specific heat is the ratio of a thermal capacity of a substance compared with water.

Higher specific heat means it will heat and cool more slowly (e.g. water compared with land).

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14
Q

Latent Heat of Evaporation

(definition)

A

Evaporation - when a liquid changes into a gas.

Latent Heat - the heat energy required for the change of state to take place.

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15
Q

What is the effect of Opacity on the temperature of the sea?

A

Water is transparent therefore some of the incoming radiation penetrates to a considerable depth before being entirely absorbed.

This means small temp changes in the sea. For opaque land surfaces heating is rapid in the layer a few inches deep.

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16
Q

What are the ISA standard values of MSL pressure, temp, lapse rate and tropopause height and temp?

A

MSL pressure = 1013.25hPa

MSL temp = PS 15 degrees celcius

Environmental Lapse Rate = 1.98 degrees celcius / 1000ft

Tropopause height = 36, 090 ft

Tropopause temp = MS 56.5 degrees celcius

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17
Q

In cold dense air would you expect pressure to fall gradually or quickly with height?

A

More quickly

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18
Q

In wame climates would you expect the tropopause to be high or low?

A

Tropopause higher in warm climates

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19
Q

What instrument is used to measure pressure?

A
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20
Q

What does a pressure altimeter measure and how does it work?

A

It measures height above the ground.

By measuring the difference between barometer value and altimeter sub scale value and converts to feet using ISA conditions.

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21
Q

Is an inversion associated with stable or unstable conditions?

A

Stable

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22
Q

What process occurs when a gas changes into a solid?

A

Deposition

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23
Q

What process occurs when a solid changes into a gas?

A

Sublimation/Vaporisation

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24
Q

Is there more convection over the sea or land during summer?

A

Summer - more convection over land therefore clouds and showers form over land

Winter - more convection over sea as it cools more slowly, clouds form over the sea

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25
Q

What effect does friction have on the surface wind when compared to the wind at 2000ft?

A

The wind backs and slacks at the surface.

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26
Q

Name the force that moves air from high pressure to low pressure?

A

Pressure Gradiant Force

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27
Q

What is QFE?

A

The corrected barometric pressure for a specified datum (Field Elevation).

Height above touchdown when in the circuit, gives 0ft on the runway.

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28
Q

What is QNH?

A

The pressure at Mean Sea Level (Nautical Height).

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29
Q

Regional Pressure Setting

(definition)

A

The lowest forecast value of MSL pressure in that region for that hour (forecast 1 hour in advance). For transit flying at or below transition altitude.

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30
Q

The Standard Altimeter Setting

(definition)

A

Used when flying above the transition atlitude. Assumes MSL pressure of 1013.35hPa.

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31
Q

What is an isobar?

A

A line of equal pressure.

Isobars closer together means stronger winds.

Wind direction parallel to isobars

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32
Q

Identify the symbols on the synopsis.

A
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33
Q

Where does a col occur?

A

Between two high pressure systems and a low pressure system.

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34
Q

How does the air behave above

a) high pressure system
b) low pressure system

A

a) more dense air therefore more stable, air sinks causing weakening weather systems (cross)
b) air less dense so more active and causing developing weather (dot)

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35
Q

At what temperatures does ice exist?

A

Only at temperatures at or below 0 degrees celcius

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36
Q

What temperatures does water exist as a liquid?

A

>MS 40 and <100 degrees celcius

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37
Q

What temperature does water vavpour exist at?

A

At any temperature

38
Q

What results from cooling air below the saturation point?

A

Clouds, mist, fog, dew and frost form.

39
Q

How are contrails formed?

A

The water vapour from an aircraft’s exhaust gases saturates the surrounding air causing condensation.

40
Q

What is the SALR?

A

Saturated Adiabatic Lapse Rate

1.5 degress celcius per 1000ft

41
Q

What is the DALR?

A

Dry Adiabatic Lapse Rate

3.0 degress celcius per 1000ft

42
Q

Relative Humidity (RH)

(definition)

A

RH = (Actual water vapour content / Max water vapour content ) x 100%

43
Q

Dew Point

(definition)

A

Dew point is the temperature at which a sample of air would become saturated. RH = 100%

(if cooled at constant pressure)

44
Q

What are the effects of condensation on Aircraft?

A

Misting of the canopy, icing of the airframe and engine and loss of visibility.

45
Q

Can air hold more or less water vapour at higher temperatures?

A

The higher the temperature, the more water vapour it can hold.

46
Q

Dry Air

(definition)

A

Unsaturated air.

47
Q

Coriolis Force

A

Only affects moving air and is caused by the Earth’s rotation.

48
Q

What is wind measured in?

A

Wind velocity is measured in Knots and degrees (True) by the MET office.

ATC adjust to magnetic to compare with runway direction.

49
Q

Veering and Backing

(definition)

A

If the wind changes direction clockwise = veering

If the wind changes direction anticlockwise = backing

50
Q

Draw a wind barb

51
Q

Eddies

(definition)

A

Eddies are variations in the horizontal and vertical planes due to air flowing around obstacles such as hills, buildings etc.

52
Q

Gusts

(definition)

A

Gusts are sudden, brief (1/2 seconds) increases and decreases in wind speed and direction.

Must be 10 kts higher than average speed to be included in METAR

E.g. 18014G38KT

53
Q

Squall

(definition)

A

A squall is a sudden blast of wind lasting several minutes. Tend to accompany vigorous showers, thunderstorms or cold fronts.

54
Q

Gales

(definition)

A

Gales are strong winds with a mean speed of 34kt or more, or gusts of 43kt or more.

55
Q

How would you code the following for METAR?

S’ly wind meaning 14 kt with gusts up to 38kt

Varying wind direction with mean speeds of 3kt

Wind varying between 30 and 160 deg, majority at 90 deg speeds of 10kt

A

18014G38KT

VRB3KT

09010KT 030V160

56
Q

In what direction does Coriolis Force act?

A

Acts at right angles to the instantaneous motion.

Acts to the right in the Northern Hemisphere

Acts to the left in the Southern Hemisphere

57
Q

What value does Coriolis Force have at the equator?

A

Zero

Sin 0 = Zero

58
Q

Below what height does Gradient Wind/Geostrophic flow occur?

59
Q

At night does CF have more or less of an effect on Gradient Wind?

A

At night, colder air is more dense therefore friction reduces the wind speed. CF will reduce.

=More Backing and Slacking

60
Q

Will there be more backing over land or sea due to Coriolis Force?

A

More backing over land due to surface roughness, increased friction, reduced wind speed, reduced coriolis force.

61
Q

What are the 4 trigger actions initiating vertical motion? (COMM)

A

1. Convection. Surface heating causes thermal currents to develop = heaped cloud.

2. Orographic Uplift. Air is forced to rise over high ground.

3. Mass ascent and descent. Relatively slow but widespread vertical movement.

4. Mechanical Turbulence. Eddies may be created by the frictional effect of the Earth’s surface.

62
Q

ELR less than SALR and DALR more or less stable?

A

Stable. DALR and SALR cooling more quickly than ELR so tending to sink.

63
Q

ELR between SALR and DALR?

A

Conditionally unstable

64
Q

What are the symbols for moderate and severe turbulence?

65
Q

If the atmosphere was heated from below would it become more or less stable?

A

Less stable

66
Q

What are the main types of turbulence?

A

Mechanical - friction/obstructions

Convective - convection currents

Clear Air - wind shear

67
Q

What factors lead to the development of mountain waves?

A

Wind Speed: 15kt at crest, increasing with height

Wind Direction: +/- 30 degrees perpendicular to ridge, little change with height

Stability: Markedly stable above crest, less stable above and below

A mountain/hill

68
Q

Explain the Fohn Effect

A

The Fohn effect occurs if a moist stable airstream loses some of its moisture on the windward side of a hill or mountain range, thus arriving on the lee side as a much warmer, drier airstream.

69
Q

What cloud type forms from Mountain waves?

A

Alto Cumulus - Lenticular

70
Q

Describe the formation of anabatic and katabatic winds

A

Anabatic wind - warming of slopes decreases air pressure and sucks air from lower levels.

Katabatic - downslope flow of air as it cools and becomes more dense

71
Q

Explain the formation of valley winds

A

Air funnels through valley at greater speed.

72
Q

Explain the development of sea and land breezes.

A

Land cools more quickly than the sea creating a pressure difference at night/winter (L over the land, H over the sea). Air flows from H to L creating sea breeze. Opposite flow upperloft.

73
Q

What is the standard procedure for reporting cloud?

A

The sky is split into 8 sections - OKTAS

Internationally recognised abbreviations:

SKC = 0 OKTAS

FEW = 1-2

SCT = 3-4

BKN = 5-7

OVC = 8

VV/// = 9 (obscured)

74
Q

What are the cloud height datums?

A

Cloud base datum

Airfield reports (METARs & TAFs): above airfield height

Area forecasts: above MSL

75
Q

What are the two basic cloud shapes?

A
  1. Heaped (convection)
  2. Layered
76
Q

What are the main high cloud types?

A

HIGH 16,500 - 45,000ft

CI Cirrus

CS Cirrostratus

CC Cirrocumulus

77
Q

What are the main medium cloud types?

A

MEDIUM 6500-23,000ft

AS Altostratus

AC Altocumulus

  • Castellanus (castles)
  • Lenticularis (lense)
78
Q

What are the low cloud types?

A

LOW <6500ft

CU Cumulus (heaped)

ST Stratus (layered)

SC Stratocumulus (layered)

79
Q

What are the heaped types of cloud?

A

TCU Towering Cumulus

and CB Cumulonimbus

80
Q

What are the 4 trigger actions for cloud formation?

A
  1. Turbulence - mechanical lifting
  2. Convection - heating from below
  3. Orographic - over hills
  4. Mass ascent - associated with depressions and fronts
81
Q

Describe drizzle

A

Fine liquid water droplets, no visible impact on puddles,

ST, SC

Poor vis <4km

low cloud base, low vis

82
Q

Describe Rain

A

Large liquid water droplets

Ripples on puddles

Deep cloud = NS, CU, CB

Moderate - poor eg 8km

low vis, standing water on runway, potential for icing

83
Q

Describe snow

A

Solid icecrystals, varying size

crystalline, opaque/white

Deep cloud NS, CU, CB

Very poor vis 200m-2km

Ice/snow builds up on runway

V. poor vis

84
Q

Describe hail

A

<5mm

solid icecrystalls, hard ‘onion rings’ formed by rising and falling within the cloud

bounces on the ground

ONLY CB

Moderate to poor vis eg <6km

Potential to damage airframe or go into the engine intake

85
Q

What are the METAR codes for:

Drizzle, Rain, Snow, Hail

Showers

Slight/Heavy

A

Drizzle DZ, Rain RA, Snow SN, Hail GR(large) GS(small)

Showers SH (e.g. SHRASN = showers of rain and snow)

Slight/Heavy -/+

86
Q

What are the effects on aviation of precipitation?

A

Lowering of cloud base (saturation of air below cloud)

Lowering of freezing level

Stronger down currents of air known as down draughts, gust fronts and micro bursts.

Reduced visibility (greatest with snow, then drizzle, then rain.

Hail damage to aircraft structure.

Afffecting runway surfaces

87
Q

What are the effects of cloud on air operations?

A

Reduced visibility

Turbulence

Icing

Interference with comms (lightning, static, icing)

Increased airframe fatigue (turbulence stresses)

Instrument approaches required

88
Q

Which cloud types are associated with severe icing?

A

CB, TCU, NS

Georgie Ground School (9 decks)

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