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aviation dispatcher > Aviation weather > Flashcards

Aviation weather Flashcards

1
Q

what is ideal air

A

lacks moisture. N2 78%, O2 21% and other 1%

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2
Q

air in coastal regions

A

water vapor 5% other 1% nitrogen 74% and oxygen 20%

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3
Q

Characteristics of troposphere

A

temp lapse rate. avg height in mid latitude 36000’. wind speed increase with altitude highest in trop. thicker at equator and thinner at poles (solar radiation). wx occurs here. unstable layer.

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4
Q

characteristics of tropopause

A

non continuous layer. abrupt change in temp lapse rate. jet streams are located in the breaks. avg depth no more than 1000’. turbulence due to strong windshear from jet streams

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5
Q

stratosphere

A

isothermal layer. thicker. wind speed decreases with altitude.

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6
Q

isa

A

29.92” of hg or 1013.25 hpa/mb 15deg c or 59 f. aircraft instrument are calibrated. standard for wx parameters. aircraft performance.

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7
Q

air desity

A

high elevation - density decreases. high temperature - density decreases. humidity increases - density decreases.

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8
Q

adiabatic

A

temp change by expansion and contraction with no heat added to or removed from the system.

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9
Q

freezing level

A

level at which temp is 0 degree c

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10
Q

temperature variation

A

LSDTA (lsd taste awful) latitude - high temp at equator
Seasonal- tilt of the earth. Diurnal variation- temp change during day and night. Topography- dessert semi arid land compared to vegetation or water bodies. Altitude- temp lapse rate 2 degree c per 1000’.

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11
Q

inversion

A

inverted temp lapse rate. increase in temp with increase in altitude.

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12
Q

surface based and aloft inversion

A

if the base is at surface then its called surface based inversion if not at surface then called aloft.

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13
Q

when does ground based inversion occur.

A

clear cool calm nights associated with stable layer of air

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14
Q

hazards of inversion

A

PIT poor visibility, icing and turbulence

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15
Q

station pressure QFE

A

actual pressure at field elevation

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16
Q

Altimeter setting QNH

A

the sea level pressure value. indicates true altitude and field elevation.

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17
Q

pressure lapse rate

A

1” per 1000’ upto 10000’ MSL

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18
Q

how temperature effects pressure

A

cold air- pressure decreases faster in colder air since its more dense.

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19
Q

true altitude

A

actual height above mean sea level

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20
Q

absolute altitude

A

actual height above the ground

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21
Q

indicated altitude

A

altitude that the altimeter reads when set to the local altimeter setting. (MSL)

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22
Q

Altimeter errors

A

high to low look out below. high temp/pressure to low tem/ pressure TA is less than indicated altitude.
TA=field elevation.

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23
Q

pressure altitude

A

indicated altitude when set to 29.92” of hg, at or above 18000’MSL.

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24
Q

why use PA

A

to simplify high speed flight procedure. to calculate aircraft performance. a/c have pa limits for takeoff and landing also called flight levels.

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25
Q

what is density altitude

A

pa corrected for non standard temp

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26
Q

what affects density altitude

A

high temp = low air density = high da
high humidity = low air density = high da
high elevation = low air density = high da

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27
Q

effects of high da on aircraft performance

A

increased ground roll, climb reduces, decreased performance

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28
Q

isobar

A

line of equal pressure. wind flow nearly parallel ( surface friction). close together wind speed increases. found on surface analysis chart.

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29
Q

isotach

A

line of equal wind speed. on aloft chart

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30
Q

isotherm

A

line of equal temp. on aloft chart

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31
Q

contour

A

line of equal height. winds flow parallel. found on aloft chart. wind speed increases as spacing decreases.

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32
Q

convection

A

rising air

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33
Q

advection

A

horizontal flow of air

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34
Q

pressure gradient force

A

force that drives winds from high pressure to low pressure

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35
Q

coriolis force

A

caused due to earths rotation, more at poles zero at equator. causes clockwise rotation around high in northern hemisphere. winds deflected to right in NH. Winds in US are westerlies high altitude. surface friction reduces wind speed and cf effects. no effect above 2000’agl

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36
Q

low

A

area of low pressure surrounded by high on all sides.
wind flow- cyclonic or anti clockwise, upward and inward.may have pressure higher than 29.92” of hg. cold low- blizzards warm low-tropical storms.

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37
Q

wx in low

A

bad except when lacks moisture

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38
Q

leaning low

A

when upper level winds are fast and the low moves with wind. poor wx will move quickly from the area

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39
Q

general movement of low in us

A

west or south west to east or north east. if no upper level winds than no horizontal movement in low. poor wx will linger in that area.

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40
Q

trough

A

elongated low pressure area. associated with turbulence

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41
Q

high

A

area of relatively high pressure surrounded by low on all sides. can have pressure lower than 29.92”hg. clockwise, anti cyclonic, downward and outward.

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42
Q

wx with high

A

good wx

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43
Q

Movement of high

A

similar to low

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44
Q

ridge

A

elongated area of high pressure. turbulence due to wind shear.

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45
Q

wind shear

A

change in speed over a relatively short distance, time or altitude

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46
Q

vertical wind shear

A

change in speed per 1000’ change in altitude. climb and descent. primarily experienced in vicinity of trop. step up climb

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47
Q

moderate vws

A

6kts or greater per 1000’

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48
Q

severe wind shear

A

10 kts or greater per 1000’

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49
Q

horizontal wind shear

A

change in speed over a distance of 150Nm. primarily experienced during cruise

50
Q

moderate hws

A

18kts or greater per 150nm

51
Q

severe hws

A

40kts or greater per 150nm

52
Q

land breeze

A

at night

53
Q

sea breeze

A

at day

54
Q

relative humidity

A

amount of water vapor present in the air to the amount it can hold at that temp. expressed as percent

55
Q

what determines how much water vapor that air can hold

A

temp

56
Q

dew point

A

temp to which air must be cooled to be 100 percent saturated

57
Q

spread

A

temp - dewpoint always positive

58
Q

change of state

A

melting freezing condensation evaporation sublimation and deposition

59
Q

virga

A

rain that evaporates before reaching the ground. implies turbulence common in south west us because of dry air

60
Q

supercooled water

A

water that does not freeze at 0 deg c, eg FZRA and FZDZ these drops increase the rate of icing.

61
Q

supercooled water in abundance

A

0 to -10 deg c in stratiform clouds

0 to -15 deg celcius in cumuliform clouds

62
Q

what is dew

A

is liquid that forms when surface temp of an object decreases to dew point

63
Q

what is frost

A

forms when dew point is 0 deg or colder and temp is close to dew point

64
Q

what does freezing rain indicate

A

warmer air above

65
Q

what does ice pellets indicate

A

freezing rain at higher altitudes

66
Q

what is stable air

A

air that resists vertical displacement

67
Q

what determines stability

A

ambient lapse rate

68
Q

when is air unstable

A

ambient lapse rate greater than 2deg c per 1000feet

69
Q

characteristics of unstable air

A

cumuliform clouds, showery ppt, turbulent flying condition and good visibility

70
Q

characteristics of stable air

A

stratiform clouds, smooth flying condition, poor visibility and continuous ppt

71
Q

unsaturated cools at or dalr

A

3 deg Celsius per 1000 feet

72
Q

dew point cools at

A

0.5 deg c per 1000feet

73
Q

salr

A

cools slower than dalr

74
Q

four families of clouds

A

low, middle high and clouds with extensive vertical development

75
Q

what are high clouds made of

A

entirely ice crystals therefore contribute least to icing.

little or no turbulence problem.

76
Q

middle cloud composition

A

primarily water drops may also have supercooled water droplets ice crystals when temp are below frreezing

77
Q

whats an air mass

A

uniform temp and moisture content

78
Q

what is a front

A

a boundary between the two air masses

79
Q

types of fronts

A

cold, warm stationary and occluded

80
Q

what is a cold front

A

when colder air takes over warmer air. often lies in a trough. has a steep slope. warmer air gets lifted above. bad wx lies on the side of the cold air.

81
Q

warm front

A

when warmer air overtakes a cold air mass. shallow slope thus wide areas of ppt and cloudiness. bad wx ahead of the warm front where there is cold air.

82
Q

stationary front

A

when neither air mass takes over.

83
Q

occluded front

A

indicates frontal wave

84
Q

formation of frontal wave

A

strong indication of poor wx. usually forms on slow moving cold front or stationary front, beginning stage of low pressure system usually develops into an occluded front

85
Q

dry line or dew point front

A

moisture differences in air mass ex. dallas dry air from west and moist air from gulf of mexico. leads to thunderstorm and tornado

86
Q

mountain wave formation

A

winds greater than 30 or 40kts, blowing perpendicular to the mountain and stable air on the lee side

87
Q

where does mountain wave occur

A

on the lee side of the mountain, turbulence. can extend upto 5000feet above trop and 100 miles downwind of a mountain range

88
Q

clouds associated with mountain wave

A

ciro cumulus standing lenticular, strato cumulus standing lenticular, alto cumulus standing lenticular and rotor clouds.(lowest under wave crest)

89
Q

conditions required for icing

A

visible moisture and temperature 0 deg or colder

90
Q

what are the intensities of icing

A

trace, light, moderate and severe

91
Q

what is severe icing

A

the rate of accumulation is such that your system fails to remove it or it gets accumulated in weird spots like underside of a wing or aft of the leading edge.

92
Q

what are the types of icing

A

clear rime and mixed

93
Q

how is clear icing formed

A

large water droplets(cumulus clouds), difficult to remove, transparent.

94
Q

rime icing how is it formed

A

small water droplets(stratus clouds), milky or opaque in appearance due to air being trapped freezes quickly easily removed, most frequently reported

95
Q

mixed icing

A

combination of both small and large water droplets, irregular shape and difficult to remove

96
Q

effects of icing on the aircraft

A

thrust decreases drag increases lift decreases and weight increases stall speed increases

97
Q

when does frost forms

A

clear stable air with light winds

98
Q

how does frost affect aircraft

A

produces roughness on the surface decreases lift by 30% and increases drag by 40%. prohibited to take off with ice snow frost on control surface, wings or props.

99
Q

three conditions necessary for the formation of ts

A

lifting mechanism, unstable air and moisture

100
Q

example of lifting mechanism

A

orographic lifting, front, convection, low pressure and surface convergence

101
Q

types of thunderstorm

A

air mass and steady state

102
Q

why are steady state thunderstorm more destructive

A

longer duration, associated with pressure systems

103
Q

what are air mass thunderstorm

A

formed from convection ex florida afternoon shower short duration therefore less destructive in nature

104
Q

three stages of thunderstorm

A

cumulus-updrafts. mature-updrafts and downdrafts beginning of rain on earth. dissipating- downdrafts

105
Q

thunderstorm hazards

A

lightning, tornado, hail, microburst, icing, wind shear, turbulence, embedded cbs

106
Q

what is a squall line

A

often develops ahead of a cold front. narrow band of bad thunder storm

107
Q

what is severe thunderstorm

A

surface winds atleast 50 kts or greater and or surface hail 3/4 inches in diameter

108
Q

cloud coverage

A

clear none. few 0-2/8 th of the sky, sct 3-4/8, bkn 5-7/8 th of the sky, ovc more than 7/8th and vv 8/8

109
Q

what is ceiling

A

ceiling is defined as the height above earths surface of the lowest base of a cloud or any obscuring phenomena aloft classified as broken or overcast or vertical visibility into a total surface based obscuration.

110
Q

low ifr

A

ceiling less then 500 feet and or visibility less than 1sm

111
Q

ifr wx

A

ceiling less than 1000feet and or visibility less than 3sm

112
Q

mvfr wx

A

ceilings 1000-3000feet and or visibility 3-5sm

113
Q

vfr

A

ceilings 3000feet or more and visibility 5sm or more

114
Q

when does fog form

A

when temp decreases and dew point increases

115
Q

types of fog

A

radiation, advection, ppt induced, upslope fog ice and frontal fog

116
Q

radiation fog how does it form

A

terrestrial radiation, clear cool calm nights restricted to land. winds greater than 5kts it will be lifted or dissipate

117
Q

advection fog

A

warm moist air moves over cold surface(land or water), wind speed upto 15kts deepens it more than 15kts will lift it into low clouds

118
Q

frontal fog

A

warm moist air gets lifted over a front

119
Q

upslope fog

A

ex san antonio warm moist air from gulf moving over gradually rising terrain thus cooled adiabatically (Stable air)

120
Q

ice fog

A

same like radiation fog when temp are -32cel or colder

aviation dispatcher (1 decks)

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