Meteorology Flashcards
1
Q
Most visible weather phenomenon occurs in the _____
A
Troposphere
2
Q
The troposphere goes from ___ up to ~___ also known as the _____
A
MSL (mean sea level)
~11km (36,090ft)
Tropopause
3
Q
Temparature decreases at a rate of ___ per 1,000ft (__ per 100m) up to a hight of ___. This is known as the _____ _____
A
1.98°C
0.65°C
Lapse rate
4
Q
___ of water vapour is in the troposphere
A
90%
5
Q
___ of total mass of air is in the troposphere
A
75%
6
Q
ISA Sea level pressure
A
1013.25Hpa
29.92InHg
760mmHg
7
Q
ISA Sea level temp
A
+15°C
8
Q
ISA Density
A
1.225Kg/m³
9
Q
ISA temp 11-20km (36,090 - 65,000ft)
A
-56.5°C
10
Q
The composition of air:
A
78% Nitrogen
21% Oxygen
1% Other Gases
11
Q
The closer to the poles you are, the _____ the tropopause, at an altitude of aprox. __ -__km
A
Lower
8 - 10km
12
Q
The closer to the equator you are, the _____ the tropopause, at an altitude of aprox. __ - __km
A
Higher
16 - 18km
13
Q
The closer to the poles you are, the _____ temperature is at the tropopause, aprox. __ to __°C
A
Higher
-40 to -50°C
14
Q
The closer to the equator you are, the _____ temperature is at the tropopause, aprox. __°C
A
Lower
-75°C
15
Q
Summer tropopause height at Latitude 30°
A
16km (52,000ft)
16
Q
Winter tropopause height at Latitude 30°
A
16km (52,000ft)
17
Q
Summer tropopause height at Latitude 50°
A
12km (38,000ft)
18
Q
Winter tropopause height at Latitude 50°
A
9km (29.00ft)
19
Q
Summer tropopause height at Latitude 70°
A
9km (29,000ft)
20
Q
Winter tropopause height at Latitude 70°
A
8km (26,000ft)
21
Q
Folds in the tropopause are due to
A
large air masses
22
Q
ISA = __ - ((Alt/__) x _)
A
ISA = 15 - ((Alt/1000) x 2
23
Q
If the actual temperature is warmer than ISA, the deviation is _____
A
Positive
24
Q
If the actual temperature is colder than ISA, the deviation is _____
A
Negative
25
The Stratosphere extends from the _____ , up to
| about ___
Tropopause
| 50km (164,040ft)
26
The Stratosphere holds __ of the atmospheres gases
19%
27
The Stratosphere contains the_____ ______, at __ - __km
Ozone layer
| 15 - 35km (49,200 - 114,829ft)
28
The ozone layer _____ UV radiation and emits _____ _____ _____
Absorbs
| Long wave radiation
29
Between 20km and the stratopause, temperature _____ to __
Rises
| 0°C
30
The _____ is between the stratopause and __ - __km
Mesosphere
| 80 - 90km (262,470 - 295,280ft)
31
You can find ____ but not _____ in the lower stratosphere
Clouds
| Turbulence
32
The _____ between the stratopause and the mesopause falls from __ to __
Temperature
| 0°C to -90°C
33
Above the mesopause, you will find the _____ which reaches a height of aprox. ___
Thermosphere
| 700km
34
Temperature in the thermosphere _____
Increases
35
In the thermosphere, you will find the _____ between aprox. ___ - ___
Ionosphere
| 85 - 600km
36
Potential difference (v) between the Earths surface and Ionosphere is ___ - ___
250 - 500kv
37
°C to °F
(°C x 1.8) + 32
38
°F to °C
(°F - 32) / 1.8
39
°C to K
+273
40
°F boiling point
212°F
41
°F freezing point
32°F
42
K boiling point
373k
43
A _____ records temperature over time and plots it on a graph
thermograph
44
A _____ _____ records surface temperature and humidity, must be placed __ - __ _________
Stevenson Screen
| 1 - 2m above the ground.
45
A radiosonde records 3 things:
every __
Air temperature
Humidity
Pressure
1.3 seconds
46
A radiosonde can reach a hight of ___
35km
47
Insolation
Amount of solar radiation absorbed per unit area over time
48
The Earth is tilted on an axis of
23.5°
49
In January, the Earth is _____ from the sun
91 million miles
50
In July , the Earth is _____ from the sun
95 million miles
51
The earth spins
anti-clockwise
52
Summer solstice
21st June, Northern hemisphere closest to the sun at 23.5°N - the tropic of cancer
53
Winter solstice
21st December, Southern hemisphere closest to the sun at 23.5°S - the tropic of Capricorn
54
Spring & Autumn Equinox
23rd March & 23rd September, Sun at same angle as equator.
55
Conduction
The transfer of heat by physical contact
56
Convection
The transfer of heat through the vertical
| movement of air
57
Advection
The transfer of heat through the horizontal movement of air
58
Sublimation
Direct change of a vapour to solid, or solid to vapour
59
In the day, thick cloud = _____. No cloud = _____
Cooler
| Warmer
60
At night, thick cloud = _____. No cloud = _____
Warmer
| Cooler
61
Inversion
Temperature increasing with height
62
In the day, wind = _____. No wind = _____.
Cooler
| Warmer
63
At night, wind = _____. No wind = _____.
Warmer
| Cooler
64
_____ reduces non-linearly with height, due to the _____ distribution of the mass of air
Pressure
| Non-linear
65
Colder then ISA, the _____ dense the air
More
66
Warmer the ISA, the _____ dense the air
Less
67
Natural inversions
form over night
68
Fog is caused by the temperature _____ enough to condense the _____ _____ into _____ _____
Cooling
Water vapour
Water droplets
69
At the bottom of a valley, visibility can be _____ and aircraft performance is _____ due to _____ air.
Poor
Better
Denser
70
When air is subsiding and diverging it is a _________
High pressure system
71
The greater the _____ of overlying air, the _____ the atmospheric pressure
Mass
| Greater
72
Pressure reduces by ___ per ___ up to ____
1hPa
27ft (8m)
20,000ft
73
Low pressure areas are known as
Depressions (lows)
74
High pressure areas are known as
Anticyclones (highs)
75
Whenever a pressure variation exists, the _____ created driving the air from high to low _____ is called the ________
Force
Pressure
Pressure gradient force (PGF)
76
The PGF is the _____ _____ driving the flow of air and _____ the wind speed
Primary force
| Determines
77
Trough lines
Areas of disturbances
78
Barometric pressure can be measured by 2 devices:
A mercury Barometer
| A Aneroid Barometer
79
What is the QFE?
The isobaric surface pressure at the airfield reference point
80
What is the QNH?
The barometric pressure measured at the reporting stating which has be mathematically adjusted to MSL using the airfields elevation.
81
QNH = ___ +- (Elevation/___)
QNH = QFE +- (Elevation/27ft or 8m)
82
There is a __ height difference for every __ of ISA deviation
4%
| 10°C
83
Height
The indication above ground level, normally the height above an aerodrome QFE reference point.
84
Altitude
The indication above MSL
85
Flight levels use the pressure setting of
Mean Sea Level (1013pHa)
86
When the altimeter is indicating a reading lower than the true altitude it is
Over reading
87
When the altimeter is indicating a reading heigher than the true altitude it is
Under-reading
88
Cold air: _____ altitude < _____ altitude
True
| Indicated
89
Warm air: _____ altitude < _____ altitude
Indicated
| True
90
The barometric lapse rate
27ft per 1hpa
91
To determine the IA change use the equation
IA change (ft) = Difference in hPa x 27ft
92
Most dangerous - "____ to ____, look out below"
High
| Low
93
Most dangerous - "____ to ____, don't be bold"
Hot
| Cold
94
Equation to calculate Temperature Error Correction
((ISA Devation/10) x 0.04) x altitude
OR
(4 x (Altitude/1000)) x ISA devation
95
Equation to calculate ISA Deviation
15 - ((alt/1000) x 2)
96
If an aerodrome elevation is given in the question
It must be taken into account
97
Due to the _____ effect, _____ occurs over the crest of high terrain, causing air speed to _____, and _____ and _____ to decrease.
```
Venturi
Convergence
Increase
Pressure
Temperature
```
98
In controlled airspace, controllers assign levels to ___ flights to provide _____ _____.
IFR
| Terrain Clearance
99
Controllers have no responsibility for the _____ _____ for ____ aircraft.
Terrain Clearance
| VFR
100
In temperatures warmer than ___, FL separation _____
ISA
| Increases
101
In temperatures colder than ISA, FL separation _____
Decreases
102
What is the definition of Density ? And what is ISA density at sea level
Measure of a mass of air within a given volume.
1.225 Kg/ m3
103
Under ISA, 1/2 and 1/4 of MSL density occurs at what altitude?
22000 FT and 40000 FT
104
Density in the atmosphere is affected by
Pressure
Temperature
Humidity
105
The density decreases with altitude, but at a ______-______ rate. It reduces more quickly at ________ altitudes. Mimicking the pressure lapse rate with height.
Non-linear
| Lower
106
What are the 4 main steps of the hydrological cycle
Evaporation, Condensation, Precipitation, Run-off
107
On average there’s approx. ___% of water vapour in the atmosphere. But it can vary from 0 to ___% . 90% of the water vapour is found in the __________
1, 5, troposphere
108
Humidity mixing ration tells you how much water vapour is actually in the air, it is measured in ____ of water vapour per ____ of dry air
Grams, Kilograms
g/Kg
109
Humidity mixing ratio won’t change unless......
You add/ remove water vapour
110
Saturation mixing ratio is the ______ amount of water vapour that can be in the air for a given temperature
Maximum
111
Warmer air can potentially ‘______’ more water vapour than colder air
Hold
112
Saturation mixing ratio ______ with increasing altitude and decreasing temperature. Whereas humidity mixing ratio ______ ______ constant as altitude increase and pressure and temperature decrease
Decrease
Stays constant
113
The ratio between the amount of water vapour that the air is holding and the maximum amount of water vapour that air can hold is called?
Relative humidity
114
At constant pressure, relative humidity is affected by......
Amount of water vapour
| Temperature
115
Assuming pressure is constant throughout a clear day, what is the RH like to be _______ 30 mins after sunrise and ______ 2-3 hours after noon.
Greatest
| Least
116
The close the ambient air temperature is to the ______ ______ temperature, the higher the humidity
Dew point
117
Formulas for relative humidity, using temperature and dew point
RH % = 100 - (5x (T - Td))
118
% difference between the dry bulb temperature and wet bulb temperature is equal to?
Relative Humidity
119
What is the DALR?
How does it change with height?
Dry adiabatic lapse rate
3 degrees per 1000 FT/ 1 degree per 100 m
120
What is SALR?
And how does the temperature vary with height?
Saturated adiabatic lapse rate
1.8 degrees per 1000 FT / 0.6 degrees per 100 m
121
A parcel of saturated or dry air is said to ________ ________ if it is cooler than the environment. it will sink back down to its original level even when forced to rise
Absolutely stable
122
ISA ELR is?
2 degrees per 1000 FT / 0.65 degrees per 100 m
123
When an air parcel is rising and subsiding along the saturated adiabatic lapse rate, the RH must ______ ______, until ______ ______ is removed from the parcel.
Remain constant (at 100%).
Water vapour
124
The ______ the saturated air, the ______ it cools, because warmer saturated air holds ______ moisture than cold saturated air,
therefore ______ condensation will take place when it is cooled, but more ______ ______ will also be released.
Warmer, slower, more, more, latent heat
125
The SALR increases ______ with height
Exponentially
126
Low pressure systems are known as
Cyclones or depressions
127
Low pressure are always accompanied by _____ and _____
Cloud
| Precipitation
128
Low pressure systems have isobars that are _____ _____ than other systems.
Closer together
129
In Low pressure systems, air flows _____ in the Northern Hemisphere and _____ in the Southern Hemisphere
Anti-clockwise
| Clockwise
130
As air rises, it _____, causing water vapour to _____ and _____ _____ with possible _____
Cools
Condense
Form clouds
Precipitation
131
With your back to the wind in the Northern Hemisphere, the low pressure system is to your _____
Left
132
Small scale low pressure systems can be ___ to ___NM across and usually occur over _____
1 to 20NM
| Land
133
Large scale low pressure systems can be ___ to ___NM across
300 to 1000+NM
134
Small scale warm, lows can _____ during the day over land masses in _____.
Develop
| Summer
135
Warm lows are low pressure systems in which the _____ is _____ than the surrounding environment
Core
| Warmer
136
Warm lows can produce 3 things:
Heavy rain
Thunder Storms
Flash Floods
137
Large thermal lows usually form over land in summer where the _____ is present
Inter-tropical Convergence Zone (ITCZ)
138
In July the ITCZ is in the _____ hemisphere and ranges from latitudes ___ to ___
Northern
| 15-20°N
139
In January the ITCZ is in the _____ hemisphere and ranges from latitudes ___ to ___
Southern
| 0-20°S
140
When the ITCZ moves it affects local _____ _____ and has a large effect on the _____
Tropical winds
141
Inland Water warm depressions can form over _____ in winter, when colder air over _____, moves over warmer _____ or _____.
Water
Continents
Seas
Lakes
142
Small but intense maritime meso-scale cyclones that form in in winter, by cold polar or arctic air advected over relatively warmer water.
Polar lows
143
Low pressure systems in which the entire core is colder than the surrounding environment
Cold lows
144
Cold lows can produce 5 things:
```
Snowfall
Thunderstorms
Heavy rain
Floods
Windshear
```
145
Cold depressions are typically _____ _____ and move with medium airflow at _____ to _____ft.
Frontal depressions
| 2,000 to 3,000ft
146
A low-pressure area which forms in the lee of mountains
Orographic Depression
147
With a strong wind blowing at approx. ___ towards a mountain range at, the wind will tend to blow _____ ___ _____ of the mountain rather than _____ ___ _____
90°
Around the side
Over the top
148
Isobaric troughs indicate
An area of low pressure going into another system
149
Trough lines indicate
Areas of stronger surface convergence
150
High pressure systems are also known as
Anticyclones
151
An anticyclone is
an area of relatively high surface pressure.
152
Air is _____ in a high pressure system
Subsiding
153
As the air _____ it warms due to _____ and so cloud formation is _____, causing the weather to usually be settled with only _____ amounts of cloud cover
Subsides
Compression
Inhibited
Small
154
High pressure systems can be up to ____NM and are _____ _____ _____
1500NM
| Slow moving systems (quasi-stationary)
155
Warm highs
High pressure systems in which the entire core is warmer than the surrounding environment
156
Pressure levels are pushed _____ in the core due to excess air in the upper troposphere as the warm air _____
Higher
| Rises
157
Warm High pressure systems can produce 4 things:
Heatwaves
Drought
Poor air quality
High pollen count
158
High pressure areas are associated with _____ _____
Light winds
159
High pressure systems usually occur around
30°N/S
160
Cold highs
High pressure systems in which the entire core is colder than the surrounding environment
161
In high pressure systems air flows _____ in the Northern Hemisphere and _____ in the Southern Hemisphere
Clockwise
| Anticlockwise
162
Due to the colder, _____ air, the pressure levels bulge _____ at higher altitudes
Heavier
| Downwards
163
Cold High pressure systems can produce 6 things:
```
Droughts
Frosts
Snowfall
Mist/Fog
Low level cloud
Poor air quality
```
164
Cold anticyclones are permanently found over the _____ know as _____ _____.
Poles
| Polar Highs
165
Blocking high
Highs that can become stronger in summer, pushing lows around them
166
Blocking highs are _____ and between __ and __
Quasi-stationary
| 50° and 70°
167
Ridges are indicated by _____ extending out from the area of _____ pressure
Isobars
| High
168
Cols
An area of relatively high pressure shown on a synoptic chart, situated between two areas of higher pressure and low pressure
169
Flat-Pressure Patterns
An area clear of isobars
170
The 3 cells from the poles to the equator
Polar cell
Ferrell cell
Hadley cell
171
The polar cell ranges from the latitudes ___ and ___
90°
| 60°
172
The Ferrell cell ranges from the latitudes ___ and ___
60°
| 30°
173
The Hadley cell ranges from the latitudes ___ and ___
30°
| 0°
174
At 90° you can find _____ pressure
High
175
At 60° you can find _____ pressure
Low
176
At 30° you can find _____ pressure
High
177
At 0° you can find _____ pressure
Low
178
Warm high pressure regions:
Azores high, 1020hPa, (all year)
| Pacific high, 1020hPa (all year)
179
Cold high pressure regions:
Siberian high, 1035hPa (Jan)
| Canadian high 1020hPa (Jan)
180
Warm Low pressure regions:
North Australian low, 1005hPa (Jan)
Asian low, 1000Hpa (July)
North American low, 1010hPa (July)
181
Cold Low pressure regions:
Icelandic low, 1000hPa (Jan)
Aleutian low, 1000hPa (Jan)
Icelandic low split, 1010hpa (July)
182
Density
Measure of a mass of air within a given volume (kg/m3 or gm/m3)
183
As altitude increases, density _____ at a _____ rate
Decreases
| Non-linear
184
In ISA conditions atmospheric density is at 3/4 of MSL at _____, 1/2of MSL at _____ and 1/4 of MSL at _____
10,000ft
22,000ft
40,000ft
185
If pressure decreases, the mass of air within the same given volume _____
Decreases
186
More humid air is _____ _____ than than dry air
Less dense
187
In cold air density decreases ______ with height than warm air.
quicker
188
Equation for pressure difference:
PA diff = 120ft x ISA temp devation
189
If colder, it will be a ______ pressure difference. If warmer, it will be a _____ pressure difference.
Negative
| Positive
190
There is __% of water vapour in the atmosphere
1%
191
Warm, air can hold _____ water vapour than cold air.
More
192
The HMR (Humidity mixing ratio) tells you:
How much water vapour is actually in the air measured in g/kg (or kg/kg)
193
The HMR's value won't change unless you _____ or _____ water vapour from the air:
Add
| Remove
194
The MR is constant as altitude _____ and pressure and temperature _____
Increases
| Increase
195
The SMR (Saturation mixing ratio) is:
the maximum amount of water vapour that can be in the air at a certain temperature, measured in g/kg (or kg/kg)
196
The SMR _____ with increasing altitude and decreasing temperature
Decreases
197
Relative humidity equation:
RH% = (HMR/SMR) x 100
198
At a constant pressure the RH is affected by the:
Amount of water vapour
| Temprature
199
The RH is
The ratio (%) between the amount of water vapour that the air is holding, and the maximum amount of water vapour that the air can hold.
200
The RH is greatest ____________ and weakest ____________
30 mins after sunrise
| 2-3hrs after midday.
201
The closer the ambient air temperature to the dew point temperature, the _____ the humidity and the further away the ambient air temperature to the dew point temperature, the _____ the humidity
Higher
| Lower
202
The dew point
The temperature, to which the air must be cooled for it to become saturated and start to condense
203
Equation to calculate RH with the dew point:
RH% = 100 - (5x (T - TD)
204
A Psychrometer is used to determine 3 things:
Temprature
RH%
Dew point
205
Adiabatic
A process that occurs without the transfer of heat or matter with the surroundings
206
DALR
-3°C per 1,000ft (-1°C per 100m )
207
SALR
-1.8°C per 1,000ft (-0.6°C per 100m)
208
In the tropics SALR can be _____ and in Polar regions it can be _____
0. 4°C per 100m
| 0. 9°C per 100m
209
Absolute stability is when
ELR < Both DALR & SALR (they subside)
210
Absolute instability is when
ELR > Both DALR & SALR (they rise)
211
Conditional stability is when
DALR (Subsides) > ELR > SALR (rises)
212
Neutral Stability is when
ELR = DALR or ELR = SALR
213
If cooled from below, the air is _____, if warmed from below, the air is _____.
Stable
| Unstable
214
Clouds form when the invisible water vapour in the air, _____ onto microscopic nuclei, becoming ___________ or __________
Condenses
Visible water droplets
Ice crystals
215
Cumulus clouds from through _____ when the atmosphere is _____
Convection
| Unstable
216
A front is where ____________, here _____ air rises over _____ air.
2 air masses meet
Warmer
Colder
217
On a warm front you can find:
Stratus and Cirro clouds
218
On a cold front you can find:
Cumulus clouds
219
A cold front is _____ lifting and moves _____.
Steeper
| Faster
220
The quicker a front is moving, the ______ _____ the uplift.
More instense
221
Unstable orographic uplift is when air is forces to rise by _____ and _____. The air then continues _____.
Mountains
Convects
Upwards
222
Stable orographic uplift is when the _____ effect takes place. _____ takes place decreasing the _____ _____. Air then _____ on the lee side.
Foehn
Precipitation
Dew point
Descends
223
Convergence is when
Two air masses coming from different directions meet and are forced to rise.
224
Turbulent layers are formed by
Air blowing over solid objects such are buildings, trees and hills.
225
Turbulent layers tend to form up to a depth of about
2,000-3,000ft
226
If the _____ _____ is reached within the turbulent layer, _____ will form at the top of the layer
Dew point
| Cloud
227
Inversions cause an increase in _____ and _____ the upward growth of cloud by preventing further _____
Stability
Limit
Convection
228
```
Oktas leves:
Few -
Scattered (SCT) -
Broken (BKN) -
Overcast (OVC) -
```
1 - 2
3 - 4
5 - 7
8
229
Cloud base
The height of the base of the cloud is measured above ground level in ft. measured by a Ceilometer
230
Cloud base equation:
Cloud Base Height ft = Temp. − Dew Point X 400
231
The height above the ground or water of the base of the _____ layer of cloud below _____ covering more than _____ the sky
Lowest
20,000ft (6,000m)
Half
232
Vertical visibility is used
When the sky is obscured by precipitation, and cloud details cannot be assessed but information on vertical visibility is available.
233
High level clouds: name group
Cirro
234
High level clouds: Polar altitudes
3-8km (10,000 - 25,000ft)
235
High level clouds: Temperate altitudes
5-13km (6,500 - 23,000ft)
236
High level clouds: Tropical altitudes
6-18km (20,000 - 60,000ft)
237
Mid level clouds: name group
Alto/Nimbo
238
Mid level clouds: Polar altitudes
2-4km (6,500 - 13,000ft)
239
Mid level clouds: Temperate altitudes
2-7km (6,500 - 23,000ft)
240
Mid level clouds: Tropical altitudes
2-8km (6,500 - 25,000ft)
241
Low level clouds: name group
Status/cumulo
242
Low level clouds: Polar altitudes
0-2km (0-6,500ft)
243
Low level clouds: Temperate altitudes
0-2km (0-6,500ft)
244
Low level clouds: Tropical altitudes
0-2km (0-6,500ft)
245
Cumulonimbus clouds can range from _____ to very _____ levels
Low
| High
246
Cirrus clouds tend to look
Curly/feathery/wispy
247
Stratus clouds tend to look
Flat, wide and layered
248
Nimbus clouds tend to be
Rain bearing
249
Cumulus (Cu)
Base height: 1,200-6,000ft - low level
Detached, generally dense with sharp outlines
Sunlit white, base dark.
Mainly water droplets, little precipitation
250
Stratocumulus (Sc)
Base height: 1,200-7,000ft - low level
Grey/white
Little precipitation
Composed of water droplets
251
Stratus (St)
Base height: 0 - 1,500ft - low level
Grey cloud layer
Drizzly precipitation
low temperatures
252
Cumulonimbus (CB)
```
Base height: 1,000-5,000ft - low level
Heavy dense cloud
Reaches extreme heights
Base dark,
water droplets + Ice crystals
Large raindrops, snow & hail
```
253
Altostratus (As)
```
Base height: 8,000 - 17,000ft - mid level
Greyish cloud sheet
Great horizontal extent
thin
water droplets + ice crystals
```
254
Nimbostratus (Ns)
```
Base height: 1,500-10,000ft - low/mid level
Grey cloud layer
Thick, blocks out sun
covers wide area
Great vertical extent
Water droplets
Produces precipitation
```
255
Altocumulus (Ac)
Base height: 7,000-17,000ft - mid level
White,
small, detached but frequent
water droplets
256
Cirrus (Ci)
Base height: 17,000-35,000ft - high level
White detached clouds
Small Ice crystals
Silky
257
Cirrostatus (Cs)
```
Base height: 17,000-35,000ft - high level
Transparent, whitish cloud
smooth appearance
Very wide
Small Ice crystals
```
258
Cirrocumulus (Cc)
Base height: 17,000-35,000ft - high level
white patch layer
grains and ripples
Ice crystals
259
Species - Humilis (hum)
flattened, never produce precipitation
| Coulds - Cu
260
Species - Medicoris (med)
moderate vertical extent, no precipitation
| Clouds - Cu
261
Species - Congestus (con)
Strongly sprouting, great vertical extent, bulging upper part, may produce perciptation.
Clouds - Cu
262
Species - Fractus (fra)
small, ragged edges, rapid changes
| Clouds - Cu, St
263
Species - Lenticaularis (len)
Shape of lense/almond, elongated, well defined outlines.
| Clouds - Sc, Ac, Cc
264
Species - Castellanus (cas)
turrets rising vertically, horizontal base, evident when seen from side.
Clouds - Sc, Ac, Ci
265
Species - Virga
Trails of precipitation which does not reach earths surface, attached to under surface of cloud
Clouds - Sc, Cb, As, Ns, Ac, Cc
266
Species - Calvus (cal)
Sprouting of upper parts are flattened, whitish mass without sharp outlines.
Clouds - CB
267
Species - Capillatus (cap)
Upper portion is fibours/striated stucture, shape of anvil or plume. accompanied by shower/thunderstorm.
Clouds -CB
268
Low base cloud types:
Stratus (St)
Stratocumulas (Sc)
Cumulus (Cu)
Cumulonimbus (CB)
269
Middle base cloud types:
Altocumulus (Ac)
Altostratus (As)
Nimbostratus (Ns)
270
High base cloud types:
Cirrrus (Ci)
Cirrocumulus (Cc)
Cirrostratus (Cs)
271
When water vapour first condenses onto a _____, the water droplet has an average diameter of approx. _____
Nuclei
| 0.02mm
272
The Bergeron-Finderson theory:
- If parcels of air are uplifted to a sufficient height in the troposphere, the dew-point temperature will be very low, and minute ice crystals will start to form.
- The supercooled water droplets will also freeze on contact with these ice nuclei.
- The ice crystals subsequently combine to form larger flakes which attract more supercooled droplets.
– This process continues until the flakes fall back towards the ground.
– As they fall through the warmer layers of air, the ice particles melt to form raindrops
– However, some ice pellets or snowflakes might be carried down to ground level by cold downdraughts.
273
The Coalescence theory:
- Applies to warm clouds
- They contain water droplets of many differing sizes, which are swept upwards at different velocities so that they collide and combine with other droplets
– When the droplets have a radius of approx. 3mm, their movement causes them to disintegrate, forming a fresh supply of water droplets
– This theory allows droplets of varying sizes to be produced
274
Drizzle (DZ)
Fine drops of water very close to one another that falls from a cloud.
Diameter 0.2-0.5mm
terminal velocity = 4m/s
275
Rain (RA)
Precipitation of drops of water that falls from a cloud.
Diameter 0.5-0.6mm
Terminal velocity = 9m/s
276
Freezing Precipitation (FZRA/FZDZ)
Forms ahead of warm fronts,
| Starts frozen, melts, falls through air <0°C, freezes upon contact with a surface.
277
Snow (SN)
Solid precipitation of ice crystals, singly or stuck together, that fall from a cloud.
Falls upto 2°C, heaviest when -2°-0°C
Largest flakes can be >25mm (adv. >4mm)
278
Sleet
Melting snow or mix of rain and snow,
| above 2°C
279
Snow grains (SG)
Precipitation of very small opaque white particles of ice that falls from a cloud.
diameter <1mm
between -10°-0°C
Do not bounce
280
Diamond Dust
Precipitation that falls from a clear sky in very small ice crystals, often so tiny that they appear to be suspended in the air.
Diameter 100μm (micrometer)
281
Snow pellets
Precipitation of white and opaque ice particles that falls from a cloud.
Diameter <5mm
Brittle, easily crushed
Bounce when hit ground
282
Small Hail (GS)
Diameter <5mm
283
Hail (GR)
```
Hailstones form when a nucleus, collects cloud droplets or drops of rain as it repeatedly rises and falls, through a cloud
From CB clouds
Can be found up to 45,000ft
as large as 100mm at 10,000ft
Diameter 5-50mm
```
284
Ice Pellets (PL)
Precipitation of transparent ice particles that falls from a cloud.
They fall into a sub-cloud layer of warm air where the snowflakes melt or partially melt, and then fall into a cold layer of air, where they freeze and reach the ground as frozen precipitation
Diameter <5mm
Bounce when hity the ground
285
Light: DZ, RA and SN
N/A,
<2mm/hr,
<0.5cm/hr
286
Moderate: DZ, RA and SN
Some run-off,
2-10mm/hr
0.5-4cm/hr
287
Heavy: DZ, RA and SN
>1mm/hr
>10mm/hr
>4cm/hr
288
Continuous -
Lasts over 1 hour
289
Intermittent -
Continuous with breaks
290
Showers -
Short lived
291
The 3 fundamental requirements for thunderstorms
Instability at least 10,000ft above the freezing level
An adequate supply of moisture
A trigger to start uplift
292
Air movement that can cause thunderstorms:
Convective
Frontal
Orographic
Convergence
293
Features of a Convective TS:
Uplift trigger is usually thermal uplift cause by surface warming.
Most common in summer
Maximum in the early afternoon
Most server TS
294
Features of a frontal TS:
```
Occur where a cold air mass undercuts a warm air
mass and forces it upwards
Ahead of the cold front
More common in winter
Fastest moving TS
```
295
Orographic TS formation:
Orographic convection forms large CB clouds due to unstable air accelerating the convection process
296
Single cell TS are made up of a single _____ cloud, that develops into a _____ and then into a _____ before dying away.
CU
CB
Thunderstorm
297
Features of single cell TS:
Small
Brief
Weak
Grow and start to die within an hour
298
The initial stage of single cells has updraughts of around _____, it is fed with _____ _____ _____ and can reach the tropopause. This stage lasts _____
30m/s, 60kts, 5000-6000ft/min
Warm moist air
15 - 20 mins
299
The mature stage of single cell TS, updraft are now at _____ and downdrafts are caused by _____ and reach approx. _____. This stage can last _____
50m/s, 100kts, 10,000ft/min
Precipitation
2,000ft/min
15-30mins
300
The 9 hazards of a TS:
```
Rain
Hail
Ice
Turbulence
Windshear
Lightning
Static electricity
Pressure
Visibility
```
301
When rain strikes the aircraft is has a _____ and _____ momentum. It can also cause a _____ moment if it impacts unevenly.
Downward
Rearward
Pitching
302
Rain increases the airframe's _____ and produce _____
Mass
| Drag
303
Turbine engines have a limit on the amount of ______ they can ingest.
Water
304
+RA can cause pressure sensing ____________
Instrument errors
305
It should always be assumed that where there's a thunderstorm, there is _____.
Hail
306
The higher the ______ _____, and the ______ the moisture content of the air mass, the stronger the convective activity and the damaging hail.
Lapse rate
| Greater
307
Airframe ice is likely in cloud or rain at a temperatures below _____
0°C
308
You can get ______ turbulence inside CB & TS
MOD - SEV
309
Clear Air Turbulence (CAT), occurs __________.
| Severe turbulence can also be encountered several thousand feet _____ active thunderstorm clouds
Outside the cloud
| Above
310
Windshear conditions occur with thunderstorms where there are _____ _____. As the cold downdrafts reach the ground, the air is forced to spread out, up to _____ ahead of the TS and up to _____. Can reach speeds of _____ changing at _____.
```
Gust fronts
25-30km
6000ft
80kts
90°
```
311
Windshear can be indicated by _____ clouds or _____ clouds.
Shelf
| Roll
312
Downbursts
Highly concentrated and powerful downdraughts
| of air caused by precipitation at the top of the cloud, drawing cold, dense down with it as it falls.
313
Microbursts:
3,000-4,000ft/min
Less than 5 mins
Less than 5km across
314
Macrobursts:
More than 5 mins
More than 5km across
As high as 11,800ft
315
Wet Microburst / Macrobursts:
Downdraft from a Micro/Macroburst is started by
precipitation and is often marked by a column of
+RA
316
Dry Microburst / Macrobursts:
If the air below the cloud base is dryer, the rain can
evaporate. Evaporation will cool the descending air,
making it denser and even more powerful
317
Lightning is a sudden _____ _____ on a large scale. Caused by _____ and _____ water droplets producing a build up of _____ _____.
Electrical discharge
Rising
Falling
Static electricity
318
Lighting discharges at a heat of _____ and travels up to _____ with a current around _____
5000K
140,000mph
30,000Amps
319
Lighting can cause:
Holes in the airframe
Temporary blindness
Noise Induced Hearing Loss
Errors with instruments
320
_____ _____ is another form of electrical discharge and it appears as a _____ glow around the windscreens and external parts of the aircraft. A high voltage differential of min _____ required
St Elmo's fire
Blue/violet
100kv
321
St Elmo's fire can cause:
Very occasionally cracked windscreens
Errors with navigational aids such as ADF
Noise on high and medium frequency radio bands
322
Dissipating is where:
Down draughts becoming stronger than the updrafts.
| The cloud base rises due to adiabatic warming of sinking air, causing evaporation and the cloud can spread into Sc/St
323
Multi-cell thunderstorms are more_____ than single cell. New updrafts form along the _____ _____ of rain cooled air. Individual cells usually last ______ , while the whole system can last _____.
Common
Leading edge
30-60 mins
Hours
324
The weather Multi-cell's produce is _____ _____ than a single-cell
More severe
325
Squall lines can be _____ _____ long but only _____ wide. The gust fronts can be felt _____ ahead.
Hundreds of miles
16-32km
50-60km
326
Mid-latitude squall lines:
Usually form in the warm air mass, ahead of & parallel to the cold front
Tend to move from west to east with the westerly situations
Tend to pass quickly with the cold front
Most common over large continental areas,
327
Tropical squall lines:
Structurally very similar to mid-latitude squall lines, but because the tropopause is higher in the tropics, they are generally taller
Tend to move from east to west with the Trade Winds
Most last 1-2 days
GR rarely occurs due to the warmer tropical air masses
328
Mesoscale Convective System (MCS):
Collection of thunderstorms that act as a system and they can last more than 12 hours (normally 1-2 days)
329
They can be round or linear in shape, and include systems such as:
Tropical storms
Squall lines
Polar lows
Mesoscale convective complexes
330
Supercells are the _____ common type of TS, but have the _____ severe weather. They can last for _____
Least
Most
Hours
331
Supercells have a contains a deep and persistent rotating updraft (approx. 8000-10,000fpm), called a _____
Mesocyclone
332
Single cells need:
Moderate to strong speed and directional wind shear between the surface up to about 20,000ft
333
‘A tornado is a _____, violently _____ column of air that extends from the base of a _____ to the ground’
Narrow
Rotating
Thunderstorm
334
They are the _____ _____ of all atmospheric storms
Most violent
335
Tornadoes are most likely in __________ and occur between the times _____
Late Spring/early Summer
| 16:00 - 21:00
336
Once a TS has formed, if the winds increase strongly with height, the TS updraught may begin to _____. Downdraughts within the supercell storm help to concentrate the rotation and to bring it down
to ______ ______.
Rotate
| Lower levels
337
Speed of a tornado's horizontal movement:
20-40kts
338
Wind speeds in funnel:
200kts
339
Life span:
up to 30mins
340
Average diameter:
100-150m
341
Water spouts are:
Tornadoes over water
342
Tornadoes are measured on the _____ scale which is based on the funnel wind speed and damage it incurs.
Fujita
343
A Funnel Cloud:
This is a rotating column of air, often a violent whirlwind, indicated by the presence of an inverted cone-shaped cloud, extending downwards from the base of a Cb, but not necessarily reaching the surface.
344
You can anticipate each type of thunderstorm through what 4 things:
Pre-flight weather briefs
Observation in flight
Meteorological information (charts, reports, etc.)
Information given by ground and airborne weather radar
345
If using weather radar avoid the thunderstorm by:
Below 20,000ft - 10NM
| Above 20,000ft - 20NM
346
In VFR or no radar available, avoid TS by at least
10 miles
347
Dust devils:
Small, rotating columns of air that occur when one piece of ground heats up faster than the ground surrounding it on a hot, calm, dry day
348
Dust devils have an average height of _____ and width of about _____
650ft
| 10-100ft
349
Tropical revolving storms must have oceans with a temp. of ______ and are at least _____ deep.
26.5°C
| 50m
350
TRS cannot form within ___ of the equator and usually form between the latitudes of _____
5°
| 10 - 20°
351
The 4 stages of TRS development:
Tropical disturbance
Tropical depression
Tropical storm
Tropical Revolving storm
352
Tropical disturbance:
A discrete tropical weather system of apparently organized convection - generally 200-600km (100-300NM) in diameter
353
Tropical depression
The maximum sustained wind speed is up to 33kts
| Depressions have a closed circulation.
354
Tropical storm
The maximum sustained surface wind
speed ranges from 34kts to 63kts
Convection is more concentrated near the center
355
Tropical Revolving storm:
```
Windspeeds >64kts
eye is 20-50km in diameter
Fastest winds are at the "eye wall" - up to 175kts
Vertical winds up to 43kts
averiging 500km in diameter
```
356
The wind speeds are the top speeds sustained for at least _____ at _____ above the surface and are compares to the _____ Scale
1min
10m
Beaufort
357
TRS travel:
<15kts
| East to West and then curve Northwards, away from the Equator, before turning East again
358
Hurricanes:
North America
| May - Nov
359
Cyclones:
Central Asia + Oceania
N. Hemisphere: Apr - Dec
S. Hemisphere: Oct - May
360
Typhoons:
East Asia
| April - Jan
361
Easterly Waves
```
Generated by an instability in the African Easterly Jetstream, causing troughs to extend out and away from the ITCZ, towards the sub-tropical high pressure belt to the North
Move east to west
April - October
between 5-15°
Wavelength 2000 - 25000km
last 3-4 days
travel at 18-36km/h
```
362
Approximately __ easterly waves per week travel from Africa to _____ _____ during hurricane season
2
| North America
363
Only __ out of ___ easterly waves survive to develop into gale-force tropical storms, or full-fledged hurricanes.
9
| 100
364
___ of the Atlantic tropical storms and minor hurricanes originate from easterly waves.
60%
365
Nearly ___ of the intense (or major) hurricanes have their origins as easterly waves. _____ easterly waves become a TRS
85%
| 1 in 5
366
Ice can:
```
Add drag
Reduce thrust
Increase stall speed
Reduce lift
Add weight to the aircraft
Block pitot tubes and static vents
```
367
Airframe icing is caused by an aircraft with airframe temperatures ___, striking a _____ _____ _____
<0°C
| Supercooled water droplet (SCWD)
368
SCWDs can exist in clouds from __ to __. For every __ below 0°C, only ___ of a droplet will freeze
instantly on impact
0° to -40°C
1°C
1/80
369
Large SCWD's need:
Great vertical depth of cloud
370
Small SCWD's need:
Shallow vertical depth of cloud
371
Rime Ice
Formed when small SCWDs freeze on contact with a surface which is <0°C
Freeze almost instantly creating a mixture of tiny ice particles and trapped air.
Rough, crystalline and opaque / milky in colour
Brittle
Accumulates slowly (>20mins)
372
Clear Ice
Formed when large SCWDs start to freeze on contact with a surface which
is <0°C
Do not freeze instantly on contact with the aircraft surface but freeze gradually as they flow back across the surface, leaving a smooth, hard, glossy, and transparent covering of ice
Heavy and difficult to see and to remove with de-icing methods,
Accumulates quickly (<20mins)
373
How to avoid freezing precipitation:
TOGA and climb
Descend
Turn back
374
Mixed ice is the blending of _____ _____ and _____ _____
Rime ice
| Clear ice
375
_____ _____ is the most common form of icing
Rime Ice
376
Hoar frost
When a surface <0°C comes into contact with moist air, the water vapour turns directly into ice by sublimation
377
Hoar frost occurs when:
When an aircraft has been parked overnight in temperatures <0°C.
When an aircraft flies from temperatures <0°C, into warm moist air, such as in descent, or climbing through a temperature inversion layer, or flying through a front
378
Hoar frost can reduce lift by _____
10-15%
379
Packed snow can be mixed with _____ _____ and can contribute to the accumulation of
_____ _____ _____.
Liquid water
| Hazardous frozen deposits
380
At faster speeds _____ SCWDs collide with the airframe,
More
381
Kinetic heating
Airflow causes a rise in the temperature of the airframe due to compression and friction (Rise = (TAS / 100)2)
382
Total Air Temperature (TAT) indication includes the temperature rise due to _____ _____ and is therefore used to indicate the possibility of _____.
Kinetic heating
| Icing
383
The bigger the stagnation point -
The less moisture hits the wing, less ice.
384
Carburettor icing is caused by
sudden temperature drop due to fuel
| vaporisation and the reduction in pressure at the carburettor Venturi
385
Carburettor icing can occur in _____ _____ and at tempratures up to ___.
Clear air
| 25°C
386
When information on the dew point is not available...
You should always assume a high relative humidity.
387
Visibility definitions:
"The greatest distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognized when observed against a bright background"
or
"The greatest distance at which lights in the vicinity of 1000 candelas can be seen and identified against an unlit background."
388
Ground visibility
‘The greatest known distance at which objects can be seen by an observer under conditions of normal daylight observation’
389
Prevailing visibility
‘The greatest visibility value, observed in accordance with the definition of “visibility”, which is reached within at least 1⁄2 the horizon circle or within at least 1⁄2 of the surface of the aerodrome. These areas could comprise contiguous or non-contiguous sectors.’
390
Prevailing visibility should be measured ___ above the runway and updated every __ seconds.
2.5m
| 60
391
The averaging periods should be:
1 min for local routine reports
| 10 mins for METAR and SPECI
392
Visibility should be reported in steps of:
50m when <800m
100m when 800m - 5km
1km when 5 - 10km
given as 10km or 9999 when >10km
393
If visibility is observed from more than 1 location, the _____ _____ is reported first
Touchdown zone
394
In METAR + SPECI, visibility should be reported as prevailing visibility when .....
Vis is not the same in different directions
lowest vis is diffrent from prevailing vis and
<1500m or
<50% of the prevailing vis and <5000m
395
Runway visual range (RVR)
“The range over which the pilot of an aircraft on the centre line of a
runway can see the runway surface markings or the lights
delineating the runway or identifying its centre line”
396
RVR is determined by...
Transmissiometer
Forward-scatter meter
Human observer, by counting no. of visible lights
397
RVR is reported in reported in m when vis or RVR is _____
<1500m
398
Assessed at a height of...
2.5m
| 5m if human observer
399
Assessed _____ from runway center line
<120m
400
Observations of touchdown zone should be...
300m along runway threshold
401
Midpoint -
1000 - 1500m along runway threshold
402
Visual range shall be reported in steps of:
25m when <400m
50m when 400 - 800m
100m when >800m
403
R23/p1500 means
RWY 23
| Greater than max. valus (1500m)
404
R23/0400N means
RWY 23
| Fluctuating over last 10 mins, avg 400m
405
R23/1200U means
RWY 23
| 1200m with an upwards tendency
406
R23/0750D means
RWY23
| 750m with a downwards tendency
407
ILS
Instrument landing system
408
MLS
Microwave landing system
409
PAR
Precision approach radar
410
GLS
Global Navigation landing system
411
Aerodrome operating minima are expressed in
Terms of visibility and/or RVR and Decision Altitude/height (DA/DH).
412
Slant visual Range (SVR)
‘The visual range of a specified object or light along a line of sight which differs significantly from the horizontal; for example, the visual range of ground objects or lights as seen from an aircraft on the approach (metre, m).’
413
Flight visibility
The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be
seen and identified by night.
414
Mist (BR) and Fog (FG) are known as
Hydrometeors
415
Mist limits of visibility and relative humidity
lower limit: 1000m
upper limit: 5000m
RH: >90%
416
Fog limits of visibility and relative humidity
Lower limit: 0m
upper limit: 1000m
RH: 100%
417
Radiation fog:
When ground surface cools through radiation, usually at night, cooling air above ground to the saturation temperature.
More common in Autumn/winter
Requites: clear skies, long nights, light winds
418
Radiation fog is densest __________ due to __________ and goes up to heights of _____
1 hour after sunrise
increase in thermal turbulence
1500ft
419
Radiation fog is dispersed by
drier air
Increase in wind speeds (>8kts)
Surface heating
420
Valley fog is caused by
Cool air flowing down the hill (katabatic effect)
421
Upslope fog is caused by
Air flowing upwards over rising terrain and
| adiabatically cooled to its saturation temperature.
422
Hill fog is
Low cloud covering high terrain
423
Advection fog is caused by
Relatively warm, moist air moves (advects)
over a cooler surface, and the temperature of the air is cooled to saturation by contact with the cold surface. Requires wind of at least 15kts
can be up to 1000ft thick
424
Evaporation fog is caused by
cold, stable air moving over a much warmer body of water.
| Can be upto 500ft
425
Frontal fog forms:
In frontal zones when rain falls from warm air into cold, stable air
Up to 200NM and be increase by orographic lifting
426
Freezing fog FZFG
Occurs at temp <0ºC
| Supercoold fog droplets freeze on impact with ground or other objects
427
All fog below 0ºC is reported as
Freezing fog
428
Ice fog forms when:
Water vapour, is introduced into the atmosphere and condenses, forming droplets that freeze rapidly into ice
particles.
429
Ice fog is
Suspension of numerous minute ice particles in the air, reducing the visibility at the Earth’s surface
Observed at high latitudes, usually in clear, calm weather when the temperature is
430
Shallow fog/mist is
MIFG/MIBR
2m high on land
10m high at sea
431
Patches is:
BCFG
only with fog
Randomly covering aerodrome where horizontal vis is >1000m, but observer can see parts where there is less.
432
Partial is:
PRFG
| only part of aerodrome is covered by fog
433
Precipitation can be considered a
Hydrometeor
434
Low Drifing snow (DRSN)
Snow picked up by wind, <2m
435
Blowing snow BLSN
Snow picked up by wind, >2m
436
Lithometeors
A suspension in the air of extremely small (microscopic), dry particles invisible to the naked eye and sufficiently numerous to give the air an opalescent appearance
437
Haze (HZ)
Blue light is scattered more than red light such that dark objects are seen as if viewed through a veil of pale blue.
438
HZ and other lithometeors (VA, FU, SA, DU), are reported only when the visibility is _____ (except for low drifting _____ and ______ _____ which are
always reported for operational reasons)
<5000m
Sand
Volcanic ash
439
Dust/Sand haze (DU/SA)
A suspension in the air of dust or small sand particles, raised from the ground prior to the time of observation by a dust storm or sandstorm.
440
Low drifting dust/Sand (DRDU/DRSA)
Dust or sand raised by the wind to small heights (<2m), above the ground. The visibility is not sensibly diminished at eye level (eye level is defined as 1.80m above the ground).
441
Blowing dust/Sand (BLDU/BLSA)
Dust or sand raised by the wind to moderate heights (>2m), above the ground. The horizontal visibility at eye level is sensibly reduced (eye level is defined as 1.80 m above the ground).
442
Sandstorm (SS)
Need a minimum of 15-20kts to form
sand particles are mostly confined to the
lowest 2m, and rarely rise more than 15m above the ground.
Due to strong winds caused or enhanced by surface heating and tend to form during the day and die out at night.
443
Dust storm (DS)
Need a minimum of 15-20kts to form
Particles of dust are energetically lifted by a strong and turbulent wind over an extensive area.
A duststorm usually arrives suddenly in the form of an advancing wall of dust which may be kilometres long and is commonly well over 3000m in height.
444
Smoke (FU)
The suspension in the air of small particles produced by combustion
Reduces horizontal visibility to <5000m
445
Volcanic Ash (VA)
Atmospheric dust or particles varying considerably in size, originating from active volcanoes.
446
Smog
A mixture of smoke and fog.
| Where significant industrial pollution is present
447
Horizontal pressure gradient - the steeper the gradient....
The faster the wind is going to be
448
_____ _____ _____ is what moves air from high to low pressure
pressure gradient force
449
In the Northern hemisphere, the Coriolis deflects to the _____, and in the Southern hemisphere it deflects to the _____
Right
| Left
450
Coriolis equation:
CE = 2ΩρVsinθ
```
Ω = speed of earth
ρ = air density
V = wind speed
θ = latitude
```
451
Buys ballot law
If an observer stands with his back to the wind, the low pressure system will be on his:
Left in the northern hemisphere
Right in the southern hemisphere.
452
Gradient wind is the result of what 3 forces
PGF
Coriolis
Centrifugal
453
Around a high pressure system centrifugal force acts in the _____ direction as the pressure gradient force
Same
454
Around a low pressure system centrifugal force acts in the _____ direction as the pressure gradient force
Opposite
455
Global winds from 90º to 0º
Polar Easterlies
Upper Westerlies / Prevailing Westerlies / Variable Westerlies
Tropical Easterlies / NE(or SE) Trades
456
Surface winds occur below the _____ _____
Friction layer
457
The friction between moving air and the Earth’s surface will reduce the _____ _____and _____ near the ground and therefore, the wind direction
Wind speed
| Coriolis
458
In the day, the friction lay can reach heights of _____ due to __________
3,000ft
| Rising thermal currents
459
At night, the friction layer drops to __________
1000 - 1500ft
460
Factors affecting the vertical extent of the friction layer:
Terrain – the rougher the terrain, the deeper the layer
–Wind speed – the stronger the wind, the deeper the layer
Stability – the more unstable the atmosphere, the deeper the layer
461
In low pressure systems, isobars are _____ _____
Closer together
462
Over water, the wind speed in the friction layer is ___ that of 2,000ft, at ___
70%
| 10°
463
Over land (day), the wind speed in the friction layer is ___ that of 2,000ft, at ___
50%
| 30°
464
Over land (night), the wind speed in the friction layer is ___ that of 2,000ft, at ___
25%
| 45°
465
Most reports report the wind direction in °_, except HTIS or ATC which report it in °_
°T
| °M
466
Wind speeds are measued at __ - __ above the ground by a
8 - 10m
| anemometer
467
The avg. observation period is ___ for local routine + ATC, and ___ for METAR + SPECI, which are reported in steps of __°
2 mins
10 mins
10°
468
When wind speeds are
<0.5m/s (1kt)
469
Gale force winds:
34-47kts
470
Storm force winds:
48 - 63kts
471
Squall
A sudden increase in wind speed often with a change in direction. Lasts for some minutes and can cover a much wider area.
472
Lull
A sudden decrease in wind speed
473
Sea/Land breezes only occur where...
there is little or no pressure gradient
474
Sea breezes are caused by
A temperature difference between warm land and a cooler adjacent sea
475
As the day goes on, sea breezes:
Increase in speed
Veer in NH, back in SH by approx 20- 30°
Goes further inland/out to see
476
At mid latitudes, sea breezes are
around 20 -30 kph
| 10 - 15 miles either side of coastline
477
Land breezes are caused by:
temperature difference between cooler land and a warmer adjacent sea
478
Anabatic winds:
Light winds that blow up a mountain side due to insolation, during the day in calm weather
479
Valley winds
Air flowing into and through a valley due to low pressure
480
Katabatic winds
wind that carries high density air from a higher elevation down a slope under the force of gravity, occurring at night
481
Mountain winds
Air flowing through/leaving the valley due to high pressure
482
Valleys and mountain winds are prone to the _____ effect
Venturi
483
Mistral
```
South France
cold, often violent + dry
+50kts
Blows through the valley of the Rhône River to the Mediterranean. effecting Sardinia, Italy
Accompanied by clear, sunny weather
```
484
Bora
The Balkans + Italy
In winter/Spring
70-100kts
Blowing on the north Adriatic coast and north Italian
plains
It forms when a high pressure lies over Central Europe and a low pressure area over the Mediterranean
Lasts many days, clouds + heavy rain
485
Mountain Waves formation:
Occur when an air mass blows over a mountain range,
Must have:
Stable air at ridge, slightly less stable air above and below
An increasing wind velocity with altitude and wind velocity >15kts near mountaintop level
Wind direction staying roughly the same with height and within 30° of the perpendicular to the ridge line
486
Mountain waves may extend _____ _____ with an average wave length of approx. _____
50 - 100NM downwind
| 5NM
487
Mountain waves can extend
_____ in the Rockies
_____ in the Andes
300NM
| 500NM
488
Detection of mountain waves:
Lenticular clouds
Rotor/roll clouds
Cap clouds
489
To avoid mountain waves:
Cross at an angle of 30 - 45°
490
Jet Steam
a strong narrow current, concentrated along a quasi-
horizontal axis in the upper troposphere or in the stratosphere, characterised by strong vertical and lateral wind shears and featuring one or more velocity maxima
491
Speed of jet stream must be
>60kts
492
Jet steam ratios
Depth:width:length
1:100:1000
493
All year jet streams:
Polar Front jet steam (polar - tropical air masses)
| Sub-tropical jet stream (tropical - equatorial air masses)
494
The arctic jet stream is
winter only
495
Equatorial jet stream is caused by
Summer heating of India and coastal regions of Africa, flows from east to west
496
The Polar and Sub-tropical jets are strongest in the _____ due to....
Winter
| greater temperature differences between the respective air masses
497
The ‘Jet Core’ always occurs at the point of _____ _____ _____, and it is always in the _____ air mass, just below tropopause
maximum pressure gradient
| Warm
498
Maximum windshear and CAT is also always in...
warm air, on cold air side of core, level with and slightly below the core
499
Jet stream are _____ away from the cold front and _____ away from the warm front
50 - 200NM
| 300 - 500NM
500
Climbing up through a warm front to jet stream – wind _____
| Climbing up through a cold front to jet stream – wind _____
Veers
| Backs
501
Flying above the Jet Core:
You are in the Stratosphere
The air above the cold sector is slightly warmer than the air above the warm sector
On this track the OAT would steadily decrease
Max. CAT will be where the isotachs are closest
502
Flying at the level of the Jet Core:
The temperature would only change slightly
Wind speed would increase as you flew into the jet stream and you would reach max. CAT
No turbulence in the jet core
The wind would decrease on the way out as you fly into the warm air
503
Flying below the Jet Core:
The temperature would increase slightly in the cold air and would increase quickly as you cross into the warm air
The temperature would continue to increase through the warm air
Highest wind speeds would be just after crossing the frontal layer
504
Isotach
Line connecting points of equal wind speed
505
Isotherm
Line connecting points of equal temperature
506
Jet stream clouds -
Cirrus
507
Isohypes
Line of equal windshere
508
Low level jet streams:
Due to great temp. difference between air masses or low level inversions
500 - 5000ft
70kts
509
Windshear
change in headwind or tailwind sustained for more than a few seconds, that results in changes to the lift of the aircraft
510
Gust
The extreme values of wind direction and speed between which the wind has varied during the last 10mins
511
Turbulence is caused by
a rapid irregular motion of air
512
Wind shear and turbulence can be found in areas of:
```
Rough surfaces
Relief
Inversions
Cb and TS
Unstable atmospheric layers
```
513
Wind shear and turbulence can cause
Airspeed + AoA fluctuations
| Structural fatigue and possible damage
514
The response of aircraft to wind shear depends on:
Type of aircraft
Phase of flight
Scale of the wind shear relative to aircraft size
Intensity and duration of the wind shear encountered.
515
Information used to avoid turbulence/windshear:
Weather reports and forecast
Routine or Special Pilot’s reports
Visual observation
On-board predictive wind shear system
516
Buildings near the runway can...
cause the wind flow to divert around them, resulting in the surface wind varying along the runway.
517
If hills near a runway are low...
Range unable to divert the low-level wind flow and so the wind blows vertically downward towards the runway
518
If hills near a runway are high...
Range able to divert the low-level wind flow and the surface wind may be funnelled along the range
519
Windshear/turbulance can be caused by:
```
katabatic flow
fohn wind
rotors (mountain winds)
fronts
land/sea breeze
friction layer
inversions
thunderstorms
- downdrafts, gust fronts, micro/macrobusts
wingtip vortices
```
520
Types of turbulence:
```
Convective
Orographic
Mechanical
Frontal
Clear air (CAT)
```
521
MOD TURB:
```
mod changes in aircraft attitude/altitude
small variations of airspeed
accelerometer readings of 0.5 - 1g
difficulty in walking in cabin
loose objects move about
```
522
SEV TURB:
Abrupt changes in attiude/altitude
large variations of airspeed
accelerometer readings of >1g
Violent in cabin
523
the 4 temperature groups
Arctic (A)
Polar (P)
Tropical (T)
Equatorial (E)
524
the 2 humidity groups
Maritime (m)
| Continental (c)
525
Maritime journey:
A track predominantly over the sea, will increase the
| moisture of the air mass, particularly in its lower layers
526
Land journey:
A track predominantly over the land keeps the air mass dry
527
Cool journey:
A warm air mass moving over a cooler surface is cooled from below and becomes stable in low layers
528
Warm journey:
A cold air mass moving over a warmer surface is warmed from below and becomes unstable in low layers
529
Weather fronts
When a warm air mass meets a cold air mass, they will mix with each other, but only in a relatively thin layer, due to temperature and density differences
530
The thin mixing layer is known as the _____ _____ and is __ - __ wide at the surface
Transition zone
| 3 - 5km
531
creation of fronts
Frontgenesis
532
destruction of fronts
Frontolysis
533
Arctic front:
Only tends to occur in winter
The arctic front separates the colder arctic air to the north, from the warmer polar air to the south
Greenland to Northern Norway (70N), but drops down over Iceland
534
Polar front:
Effects the UK all year
In the UK, the polar front usually separates warm moist air from
the tropics and cold, relatively dryer air from polar regions
Winter: Between Florida and SW UK (30-50N)
Summer: Between Newfoundland / Nova Scotia and Scotland (60N)
535
Mediterranean Front:
Forms in winter
The low-pressure systems along the Mediterranean front can develop storms, even small Hurricanes known as ‘Medicanes’
With the sand from North Africa, the RA can fall in a red colour
The local Mediterranean winds converge towards these low-pressure systems
536
Stationary Front (Quasi)
when a cold air mass and a warmer air mass first meet, or when a front stops moving (stalls), or moves very slowly over the surface (<4kts)
Neither air mass has enough force to move or replace the other, but the air
in each airmass can still move along the front
537
Stationary Front cause (if air is dry)
Clear to partly cloudy, with no precipitation
538
Stationary Front cause (if air is humid)
Clouds can form and precipitation can fall
Can cause flooding if the precipitation falls continuously over an
area for several days
539
Formation stage 1 - Origin + Infancy:
The depression starts as a small wave or ‘buckling’ along the front.
The air to the south of the front is warm tropical air
The air to the north of the front is cold polar air
540
Formation Stage 2 – Maturity
The pressure around it falls, leading to closer isobars
This causes stronger winds and, the wave / ‘buckle’ in the front to be much more pronounced
There will be distinct warm and cold fronts being formed as the warm air is pushed towards the north and the colder pushed towards the south
541
Warm front:
Warm air is advancing and rising up over cold air. moves at 2/3 of the wind at 2,000ft (avg. 10 -20kts)
542
Warm-frontal surface:
Shallow - 1:100 - 1:300
543
Cold front:
Cold air is advancing and pushing underneath warmer air. Moves at speed of wind at 2,000ft
544
Cold-frontal surface:
Steep - 1:50 - 1:100
545
An occluded front (occlusion - stage 3), is formed when
a cold front catches up with a warm front because the cold front is moving faster than a warm front and convergence takes place at the fronts and the warm sector of a PFD
546
In a occlusion:
The warm sector is lifted from the surface of the earth, becomes smaller and is reduced to a trough line known as the line of occlusion
547
Warm occlusion
The air ahead of the occluded front is colder than the air behind
More common in winter
The cloud and precipitation will be ahead of the surface occlusion
548
Cold occlusion
The air behind the occluded front, is colder than the air ahead
More common in summer
The cloud and precipitation will be a narrow band over the whole surface occlusion
549
Stage 4 – Death
The frontal system dies as all the warm air has been pushed up from the surface and all that remains on the surface is cold air
The occlusion dies out as temperatures are similar on both sides of the
front known as Cyclolysis
550
Each section of a front moves at _____ to itself
90 ̊
551
A frontal system moves in the direction of the _____ _____ blowing _____ to the isobars inside the warm sector, at approx. _____ of the geostrophic wind speed (_____kts)
Geostrophic wind
parallel
80%
15-25kts
552
The time between Polar waves is approx. _____ in Europe
1 - 2 days
553
Each PFD generally takes _____ to pass over the UK
9 - 12 hours
554
There is a sharp change in the direction of the isobars at the front approx. ____. The isobars always turn to orient themselves towards the area of _____
pressure
20°
| Low
555
Windshear characteristics on a cold front:
A vigorous cold front poses the greater risk but through a shorter period
The cold front surface can stop briefly and then jump several miles, bringing very sudden gusts and wind shear
556
Windshear characteristics on a warm front:
The effect will be ahead of it and will be more
| prolonged.
557
Temporary Cold Anticyclones
Occur between polar front depressions and provide a respite from polar front weather.
They are of significantly higher pressure than lows either side of it.
558
Secondary Lows
Can be found behind the cold front of the primary depression.
Can be more intense than the main depression as the flow to the west of the low center is from the pole towards the equator = highly unstable
559
Secondary lows move around the main depression _____ in the northern hemisphere
Anticlockwise
560
Freezing levels in January
Equator - 16,000ft
40°N/S - 10,000ft
60°N/S - 0ft
561
Freezing levels in July
```
Equator - 18,000ft
40°N - 16,000ft
40°S - 8,000ft
60°N - 8,000ft
60°S - 0ft
```
562
Temperature difference is greater in the _____ hemisphere due to __________
Northern
| Greater land mass
563
Doldrums
Around the equator (5°N-5°S)
Intense surface heating causes the air to warm and rise
straight up rather than blow horizontally, resulting in little or no wind
564
Horse latitudes
At the subtropical high pressure belts (30°N/S)
Near vertical downwards motion causes little or no wind at the surface
Clear skies but with possible poor visibility due to haze and inversions
565
Roaring, Furious & Screaming
Due to temperature variations and a greatly reduced amount of friction over the southern oceans near Antarctica, wind speeds can reach very fast speeds
Roaring 40's
Furious 50's
Screaming 60's
566
Monsoons
Characterised by a dramatic seasonal change in the
direction of trade winds
Cause dry/wet seasons
567
When crossing the ITCZ:
NE trade winds become ___ trades winds
SE trade winds become ___ trade winds
NW
| SW
568
January monsoons:
```
Oct - Apr
NW. Africa, India & Eastern Asia:
- large areas of high pressure
- dry air to south of tropics - cool dry season
- NE monsoon
```
N. Australia:
- large areas of low pressure
- warm rainy season
- NW monsoon
569
July monsoons:
```
Apr - Oct
NW. Africa, India & Eastern Asia:
- Large areas of low pressure
- warm rainy season
- SW monsoon
```
N. Australia:
No monsoon in winter
570
Polar outbreak
The movement of a cold air mass from its source region towards the equator bringing cold weather and strong winds.
571
Pampero
Outbreak of cold, dry polar air blowing towards the N/NE across the pampa of Argentina and Uruguay
Sometimes RA/TS
Most common Oct - Jan
572
Southerly Buster
Outbreak of cold, polar air behind a trough of low pressure crossing SE Australia, manifesting itself as a strong, dry southerly wind which causes rapid falls of temperatures (10°C)
Most common Oct- Feb
573
Cut-off low
Closed upper-level cold low, which has become
completely displaced (cut-off) from the westerly situation
Can remain stationary for days
Occasionally moves westward, opposite to the prevailing flow
Unsettled weather (in summer TS)
574
Cold-Air drop
Slow moving cold low pressure in the central
troposphere between 10,000ft and 30,000ft
Normally occur in august/winter, and their diameters are approx. 2000km
Their direction and speed of movement is difficult to forecast
Lifespan of several days
575
El Nino (ENSO) - Neutral
Trade winds blow from east to west across the surface of the tropical Pacific Ocean
Brings warm moist air and warmer surface waters to the western Pacific and keeps the central Pacific cool
Warm sea temp. in W. Pacific cause CB, RA
Dry air then travels east before descending over the cooler eastern tropical Pacific
576
El Nino
Every 3-4 years
Easterly trade winds weaken/reverse
Allows the Pacific to warm in central + eastern areas
N + S America suffers HVY RA, floods and extream temps.
Australia, NZ, Philippines + Indonesia have droughts
577
La Nina
```
every 2 - 7yrs
Easterly trade winds strengthen
Warm water pushes to far west tropical pacific
Australia, HVY RA, floods
S america experiences droughts.
```
578
Koeppen 5 zones
A. Equatorial Zone / Tropical Rain Climate
B. Arid Sub-tropical Zone / Dry Climate
C. Temperate Zone / Mid-Latitude Climate
D. Snow Zone / Sub-arctic Climate / Disturbed
Temperate Climate / Boreal
E. Polar Zone / Snow Climate / Tundra Climate / Cold Desert
579
A. Equatorial Zone - Tropical rain forest:
```
0° - 10°
Lowest diurnal/annual temp. variation
Max. 30 - 35°C, Min 20 - 25°C
Highest annual rainfall on earth
No dry season
Always under influence of ITCZ
```
580
A. Equatorial zone - Savannah:
10° - 20°
lowest diurnal/annual temp. variation
20° - 30°C
1 rainy season in summer
581
B. Arid zone - Desert:
20° - 35°
Hot in summer, large daily/seasonal variation
Dry, no wind or cloud
High evaporation
582
B Arid zone - Steppe:
30° - 35°
Hot in summer, large variation in temp.
Dry, no wind or cloud
Slightly higher rainfall (still very little)
583
C. Temperate zone - Warm:
35° - 40°
18 - -3°C
Summer - Hot + Dry
Winter - Cool + Wet (Rain <700mm)
584
C. Temperate zone - Cool:
```
40° - 65°
18 - -3°C
Little season variation
Generally wet + windy
Predominantly westerly winds
```
585
D. Snow zone:
40° - 65°
avg. temp <0°C (can be up to 60°C in peak summer)
Cool + Dry
Mostly high pressure
586
E. Polar Zone:
65° - 90°
<10°C
Cool + Dry
Mostly high pressure
