Meterology Flashcards
(309 cards)
1
Q
Where does troposphere go up to?
A
11 km or 36,090 ft
2
Q
What is the lapse rate?
A
1.98 C per 1000 ft
3
Q
What is the gas composition of the troposphere?
A
78% Nitrogen
21% Oxygen
1% Other Gases
4
Q
How much water vapour can be in the atmosphere?
A
0-5%
5
Q
ISA Mean sea level temp?
A
15 C
6
Q
ISA average pressure?
A
1013.25 hPa
7
Q
ISA average density?
A
1.225 kg/m^3
8
Q
How much water vapour in troposphere?
A
90%
9
Q
What is the boundary between the troposphere and stratosphere called?
A
Tropopause
10
Q
What are the ‘pauses’?
A
Boundaries separating layers, layers are ‘Spheres’, i.e troposphere
11
Q
What is a layer of constant temperature called?
A
Isotherm
12
Q
What is the temperature of the tropopause?
A
-56.5 C
13
Q
What is the height of the tropopause at the poles?
A
8 km
14
Q
What is the temperature of the tropopause at the poles?
A
-45 C
15
Q
Height of tropopause at equator?
A
16 km
16
Q
Temp of tropopause at equator?
A
-75 C
17
Q
What is a tropopause fold?
A
A break in the tropopause due to a division of differing air masses. Also large surface temp changes over a short distance can cause.
18
Q
What equation can we use to work out ISA temp?
A
ISA Temp = 15 - (Alt/1000 * 2)
19
Q
What is ISA Deviation?
A
Difference between ISA temperature and OAT (Ambient air temperature)
20
Q
Which layer is after troposphere/tropopause?
A
Stratosphere
21
Q
What altitudes does the stratosphere exist between?
A
11 km - 50 km
22
Q
Where is the ozone layer within the stratosphere?
A
15-20 km
23
Q
What does ozone do?
A
Absorb UV (shortwave) and causes heating in the stratosphere above 20 km.
24
Q
What comes after the stratosphere?
A
Mesopause/Mesosphere
25
What do we see from the ozone layer?
Inversion (heating with height) due to Ozone heating between 20-50 km converting shortwave to longwave (IR) heating to the top of the stratosphere to 0c.
26
What is temperature increasing with height called?
Inversion
27
Where is there no turbulence but you can get clouds?
Stratosphere
28
What are the altitudes the mesosphere exists between?
from 50-90 km
29
How does lapse rate change in the mesosphere vs stratosphere?
Temperature now reducing with height again (no more inversion)
30
What is the important property of the mesosphere?
It is the coldest layer
31
What comes after the mesosphere?
The thermosphere?
32
What altitude does the thermosphere exist in?
90 km +
33
Which layer does the ionosphere exist in?
The thermosphere
34
Where does the ionosphere start?
85 km
35
What is important to know about the ionosphere?
Lots of positive ions and free electrons, it disturbs EM and radio comms.
36
Convert Kelvin to Celsius
K = C + 273
37
What is Fahrenheit?
32 + 1.8*C
38
How do we measure surface air temperature and humidity?
Stevenson screen
39
What does a radiosonde measure?
Pressure, humidity and temperature, can measure winspeed/direction with addition of GPS.
40
What is the amount of radiation per unit area that reaches the earth called?
Insolation
41
What direction does the Earth orbit the sun
Anticlockwise, like the rotation of the Earth
42
What plane does the Earth orbit the sun around?
Elliptical
43
What is the name of the closest distance to the sun and the month it occurs?
Perihelion - 91 Million miles
| Winter - 4 Jan
44
What is the name of the farthest distance from the sun and the month is occurs?
Aphelion - 95 Million miles
| Summer - 4 July
45
What is the tilt of the Earth's rotational axis?
23.5 Degrees
46
What latitude is the summer solstice at?
Precisely equal to the tilt of the Earth - N23.5
47
What is the circle of latitude at the summer solstice called?
Tropic of Cancer
48
What latitude is the winter solstice at?
S23.5 - Equal to the tilt of the earth
49
What is the circle of latitude at the winter solstice called?
Tropic of Capricorn
50
Explain greenhouse effect
Sun emits shortwave radiation, earth emits longwave (terrestrial) radiation. Longwave radiation heats the air but greenhouse gases trap this terrestrial radiation, heating the atmosphere.
51
Explain surface heating
Sun emits shortwave radiation, earth emits longwave (terrestrial) radiation. Longwave radiation heats the air
52
Why does temp decrease with alt?
Atmosphere densest near surface, lots of air to heat from absorption of terrestrial radiation (surface heat), as you go higher, less dense and terrestrial radiation weaker combine to reduce temperature.
53
Where is the spring equinox?
0 Latitude, but when tending toward summer solstice (N23.5)
54
When is autumn equinox?
0 Latitude, but when tending toward Winter solstice (S23.5)
55
What is the name for less dense warm air rising?
Convection
56
What is the name for cooler more dense air falling?
Subsidence
57
What 4 things can convection be started by?
Surface heating
Converging air masses
Orographic uplift (Mountain - Windward forces air up)
Polar front depression (cold front moves faster than the warm front pushing warm air up)
58
What is advection?
Horizontal transfer of heat - movement of air current i.e wind
59
What is latent heat?
Heat released or absorbed by a body without a change in temperature.
60
When is no latent heat released?
From ice->water->vapour (Breaking bonds harder, energy required) energy absorption with no change in temperature
61
When is latent heat released?
From vapour->water->ice - Latent heat released heating air up!
62
What are nuclei and what are their purpose?
A Nuclei is a solid particle of impurity in the air, required for freezing/condensation and sublimation to occur.
63
What is sublimation?
A instant phase change from solid->gas or gas->solid.
64
What is Diurnal surface temperature variation?
A variation of surface temperature between the day and night. During the day, surface temp increases, during night, decreases.
65
When does the coldest time of day occur?
30 minutes after sunrise
66
When does the warmest time of day occur?
2-3 hours after midday
67
What 3 things affect the minimum and maximum diurnal temperatures?
Type of surface, Wind, Cloud cover
68
How does the wind affect diurnal temperatures?
Turbulent mixing occurs in the lower atmosphere. During the day, warmer surface temperatures mix with the cooler air at higher levels, creating a lower surface temperature.
During the night it mixes the warmer air above with the cooler air below causing increased temperatures.
Wind reduces the amount of diurnal variation in surface temperature.
69
How do clouds affect diurnal temperatures?
During the day, clouds refelect solar radiation, less insolation during the day and lower day temperatures.
During the night, clouds emit terrestrial (longwave) radiation from the absorbed during the day, resulting in increased night temperatures.
Cloud reduces the diurnal temperature variation.
70
What is ground inversion?
During the night surface temperatures decrease, we get warmer air above.
So we get a ground/radiation inversion as air is warming with altitude.
This only occurs at night!
71
What is a Valley inversion?
Cold dense air at night subsides down a valley, creating a 'pool' at the bottom.
The air in the centre is warm due to it being a bad conductor and so an inversion forms with cold air at the bottom 'pool' and warm air at the top.
72
What do we find under an inversion?
```
Poor visibility (trapped pollen etc.)
Good performance (Cold, dense air)
```
73
What do we find above an inversion?
```
Good visibility (particles move freely again)
Poor performance (Warm, less dense air)
```
74
What is a subsidence inversion?
As air falls, warms due to compression.
It could become warmer than the air at the surface.
High pressure system with subsiding air
The less dense air can't get through the denser air
75
What is a frontal inversion?
Form at boundaries between warm and cold air.
Due to different densities, heavier colder air slides under warm lighter air.
76
What is a turbulence inversion?
Due to mixing, the cool air above is drawn down.
It can be mixed enough to produce warm air above.
77
What are the 3 hazards and weather associated with an inversion?
Warm air is usually rising, but inversions stop cloud growth.
We can have:
Wind shear
Low level jet streams
Poor visibility
78
Where does the pressure reduce more quickly?
Lower altitudes
79
What is the pressure at FL100 (10,000 ft)?
700 hPa
80
What is the pressure at FL180 (18,000 ft)?
500 hPa
81
What is the pressure at FL200 (20,000 ft)?
400 hPa
82
What is the pressure at FL300 (30,000 ft)?
300 hPa
83
What is the pressure at FL400 (40,000 ft)?
200 hPa
84
What is the pressure at FL500 (50,000 ft)?
100 hPa
85
What is the equation for distance for a pressure change? (Pressure lapse rate)
ft per hPa = (96 * Kelvin)/Pressure
86
What is an isobar?
Line of equal pressure on a surface pressure chart (horizontal pressure)
87
What are the names for a high pressure system?
Anticyclone / High
88
What causes/happens in a high pressure system? (4 Stages) (Page 123)
Air enters quickly at the tropopause, like venturi static pressure. (At high alt, rising air from surface cools and flows outward, cool air sinks causing localiser low pressure which air converges to).
Compression warms air as it falls (falling air - subsidence)
Pressure increases at the bottom
Friction from high pressure (traffic jam) slows air, makes air leave slower than it enters.
89
How is a high pressure system linked to subsidence inversion?
When subsiding air falls and is compressed it becomes warm, temperature rises.
Temp can get warmer than surface.
-> Inversion
90
Which pressure systems can clouds not form in?
High pressure system (subsiding, falling, dry air from tropopause)
91
What direction does a high pressure system (anticyclone) rotate in the Northern Hemisphere?
Clockwise
92
What direction does a high pressure system (anticyclone) rotate in the Souther Hemisphere?
Anticlockwise
93
What winds are high pressure systems associated with?
Lighter winds than low pressure systems (Diverging air, venturi effect, lower velocity).
94
What are the isobars like in high pressure vs low pressure?
More spread out
95
What are 2 other names for a low pressure system?
Cyclone
| Depression
96
What 4 stages causes a low pressure system (Page 107)?
Small scale heat lows develop over the day (some areas of surface heat up more than others, depending on material)
Air in contact warms, less dense, convection occurs.
Venturi effect causes drop in static pressure
Draws in more air from relatively higher pressure zones in surrounding areas.
97
What pressure systems do clouds form in?
Low pressure systems (convecting air)
98
What direction does a low pressure system (cyclone/depression) rotate in the Northern Hemisphere?
Anticlockwise
99
What direction does a low pressure system (cyclone/depression) rotate in the Southern Hemisphere?
Clockwise
100
What winds are low pressure systems associated with?
High surface winds (Venturi effect for converging air, velocity increase)
101
What are isobars in a low pressure system like vs high pressure system?
More compact isobars
Pressure changes at greater rate over distance (faster windspeeds, higher pressure changes over surface associated with higher winds).
102
What is an isohype?
Isohypes show heights of a given pressure level.
103
What chart are isohypes in?
Constant pressure charts
104
What does a constant pressure chart show?
The height which we find given pressures.
105
What happens to the vertical pressure levels with higher temps?
They occur at higher altitudes (higher pressure due to temp)
106
What happens to the vertical pressure levels with lower temps?
They occur at lower altitudes (lower pressure due to temperature)
107
What is the spacing of an isobar on pressure charts?
4 hPa
108
How does a mercury barometer work?
Evacuated tube with mercury in reservoir, static pressure pushes on reservoir causing height of mercury to increase up tube.
109
How does aneroid barometer work?
Pressure compress/expand cell mechanically linked to needle.
How altimeter works
110
What is QFE (3 facts)?
Measured from pressure station
Reads 0 ft at station
Reads height - Vertical above ground
111
What is QNH (3 Facts)
QFE adjusted to mean sea level in ISA temp conditions
Reads altitude
Gives elevation above see level
112
What is a problem with QNH?
It is incorrect if ISA temperature conditions are not present.
113
How do we work QNH from QFE?
QNH = (Elevation/27 ft) +/- QFE (AMSL/BMSL)
114
What atmospheric report do we only get QNH in?
METAR
115
What atmospheric report can we find QNH or QFE in?
Local report
116
What is QFF and how does it differ from QNH?
QFF uses actual temperatures instead of ISA temperatures when calculating pressure for sea level.
If it could be used in flight it would read correct altitude.
117
Which pressure datum is used on surface pressure chart (Isobars)
Isobars use QFF on surface pressure charts.
118
What happens to QNH compared to QFF in warmer ISA conditions AMSL?
QNH>QFF
119
What happens to QNH compared to QFF in cooler ISA conditions AMSL?
QNH < QFF
120
What happens to QNH compared to QFF in warmer ISA conditions BMSL?
AMSL is: QNH > QFF
WE FLIP FOR BMSL: QNH < QFF
121
What happens to QNH compared to QFF in cooler ISA conditions BMSL?
AMSL is QNH < QFF
WE FLIP FOR BMSL: QNH > QFF
122
What can we say about QNH and QFF at MSL?
QNH = QFF = QFE
123
What is the standard pressure setting?
1013 hPa
Datum at sea level for ISA conditions
124
What do we read Standard pressure setting altitudes?
Flight level (FL) or Pressure altitudes
125
What altitude do we change from QNH->SPS
Transition altitude
126
What altitude do we change from SPS->QNH
Transition level (We are in SPS so altitudes are read as levels)
127
What is the difference between the transition altitude and transition level called?
Transition layer
128
If we reset our altitude subscale, what does adding pressure do?
Increase altitude (Higher pressure for zero point lower down)
129
If we reset our altitude subscale, what does reducing pressure do?
Decrease altitude (Lower pressure as zero point gets higher)
130
What happens to our true altitude if our pressure level is set higher than the actual?
Zero point is set artifically low (higher pressure)
Reads higher than we are (Indicated altitude)
Overreading so we take off difference (for true altitude)
131
What happens to our true altitude if our pressure level is set lower than the actual?
Zero point is set artificially high (lower pressure)
Reads lower than we are (indicated altitude)
Under reading so we add difference. (for true altitude)
132
What happens to your true altitude as you follow Indicated altitude and there is an increase in temperature above ISA?
True altitude increases as you follow Indicated altitude
133
How does temperature affect pressure levels?
Spreads them further apart as the pressure lapse rate is lower at smaller temperatures.
134
Why is temperature error particularly dangerous vs pressure error?
It can't be dealt with by changing the pressure datum, manual adjustments have to be made
135
What is the equation for the temperature error correction (TEC)?
TEC = (ISA Deviation/10)*0.04*Altitude
Where altitude is the altitude after pressure corrections have been applied.
If aerodrome elevation has been given in the question this has to be taken into account, we can only apply this formula to the altitude which contains air (from layer to ground).
136
If we have a different ISA temperature and a pressure error on our altimeter, which do we consider first?
The pressure error
137
What happens when we fly over a mountain to our true altitude?
Velocity increase due to venturi,
Pressure and temperature drop
True altitude drops
138
Where do we get a band of low pressure systems?
Around the equator due to high surface temperature, these are known as the thermal lows.
139
At N30/S30 what pressure systems form and what is their name?
High pressure systems, sub tropical highs
140
At N60/S60 what pressure systems form and what are their names (4 names)?
Low pressure systems
Polar low/ Polar frontal depression / Westerly Waves/ Westerly situations
141
At N90/S90 what pressure systems form and what is their name?
High pressure system
Polar highs
142
How many pairs of cells are there and what are their names?
3 pairs of 2 cells
Polar
Ferrell
Hadley
143
What is the inter-tropical convergence zone? (ITCZ)
A band of thermal lows following the hottest places around the world.
144
What is the maximum location of the ITCZ during Summer (July) in the Northern Hemisphere?
N25
145
What is the maximum location in the Souther Hemisphere of the ITCZ during winter (Jan)
S20
146
How does the position of the ITCZ over oceans change over the year?
Hardly affected as water has higher specific heat capacity so temperature doesn't vary as greatly as land.
147
What is the position of the ITCZ over Dakar?
N5
148
Name two cold high pressure systems in winter (Jan) over the Northern hemisphere?
Siberian high and Canadian high
149
Name two warm high pressure systems in Winter (Jan) over the Northern hemisphere?
Azores high
| Pacific high
150
In the northern hemisphere name two cold polar lows?
Icelandic low
| Aleutian low
151
What happens to pressure systems in the souther hemisphere in Winter (Jan)?
Thermal lows where ITCZ is, otherwise sub tropical highs.
152
Name two warm low pressure systems in the Northern hemisphere in Summer (July)
```
Asian low (Was Siberian High)
North American low (Was Canadian High)
```
153
What happens to the pacific high in Northern Hemisphere in summer (July)
Stays the same (over ocean)
154
What happens to the Azores high in the Northern Hemisphere in Summer?
Goes to Bermuda high (Could refer to Azores in exam)
155
What happens to the icelandic low in summer (Northern hemisphere)?
Splits into 3 covering Greenland, Iceland and the Baltics
156
What happens in the Southern hemisphere to pressure systems in summer?
Sub tropical highs, warm
157
What is the radius of a small scale low? (Cyclone)
1-20 Nautical miles
158
What is the radius of a large scale low (Cyclone)?
300-1000 Nautical miles
159
How does orographic depression form a small scale low?
As air travels toward the windward side of the mountain it is forced up convecting.
Sometimes air travels around the mountain rather than over it creating a lack of air and pressure on the lee side developing a small scale low.
160
What clouds are associated with small scale lows?
Depression so rising air, cumuliform clouds are associated with these.
Cumulus
Towering cumulus
Cumulonimbus
161
What type of rain is associated with small scale low pressure systems?
Showers (Fast onset and stopping of precipitation)
162
What happens if a cold front passes over the ridge of a mountain (think small scale low)?
It will make conditions even worse in the orographic depression (small scale low)
163
Two examples of large warm depressions? (large scale warm low pressure systems/lows)
North American low and Asian low
| They often follow the ITCZ
164
What happens to the pressure levels at SFC and altitude for a warm depression?
Lower pressure levels at SFC
| Higher pressure levels at altitude (warmer air in centre)
165
What is the temperature of the air inside a warm depression?
Relatively warmer
166
What weather is associated with a warm depression and why?
We get loads of uplift so:
Lots of Cumuloform clouds
Showers and precipitation
167
Where are warm depressions likely to form during winter and why?
Landlocked oceans in the winter are still warm (higher specific heat capacity) and the land is cooler.
We get a warm depression.
eg. Mediterranean low
168
What happens to the pressure levels at SFC and altitude for a cold depression?
Lower pressure levels at the SFC
| Lower pressure at altitude
169
Another name for cold depressions?
Polar front depression (N/S 60)
170
Why are fronts formed in cold depressions?
Cooler polar air mixes with warmer sub tropical air forming a front
The warmer air is forced to convect
171
Weather we can expect in a cold depression?
Cold low pressure system so:
- Cumuloform clouds
- Rain precipitation
172
Name two examples of cold depressions?
Icelandic / Aleutian low
173
What is an extended area of low pressure called?
A trough where we see isobars extending away from low pressure system
174
What weather can we expect in a trough for a low pressure system?
The wind changes direction very quickly so we get more convergence and convection activity and consequently more intense weather.
Stronger low pressure weather:
- Cb clouds
- Heavy showers
- Strong wind
- Hail
- Gusts
175
How do we identify a trough on a surface pressure chart?
A trough or convergence line is identified as a solid black line on a surface pressure chart.
176
Weather for low pressure system? (4)
Good visibility
Significant cloud
Significant precipitation
Small diurnal variation of pressure
177
Size of high pressure system?
Much larger - 1500 nm across
178
What do high pressure systems look like in terms of isobars?
More spread out isobars
| => Slower windspeeds
179
What happens to pressure levels at the surface and altitude in a warm high pressure system?
SFC pressure levels increase (high pressure due to compression)
Pressure levels at altitude increase (due to warm air in centre)
EASA might say increase in intensity with altitude! - Warm high pressure system
180
Name two examples of warm high pressure systems?
Azores (Bermuda) high / Pacific high
| Sub tropical highs N/S 30
181
Over what land masses do we usually find warm high pressure systems?
Desserts
182
What weather is associated with warm high pressure systems?
Hot, dry, clear skies, visibility rapidly reduce (subsidence inversion), haze
183
What are pressures at the surface and altitude like for cold high pressure systems (anticyclones)
Pressure levels higher at surface (compression)
| Pressure levels lower at altitude
184
Two examples of cold high pressure systems ? (Anticyclones)?
Siberian high
| Canadian high
185
How can clouds form in high pressure systems?
If there is enough isolated/localised surface heating we can generate enough convection to form clouds.
These will be stratoform type clouds only.
As the inversion prevents cloud growth.
However, if there is enough surface heating we can generate Cb clouds but generally St types.
186
Which clouds form in low pressure systems?
Cumuloform
187
Which clouds form in high pressure systems?
Stratoform
188
What is a blocking anticyclone?
Sub tropical highs (Azores high) massive and doesn't move a great deal deflecting depressions (lows) Northwards as they move from West to East.
Quasi/Large stationary pressure systems occuring at N50-N70 which can stay for long periods of days/weeks.
189
What is a ridge?
Extension of a high pressure system, protrudes outwards.
190
What weather do we expect in a ridge?
| Skies, clouds etc.
Clear skies, fog, haze, St clouds
191
What is a col?
Is between 2 high pressure systems and 2 low pressure systems.
There will be a lack of isobars (little or no wind)
192
What weather do we get in a col?
Summer - No moving air mass so thunderstorms
| Winter - No air moving forms fog
193
What is a flat pressure area?
An area with no isobars at all
194
What is density altitude?
Density alt = 120 ft * ISA Deviation
Tells equivilent altitude aircraft will perform to.
195
What is humidity mixing ratio?
Mass of water vapour to mass of dry air
Remains constant no matter what it's doing
196
What is humidity mixing ratio in mid latitude?
50g/kg
197
What is humidity mixing ratio in polar vs tropical?
Lower in polar than tropical
198
What is saturation mixing ratio?
Mass of water vapour per unit mass of saturated air
Maximum amount of water vapour we can get into air before it saturates
199
Why is saturation mixing ratio affected by temperature?
Warmer air can hold more water vapour
So saturation mixing ratio increases with temp
Saturation ratio also increases with decreases in altitude (warmer air)
200
How do we work out relative humidity from humidity mixing ratio and saturation mixing ratio?
RH = (HMR/SMR)*100
201
How does temperature affect Relative humidity?
Increases saturation mixing ratio
So DECREASES RELATIVE HUMIDITY (HMR/SMR)*100
202
When is Relative humidity greatest during the day?
30 minutes after sunrise (coolest temp so lower SMR in HMR/SMR) saturation mixing ratio
Cold air holds less moisture
203
When is relative humidity lowest during the day?
2-3 hours after Midday
SMR is greatest - saturation mixing ratio
HMR/SMR is smallest
Warm air holds more moisture
204
What is in a psychrometer?
```
Normal thermometer (dry bulb)
Thermometer wrapped in wet cloth (wet bulb)
```
205
What happens to the wet bulb in a psychrometer in dry humidity conditions?
More evaporation occurs absorbing latent heat causing a drop in temperature of the wet bulb vs dry bulb.
206
What happens in saturated air to the psychrometers wet bulb?
No evaporation can take place so the temperature remains the same as the dry bulb.
207
How does a hair hygrometer work?
Hair expands when wet showing higher humidity on a scale.
208
What is the dew point?
The temperature the air must be cooled for it to become fully saturated.
209
How are dew point and relative humidity related? (Give equation)
RH = 100-5*(T-Td)
T - Temp
Td - Dew point temp
210
What does closer ambient temp to dew point mean?
More humid air
211
On reports what are dew points rounded to?
Nearest warmest degree
212
What is an adiabatic process?
A process of warming or cooling where no heat (energy) is transferred to or from the system.
i.e Parcel of air warming or cooling with no external heat source
213
Adiabatic cooling example?
Air risises, expands, loss of pressure and drop in temperature.
Gas expansion
214
Adiabatic warming example?
Air forced to descend compresses and warms
Gas compression
215
What is the environmental lapse rate?
2C per 1000 ft
216
What is the dry air lapse rate? (DALR)
3C per 1000 ft
217
What is the saturated air lapse rate? (SALR)
1.8 C per 1000 ft
218
Why is the SALR < DALR?
Because saturated air condenses as it rises releasing latent heat, warming surroundings and slowing down the cooling process
219
Why does SALR go greater higher up?
Colder air can't hold as much water vapour, less condensation occurs and less release of latent heat to warm surroundings.
220
What is absolute stability?
When the ELR < Both DALR & SALR
Because as vapour/dry air rises, it wants to fall back down as it's temperature is less than the environment surrounding it.
221
What weather do we get with absolute stability?
ELR < Both DALR&SALR
```
Stratoform clouds (started to lift up and then fell again)
Smaller droplets, drizzle rather than rain. Continous or intermittent
```
Possibly fog/haze / low vis (high pressure system)
222
What is absolute instability?
ELR > Both DALR & SALR
Environment cools more rapidly than dry air / saturated water vapour.
Vapour and air warmer so want to continue to rise further
Linked to low pressure system
223
Weather associated with absolute instability?
Cumuloform clouds
Rain showers
Good visibility
Bad turbulence
Think low pressure system.
224
What is conditional instability?
DALR > ELR > SALR
Saturated particles rise, dry fall
Weather similar to absolute instability (rising particles)
225
What is indifferent stability?
ELR=DALR
or
ELR = SALR
226
What does a tephigram measure?
Amount of energy - > Stability/instability
- Pressure levels
- Temperature
- DALR
- SALR
- Dew point
227
What is convective uplift?
Air at low levels warmed by surface and rises, it cools adiabatically and at the codensation level begins to form cloud.
228
What cloud is formed first in convective uplift?
Fair weather cumulus
229
What sort of stability occurs when warm air mass passes over a cold surface?
Stable as cold air mass cools warm one causes dropping of air parcels.
230
What sort of stability occurs when cool air mass passes over warm?
Unstable as warm air mass warms cool one causing parcels to rise within it.
231
What happens in convective uplift if we continue to feed moisture and convection?
Cumulonimbus
232
What are blue thermals?
Where there are convective currents from insolation but not enough moisture to form clouds.
Also called clear air turbulence
233
What conditions do we get with a warm front?
Stable conditions as a cooler air mass is below (polar in front of warm air mass and tropical air in between)
234
What clouds do we get along a warm front?
Stable conditions so:
Stratoform type clouds
235
What are the stratoform type clouds ? (5)
```
St - Stratus
Ns - Nimbostratus
As - Altostratus
Cs - Cirrostratus
Ci - Cirrus
```
236
Which is the only stratoform cloud associated with heavy rain?
Nimbostratus
237
What is a cold nose?
The area near the surface of a cold front pertrudes out because cold front follows warm faster, colder air at the surface is affected by friction which slows it down relative to the rest
238
What weather do we get along cold front?
Unstable conditions (cold nose so warmer air below cold in this region)
Cumuloform clouds
239
Why should we be concerned at the cold front in terms of cloud formation?
We get embedded Cb clouds behind stratoform clouds.
240
What happens in orographic uplift if we have unstable conditions?
Air will rise over the mountain and continue to rise forming Cumuloform type clouds
241
What happens in orographic uplift in stable conditions?
Moist air forced to rise up mountain side, might cool enough and reach dew point forming cloud.
Cloud might become heavy enough for rain / precipitation
Now rising at SALR depositing more moisture.
When it gets to lee side it has deposited moisture so falls warming at DALR which is greater, we get much warmer air on the lee side of the mountain.
242
What do we get on the windward side of a Fohn wind? (Stable orographic uplift)?
Cooler temps
Lower cloud base
Precipitation
243
What do we get on the leeward side of a Fohn wind? (Stable orographic uplift)?
Warmer temps
Higher cloud base
No precipitation
244
What type of clouds form for stable environments?
Stratoform
245
In stable orographic uplift, what clouds do we get on top?
Drier - Cap clouds
or
Lenticular clouds which extend down and away from ridge
246
What conditions clouds etc. in convergence uplift?
More unstable types
| Cu clouds etc.
247
What clouds will form from turbulent uplift and how high?
Can get uplift from turbulence forming stratocumulus clouds due to the friction layer of wind above the turbulence
form at 2000-3000 ft
248
What is the cloud base?
Height at which we go from solid particles to water droplets/ice crystals above ground.
249
What is cloud ceiling?
Lowest level of cloud that is
- Measured below 20,000 ft
- More than 4 Oktas (Broken or Overcast)
250
What is an oktar?
Section of sky split into 8 pieces
251
What are clouds classified into in cloud reports?
| How many oktas do they require for their class?
Few - 1/8 - 2/8
Scattered - 3/8 - 4/8
Broken - 5/8 - 7/8
Overcast - 8/8
252
What does NSC stand for in cloud report?
No significant cloud
253
What are the conditions for CAVOK?
Visibility > 10 km
No clouds below 5000 ft or MSA (whicever is lower)
No TCU/CB/TS (Towering cumulus/ cumulonimbus/ thunderstorm)
No significant weather
254
What are the 3 heights clouds are classified into?
Low - Strato - 0-6500 ft
Middle - Alto - 6500-23,000 ft
High - Cirro - 16,500 - 45,000 ft
255
What appearance (genera) are clouds classified into? (4)?
Cumulus - Fluffy, heaped
Stratus - Flat, layered
Cirrus - Wispy, feathered
Nimbo - Rain bearing
256
What is the average cloud droplet size?
0.02mm
257
What cloud does drizzle form in?
Stratiform clouds
258
What is drizzle drop's diameter?
0.2-0.5 mm
259
Drizzle's terminal velocity?
4 m/s
260
What clouds does rain form in?
```
Convective clouds (Cumulus types)
Any cloud with prefix nimbo
```
261
What is the diameter of a rain drop?
0.5mm to 6 mm in diameter
262
What is the terminal velocity of rain?
9m/s
263
Where does freezing rain usually form??
Ahead of warm fronts
Fall out of nimbostratus onto cooler polar air below warm front, form supercooled droplets. Ice risk!
264
When does snow form?
Temps above -5C
265
Heaviest snow occurs when?
Between 2 and -2 C
266
Snowflake average diameter?
4mm
267
What temp will snow melt and form sleet?
Above 2c
268
Snow grains diameter?
< 1mm
269
Snow grains temperature for formation?
0 and -10c
270
Snow grains appearance?
Opaque, white in colour
| Mace of ice, elongated in shape
271
Diamond dust made of?
Tiny ice crystals 100 micrometers
272
Diamond dust forms in temps?
< -10 C
273
Snow pellets appearance?
```
White and opaque in colour
Shape is conical
Mix of snowflake and ice
Brittle
Bounce on ground often break
```
274
Snow pellets diameter?
up to 5mm
275
Clouds snow pellets form in?
Cu or Cb
276
Small hail diameter?
< 5mm
277
Hail diameter?
> 5mm
278
Hail formed in which clouds?
Cb
279
What is a rain shower?
Shower is when precipitation stops and starts very suddenly
280
What is intermittent and continous rain?
Comes from stratoform clouds
| Continous when lasts for over an hour
281
3 requirements for Thunderstorm formation?
Need instability over 10,000 ft
Need lots of moisture
Need uplift trigger
282
Most common time for tornado to form?
5:00 PM
283
Speed tornadoes travel over ground?
20-40 kts
284
Tornado duration?
few mins up to 30 mins
285
Tornado funnell speed?
200 kts
286
Tornado average diameter?
100-150m
287
VFR thunderstorm avoidance range?
10 NM
288
IFR TS avoidance range?
<20,000 ft - 10nm
| >= 20,000 ft - 20 nm
289
Height you fly above a TS for avoidance?
5000 ft
290
Earth-Ionosphere potential?
250-500 kv
291
What ocean temps for tropical rotating storms?
26.5 C
292
What latitudes to TRS form at?
N/S 10-20
293
TRS Stage 2 - Tropical depression wind speed?
up to 33 kts
294
TRS Stage 3 - Tropical storm wind speed?
34-63 kts
295
TRS Stage 4 - Tropical revolving storm wind speed?
> 64 kts
296
TRS Eye wall wind speeds?
175 kts
297
TRS Eye wall vertical movement speed?
43 kts
298
Which way do tropical storms move?
East to West
299
Where do tropical storms turn in Northern Hemisphere?
North (Coriolis)
300
Where do tropical storms turn in Southern Hemisphere?
South (Coriolis)
301
Hurricane Season in America?
May to Nov
302
Typhoon season in Japan/China?
April-Jan
303
Cyclone season rest of world?
Oct-may Souther hemisphere
| April-Dec Northern hemisphere
304
When do easterly waves form?
Apr-Nov
| N5-N15
305
How many easterly waves become TRS?
1 in 5
306
What percentage of all hurrianes start in Easterly Waves?
85%
307
Diameter of eye of storm?
20-50 km
308
TRS approximate diameter?
500-1000 km
309
TRS average height?
12 km (Tropopause height)
