Met Chapter 1 Flashcards
1
Q
In the ISA, between 11km and 20km altitude, the temperature laps rate is?
A
Isothermal
2
Q
Why is there a lack of weather in the Stratosphere?
A
The isothermic or inversion conditions in the stratosphere create a physical barrier to further the vertical development of clouds.
3
Q
Stevenson Screen
A
Kept 4ft (1.2m) off the ground, Slats to prevent sunlight and heat radiation affecting the instruments, door always opens to the closest pole. Used to measure temperature and dew point
4
Q
Height of the troposphere
A
36,060
5
Q
Height of the stratosphere
A
36,000
6
Q
Height of the mesosphere
A
164,000
7
Q
Height of the thermosphere
A
280,000
8
Q
Gasses which make up the atmosphere
A
Nitrogen - 75%
Oxygen - 21%
Other gases 1%
9
Q
What percentage of the atmospheres water vapour is found in the troposphere
A
99%
10
Q
What is the temp laps rate in the troposphere
A
2 degrees c per 1000 ft
11
Q
Average height of the tropopause according to ISA
A
11km average
8 - 10 km over the poles
16 - 18 km at the equator
12
Q
What level is the ozone layer found
A
20 - 30 km
13
Q
What makes the stratosphere desirable to fly in?
A
Cloud formations are rare due to lack of water Vapor and vertical air movement
Above hazards in the troposphere
Engine efficiency
14
Q
Where is the ozone found and what effects can it have on the aircraft
A
90% within the stratosphere
Ozone is very harmful so needs to be filtered out
15
Q
ISA conditions at mean sea level
A
15 degrees C
Temp laps rate of 1.98 per 1000ft
Pressure of 1013 at a laps rate of 1 HPA per 27ft
Density 1.225
16
Q
What is ISA deviation?
A
If the temp is warmer than isa its (+) if its colder its (-)
17
Q
What is density proportional to ?
A
Pressure/temperature
18
Q
what is temp is kelvin at 0 degrees Celsius
A
273
19
Q
What is a radio scond and what does it measure
A
Rises to an altitude of 35km
Records data in its climb at 1.3 second intervals (temp, Humidity, Pressure)
Transmits to VHF radio
20
Q
What is solar radiation?
A
Short wave, high frequency
21
Q
What is terrestrial radiation?
A
Long wavelength
22
Q
What is the ITCZ
A
The tropical convergence zone which is a band of high pressure around the earth which generally lies around the equator
23
Q
What does solar radiation reaching the earths surface depend on?
A
Absorption (Ozone layer and water Vapour)
Reflection (tops of clouds and earth)
Scattering (particals in the atmosphere)
24
Q
What is conduction?
A
Energy transfer by contact
Only happens in the bottom thousand feet
25
Convection?
Energy transfer by vertical movement of air
Heated by earths surface
Heat can be transferred to the atmosphere this way!
26
Advection
Horizontal movement of heat
Takes place when the wind is blowing
27
Turbulence
Energy transfer by mixing of air
Air from higher up is mixing with the air lower down making the surface cooler
28
Latent heat?
Energy released or absorbed by a body with out any change in its temperature
When latent heat is released (surrounding atmosphere is warmed)
Vapour to liquid (heat released)
29
What is sublimation?
When a gas is turned directly into a solid missing out a stage
30
Icolation
The angle of direct heating, if at an angle the energy will be spread out not heating as much as if it was direct
31
When is the Pherihelium
4 of jan closest to the sun
32
Aphelion
4 July furthest away from the sun
33
Solstice
22 of December shortest day
21 of June longest day
34
Equinox
When there is equal day and night
21 of march
23 of September
35
What is a diurnal variation?
The variations of surface temp over a 24 hour period.
Subject to the amount of energy from the sun verse the amount of energy received from the earth
36
When is the coolest temp in a diurnal variation
Coolest is 30 min after sunrise
37
What is the most common ground inversion?
Nocturnal surface inversion
38
What are the 4 types of inversion and their descriptions
Subsidence inversion
Air descending compresses increasing the pressure of the lower atmosphere. The warmer air is the type sinking and trapping the cooler air beneath it creating an inversion.
Turbulence inversion
The air mixing is done vertically and changes the rate in which the air cools relative to its static environment.
Usually occurs a few thousand feet above ground levels
Visible due to trapped pollutants beneath or by a top cloud layer.
Frontal inversion
The hot air is moved over the cooler more dense air. Usually formed between cold and warm fronts
Valley Inversion
Happens in the evening/night and causes the cold air to move down the sides of the valley.
They create katabatibc winds.
Cool air pools in the valleys thus crating an inversion
39
How does a Mercury barometer work
The evacuated tube is filled with mercury.
The height of the mercury column is directly proportional to the atmospheric pressure
Measured in inches of mercury
40
Aneroid barometer
Reacts to changes in atmospheric pressure by contracting or expanding
41
Barograph
Plots pressure readings against a time to give visible data for forecasting
42
Surface pressure chart
Shows horizontal variations in pressure
Isobars join places of equal sea level pressure
Usually 2 or 4 HPA apart
Air will always move high to low
43
What is QFF
Is actual pressure at sea level corrected for temperature as well
44
What is a ridge
Is an extended high pressure
45
What is a trough
A though is a valley of low pressure crossing through isobars
46
What does DALR mean and what’s it’s Laps rate
When air is less than 100% humidity
3 per 1000 ft
1 per 100
47
What is SALR and what’s it’s laps rate?
Saturated adiabatic laps rate
1.8 per 1000ft
0.6 per 100ft
48
What are the 4 states of stability
Absolute stability
Absolute instability
Conditional stability
Natural stability
49
What is absolute stability
When the parcel of air returns to its original position once the displacement has taken place. The atmosphere is absolutely stable when the DALR (1 per 100m) and SALR (0.6 per 100m) are more than the EALR (0.2 per 100m)
50
What creates very stable atmospheres?
Isotherms and inversions
51
Weather in absolute stable conditions
Clouds: will be flat or layered (stratiform clouds)
Precipitation: fairly light but could be persistent.
Visibility: poor due to contaminants staying close to the ground
Turbulence: little to none
52
Absolute instability
When the ELR is greater than both DALR (1 per 100m) and the SALR (0.6 per 100m)
53
Weather in unstable conditions
Clouds: very strong vertical movement creates cumuliform clouds
Precipitation: reasonably intense, large rain and hail tends to fall for a short period of time.
Visibility: generally good, because dust and smoke particles are lifted up.
Turbulence: moderate to severe due to strong vertical movement
54
Conditional instability
When the ELR is between the DALR and SALR. During conditional instability saturated air is unstable.
55
Neutral stability
Is when the the ELR is the same as DALR
Or
ELR is the same as SALR
56
What are the 3 classifications of turbulence
Light
Moderate
Severe
57
What is the light turbulence criteria
Caused slight erratic changes in altitude and/or attitude. IAS fluctuates 5 - 15kt.
Occupants may feel a slight strain against seat belts. Unsecured objects may be displaced. Food service may be conducted and little to no difficulty is encountered when walking.
58
Moderate
Similar to light turbulence, ISA 15 - 25kt. Causes rapid bumps or jolts without changes in altitude.
Occupants feel definite strains against seat belts. Unsecured objects are dislodged. Food service and walking difficult.
59
Severe turbulence
Turbulence causes large abrupt changes in altitude. Aircraft momentarily out of control. ISA fluctuates more than 25kt.
Occupants are forced violently against seat belts. Unsecured objects are tossed around. Food service and walking impossible.
60
What are the 2 types of turbulence
Merchanical turbulence. Caused by physical obstructions such as hills mountains and buildings.
Thermal turbulence, caused by air rising due to surface heating and around cloud formations.
61
How high is a friction layer above the surface
1KM on average
62
What conditions lead to mountain waves
Wind speed at mountain height must be 15 - 20kt
The wind direction must be 30 degrees of the perpendicular range of the hills/mountains.
There must be a layer of marked stability at mountain top height with less stable air above and below
63
What is a micro burst
Small scale downdraft produced by a thunderstorm or rain shower. They last about 5 min and are usually less than 4km diameter
64
What effects does wind sheet have on aircraft
Negative shear: a reduction in performance and airspeed (dangerous)
Positive shear: an increase in performance and airspeed (causes deviations from intended flight patch and unstable approach)
65
What creates a downburst
Strong, active, convective weather
66
What are the common mechanisms for turbulence
Convective
Mechanical
Oragrahic
Frontal
Clear air
67
What is a jet stream
Have a speed of at least 60kt
Typical dimensions 2000nm long 200nm wide and about 2nm high
68
What is an cup anemometer
A way of measuring the wind speed
69
Where is wind measured and using what SI unit
Wind is measured in Knots and is measured 10metres above the ground
70
What are the definitions for wind strength
Calm - 1kt or less
Gale fore - mean surface wind 34 - 47kt
Storm force - mean surface wind 48 - 63 knots
Hurricane force - mean surface wind more than 64KT
71
What is a gust?
A sudden increase of 10kt or more above the average wind speed and lasting less than a minute
72
What is a squall
An increase of 10ky or more above average wind speed and lasting more than 1 minute
73
What is a lull
A sudden drop in wind speed
74
What are four forces which have a fundamental influence on the strength and direction of the wind
Pressure Gradient PG
Coriolis Effect (also referred to as Coriolis Force) CF
Centrifugal Force (not a type of force, but rather direction)
Friction Force (below 1,000 ft - 3,000ft above the surface)
75
What is the Coriolis Effect
When a body of air has a faster speed than the earth is moving. Eg earths rotation speed is faster at the equator than the northern hemisphere
76
What is the Coriolis Force equation
2 Ω ρ V Sin θ
Ω (Omega)= angular rotation of the earth (radians/sec) ρ (Rho)= density
V = wind speed
θ = latitude
77
What is Coriolis Force proportional to?
-Wind speed (faster wind, more deflection)
–Latitude (higher latitude, more deflection)
–Density (greater density, more deflection)
78
How to find wind velocity
V = PGF/2 Ω p sinlt
79
Wind speed is
–Directly proportional to PGF
–Inversely proportional to density
–Inversely proportional to latitude.
–As latitude decreases, wind speed increases
–At about 5° from equator coriolis force becomes negligible.
80
Where are gradient winds most likely to be found
Around curved isobars
81
Where are Geostrophic winds most likely to be found
Along straight isobars
82
Sea Breeze
• Timing
–Usually begins around 10am and peaks 2-4 pm
• Strength
–Around 10-15kts but can vary
• Extent
–About 25-40km inland and 2-3000’ high
• Cloud
–Cumulus development over the land
• Temperature
–Air over the land is replaced by cold sea air
• Synoptic
–Usually during anticyclone due to weak PGF
83
To form a Fone wind, what prerequisites must be present?
–There must be a substantial mountain range
–The wind must be blowing close to right angles to the range
–The approaching air must have a high moisture content
84
Where might mountain waves be reported
On a SIGMET
85
What must the wind speed be to be classed as a jet stream
Over 60KT how ever they can get to speeds above 350kt (rarely)
86
What are the jet stream names and locations
Artic Jet
Polar front jet (50 - 60 degrees North at 30,000ft)
Sub tropical jet (30 - 40 degrees North at 40,000ft)
Tropical easterly jet (over the equator) also called easterly wave
Sub Tropical jet (30 - 40 degrees South at 40,000ft)
Polar front jet (50 degrees south at 30,000ft)
87
What are the jet stream dimensions
Dimensions: 2nm deep, 200nm across, 2000nm long – Ratio: 1:100:1000
88
Where is the Clear Air Turbulence (CAT)
It is found near the frontal zone, epecially at the high levels on the polar maritime side and just below the core
89
What are the low level jet streams
–Nocturnal Jet
–Valley Inversion
–Coastal Jet
–Ahead of cold front
