Meteorology Flashcards
What’s the percentage of N2 in the atmosphere?
78%
What’s the percentage of O2 in the atmosphere?
21%
What’s the percentage of CO2, O3 and other gases in the atmosphere?
1%
Which atmospheric layer is ozone most prevalent in?
Upper Stratosphere
50,000ft to 100,000ft
Ozone absorbs _______ radiation. This causes the temperature to _____.
Ultra-violet
rise
Maximum heating of the ozone layer occurs at which altitude?
160,000ft
What is the relationship between pressure, volume and temperature in the atmosphere?
PV=RT
Where R is the gas constant
What is density in terms of pressure and temperature?
density = P/RT
At constant temperature, if pressure increases, density _________
increases
At constant pressure, if temperature increases, density _______
decreases
Warm air ______, cold air ______.
Rises
Sinks
What is the average pressure of the atmosphere at sea level?
1013.25 hPa
°C → K
+ 273
What is the average temperature at sea level?
15°C
What is the average air density at sea level?
1225gm/m3
At constant temperature and pressure, moist air is ____ dense than dry air.
Less
As altitude increases, pressure and density reduce at a _____ rate in cold air than in warm air.
Higher
A warm air mass means _____ pressure aloft.
High
A cold air mass means ____ pressure aloft.
Low
What is standard pressure at 10,000ft?
700mb
What is standard pressure at 18,000ft?
500mb
What is standard pressure at 30,000ft?
300mb
From sea level to 10,000ft, at what rate does pressure decrease with altitude.
1mb per 27ft
50% of atmospheric mass is in the bottom _____ft of the troposphere.
20,000ft
90% of the water vapour in the atmosphere is contained in the _________.
Troposphere
In which section of the atmosphere is the ozone layer.
The Stratosphere
Describe the temperature changes in the atmosphere as altitude increases.
15°C at sea level
Decrease at -1.98 per 1000ft till tropopause -56.5°C
Increase till stratopause 0°C
Decrease above stratopause
The tropopause height is greater and the tropopause is colder at the _______
Equator
At the poles the tropopause is ______ft and ____°C
26,000ft
-45°C
At the equator the tropopause is ______ft and ____°C
52,500ft
-75°C
At mid-latitudes the tropopause is ______ft and ____°C
36,000ft
-56°C
The tropopause heights vary in the mid-latitudes - _____ in summer and _____ in winter.
higher
lower
What is the ISA environmental lapse rate of temperature in the troposphere?
-1.96°C per 1000ft
What is QFE?
Altimeter pressure setting to give height above station.
What is QNH?
Altimeter subscale setting to give altitude above MSL.
(QFE adjusted down to MSL using ISA lapse rate)
What is QFF?
QFE adjusted to MSL using actual station temperature (not ISA)
Used for met reports and isobars
What is QNE?
Touchdown height if the standard setting (1013mb) is used.
To fly at a certain height above an airfield, what pressure setting should be used?
QFE
To fly at a certain altitude above MSL, what pressure setting should be used?
QNH
To fly at a flight level (e.g FL65) which pressure setting should be used?
1013mb
There is approximately ____% height difference for every ____°C temperature deviation from ISA.
4%
10°C
For an airfield above MSL on a hot day, is QNH higher or lower than QFF?
Higher
For an airfield below MSL on a hot day, is QNH higher or lower than QFF?
lower
When the temperature is low, the true altitude will be _______ than indicated.
lower
What is the density altitude lapse rate?
120ft per °C temperature deviation
1 cal is the amount of heat energy required to…….
Raise the temperature of 1 gm of water by 1°C
What is the specific latent heat of water?
1.0
What is sublimation?
The conversion of solid to gas (or vice versa) skipping the liquid phase.
A change of state _____ or ______ energy
Releases
Absorbs
The sun’s radiation heats the _____. The earth heats the atmosphere by ______, _______ and _______.
Earth
Radiation, Conduction and Convection.
The percentage of radiation absorbed is dependent on the _______ and _______.
Type of surface
The angle of arrival of the radiation.
What is advection?
The horizontal movement of air transfering heat.
When do minimum surface temperatures occur?
30 minutes after sunrise
When do maximum surface temperatures occur?
2 to 3 hours after mid-day
Cloud cover _______ the diurnal variation of surface temperature.
Reduces
ISA temp is -56.5°C above what height?
FL360
By volume, what percentage of air in the lower troposphere is water vapour?
0 - 5%
Half the mass in the atmosphere is found in the lowest ___km.
5km
What is the SVP?
Saturation Vapour Pressure
The water vapour is at a high nough pressure to push water molecules back into the liquid at the same rate as they escape.
What does the saturation vapour pressure depend on?
Temperature and the evaporating surface.
Warm air can hold ____ water vapour than cold air.
more
What does absolute humidity measure?
What does specific humidity measure?
mass of water vapour per unit volume of air
mass of water vapour per unit mass of air
In ISA conditions the mass of water the air can hold _______ with height.
decreases
What are the 3 indicators used to describe the saturation of the air?
Relative humidity
Dew point
Wet bulb temperature
Increasing the temperature will ______ the relative humidity.
decrease
What is the dew point?
The temperature at which cloud or dew forms
The dew point spread indicates _______ ________. It tells you roughly ___ ______ ___ ___ __.
relative humidity
how moist the air is
The wet bulb temperature lies between _______ and ____.
dew point
outside air temperature
More water vapour means ____ latent heat energy.
more
What is the equipment that measures actual environmental lapse rate called?
radio sonde
What does adiabatic mean?
No energy lost or gained by the system
What is the DALR?
Dry adiabatic lapse rate
3º per 1000ft
What is the SALR?
Saturated adiabatic lapse rate
1.8º per 1000ft
What is meant by stable and unstable air?
Stable will sink down again after rising
unstable will continue to rise
When the ELR is greater than the DALR, is the air stable?
No
When the ELR is less than the SALR is the air stable?
yes
If the ELR is between the SALR and the DALR, the air is stable if _____ and unstable if ______.
dry
saturated
What rate does the wet bulb temperature fall at?
SALR
What are the 5 main convection triggers?
Orographic
Thermal
Frontal convergence
Non-frontal convergence
Low level turbulence
The more moisture in the air the _______ the cloud base and the _______ the tops.
lower
higher
What are the two effects of surface heating?
low level turbulence
convective cloud
How do turbulence cloud layers at night compared to those at day?
deeper, denser cloud
What are the 4 conditions which cause temperature inversions?
fronts
surface cooling
subsidence in stable air masses
above turbulence layers
How are temperature inversions cleared?
heating from below
e.g. daytime heating of land or new air mass being brought in
At a cloudbase the _____, ______ and _____ are equal.
Dew point
wet bulb
dry bulb
Name the force that tries to move air from high to low pressure regions.
It acts _________ to the isobars.
Pressure gradient force
perpendicular
In the northern hemisphere the coriolis force makes moving air turn _____
right
Geostrophic wind blows along the _______. In this condition the _____ ______ force and ________ force are equal.
isobars
pressure gradient
coriolis
What does Buys Ballot’s law state about wind and pressure in the northern hemisphere?
If you stand with your back to the wind in the northern hemisphere, low pressure is on your left
In which direction do winds circle a low pressure area in the northern hemisphere?
anti-clockwise
The closer the isobars, the ________ the wind.
stronger
How many degrees N/S of the equator is the geostrophic wind scale useless?
10º
For the same isobar spacing, geostrophic wind speed is ______ nearer the equator.
higher
Geostrophic wind speeds are ______ at altitude.
higher
The gradient wind is the geostrophic wind modified by _________ _____.
centrifugal force
Why is the gradient wind, ‘high around a high’?
because centrifugal force and pressure gradient force are acting in the same direction
Why is the gradient wind, ‘low around a low’?
Because the centrifugal force is opposing the pressure gradient force
Between which altitudes is Ozone a potential danger?
40000 to 75000ft
Ozone is usually destroyed by the __________ process
pressurisation
Dedicated cosmic radiation monitoring equipment must be carried on aircraft operating above _____ft
49 000ft
Low humidity creates the same symptoms as ________
ozone poisoning
Why is cabin humidity so low?
Low humidity of bleed air and humidifiers are expensive to run
Very ___ temperatures increase the susceptibility to hypoxia
low
Surface friction is greatest over ____ at _____ when the air is coldest and densest.
land
night
Surface friction is least during the ____ when the air is warmer and less dense
day
Where are jetstreams found?
air mass boundaries
In winter jetstreams have ______ speed and are closer to the _______.
faster
equator
When crossing the jet core what happens to the outside air temperature?
Remains constant
Which jet stream is connected with a surface front system?
Polar front jet stream
Where is the core of the Polar front jet stream found?
In the tropical air mass
