Met Exam Flashcards
What is the average pressure at mean sea level??
1013.25hPa
Describe the composition of the atmosphere.
Nitrogen 78.09%
Oxygen 20.95%
Argon 00.93%
Carbon Dioxide 00.03%
What are the layers of the atmosphere from highest to lowest?
Thermosphere (Ionosphere is here)
Mesosphere
Stratosphere
Troposphere
What are the depths of the troposphere?
52,000ft/16km at the equator
36,000ft/11km at 50degrees north
30,000ft/9km at the poles
Describe the conditions of the stratosphere
Extends from the troposphere to 50km with a constant temp of around 0 degrees Celsius
What is the difference between official and unofficial met observations?
Official is provided by an appropriately trained person at a unit with the necessary equipment. Otherwise unofficial.
What are the conditions of the ISA?
International standard atmosphere
.pressure of 1013.25hPa
.air density 1225gm/m3
.temperature +15°C
. 1.98°C per 1000ft lapse rate up to 36,000ft, remains at -56.5°C thereafter up to 65,000ft
Where is most of the water, weather and flight in the atmosphere?
99% in the troposphere
Most flight happens here
What is the upper limit of the troposphere called?
The tropopause
How many feet of height does a hPa equal roughly?
30ft
What is insolation?
The incoming radiation from the sun warming the earth, as the air does not absorb the energy.
What is specific heat capacity?
The energy required to heat 1kg of a substance by 1°C
What factors affect diurnal variation?
Surface- variation is greater over land and sea.
Wind speed- wind causes turbulence that spreads the cooling effect through a greater depth of air.
Cloud- reduces heat loss.
How do inversions and isothermal layers affect the lapse rate?
Inversions cause the adiabatic effect to reverse and the air actually heats up as it rises. Isothermal layers are where the temperature remains the same in that layer and doesn’t lapse.
What four ways may a parcel of air be cooled past its dew point?
Conduction
Evaporation
Mixing
Adiabatic cooling.
Define adiabatic
The change in temperature of a parcel of air as its density changes, normally cooling as the air expands when rising.
What are the adiabatic lapse rates for dry and saturated air?
SALR= 1.5 degrees/ 1000ft DALR= 3.0 degrees/1000ft
What is the ELR?
The environmental adiabatic lapse rate that exists within the atmosphere at a particular time. (ISA global average is 1.98 degrees per 1000ft)
Define stable and unstable air.
Stable air is air that doesn’t rise and unstable rises.
Describe the Celsius Scale
Freezing point H20= 0°C
Boiling point H20=100°C
Describe the Kelvin scale
Theoretical Absolute zero= -273°C (0°K)
Freezing point H20= 273°K
Boiling point H20=373°K
Just add 273 to the celsius scale
Describe the Fahrenheit Scale
Freezing point H20= 32°F
Boiling point H20=212°F
How do you convert from Celsius to Fahrenheit?
(9x°C)/5+32
How do you convert from Fahrenheit to Celsius?
5x(°F-32)/9



