The Atmosphere Flashcards
Properties of Atmosphere
Pressure,density, temperature, humidity
What is the atmosphere
A mixture of gases but also non-gaseous substances (droplets of water, particles of ash, dust). Mixture=Air
Relationship between altitude, density and pressure
As altitude increases pressure and density decreases.
Troposphere facts
Lowest layer.
Earth is source of heat for lower atmosphere. Temperature decreases with height. 2*c per 1000ft
Holds 75% of the mass of air and almost all water vapour.
Tropopause
Top of the troposphere.
Temperature no longer decreases with height. Air is stable (resists further vertical movement)
Almost all visible weather is below tropopause.
Tropopause height
Average 11km MSL However height determined by temperature Height is greater at equator than Poles. Type of surface also affects height (land/sea)
Effect of seasons on tropopause
Winter tropopause lower as colder surface conditions. Higher for summer.
Tropopause Folds
2 regions S. Hem
3 N.Hem
Abrupt change in height of Trop.
Find fast moving air currents (jetstreams).
Tropopause Height
Lower the tropopause warmer it is and colder if higher.
Stratosphere Facts
From Tropopause to 50km AMSL
Temperature increase with height but not uniform rate.
Lowest layer Isothermal (temp constant with height). Roughly 11-20km
0*c at top
Good place to fly cruising altitude commercial airliners.
Ozone (O3) layer
In Stratosphere 25km AMSL
Absorbs UV and releases long wave radiation
Causes respiratory issues.
Planes need Ozone converters.
Atmospheric Pressure’
Air has mass. The weight of air above felt by air below. As air is fluid pressure transmitted across fluid.
What impacts air pressure
Air pressure determined by mass of overlying air
Air pressure and air density decrease with altitude.
ISA conditions
Temperature 15c
Pressure 1013.25 hpa
Density 1.225kg/m3
ISA deviation
Calculation of ISA conditions compared to actual atmospheric conditions.
Warmer temperature the ISA deviation
positive
