Atmosphere Flashcards
Name permanent constiuent gases in the atmosphere (and list there percentages)
Nitrogen (78%)
Oxygen (21%)
Trace gases (1% - Argon, CO2, Neon, Helium, Methane, Krypton, Hydrogen, Xenon, Ozone)
What type of varialbe constiuents can be found in the atmosphere
Solids (Particulates - dust, sand, salt, volcanic ash)
Liquids: Water droplets
Gases: Water vapour etc.
How does CO2 contribute to temprature control in the atmosphere?
It absorbs certain heat radiation in long wave radiation bands
What happens to Oxygen in the higher reaches of the atmosphere
Oxygen dissasociates from its molecular form (o2) to its atomic form (o) when under the influence of short wave solar radiation
re-combination takes place with some atoms to form Ozone (o3) which absorbs more short-wave rads.
these process create warmer layers in the higher parts of the atmosphere.
What is interesting about gases in the upper reaches of the atmosphere
They are moving with great speed (indicating a relative high temprature) but they are so spaced out that we see lower temprature drop.
What does water vapour do with solar radiation?
water vapour absorbs well in specific long wave radiation bands which thus promotes heat retention in the lower atmosphere.
through its absorption of heat, and changes in state thanks to latent heat (i.e. evaporating —> moving —> condensing/precipitating)
it is this process, and the varying states of water content in a specific area of the atmosphere that account for clouds/precipitaiton/fog
Name some solids that may be present in the atmosphere
Sea Salt (from cyclones/torndaoes), Dust, Sulphur, Ash
Name the layers of the atmosphere in ascending order
Troposphere, Stratosphere, Mesosphere, Thermosphere (Ionsphere/exosphere)
how high, in miles and feet, does the Earth’s atmosphere extend upwards?
350 Miles = 1848000 ft
How would you express positive or minus pressure using two letters?
PS or MS
What is the world wide height of the tropopause?
36090 ft (6.8 Miles)
where does most of the weather occur within the atmosphere?
within the Troposphere
where does the Stratosphere end?
160,000 ft (30.3 mi)
How is temperature typically controlled within the thermosphere?
conduction and convection - radiation absorption does also play a role
How is temperature typically controlled within the Stratosphere?
mainly through absorbtion of radiation
at what point does the Mesosphere end?
280,000 ft (53.3mi)
at what point does the thermosphere end?
2,000,000 ft (378 mi)
what is above the thermosphere?
exosphere
name the atmospheric boundaries, along with associated altitudes in ft
Tropopause (36090ft) Stratopause (160,000 ft)
Mesopause (280,000ft) Thermopause (2,000,000)
What can cause the thermopause to vary? and why?
Heat - temprature can cause air to rise, thus increasing the height of the tropopuase at the equators and causing it to decrease at the poles
What height range can the tropopause typically occupy and where?
25000ft (at the poles) - 55000ft (at the equator)
what three measures of atmosphereic pressure would we typically see?
hPa (hectorpascals), milibar, and inHg (inches of mercury)
What device is used to measure pressure
Barometer
how would you describe air pressure in terms of weight?
Pressure is the force of the air molecules pushing against you at a specific altitude
what is the formula for pressure?
P(ressure) = F(orce)
———
A(rea)
what is the formula for density
Rho(density) = m(ass)
———–
V(olume)
what is the SI unit for density?
Kg/m3
What is the diffence, in lay-terms, between pressure and density
density is how much stuff is in a unit area, and pressure is how quickly the stuff (molecules) move around that area - they are thus linked
what does the abbreviation MSL mean?
Mean Sea Level
What is the significance of the tropopause in terms of weather?
Clouds rarely form above the tropopause, and this is typically where wind speeds are highest
Jet streams occur here
and this is typically where you get the most significant CAT
what does CAT stand for?
Clear Air Turbulence
What is the definition of a jet stream?
wind speeds consistently above 80kts
where is a jet engine typically most efficient? and why?
at the Tropopause - the ambient temperature typically levels off at this point, with the reduction in density not being counterbalanced by any further drop in temperature.
What will happen to the temperature of the tropopause at the poles and at the equator?
at the poles the temprature of the tropopause will be higher whereas at the equator it will be lower due to variance in height.
What is the range of tempratures typically for the tropopause
as warm as -40c in the winter and as cold as -80c in the tropical summer
what is an approx value of changes in pressure with height?
1 hPa per 30ft - below 20000ft, then it is 1hPa per 50ft
how do temprature changes effect pressure?
cold = more pressure, warm = less pressure
why does density decrease despite air getting cooler as we move through the troposphere and stratosphere?
pressure effect is greater, thus causing density to decrease with height
What is the calculation for air density?
rho (p) = p/RT
rho = density (ratio of mass to volume kg/m3)
p = pressure
R = gas constant
T = absolute temperature
what is 1 millibar equal to?
1 hectopascal
what is the ICAO SPS for pressure?
1013.2 hPa
what is one bar typically? (1000mb)
the approximate atmospheric pressure at sea level
what is the SPS in in (in Hg)
29.92 in Hg
Name two different types of barometer
Mercury Barometer and Aneroid Barometer
which is more accurate, a mercury barometer or an aneroid barometer?
Mercury barometer
which type of barometer is used in aircraft?
Aneroid barometer
what does ISA mean?
international standard atmosphere - reference for the average state of the atmosphere
Who defines the ISA
ICAO (International Civil Aviation Organisation)
What is the ISA value for surface pressure
1013.2 hPa (29.92 in Hg)
What is the ISA value for surface temperature at MSL?
15 degrees celsius
What is the ISA lapse rate up to the tropopause?
1.98c (2c) for every 1000 ft (6.5c/km)
What is the ISA average temp for the tropopause
MS 56.5
what is the ISA average density AMSL?
1.225 kg/m^3
what typically happens around the ‘pauses’ with regards to temperature?
you get an isothermal layer - i.e. the temperature remains constant.
what is the avg. temp at the stratopause?
0c
what typically happens to the temprature in the stratosphere?
we see an inversion - i.e. it increases from the tropopause.
what is the avg temp at the mesopause?
-90c
what happens to the temprature in the mesosphere?
we see a drop in temps
what happens to the temeprature in the thermosphere?
we see an inversion in temps
What is density inversly proportional to? How would we express this as a formula?
rho(density = Pressure (p) / R(gas constant)*T(absolute temperature)
why can hot air hold more moisture?
because there are more gaps between air molecules
