Introduction Flashcards
How thick is earth’s atmosphere?
About 480 km thick
Where is most of the atmosphere located?
Within 16 km of the surface
What is the composition of air?
78% Nitrogen, 21% Oxygen, 0,93% Argon, 0.04% CO2 and trace amounts of other elements.
Density of air depends on what three factors?
Air temp, pressure and amount of water vapour in the air.
True of False?
Air pressure and density increase with height.
False, they decrease with height.
Warm air takes up _____ space and will have _____ density than cold air.
More & less
What effect do water molecules regarding pressure have when added to dry air? Why?
There is a decrease in pressure because one molecule of water weighs less than one molecule of air.
Define ceiling
Base of a low cloud deck which covers more than half of the sky.
What are some examples of precipitation?
Rain, snow, drizzle, freezing rain, freezing drizzle, hail, snow grains and ice pellets.
What are some examples of obstructions to visibility?
FG, BR, BLSN, BLSA, dust, blowing dust, FU, haze.
What is the lowest part of the atmosphere called?
The boundary layer
How thick is the boundary layer?
3000’ or 1000m
What are three characteristics of the boundary layer?
Wind increases with height
Vertical currents occur due to friction of wind with earth’s surface; and
Turbulent due to eddies in the wind flow caused by overturning air.
When is the boundary layer deeper/ shallower?
Deeper in the summer and during day. Shallower in the winter and at night.
Moisture in the atmosphere is mainly due to what?
Evaporation from oceans and lakes.
True or False?
Clouds form when water vapour change to liquid water droplets or ice crystals.
True
The warmer the air, the more _____ the air can hold.
Moisture
When water enters a more excited state, it _____ heat.
Absorbs
What is “Dew Point”?
A measure of how much water vapour is in the air.
What is the significance of a high Td?
The more moisture in the air, the more precipitation out and a greater release of latent heat.
What is relative humidity?
An indication of the amount of water vapour in the air vs how much water vapour the air can hold.
True of False?
High RH is related to cloud and fog formation.
True
Explain Conduction
It is the transfer of heat by direct physical contact.
Heat flows from high temperature regions to low temperature regions.
Explain Convection
Transfer of heat by the motion of a fluid
Heat flow from low to high density region.
Faster than conduction
Explain Radiation
Transfer of heat by EM waves.
Does not heat intervening medium.
Takes place at large distances.
Briefly explain radiation heating.
Solar radiation warms up ground, air surrounding the ground is heated via conduction then causes convection.
Air then rises, moving the heat upwards,
Atmospheric cooling is important for two reasons, what are they?
It increases the density of the air and when moist air cools it creates clouds, fog and precipitation in the lower levels.
True or False?
Warmer, moist air moving over a cooler surface may cause fog?
True
Explain expansion cooling
As air rises, it encounters less pressure, causing it to expand and cool.
What is the difference between stable and unstable situations?
Stable air resists vertical currents, unstable air promotes them.
What are soem unstable air characteristics?
Cumuliform clouds, showery precipitation, rough air (TURB) and good visibility except in blowing obstructions.
What are some stable characteristics?
Stratiform clouds, continuous precipitation, smooth air and fair to poor visibility in haze and smoke.
Which type of air has convective clouds and possibly thudnerstorms?
Unstable air
Which type of air has layered clouds and continuous precipiation?
Stable air
