u11 Flashcards
why is earth surface heated unevenly
earth’s rotation
land/oceans
seasons (due to earth tilt)
atmosphere is ____ nitrogen, ____ oxygen, _____ mix of CO2, water vapour and other gases
78% nitrogen
21% oxygen
1% water, CO2, gases
troposphere:
what occurs here
lapse rate
weather occurs here because of water vapor
cools at 2ºC per 1000 ft
tropopause
average height
temperature
smooth or bumpy flying
30 000 ft
isothermal layer
smooth because top of weather layer
t/f. the tropopause expands in summer
true
stratosphere
temperature / lapse rate
what absorbs incoming solar radiation
convection?
temperature increases with height to 0º
negative lapse rate
ozone layer absorbs incoming solar radiation
no convection because of warm temperature = thunderstorms cant go beyond this height
mesosphere
temperature / lapse rate
what’s up here
temperature decreases with height
very cold temperatures
only light gases up here
thermosphere
temperature
where ______ is found
temperature increases (negative lapse rate) due to intense solar radiation
northern lights
is aerodynamic lift possible in the exosphere
no because not enough air molecules for wings to generate lift
standard atmosphere conditions
height
inHg
temp
inHg drop per 1000 ft
temp drop per 1000 ft
moisture in air?
sea level
29.92 inHg
15ºC
1inHg drop per 1000 ft
1.98ºC per 1000 ft
dry air
what is station pressure vs mean sea level (MSL) pressure
station pressure - weight of the column of air extending upwards from the station to top of atmosphere
MSL pressure - station pressure if it was at sea level and using the average temperature over the last 12h
isobars connect areas of equal ______ and are drawn _____ hectopascals apart
the closer the isobars = ____ pressure gradient = ______ wind
equal pressure and 4 hectopascals apart
close isobar = steep pressure gradient = strong wind
high pressure centre
- air is rising or sinking
- diverging or converging (what does it mean)
- cyclone or anti cyclone
- _____ temperature
- how is the weather in this zone
- sinking
- diverging = clockwise and outwards
- anti-cyclone
- colder
- good weather: air cant rise so big clouds/rain cant form, light winds, morning fog
low pressure centre
- air is rising or sinking
- diverging or converging (what does it mean)
- cyclone or anti cyclone
- _____ temperature
- how is the weather in this zone
rising
converging = counterclockwise and upwards
cyclone
warm
poor weather: air rises so clouds/storms, bumpy flying, good visibility
what is a trough
elongated area of low pressure
what is a ridge
elongated area of high pressure
what is a col
what’s the weather within a col during winter vs summer
neutral region between two highs or two lows
unsettled weather
winter = fog
summer = thunderstorms
at a given pressure level, warm air has a _____ true altitude than cold air
higher
moving vertically through a warm and cold column of air, which column of air will experience a smaller pressure change as you vertically rise through it
warm
at the same altimeter setting, a plane will be closer to the obstacle in summer or winter
winter
altimeter setting vs MSL pressure
altimeter setting = station pressure at standard temperature
MSL pressure = station pressure with average temperature over last 12h
why must i use the cold correction card in the wintertime for IFR flights
because my true altitude is lower than my indicated in the winter (cold). so i have to ensure that my true altitude is making obstacle clearance
how is the atmosphere heated?
radiation heating
- sun rays absorbed by earth, gets re-radiated as IR and water vapour absorbs IR (warms atmosphere)
conduction
- layers of air in immediate contact with surface of earth
variation in heating: diurnal variation
when the sun rises, vertical currents/mixing = surface wind increases in speed, veers and gusty
when the sun sets, surface cools/no mixing = surface wind decreases and backs
- over land only because no nighttime inversions over water
variation in heating: seasonal variation
tilt of earth
- shallow light angle results in less heating over winter compared to summer and also shorter days in winter
variation in heating: latitude
equator has sun overhead through entire year = more heating
variation in heating: topography
land heats and cools faster than water
how does CONVECTION move heat in the atmosphere
- warm surface heats air and that pocket of air rises = vertical transport of heat
how does ADVECTION move heat in the atmosphere
cold air moves to warmer surface via wind (lateral transport)
that air gets warmed from the surface below eventually
how does CONDUCTION move heat in the atmosphere
heated earth warms up layers of air in direct contact with it
how does LATENT HEAT move heat in the atmosphere
- latent heat = hidden in water vapour
- water vapour carried into higher levels of atmosphere and condenses -> condensation releases hidden heat and warms the surrounding air
how does COMPRESSION move heat in the atmosphere
when a parcel of air sinks, it’s compressed and increased pressure = warms up
how does RADIATION COOLING cool the atmosphere
when the sun sets, the ground cools = air that touches the ground is also cooled
radiation cooling only in lower atmosphere
how does ADVECTION cool the atmosphere
carries warm air to cold air = the warm air cools down
how does ADIABATIC COOLING cool the atmosphere
rising air expands = cools
cooling rate depends on if the air is saturated or not:
dry rate = 3º per 1000 ft
saturated rate = 1.5º per 1000 ft
what is the standard lapse rate
1.98º per 1000 ft
what is the environmental lapse rate
actual observed rate of cooling (changes over time)
________ of the atmosphere depends on the lapse rate
stability
what is inversion
how can it occur
when does it cause wind shear
weather when an inversion has high humidity
inversion - temp increases with altitude
radiation cooling from surface or a cold front blows under a warm front (cold surface air cant rise)
wind shear during takeoff and landing
smooth air but poor visibility due to haze/fog/stratus clouds
what’s an isotherm
line that joins places of equal temperature eon map
what’s an isothermal layer
temperature remains the same at different altitudes
