HPU NCS2200 Chapter17& 18 primary atmosphere structure and function
1. 17.5 Atmospheric Structure
►Troposphere – the layer we live in
Most weather
All clouds & water vapor
Cools as you go up
►Tropopause – ~17km high, the cooling ends
abruptly, little mixing with troposphere
2. 17.5 Atmospheric Structure
►Stratosphere – temp constant to 35km
Increases up to 50km
Ozone forms here
Above 55km (stratopause) temps fall again
►Mesosphere – thin air, very cold up to 80km
►Thermosphere – above 80km, temps rise
rapidly (to just below freezing!)
Hi-energy environment
4. 18.1 Incoming solar radiation
►Light – behaves like a wave and a particle
Photons – elementary particles of light
Electromagnetic radiation – light also behave as
energy waves, perpendicular electrical and
magnetic waves
►Wavelength – distance between wave crests
►Frequency – number of waves passing a point/sec.
►Electromagnetic spectrum – continuum of
electromagnetic wavelengths
5. 18.1 Incoming solar radiation
►Absorption – when something absorbs
radiation, the photon’s energy can initiate
chemical and/or physical reactions
Excited state – absorbed photons makes
electrons get “excited”
Emission of radiation – when the exited
electrons “settle down” they emit light
►All objects emit some radiation
►Emission color (wavelength) relates to temperature
6. 18.1 Incoming solar radiation
►Reflection –electromagnetic radiation
bouncing from a surface
Albedo – proportional reflectance of a surface
►(e.g.: a perfect mirror would have an albedo of
100%)
►Glaciers & snowfields approach 80-90%
►Clouds – 50-55%
►Pavement and some buildings – only 10-15%
8. Fig. 18.5, p.455
► Scattering – gases and water droplets scatter light
in all directions
short “blue” wavelengths scatter more, so skies are
blue
9. 18.2 the radiation balance
►Earth’s surface absorbs light energy
Most is re-emitted, mainly as heat
Greenhouse effect – some gases and water
vapor absorb some of this heat
►Dust, clouds, aerosols, particulates all affect
atmospheric temperature
Hi-altitude dust can reflect light
Lo altitude particles can absorb heat
11. 18.3 Energy storage & transfer
– climate’s driving mechanism
►Temperature – is proportional to the
average speed of atoms or molecules in a
sample.
E.g.: hot water molecules move faster than cold
water molecules
►Heat – is a measure of the total energy in a
sample
average energy X number of molecules
E.g.: bathtub of ice has more heat than a cup of
tea
12. 18.3 Energy storage & transfer
– climate’s driving mechanism
►Conduction – transfer of heat by direct
collisions of molecules
Heat, good conductor; air, poor conductor
►Convection – transfer of heat by the motion
of a fluid medium
►Advection - horizontal air flow
(meteorological term)
15. p.459
Recall that the
Earth is curved
And lines of Latitude
Are horizontal to the
Equator and increase in
Degrees from 0 to 90
16. 18.4 temperature changes
with latitude & season
►Temperature decreases as latitude increases
Light strikes more directly at low latitudes
►more energy per unit area, heats more effectively
At high latitudes, the sun strikes quite obliquely
►At some point during the year at poles, it doesn’t
strike at all
19. 18.4 temperature changes
with latitude & season
►The seasons – related to orbital parameters
Earth’s axis is tilted. During northern summer,
the light hits more directly and in winter less so
Tropics – the latitudes of 23.5o N/S are where
light his directly on summer and winter solstice
Equinox, when an area gets 12 hours each of
light and dark
►On average, all areas of the globe receive the same
sunlight time annually
21. 18.5 Temperature changes
with geography
►Altitude – temperature decreases with
altitude
►Ocean effects – land heats more quickly
than water, so inlands see greater
temperature extremes
Currents often transfer heat to moderate
temperatures (e.g.: the Gulf Stream)
22. 18.5 Temperature changes
with geography
►Cloud cover and albedo
Clouds intercept light energy
►They cool during day by blocking the sun
Clouds have high albedo, turning incoming energy back
towards space
►Then warm at night by trapping ground-emitted heat
Clouds have high albedo, turning outgoing energy back to
ground
►Snow effects solar input in similar fashion, it is
reflective while soil/rock is not