HPU NCS2200 earth science for elementary education majors summer 2014 online class atmosphere structure and function lecture 1

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

3. Fig. 17.10, p.440

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%

7. Fig. 18.4, p.454

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

10. Fig. 18.6, p.455

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)

13. Fig. 18.8a, p.457
Convection example: heat from a stove heating a room

14. Fig. 18.8b, p.457
Convection within the atmosphere

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

17. Fig. 18.11, p.460

18. Fig. 18.10, p.460

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

20. Fig. 18.12, p.461

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

23. Fig. 18.18, p.466