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 photons 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 Earths 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 climates 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 climates 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 doesnt 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 Earths 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