I Axial Tilt and Orbit around Sun A Earth tilts 23 5o to orbit around Sun B Latitudes of Sun incidence 1 polar circles Arctic Antarctic 2 tropical circles Cancer Capricorn 3 equator C Days corresponding to Sun incidence 1 solstice overhead Sun at tropical circle June 22 December 22 2 equinox overhead Sun at equator March 22 September 22 D Day length varies with latitude and season due to circle of illumination 1 longest shortest at solstice at high latitudes 2 equinox equal day and night all over the world II Heating A Greater heating capability with higher Sun angle 1 latitude controls on Sun energy 2 seasonal controls on Sun energy B Low latitudes have high Sun angle year round C Incoming Solar Radiation 1 Temperature Variation greater in areas closer to poles 2 Temperature Distribution affected by land water relation as well as latitude III Heat A Thermal energy transferred from warm substances to cooler ones B Methods of heat transfer 1 conduction a through matter by molecular activity b air is poor conductor of heat energy 2 convection heat rises a transfer of heat by circulation within fluid b caused by expansion of heated fluid reduces density c lower atmosphere heated by Earth s surface 3 radiation through empty space a Solar radiation is source of energy for weather and climate 1 Electromagnetic radiation from radio waves to gamma waves 2 Visible light small segment between infra red and ultraviolet a Infrared is heat b Ultraviolet causes sunburn etc 3 microwaves and x rays bracket ir and uv b all objects emit radiant energy 1 hotter object emit more and at shorter wavelengths 2 the better absorber of radiation the better ability to emit energy a Earth is excellent absorber and emitter b Atmospheric gases selective absorbers of longer wave radiation IV Incoming solar radiation A Absorbed transmitted redirected reflected or scattered B Distribution 1 about 50 is transmitted to surface and absorbed by Earth 2 about 30 is reflected back to space 3 about 20 absorbed by atmospheric gases and clouds C reflection and scattering 1 reflection a changing direction of light without reducing intensity b Albedo fraction of radiation reflected by a surface 1 Affected by length of travel through atmosphere 2 Affected by angle of incidence upon water 2 scattering a disperses light into many weaker rays in many directions b accomplished by dust gas molecules c diffuses light to make shadows have light D absorption 1 nitrogen poor absorber of radiation 2 oxygen and ozone absorb most of uv radiation high in atmosphere 3 most atmospheric gases do not absorb visible wavelengths transmit V Atmosphere is mixture of gases with varying proportions with respect to location and timing A Nitrogen and Oxygen make up 99 of clean dry air up to 80 km B Minor components include argon 0 93 and carbon dioxide 0 037 C Variable components affect weather and climate 1 water vapor a varies from almost none to up to 4 of atmosphere b source of all clouds and precipitation c absorbs heat from Earth and Sun d change of water s phase captures or releases latent heat 2 aerosols and dust a remain suspended for extended period of time b sources include sea salt blown soil fires pollen volcanic eruptions c act as surfaces for water vapor to begin condensation d reflect and scatter incoming solar energy 3 ozone a molecular oxygen with three atoms has properties distinct from O2 1 damages tissue of organisms 2 can be created near surface by reactions in smog b concentrated 10 to 50 km above surface in stratosphere 1 Sun s radiation breaks O2 into O and O in stratosphere 2 O collides with O2 and forms O3 at this altitude 3 Lightning makes O3 in troposphere c Ozone important absorber of UV radiation VI Height and structure of atmosphere A Pressure is weight of overlying air 1 about 1000 millibars 1 kg cm2 14 7 lbs in2 2 half of all atmosphere is below 5 6 km from surface Mt McKinley 6 2 3 beyond 16 km less than 10 of atmosphere remains 4 traces exist above 100 km less than one millionth of it B temperature variation with height 1 troposphere mixed zone includes most weather phenomenon a temperature decreases with height in troposphere b average temperature change is 6 5o C km 1 normal environmental lapse rate 2 not constant monitored by weather equipment c average height of tropopause 12 km 1 height varies with location and temperature 2 end of troposphere called tropopause d temperature and humidity can be transferred in troposphere by turbulence and mixing 2 Stratosphere a Stratosphere lacks mixing of troposphere b Constant temperature to about 20 km c Gradually increases to about 50 km at the stratopause 1 Ozone concentrated in stratosphere absorbs UV energy 2 This absorbed energy creates the increased temperatures 3 Mesosphere a Temperatures in mesosphere decrease with height to 80 km b Decreases to about 90o C at mesopause 4 Thermosphere beyond mesopause a Tiny fraction of atmosphere b Subject to direct radiation from Sun c Temperature increases to 1000o C but described by speed of molecules not feeling of warmth due to extremely low density VII Sun energy heats atmosphere A Mostly between Tropical circles where direct rays fall 1 solstice when direct rays most poleward June 21 and December 21 2 equinox when direct rays at equator March 21 and September 21 3 day length varies between extremes at solstices equal on equinox B seasonal variations in Sun energy from constant axial tilt toward Polaris C additional causes of local temperature other than day length and Sun angle D Distribution of temperatures 1 Cooler in polar areas 2 Warmest at tropics in continental areas 3 Warmness follows the direct rays of Sun as it travels from tropic to tropic throughout year 4 Oceanic currents warm western side of ocean basins and the continents adjacent to them 5 Oceanic currents cool eastern side of ocean basins and the continents adjacent to them E Heating of Atmosphere greenhouse effect 1 Atmosphere transmits about 50 of energy received to Earth s surface 2 Absorbed energy by Earth s surface re emitted as longer wavelength 3 This longer wavelength is readily absorbed by atmosphere not transmitted a Result is lower atmosphere heated from Earth s surface b WHY temperature decrease with distance from surface in troposphere 4 Greenhouse effect a Incoming light is absorbed by Earth b Reradiated heat is trapped by carbon dioxide water methane c glass does not transmit heat but also rely on lack of mixing with outside air to keep
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