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Appendix A

Appendix A. Length: m 1 km = 1000 m; 1 m = 100 cm = 1000 mm = 10 6 micrometer ( μ m) 1 inch (in.) = 2.54 cm 1 foot (ft) = 12 in. = 12*2.54 = 30.48 cm = 0.3048 m 1 mile (mi) = 1.61 km 1 nautical mile = 1.15 mi = 1.85 km. (b) Area: m 2 1 mi 2 = 1.61 2 km 2 = 2.59 km 2

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Appendix A

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  1. Appendix A • Length: m • 1 km = 1000 m; • 1 m = 100 cm = 1000 mm = 106 micrometer (μm) • 1 inch (in.) = 2.54 cm • 1 foot (ft) = 12 in. = 12*2.54 = 30.48 cm = 0.3048 m • 1 mile (mi) = 1.61 km • 1 nautical mile = 1.15 mi = 1.85 km

  2. (b) Area: m2 • 1 mi2 = 1.612 km2= 2.59 km2 • Volume: m3 • 1 liter (l) = 1000 cm3 = 0.264 gallon (gal) US • (d) Mass: kg • 1 kg = 2.2 lb

  3. (e) Speed: m/s 1 km/hr = 1000m/3600s = 0.28 m/s 1 mi/hr = 1609m/3600s = 0.45 m/s 1 knot = 1 nautical mile/hr = 1850m/3600s = 0.51m/s (f) Force: newton (N) = kg m/s2 F = ma `a’ is acceleration (or change of speed with time) 1 dyne = 1 g cm/s2 =10-3 kg 10-2 m/s2 = 10-5 N

  4. (g) Energy: joule (J) = Nm • E = FL `L’ is distance • 1 J = 1 Nm = 0.24 Calorie (cal) • (h) Power: watt (W) = J/s • P = change of energy with time • 1 horse power (hp) = 746 W • Power of 10 • 10-9 10-6 10-3 10-2 102 103 106 109

  5. Pressure: pascal (Pa) = N/m2 • P = F/Area • 1 Pa = 1 N/m2 = 1 (kg m/s2)/m2 = 1 kg s-2 m-1 • 1 millibar (mb) = 100 Pa = 1 hecto Pa = 1 hPa • sea level surface pressure = 1013 mb

  6. 1 millimeter of mercury (mm Hg) = 1.33 mb because Hg density = 13,546 kg/m3; earth’s gravity = 9.8 m/s2; Over unit area (m2), 1 mm Hg mass = 10-3 * 13,546 = 13.5 kg F = mg = 13.5 *9.8 N = 133 N P = F over unit area = 133 Pa = 1.33 mb

  7. (k) Temperature: kelvin (K) K = oC + 273; oC = 5/9 (oF -32) oF = 9/5 oC + 32 For instance 104 oF = 40 oC 20oC = 68 oF (Table A.1 on p. 437 could also be used) Q: if temperature changes by 1 K, how much does it change in oC and oF? (A: 1 oC; 1.8oF)

  8. Chapter 2: Warming the Earth and the Atmosphere • Temperature and heat transfer • Balancing act - absorption, emission and equilibrium • Incoming solar energy

  9. Temperature and Heat Transfer Air T is a measure of the average speed of the Molecules Warm less dense

  10. Temperature Scales • kinetic energy, temperature and heat K.E. = mv2, Internal energy = CvT, Heat = energy transfer by conduction, convection,and radiation • Kelvin scale: SI unit • Celsius scale: • Fahrenheit scale: used for surface T in U.S. • temperature conversions • Every temperature scale has two physically-meaningfulcharacteristics: a zero point and a degree interval.

  11. Fig. 2-2, p. 27

  12. Latent Heat - The Hidden Warmth • phase changes and energy exchanges evaporation: faster molecules escape to air; slower molecules remain, leading to cooler water T and reduced water energy; lost energy carried away by (or stored in) water vapor molecules Q: does the formation of clouds warm or cool the air in the clouds? • sensible heat: we can feel and measure • Latent heat explains why perspirationis an effective way to cool your body.

  13. Stepped Art Fig. 2-3, p. 28

  14. Conduction • Conduction: heat transfer within a substance by molecule-to-molecule contact due to T difference • good conductors: metals • poor conductors: air (hot ground only warms air within a few cm)

  15. Convection • Convection: heat transfer by mass movement of a fluid (such as water and air) • Thermals • Soaring birds, like hawks and falcons, are highlyskilled at finding thermals. • Convection (vertical) vs Advection (horizontal) • Rising air expands and cools while sinking air warms by compression

  16. Radiation • Radiation: energy transfer between objects by electromagnetic waves (without the space between them being necessarily heated); packets of photons (particles) make up waves and groups of waves make up a beam of radiation; • electromagnetic waves Q: are molecules needed? In a vacuum, speed of light: 3*105 km/s • Wein’s law λmax = 2897 (μmK)/T • Stefan-Boltzmann law E = σT4

  17. All things emit radiation • Higher T leads to shorted λ • Higher T leads to higher E • Shorter λ photon carries more energy • UV-C (.2-.29 μm) • ozone absorption • UV-B (.29-.32 μm) • runburn/skin cancer • UV-A (.32-.4 μm) • tan, skin cancer • Most sunscreen • reduces UV-B only Fig. 2-7, p. 32

  18. Radiation • electromagnetic spectrum • ultraviolet radiation (UV-A, B, C) • visible radiation (0.4-0.7 μm) shortwave (solar) radiation • infrared radiation longwave (terrestrial) radiation

  19. Fig. 2-8, p. 34

  20. Balancing Act - Absorption, Emission, and Equilibrium

  21. Selective Absorbers and the Atmospheric Greenhouse Effect • blackbody radiation perfect absorber; don’t have to be colored black; radiative equilibrium T = 255K; actual T = 288K • selective absorbers snow: good absorber of infrared radiation, but not solar radiation • atmospheric greenhouse effect • The best greenhouse gas is water vapor, followed by CO2

  22. Enhancement of the Greenhouse Effect • global warming: due to increase of CO2, CH4, and other greenhouse gases; global average T increased by 0.6 C in the past 100 yr; expected to increase by 2-6 C at the end of 21st century • positive and negative feedbacks • Positive feedback: increasing temperatures lead tomelting of Arctic sea ice, which decreases the albedo. • Positive water vapor-temperature feedback • Potentially negative cloud-temperature feedback

  23. Warming the Air from Below • radiation • conduction • convection • Fog “burns off” from the bottom up.

  24. Incoming Solar Energy

  25. Scattered and Reflected Light • Scattering: blue sky, white sun, and red sun • Reflection: more light is sent backwards • Albedo: ratio of reflected over incoming radiation; fresh snow: 0.8 clouds: 0.6 desert: 0.3 grass: 0.2 forest: 0.15 water: 0.1

  26. The Earth’s Annual Energy Balance • What happens to the solar energy that reaches the top of the earth’s atmosphere? • What happens to the solar energy that is absorbed by the earth’s surface and by the atmosphere?

  27. Solar constant = 1367 W/m2 Fig. 2-15, p. 41

  28. Fig. 2-16, p. 42

  29. Fig. 2-17, p. 43

  30. Why the Earth has Seasons • earth-sun distance: closer in winter • tilt of the earth’s axis • Earth-sun distance has little effect on atmospheric temperature.

  31. Seasons in the Northern Hemisphere • insolation • summer solstice • spring and autumn equinox

  32. Seasons in the Southern Hemisphere • tilt • solstice • equinox December 21 is the 1st day of winter in astronomical definition not in meteorological definition

  33. Stepped Art Fig. 2-24, p. 50

  34. Local Seasonal Variations • slope of hillsides: south-facing hills warmer & drier • vegetation differences • Homes can exploit seasonal variations: large windows should face south.

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