Climate, Climate Change Nuclear Power and the Alternatives

1. Climate, Climate Change Nuclear Power and the Alternatives

2. Climate, Climate Change Nuclear Power and the Alternatives PHYC 40050 Peter Lynch Meteorology & Climate Centre School of Mathematical Sciences University College Dublin

3. The Energy Cycle of the Atmosphere Lecture 2

4. TRANSFER OF ENERGY • CONDUCTION • Transfer of energy through matter • Air is a poor conductor • Only important at the Earth's surface • CONVECTION • Transfer of energy by movement of mass • Can only take place in fluids - e.g. Air • Energy transported upward by convective flow • Convection on a global scale creates worldwide atmospheric circulation • ADVECTION • Horizontal movement of air • RADIATION

5. Convection

6. Advection

7. Phase Changes Fig. 2-5, p. 33

8. LATENT HEAT • Latent heat is the heat absorbed or released by unit mass of water when it changes phase. • Latent heat of melting / fusion • Latent of vaporization / condensation • Latent heat of sublimation / deposition All conversions are relevant in atmospheric physics

10. The EM Spectrum

11. Planck’s Law for blackbody radiation: Wien’s Displacement Law: Stefan-Boltzmann Law:

12. The hotter the object, the higher the curve:Stefan-BoltzmannLaw

13. The hotter the object, the shorterthe wavelength:Wien’s displacement law

14. Solar Radiation and Terrestrial Radiation Huge difference in the temperature of the Earth and of the Sun. Spectra are effectively disjoint. We speak of short wave radiation (solar) and long wave radiation (terrestrial).

15. Energy Transfer in the Atmosphere

17. The Solar Constant • The average amount of solar energy reaching the outer limits of the atmosphere. • This “constant” actually varies slightly. • Changes by about 0.1% over the eleven year solar cycle. • Mean value: 1368 W/m².

18. ZenithAngle

22. THE EARTH’S ORIENTATION • Earth's axis is not perpendicular to the plane of its orbit around the sun. • It is tilted 23.5º from the perpendicular: Inclination of the axis. • Without this inclination we would have no seasons. • This changes the solar zenith angle of the sun, and the area covered by a beam of sunlight.

23. THE EARTH’S ORIENTATION • Area covered by beam of sunlight is proportional to 1/cos of the solar zenith angle • In Belfield, solar zenith angle of the sun is 75º in December and 30º degrees in June. • Ratio of 1/cos of the angles is about 3.3. • Three times as much energy falls on unit area at the ground in Summer as in Winter.

24. Energy Fluxes 4 x 342 = 1368

25. INCOMING SOLAR RADIATION • 25% penetrates directly to earth's surface. • 26% scattered by atmosphere but then reaches the surface. • Total of 51% reaches surface. • 31% reflected back to space by clouds, atmospheric scattering, and reflective surfaces, e.g. snow and ice. • 19% absorbed by clouds and atmosphere

26. Energy and Matter • Emission • Absorption • Reflection • Scattering

27. ABSORPTION • Gases are excellent absorbers. • When radiation is absorbed, energy is converted into internal molecular motion – temperature rises. • Significant absorbers are: Oxygen and ozone Water vapour Carbon dioxide

28. REFLECTION - ALBEDO • The fraction of energy that is reflected by a surface is called its albedo. • Albedo of the earth as a whole is ~30%. • Albedo of fresh snow is 80-85%. • Thick cloud - 70 to 80%. • Water - depends on elevation of the Sun, from 50 to 80% near horizon, 3-5% at 90º. • Soil - 10%

29. SCATTERING • Produces diffuse light. • Shorter wavelengths (blue and violet) are scattered more effectively than longer wavelengths (red and orange). • Sky appears blue when viewed at noon. • At sunset, scattering depletes amount of blue light - sky appears reddish. • Scattering more efficient as particle gets larger - aerosols or dust.

31. LATITUDINAL HEAT BALANCE • The global amount of incoming solar radiation is nearly equal to the outgoing terrestrial radiation. • However is not true at any given latitude. • In general there is a surplus of energy at the equator - i.e. More radiation comes in than goes out. • There is also a deficit of energy at the poles. • Why then do the poles not get colder and the equator hotter? • Because heat is transported from the equator to the poles by ocean currents and by the atmosphere.

32. Fig. 2-20, p. 50

33. Temperature Variations

34. Diurnal Temperature Cycle

35. Air Temperature Data • Dailymean temperature is determined by two methods, • (a) average of 24 hourly measurements • (b) the average of the maximum and minimum temperatures for the day. • Dailytemperature range is the difference between the max and min temperatures. • Monthly mean temperature is obtained from the average of the daily mean for the month • Annual mean temperature is the average of the monthly means • Annual temperature range is the difference between the coldest monthly mean and the warmest monthly mean

36. Controls on Temperature • Latitude • Surface type • Elevation and aspect • Differential heating of land and water. • Ocean currents. • Cloud cover and albedo

37. Latitudinal Effect

38. Incoming Solar Energy (TOA)

39. Surface Characteristics

40. Effect of Altitude

41. Effect of Aspect

42. Effect of Aspect

43. Differential Heating of Land and Water • As water is heated, convection distributes the heat through a large mass. • In contrast, heat does not penetrate deeply into soil or rock - heat can only be transferred by conduction. • Net result: a relatively thick layer of water is heated to moderate temperatures, while only a thin layer of land is heated to much higher temperatures. • Specific heat is almost three times greater for water than for land

44. Land versus Water

45. Effect of Ocean Currents

46. Effect of clouds on the daytime energy budget at the surface

47. Effect of Cloud Cover

48. Energy in and out

49. DAILY TEMPERATURE CYCLE • Before sunrise, the temperature is controlled by net long-wave radiation from the surface ---- the ground cools. • As sun comes up, solar radiation is absorbed and the temperature of the ground increases. • In general the incoming solar energy is more than the net outgoing thermal energy, so the grounds heats up. • Ground continues to heat up until the amount of incoming solar energy equals the amount of outgoing thermal energy. • This occurs typically at about three in the afternoon.

50. CONTROLS OF TEMPERATURE RANGE • Latitude - determines the intensity of the sun, and the length of the day. • Surface type - land and water contrast, bare soil versus vegetation. • Elevation and aspect . • Relationship to large bodies of water. • Ocean currents. • Cloud cover - reduces the diurnal temperature range.