ESCI 106 – Weather and Climate Lecture 2

1. ESCI 106 – Weather and ClimateLecture 2 8-25-2011 Jennifer D. Small 

2. Weather Fact of the Day: August 25 • 2005: Hurricane Katrina made its first US landfall on Florida East coast between Hallandale Beach and North Miami Beach. • Sustained winds of 80 mph , gusts of 90+ mph. • Katrina killed 14 as it crossed extreme southern Florida, including several killed by falling trees/tree branches.

3. National Watches and Warnings

4. Current Hurricane Irene D: Tropical Depression – wind speed less than 39 MPH S: Tropical Storm – wind speed between 39 MPH and 73 MPH H: Hurricane – wind speed between 74 MPH and 110 MPH M: Major Hurricane – wind speed greater than 110 MPH

5. Current Hurricane Irene

6. Current Hurricane Irene

7. Current Hurricane Irene

8. Earth-Sun Relationships • Earth’s Motions • Rotation • Revolution • Perihelion • Aphelion • The Seasons • Earth’s Orientations • Plane of the ecliptic • Inclination of the axis • Solstices and Equinoxes • Tropic of Cancer, summer solstice • Tropic of Capricorn, winter solstice • Autumnal equinox, Sprig equinox • Circle of Illumination

9. Earth-Sun Relationships • FACT: The Earth intercepts only a tiny percentage of the energy given off by the sun! Less than one-two billionth of the suns total output!

10. Earth-Sun Relationships • FACT: Solar energy is NOT distributed equally over Earth’s surface. • Latitude, Time of Day, & Season

11. Earth-Sun Relationships • FACT: Unequal heating is responsible for winds and ocean currents (Weather).

12. Earth-Sun Relationships • FACT: To understand weather we need to know why different latitudes receive different amounts of energy.

13. Earth’s Motions • Earth’s two principle motions are: • Rotation • Revolution • Rotation • The spinning of Earth about its axis • Why we have day and night • Revolution • Movement around the Sun • Travels at nearly 113,000 km/hr (70,000 miles/hr) • Elliptical orbit – not perfectly circular (exaggerated!)

14. Earth’s Motions • Elliptical Orbit – Eccentricity is ~0.8 January 3rd July 4th 147.3 km 152.1 km Aphelion Perihelion FARTHEST from the SUN CLOSEST from the SUN

15. The Seasons • FACT: Variations in the distance between the Sun and Earth DO NOT cause the seasonal temperature change! • Change in the length of day accounts for some. • Gradual change in the angle of the sun at noon. • Affects the amount of energy received at Earth’s surface • When overhead  strongest • Lower angle  less intense

16. The Seasons • FACT: Variations in the distance between the Sun and Earth DO NOT cause the seasonal temperature change! • The angle of the Sun determines the path solar rays take through the atmosphere! • During summer, at 90 deg, it has the shortest distance (one atmosphere) • The longer the path the more likely the rays will be absorbed, reflected or refracted. • On any give day only a particular latitude will receive the 90 deg rays. At 30 deg angle, twice as much atmosphere!! At 5 deg angle, 11 times as much atmosphere.

17. The Seasons • SUMMARY: Most important reasons for variations in the amount of solar energy • Seasonal changes in the angle at which the Sun’s rays strike the surface • Changes in the length of daylight

18. Earth’s Orientation • Why does length of day and sun angle change? • Earth’s orientation to the sun constantly changes!!!

19. Earth’s Orientation • Earth’s Axis • Imaginary lines through the poles! • Inclination of the axis: 23.5 deg from the perpendicular • Plane of the ecliptic – the plane of the orbit around the sun • WITHOUT THE TILT WEWOULD NOT HAVE SEASONS!

20. Earth’s Orientation • Solstices • Summer Solstice • Tropic of Cancer • Northern limit of the Sun’s rays • 23.5 N Latitude • June 21-22 • First day of NH summer • NH tilted toward Sun • Winter Solstice • Tropic of Capricorn • Southern limit of the Sun’s rays • 23.5 S Latitude • December 21-22 • First day of NH winter • NH tilted away from Sun

21. Earth’s Orientation • Equinoxes • Occur mid way between the Solstices • Vertical rays strike along the equator (0 deg latitude) • Earth not tilted toward or away • Autumnal Equinox • September 22 or 23 • Spring Equinox • March 21 or 22 • Also called Vernal Equinox

22. Earth’s Orientation • Length of Daylight • Circle of Illumination • Boundary separating the dark and light halves of the Earth • Cerritos College • ~34 degrees latitude Land of the Midnight Sun Table 2-2 from your text!

23. Earth’s Orientation • Summer Solstice Review • Occurs on June 21 or 22 • Vertical rays of the Sun strike the Tropic of CANCER (23.5 deg N) • NH location experience their LONGEST day • (SH location experience their SHORTEST day) • NH locations experiences their HIGHEST Sun angle • (SH location experience their LOWEST Sun angle) • Farther from the equator the longer the period of daylight (i.e. Arctic Circle has 24 hours of SUN) Many cultures place importance on the Solstice days and mark them with celebrations

24. Earth’s Orientation • Winter Solstice Review • Occurs on December 21 or 22 • Vertical rays of the Sun strike the Tropic of CAPRICORN (23.5 deg S) • SH location experience their LONGEST day • (NH location experience their SHORTEST day) • SH locations experiences their HIGHEST Sun angle • (NH location experience their LOWEST Sun angle) • Farther from the equator the longer the period of daylight (i.e. Antarctic Circle has 24 hours of SUN) Many cultures place importance on the Solstice days and mark them with celebrations

25. Solstices and Equinoxes • SUMMARY: Seasonal Fluctuations in the amount of solar energy reaching various parts on Earth’s surface are caused by: • The migrating vertical rays of the Sun • The resulting variations in the Sun ANGLE and LENGTH of daylight

26. What would the seasons be like if Earth was not tilted on its axis? • All locations on the globe would have 12 hrs of day and 12 hrs of night • The sun would always follow the path that it does during the current equinox • No seasonal temperature changes, temperature would be the rough “average” at that location

28. Energy, Heat, and Temperature • Forms of Energy • Potential Energy • Kinetic Energy • Temperature • Heat

29. Energy • Universe is made up of matter and energy • Matter can be seen, smelled and touched • Energy is more abstract • Energy from the Sun reaches the Earth • Electromagnetic Radiation  Heat and Light • Energy is the Capacity to do Work • Takes many forms • Chemical energy from gas to move cars • Gravitational energy to move dirt during a landslide

30. Energy • Potential Energy • The Capability to do work. • EX: large hail stones have high potential energy because they are suspended in the cloud

31. Energy • Kinetic Energy • Energy associated with an object by virtue of its motion. • The faster the weight is dropped the more Kinetic Energy • The larger the weight is the more Kinetic Energy • Ex: Hurricanes have more kinetic energy than a light breeze

32. Heat • The TRANSFER of energy into or out of an object because of TEMPERATURE DIFFERENCES • It is theFLOW of energy!

33. Mechanisms of Heat Transfer

34. Conduction • The TRANSFER of heat through election and molecular collisions from one molecule to another. • Ability to conduct varies: • Metals are better • Air is poor, called an INSULATOR Only important for heating the air in DIRECT contact with the surface of the Earth

35. Convection • Heat transfer that involves the actual movement or circulation of substance • Air • Water • Most common form of transfer in the atmosphere • Convective Circulation/Currents transfer the heat • Thermals

36. Radiation • Travels through the vacuum of space! • How solar energy reaches the planet!

37. RADIATION CONDUCTION CONVECTION RADIATION

38. Solar Radiation • Electromagnetic Radiation! • Wavelengths – the distance from one crest to the next • All typesTraves at 300,000 km/sec or 186,000 miles/sec

39. Solar Radiation • Visible Light • Often referred to as “white light” • Using a Prism reveals that white light is composed of the other colors of the rainbow • Ultraviolet (UV) – Higher energy • Infrared Radiation (IR) – Lower energy

40. Solar Radiation • Regardless of the wavelength all behave similarly • When an object absorbs electromagnetic energy it increases their molecular motion and thus temperature • Shorter wavelengths are MORE energetic (like UV) • Can damage skin (i.e. cause Skin Cancer, why we wear UV Sun block) • Longer wavelengths are LESS energetic

41. Solar Radiation • Sun emits all wavelengths but in varying quantities • 95 % is between 0.1 and 2.5 micrometers • Visible (0.4-0.7 um) = 43% • IR = 49% • UV = 7% • X-rays, Gamma, Radio = Less than 1%

42. Laws of Radiation - 1 • ALL objects continually emit radiant energy over a range of wavelengths • Sun emits energy • Earth emits energy • YOU emit energy • EVERYTHING emits energy... • Unless it’s at “absolute zero” when molecules stop moving

43. Laws of Radiation - 2 • Hotter objects radiate more total energy per unit area than do cooler objects • Sun is 6000 K (10,000 F) • Earth is 289 K (59 F) • Sun 160,000 times more energy than the Earth • This concept is called the Stephan-Boltzman Law

44. Laws of Radiation - 3 • Hotter objects radiate more energy in the form of short wavelength radiation than do cooler objects • Hot burner on a stove glows Red • Cool burner on a stove doesn’t glow at all but could still FEEL hot • Maximum radiation emitted by Earth is ~10um • This is in the INFRARED part of the spectrum

45. Laws of Radiation - 4 • Objects that are good absorbers of radiation are also good emitters. • The perfect absorber (and emitter) is a “Blackbody” • Both the Earth and Sun are close to being blackbodies because they absorb and radiate with nearly 100% efficiency. • Atmosphere is transparent (radiation passes through) and opaque (radiation is absorbed) to different wavelengths.

46. Absorbed Transmit Reflection Scattering DEPENDS ON THE WAVELENGTH OF THE ENERGY What Happens to Incoming Solar Radiation?

47. Reflection Bounces off at the same angle Reflection and Scattering • Scattering • Produces a larger number of weaker rays • And at the same intensity Less is “Backscattered” More is scattered forward

48. Energy is returned to space via reflection and emission ALBEDO - The percentage reflected About 30% is reflected for Earth 5% from land and ocean 25% from clouds and ice Reflection and the Earth’s Albedo

49. Diffused Light Dust particles an gas molecules scatter energy in different directions Explains how light reaches beneath the shade of a tree Moon have Black shadows and Pitch Black skies Reflection and the Earth’s Albedo

50. Blue Skies and Red Sunsets Gas molecules more effectively scatter the shorter wavelengths (blue and violet) than the longer wavelengths (red and orange) At sunset light has to pass through MORE atmosphere Reflection and the Earth’s Albedo