1. Tonight February 8 Weather Review Weather map basics
Energy that Drives the Storms (chapter 2)
More Weather Maps (Isopleths)
Classwork (HW#3)
Homework #4

3. Weather Preview What is the forecast for next week? Monday? Tuesday?
Wednesday?
During the course of the week try and keep track if the forecast
Changes?
Is accurate?

5. Weather Symbols and Maps

6. Station model 80
021
-23 63

7. Weather Symbols

8. Sky Symbols

9. Wind Symbols

10. Pressure Tendency

11. Station model 80
021
-23 63

12. Station model 80
021
-23 63
Temperature
Surface: ºF
Upper air: ºC

13. Station model 80 021 -23 63 Dew point temperature Surface: ºF
Upper air: ºC

14. Station model 80 021 -23 63 Total sky cover ** Depicted by shading
in circle

15. Station model 80 021 -23 63 Current weather conditions
** If blank, “no weather”

16. Station model 80
021
-23 63
Wind direction – of wind toward center

17. Station model 80 021 -23 63 Wind speed Long barb = 10 knots
Short barb = 5 knots
Flag = 50 knots
** Notice range of wind speeds (i.e., knots)

18. Station model 80 021 -23 63 Sea level pressure
**If first number is 5 or greater, then place 9 in front
--Otherwise, place 10 in front
**Place decimal point between last two numbers

19. Station model 80
021
-23 63
Change in surface pressure during last 3 hours
** In tenths of mb
** Line describes how pressure changes over time from left to right

20. Example 1 76 953 +16 65 Temperature: 76 ºF Dew point: 65 ºF
Sky cover: Completely overcast
Current weather: Light rain
Wind direction and speed: Southwest at 15 knots
Sea level pressure: mb
Pressure tendency: Increase of 1.6 mb; rising steadily 76
953
+16 65

21. Example 2 10 105 -4 8 Temperature: 10ºF Dew point: 8ºF
Sky cover: 7/10 or 8/10
Current weather: Snow shower
Wind direction and speed: North at 3-7 knots
Sea level pressure: mb
Pressure tendency: Decrease of 0.4 mb; falling, then steady 10
105 -4 8

22. High & Low Pressure Systems
Air pressure Patterns are main organizing feature
Circulation in Northern Hemisphere
Clockwise around Highs (H)
CCW around Lows (L)
Clouds & Precip around Lows
Temperature patterns result from latitude, wind flow and cloud cover

23. Plotting Fronts
Boundary between Different Air Masses
Types of Fronts

24. Weather Maps

25. Weather Maps

26. Weather Maps

27. Weather Maps

28. Weather Maps

29. Weather Maps

30. Weather Maps

32. ENERGY THAT DRIVES THE STORMS
CHAPTER 2
ENERGY THAT DRIVES THE STORMS

33. ENERGY AND HEAT TRANSFER
Energy is the capacity to do work on some form of matter
Potential energy: The total amount of energy stored in any object is capable of doing
Kinetic energy: Any moving substance possesses energy of motion

34. Slower and closer together ….. Faster and farther apart
Cold Air vs. Warm Air
Air temperature is a measure of the aver­age speed of the molecules. In the cold volume of air, the molecules move more slowly and crowd closer together. In the warm volume, they move faster and farther apart.
Slower and closer together ….. Faster and farther apart
Fig. 2.1, p. 37

35. ENERGY AND HEAT TRANSFER
Atoms and molecules have kinetic energy due to their motion (heat energy)
Sun’s radiant energy most important
Air temperature is a measure of the average kinetic energy of its molecules

36. ENERGY AND HEAT TRANSFER
Heat = energy transferred because of a temperature difference
After heat is transferred, it is stored as internal energy
Heat is transferred in the atmosphere by
Conduction
Convection
Radiation

37. ENERGY AND HEAT TRANSFER
Latent heat: energy required to change a substance, such as water, from one state to another
Evaporation = cooling process, absorption of latent heat from the environment
Condensation = warming process, release of latent heat to the environment

38. Changes of State
Heat energy absorbed and released.
Fig. 2.2, p. 37

39. ENERGY AND HEAT TRANSFER
Conduction: the transfer of heat from molecule to molecule
Always flows from warmer to colder
Air is an extremely poor conductor of heat

40. ENERGY AND HEAT TRANSFER
Convection = heat transfer by the mass movement of a fluid (water or air)
Example: Pan of boiling water
Convection circulation: warm air expands and rises then cools and sinks
Thermal cell, convection, thermals

41. Thermal Circulations
The development of a thermal. A thermal is a rising bubble of air that carries heat energy upward by convection.
Fig. 2.5, p. 40

42. Thermal Circulations
The rising of hot air and the sinking of cool air sets up a convective circulation. Normally, the vertical part of the circula­tion is called convection, while the horizontal part is called wind. Near the surface the wind is advecting smoke from one region to another.
Fig. 2.6, p. 40

43. ENERGY AND HEAT TRANSFER
Radiation = Energy transfer via electromagnetic waves
Radiation and Temperature
Hotter objects
Emit shorter wavelengths
Emit radiation at a greater rate or intensity

44. Electromagnetic Radiation
Radiation characterized according to wavelength. As the wavelength decreases, the energy carried per wave increases.
Fig. 2.7, p. 41

45. ENERGY BALANCING ACT Radiation of the Sun and Earth
Sun (6000 K) emits mostly shortwave radiation
Earth emits mostly longwave radiation

46. SUN’S ELECTROMAGNETIC SPRECTRUM
The sun’s electromagnetic spectrum and some of the descriptive names of each region. The numbers underneath the curve approximate the percent of energy the sun radiates in various regions.
Mostly shorter wavelengths
Fig. 2.8, p. 44

47. Electromagnetic Radiation
SUN
EARTH
The hotter sun not only radi­ates more energy than that of the cooler earth (the area under the curve), but it also radiates the majority of its energy at much shorter wavelengths. (The area under the curves is equal to the total energy emitted, and the scales for the two curves differ by a factor of 100,000.)
Fig. 2.9, p. 44

48. ENERGY BALANCING ACT Selective Absorbers:
Good absorbers are good emitters at a particular wavelength, and vice versa.
Greenhouse effect: the atmosphere selectively absorbs infrared radiation from the Earth’s surface but acts as a window and transmits shortwave radiation

49. Atmospheric Absorption of Radiation
Absorption of radiation by gases in the atmosphere. The shaded area represents the percent of radiation absorbed by each gas. The strongest absorbers of infrared radiation are water vapor and carbon dioxide. The bottom fi gure represents the percent of radiation absorbed by all of the atmospheric gases. Visit the Meteorology Resource Center to view this and other Active figures at
Fig. 2.10, p. 46

50. A GREENHOUSE
Glass is transparent to short visible wavelengths (SW) but opaque to long infrared (LW) wavelengths.

51. w/o GREENHOUSE GASES

52. w/ GREENHOUSE GASES

53. ENERGY BALANCING ACT Greenhouse Enhancement
Global warming is occurring due to an increase in greenhouse gases
Carbon dioxide, methane, nitrogen oxide, chloroflourocarbons (CFCs), ozone
Positive feedbacks continue the warming trend.
Negative feedbacks decrease warming.

54. Positive Feedback
When the response in a second variable reinforces the change in the initial variable
Example of positive feedback:
Global temperatures increase
Increase in temperature melts the ice and snow in the upper latitudes
Loss of ice and snow results in a lower albedo at the surface in the upper latitudes
Lower albedo leads to less reflection and more insolation
More insolation results in warmer temperatures

55. Negative Feedback
When the response in a second variable lessens the change caused by the initial variable
Example of negative feedback:
Global warming leads to more atmospheric water vapor
Increased water vapor leads to increased cloud cover
Increased cloud cover leads to a higher albedo
Higher albedo results in less insolation at the surface
Reduced insolation at the surface leads to cooling

56. Solar Radiation
On the average, of all the solar energy that reaches the earth’s at­mosphere annually, about 30 per­cent (30/100) is reflected and scattered back to space, giving the earth and its atmosphere an albedo of 30 percent. Of the remaining solar energy, about 19 percent is absorbed by the atmosphere and clouds, and 51 percent is absorbed at the surface.
Fig. 2.13, p. 50

57. ALBEDO Percent of sunlight reflected from clouds and earth surfaces
Earth average albedo = 30%
Surface
Albedo (%)
Earth and Atmosphere 30
Clouds (Thick)
60-90
Clouds (Thin)
30-50
Fresh Snow
75-95
Ice
30-40
Sand
15-45
Grassy Field
10-30
Plowed Field
5-20
Water 10
Moon 7

59. Atmospheric Energy Balance
The earth-atmosphere energy balance. Numbers represent approximations based on surface observations and satellite data. While the actual value of each process may vary by several percent, it is the relative size of the numbers that is important.
Fig. 2.14, p. 51

60. Global Energy Balance
The average annual incoming solar radiation (yellow lines) absorbed by the earth and the atmosphere along with the average annual infrared radiation (red lines) emitted by the earth and the atmosphere.
Fig. 2.15, p. 52

61. ENERGY BALANCE

62. WHY THE EARTH HAS SEASONS
Earth revolves in elliptical path around sun every 365 days.
Earth rotates counterclockwise or eastward every 24 hours.
Earth closest to sun (147 million km) in January, farthest from sun (152 million km) in July.
Distance not the only factor impacting seasons.

63. Elliptical Orbit
The elliptical path (highly exaggerated) of the earth about the sun brings the earth slightly closer to the sun in January than in July.
Fig. 2.16, p. 52

64. Sun Angle
Sunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly. Oblique sun rays deliver less energy (are less in­tense) to a surface than direct sun rays. Visit the Meteorology Resource Center to view this and other active figures at www. cengage.com/login.
Fig. 2.17, p. 53

65. WHY THE EARTH HAS SEASONS
Energy reaching the earth’s surface, result of:
Distance from the sun
Solar angle
Length of daylight.
Earth tilted toward the sun:
Higher solar angles and longer days

66. Sun Angle
During the Northern Hemi­sphere summer, sunlight that reaches the earth’s surface in far northern latitudes has passed through a thicker layer of absorbing, scattering, and reflecting at­mosphere than sunlight that reaches the earth’s surface farther south. Sunlight is lost through both the thickness of the pure at­mosphere and by impurities in the atmosphere. As the sun’s rays become more oblique, these effects become more pronounced.
Fig. 2.20, p. 56

67. Sun and the Seasons
As the earth revolves about the sun, it is tilted on its axis by an angle of 23½°. The earth’s axis always points to the same area in space (as viewed from a distant star). Thus, in June, when the Northern Hemisphere is tipped toward the sun, more direct sunlight and long hours of daylight cause warmer weather than in December, when the Northern Hemisphere is tipped away from the sun. Visit the meteorology Resource Center to view this and other active figures at
Fig. 2.18, p. 53

68. WHY THE EARTH HAS SEASONS
Seasons in the Northern Hemisphere
Summer solstice: ~ June 21
Sun directly above Tropic of Cancer (23.5° N)
Longer days in N Hemisphere
Winter solstice: ~ December 21
Sun directly above Tropic of Capricorn (23.5° S)
Shorter days in N Hemisphere
Autumnal and Vernal Equinox: ~ Sep 22, Mar 20
Sun directly above Equator
All locations have a 12 hour day

69. Table 2.3, p. 57

70. Sun’s Seasonal Path
Stepped Art
Fig. 2.22, p. 58

71. Sun’s Seasonal Path
Land of the Midnight Sun. A series of exposures of the sun taken before, during, and after midnight in northern Alaska during July.
Fig. 2.19, p. 56

72. WHY THE EARTH HAS SEASONS
Seasons in the Southern Hemisphere
Opposite timing of N Hemisphere
Closer to sun in summer but not significant difference

74. ISOPLETHS

75. Contour Maps

76. Contour Maps

77. Contour Maps

78. ISOBARS

79. ISOTHERMS

80. ISOTACHS

81. ISOHYET

82. ISOPLETHS Connects all points that have the same value
Iso = equal (Greek)
Also called “Isolines”
Types
Isobar = pressure
Isallobar = pressure change per time
Isotherm = temperature
Isohyet = rainfall
Isonif = snowfall
Isoryme = frost incidence
isoneph = cloudiness
isotach = wind speed

83. ISOPLETHS (cont’d) Rules Only through exact value of isopleth
Higher side and lower side
All higher should be on the same side of the line
Draw for all values
Spacing by interpolation
Spacing indicates rate of change (I.e., gradient)
Isopleths form closed loops
Isopleth never cross one another

84. ISOPLETHS (cont’d) DRAWING HINTS
Note location of lowest and highest values
Begin around these low or high values and gradually work outward
Sketch lightly to get spacing and orientation of
Smooth the isopleths. Isopleths generally do not have sharp bends

85. ISOPLETHS
Draw 6.5 contour

86. ISOPLETHS

87. ISOPLETHS
Draw even contours

88. ISOPLETHS

89. ISOTHERMS
Draw 10, 20, 30,40, 50, 60, 70 degree contours

90. ISOTHERMS

91. Isodrosotherms

92. Isodrosotherms

93. Due next week (2/15/11) at the beginning of class.
HOMEWORK #4
Due next week (2/15/11) at the beginning of class.
Draw Isotherms at 10 degree intervals( i.e., 50, 60, 70, 80, 90 degrees).