1. Temperature and Humidity

2. How is heat distributed over the Earth’s surface
How is heat distributed over the Earth’s surface? How does this distribution change over the year?
Let’s see…

3. JANUARY
(oC )

4. FEBRUARY

5. MARCH

6. APRIL

7. MAY

8. JUNE

9. JULY

10. AUGUST

11. SEPTEMBER

12. OCTOBER

13. NOVEMBER

14. DECEMBER

15. JANUARY

16. 1. Heat is concentrated in the tropics (23. 5oN – 23. 5oS) 2
1. Heat is concentrated in the tropics (23.5oN – 23.5oS) 2. Heat shifts NORTH in the summer 3. In the winter months… 4. Earth is heated unequally…this causes changes in WEATHER!

17. Heat also moves across the surface on a daily basis
Heat also moves across the surface on a daily basis..the following maps show this! Describe what you see in the map sequence….

44. When the cold air (from Canada) meets the warm air…
WEATHER HAPPENS!!

45. Temperature is shown on maps with ISOTHERMS...lines of equal temperature. See the 70o isotherm below

46. Complete drawing the isotherms in your notes!!

47. Water vapor (moisture) in the air!
HUMIDITY
Water vapor (moisture) in the air!

48. How Does Water vapor get in the Air?

49. Where does the most EVAPORATION happen on Earth?
Warm air will absorb more moisture!

50. Measuring HUMIDITY
Water vapor mixes with air
Humid air weighs LESS than dry air!!
Warm air can hold more humidity than cold!

51. Relative Humidity
Relative Humidity: Amount of humidity in the air COMPARED to the maximum it could contain.
100% R.H. means air is saturated (very humid, rain)
Less than 10% humidity is a desert!
Relative humidity changes when temperature changes
When is R.H. usually highest? Lowest? See next slide!

53. Dew Point Temperature
Dew Point: the temperature at which condensation occurs (humidity turns to liquid)
When the AIR temperature is equal to the DEW POINT temperature…
Condensation Occurs
Dew forms on surfaces
Clouds form in the air
Fog forms in the air near the ground

55. Measuring DPT & Relative Humidity
Use charts on
Handy Dandy
ESRT
Page 12

56. The “Dry Bulb” Don’t let it fool you- - It is just a thermometer!
It measures the air temperature…
Dry bulb…
Is the air
temperature

57. The “Wet Bulb” Just a thermometer..
That has a little wet booty on the bulb
Gets cool when water evaporates
Wet Booty

58. Dry Air… A lot of moisture will evaporate from the booty…
The wet bulb will be a lot cooler than the dry bulb
20°C
8°C
Difference between wet bulb & dry bulb is 12 °C.

59. Dry Air… Use ESRT p12… What’s the Dew Point? -100C
LOW DPT means dry air!

60. A Humid Day… ONLY A little bit of moisture will evaporate…
The wet bulb will be close to the air temperature…
20°C
18°C
Difference between wet bulb & dry bulb is only 2°C

61. Humid air… Use ESRT p12… What’s the Dew Point? 170C
HIGHER DPT means HUMID air!

62. Relative Humidity Use ESRT p12… Dry Bulb = 20 Wet Bulb = 8
Difference between dry and wet = 12
What’s the RH?
20°C
8°C

63. Put it all together
20°C
8°C
20-8=12
Relative Humidity = 11%

64. Relative Humidity Use ESRT p12… Wet Bulb = 20 Dry Bulb = 18
Difference = 2
What’s the RH?
18°C
20°C

65. Put it all together
18°C
20°C
20-18=2
Relative Humidity = 82%

66. Summary Problems
Find the dew point and RH when the air temp is 3oC and the wet bulb temp is 2oC
Find the DPT and RH for when the air temp is 15oC and the wet bulb is 0oC