1. Seasons and Atmosphere

2. Bell Ringer Start a new sheet of paper labeled Unit 2 Bell Ringers:
Create a circle map on what you know about Earth’s Rotation and Revolution

3. Revolution Motion of a body along a path around some point in space.
Earth’s orbit is elliptical
Earth’s distance from the sun varies
Perihelion
Earth is closest to the sun
147 million km away
Occurs on January 3rd
Aphelion
Earth is farthest from the sun
152 million km away
Occurs on July 4th 3

4. Rotation The turning or spinning of a body on its axis
Causes day and night
Two kinds of measurement
Mean Solar Day – time interval from one noon to the next (24 hours)
Sidereal Day – time it takes for Earth to make one complete rotation (360’) with respect to a star other than the sun (23 hours, 56 minutes, 4 seconds) 4

5. Seasons are caused by the tilting of the earth on its axis (23.5°)
When the Earth is tilted towards the Sun – warmer seasons
When the Earth is tilted away from the Sun – cooler seasons 5

6. Why do we have seasons?
Summer is warmer than winter because the Sun's rays hit the Earth at a more direct angle during summer than during winter

7. Seasons and days
The number of daylight hours is greater for the hemisphere, or half of Earth, that is tilted toward the Sun

8. Why do we have seasons?
The days are much longer than the nights during the summer.
During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.

9. The Atmosphere: Structure and Temperature

10. What is the Atmosphere
The gaseous portion of a planet
The planet’s envelope of air

11. Composition of the Atmosphere
78% Nitrogen (N2)
21% Oxygen (O2)
1% Other gases

12. Other Components Water Vapor Carbon Dioxide (CO2) Ozone (O3)
Most important gas for atmospheric processes
Source of all clouds and precipitation
Carbon Dioxide (CO2)
Absorbs energy given off by the Earth
Ozone (O3)
Absorbs harmful ultraviolet (UV) radiation from the sun

13. Layers of the Atmosphere
Divided into layers based on temperature
Rapidly thins as you travel away from Earth

14. Layer 1: Troposphere Bottom layer
Temperature decreases as altitude increases
Where weather occurs here, we live in it

15. Layer 2: Stratosphere
Temperature remains constant then slowly increases with height
Contains the ozone layer
Stratopause: boundary of the stratosphere

16. Layer 3: Mesosphere Layer 4: Thermosphere
Temperature decreases with height
Meteors occur here
Mesopause: boundary of the mesosphere
Layer 4: Thermosphere
Temperature increases with height
Thins out to space
Auroras occur here

17. Pressure Changes
As you increase in altitude, or travel away from Earth, pressure decreases

18. Temperature Changes
As you increase in altitude in the Troposphere the temperature decreases.
As you increase in altitude in the stratosphere, the temperature gradually increases.

19. Temperature: measure of the amount of heat
Heat: Is the energy transferred from one object to another because of a direct difference in their temperature
Temperature: measure of the amount of heat 19

20. Ways Heat Can be Transferred
Heat transfer from HOT to COLD objects
Conduction
Is the transfer of heat through matter by molecular activity
Transfer by touching

21. Convection
Is the transfer of heat by a mass movement or circulation within a substance
Radiation
Travels out in all directions
Solar energy reaches earth by radiation

22. What Happens to Solar Radiation? Reflection vs. Scattering
when light bounces off an object.
30 % of all radiation is reflected back to space
Scattering produces more rays that travel in many directions.

23. Absorption:
50 % of the solar energy that hits the top of the atmosphere reaches Earth’s surface
20% is absorbed in the clouds
30% is reflected back to space

24. Why Do Temperatures Vary?
Factors:
Land
Water
Altitude
Geographic position
Cloud cover
Ocean currents

25. Land and Water Temperatures
Land heats and cools more rapidly and to higher temperatures than water
Water – heats up longer and will keep the heat longer

26. Albedo Daylight Cloud Cover Nighttime Cloud Cover
Is the fraction of total radiation that is reflected by any surface
Daylight Cloud Cover
Temperatures lower than on a clear day
Clouds reflect radiation back to space
Nighttime Cloud Cover
Temperatures higher than on a clear night
Clouds absorb radiation from Earth, and send it back down

27. Isotherms – are lines on a weather map that connect points that have the same temperatures27

28. amount of water vapor in air.*

29. Instrument: Hygrometer
Psychrometer : a type of hygrometer consisting of two identical thermometers mounted side by side
Dry bulb: give the present air temperature
Wet bulb: has thin wet wick tied around the end *

30. What is Relative Humidity?
Is the ratio of the actual water vapor content compared with the amount of water vapor air can hold
Lowering air temperature causes an increase in relative humidity

31. What is Dew Point?
The temperature to which air would need to be cooled to be saturated.
If cooled past this point, water will condense

33. Clouds & Precipitation

34. Clouds form when air is cooled to its dew point as it rises
Cloud Formation
Clouds form when air is cooled to its dew point as it rises
Video: How Clouds Form

35. Clouds are classified on their form and height.

36. Classified By Form
Cirrus (cirrus = curl of hair) high, white, and thin
Cumulus (cumulus = a pile) rounded individual cloud masses that have a flat base and the appearance of rising domes or towers
Stratus (stratus = a layer) best described as sheets or layers that cover much or all of the sky

37. FOG
A cloud with its base at or very near the ground.

38. How does precipitation form?
For precipitation to form, cloud droplets must grow in volume by roughly one million times.

39. Forms of Precipitation
The type of precipitation that reaches Earth’s surface depends on the temperature profile in the lower few km of the atmosphere

40. Types of Precipitation
Rain: drops of water that fall from a cloud and have a diameter of at least 0.5 mm
Snow: light, fluffy, six-sided ice crystals
Sleet: fall of small particles of clear to translucent ice

41. Forms of Precipitation
Glaze: when raindrops become supercooled as they fall through subfreezing air and turns to ice when they impact objects
Hail: form of solid precipitation which consists of balls of irregular lumps of ice produced in cumulonimbus clouds 41