1. DO NOW Pick up notes and Review #21.
Get out your notes (#1-9) and Study Guide for Unit 8 so we can staple them together.
You turned in your article summary last Friday, right?!?

2. REVIEW
How does the angle of insolation affect the amount of energy a location received?
How does it affect the weather?

3. SUN AND SEASONS
SES5d. Describe how temperature and precipitation produce the pattern of climate regions (classes) on Earth.

4. Seasonal Variations in Solar Radiation
Insolation
Incoming Solar Radiation. 
The amount of solar radiation reaching a given place.

5. Seasonal Variations in Solar Radiation
Amount of insolation received is primarily controlled by:
Exposure time
Daily variation
Seasonal Variation
Latitude (Angle of Incoming Solar Radiation)
Daily Variation
Latitude Variation

6. REASON FOR THE SEASONS Earth tilts 23.5 degrees on its axis.
Different hemispheres receive more or less direct sunlight as Earth orbits the Sun.
Northern and Southern hemispheres seasons are reversed.

7. SEASONS As Earth orbits the Sun, the angle of the Sun changes.
Earth’s tilt on its axis causes seasons.
Summer – Sun higher in sky, more energy.
Winter – Sun lower in sky, less energy.

8. SEASONS

9. SEASONAL DIFFERENCES SUMMER WINTER Sun is higher in sky.
Increased angle of insolation.
Solar path is longer.
More solar energy
Sun is lower in sky.
Decreased angle of insolation.
Solar path is shorter.
Less solar energy

10. FIRST DAY OF WINTER/SUMMER:
WINTER SOLSTICE: Northern/Southern-most latitude of indirect sunlight.
Dec. 21 – Northern winter –longest nights, shortest days.
Farther away from the equator is the greater difference.
Sun’s position appears to rise/set in same place for about a week before changing direction.
SUMMER SOLTICE:
Northern/Southern most latitude of direct sunlight
June 21 – Northern summer – longest days, shortest nights.
Farther away from equator, greater difference.
Solstice means “stand still”

12. FIRST DAY OF SPRING: VERNAL EQUINOX
Sun’s rays direct on equator.
Equal day and night
Equinox means equal night.
Vernal Equinox - beginning of Spring (approx. March 21)

13. FIRST DAY OF FALL: AUTUMNAL EQUINOX
Autumnal Equinox - beginning of Fall (approx. Sept. 21).
No matter where you live on our planet, there are 12 hours of day and 12 hours of night.

14. SUNRISE CHANGES OVER THE YEAR

15. REVIEW Which season does each position in the diagram represent?
Which position would be the Vernal (spring) equinox?
Which position would be the Autumnal (fall) equinox?
2 - Spring
Summer
Spring
Winter
Fall
4 - Fall

16. Practical Applications
Why is length of photoperiod important for agriculture?
Why is angle of insolation important for solar energy panels?

17. LENGTH OF DAY VARIES BY SEASON
Winter = shorter days
Summer = longer days

18. LENGTH OF DAY VARIES BY SEASON
The farther north or south of the equator, the longer or shorter the days.
Spring and Fall = ALL places on Earth have 12 hours sun, 12 hours night.

19. PHOTOPERIODS Photoperiods: Photo = light Period = time
Amount of daylight on a given day
All places – 12 hours day and night on Equinoxes.
Farther away from equator has longer days in summer, shorter days in winter
Average yearly photoperiods = 12 hours for everywhere on Earth.

20. PHOTOPERIODS Commerce is at 34ºN – in the red band shown
Where are summer days longer?
Shorter?
How long are days on the Equinoxes?

21. Using Photoperiods to Determine Location
Summer Solstice
Cities farther north have longer days.
Cities farther south have shorter days.
Locations on the equator have 12 hours of day and night every day.
The farther the location is from the equator, the greater the difference.
Winter Solstice = opposite

22. Using Photoperiods to Determine Location
Summer Solstice Data:
City “A” has 14:23 hours of daylight.
City “B” has 9:57. hours of daylight
Which city is farther north? South?
Which city is ABOVE the equator?
Which city is BELOW the equator?

23. REVIEW You are standing at point A. What season is it? Summer Fall
Spring
Winter

24. REVIEW AGAIN!

25. LAB: MYSTERY CITIES

26. LAB: MYSTERY CITIES 16:21 7:55 CALCLATING PHOTOPERIOD: Method A
Change the sunset time for each location into military time by adding 12 hours.
Subtract – SUNSET – SUNRISE to determine photoperiod.
Remember to only add units of 6 when borrowing from hours to minutes! There are only six, 10 minute segments in each hour!
16:21
7:55

27. LAB: MYSTERY CITIES 7:39 to 5:33 CALCULATING PHOTOPERIOD: Method B
Calculate the number of hours from sunrise to sunset.
Then calculate the leftover minutes.
Put the photoperiods (#1 – 12) in order, from shortest photoperiod to longest in the ORDER column.
7:39 to 5:33

28. LAB: MYSTERY CITIES
Put the cities (A – L) in order, from the farthest north to the farthest south in the RANK column. Remember that as you go from north towards the equator, the latitudes will be smaller. As you continue farther south past the equator, the latitudes will be larger.

29. LAB: MYSTERY CITIES

30. LAB: MYSTERY CITIES
Finally, place the City letter in the column in your data table to match the city with the Location.

31. LAB: MYSTERY CITIES Homework
Do the same thing for the summer solstice.
Summer Solstice – farthest north is longest, south is shortest

32. Activity: Modeling the Seasons Lab
Purpose: To see how the Earth’s tilt and orbit around the Sun combine to produce seasonal variations in weather and climate.
Model the seasons
Answer the questions