1. 17.1 Climate and its causes

2. Learning Targets
Describe the effect of latitude on climate
Diagram the Hadley, Ferrell, and Polar atmospheric circulation cells and show how they influence the climate of various locations
Discuss position in the global wind belts, proximity to a large water body, position relative to a mountain range

3. Climate Climate is the long-term average of weather
Weather is unpredictable
Climate is predictable

4. Climate Factors influencing region’s climate: Latitude
Three Global Wind Belts
Prevailing Winds
Continental Position
Ocean Currents
Altitude

5. Factor # 1 - Latitude The main factor influencing region’s climate
Low latitude = high solar energy
Equator
Sun directly overhead; equal night and day
High latitude = low solar energy
Poles
Sun at low angle; long days, long nights
High albedo
What is latitude?
The amount of solar energy a particular location receives is the most important factor in determining that location’s temperature.
Tropics are warmer and polar regions are colder. Temperate regions are in between, both in latitude and average air temperature.

7. Factor # 2 – Global Wind Belts #1
ITCZ – Intertropical Convergence Zone
Low Pressure boundary between two Hadley Cells, lots of precipitation.
Equator 00 - Doldrums
Areas where air mostly rises or sinks creates no wind.
ITCZ migrates north in Northern Hemisphere summer, because there are more land areas than in Southern Hemisphere

8. The ITCZ migrates slightly with the season
The ITCZ migrates slightly with the season. Land areas heat more quickly than the oceans. Since there are more land areas in the Northern Hemisphere, the ITCZ is influenced by the heating effect of the land. In Northern Hemisphere summer, it is approximately 5 o north of the equator while in the winter, it shifts back and is approximately at the equator. As the ITCZ shifts, the major wind belts also shift slightly north in summer and south in winter, which causes the wet and dry seasons in this area

9. Factor # 2 – Global Wind Belt #2
Hadley and Ferrell Cell Boundary
High Pressure – sinking cold air causing evaporation
Horse latitudes N/S
Areas where air mostly rises or sinks creates no wind.
Where did all the moisture go at the Hadley and Ferrell Cell Boundary?

10. Factor # 2 – Global Wind Belt #3
Ferrell and Polar Cell Boundary
Polar jet stream – cold air from poles meet warmer air from tropics, very stormy
500 to 600 N/S latitude
Areas where air mostly rises or sinks creates no wind.
As Earth orbits the Sun, the shift in angle of incoming sunlight causes polar jet stream to move.

11. Factor # 3 - Prevailing Winds
Global wind belts create H and L zones
Bring weather from locations they come from
H  Dry
Cold air descending causes evaporation
L  Wet
Warm air rising and losing its water

12. Where are low pressures located in regards to the three global convection cells? At equator between the 2 Hadley cells & 60 degrees where Ferrel and Polar cells meet. (warm and rainy)
Where is the high pressure? 30 degrees where Hadley and Ferrel cells meet, areas where deserts are located such as Sahara and Sonora. (cooler and drier)
ITCZ – Intertropical Convergence Zone - air rises up at the equator and then travels away from the equator. As the air rises, it cools and condenses to create clouds and rain. Climate along the ITCZ is therefore warm and wet. In an area where the air is mostly rising, there is not much wind.

13. Due to Coriolis Effect – winds are deflected to right.

14. high pressure zone where the Hadley cell and Ferrell cells meet, air is fairly warm since much of it came from the equator. It is also very dry for two reasons: (1) The air lost much of its moisture at the ITCZ, and (2) Sinking air is more likely to cause evaporation than precipitation.
low pressure zone is between the Ferrell and Polar Cells at around 50-60o. This is the usual location of the polar jet stream, where cold air from the poles meets warmer air from the tropics and storms are common.

15. Factor # 4 - Continental Position
Water regulates air temperature
Higher specific heat than land
Maritime climate – influenced by nearby large body of water
Less extreme
Continental climate – greater temperature differences between day/night & summer/winter
More extreme
Maritime climate its climate is strongly influenced by the nearby sea: summers are not too hot and winters are not too cold. Temperatures also do not vary much between day and night.
Continental climate is more extreme, with greater temperature differences between day and night and between summer and winter.

16. What this means is that it takes 4
What this means is that it takes Joules of heat to raise 1 gram of water 1 degree Celsius.

17. cities is located at 37°N latitude within the westerly winds (prevailing winds)

18. Factor # 5 - Ocean Currents
Surface and deep water currents affect air temperatures along the coast
Cold water moves towards the equator
California current cools Southern California
Warm water moves towards the poles
Gulf stream warms Northern Europe
Cold upwelling can cool or heat surrounding land
Coastal upwelling also brings cold, deep water up to the ocean surface off of California, which contributes to the cool, coastal temperatures. Further north, in southern Alaska, the upwelling actually raises the temperature of the surrounding land because the ocean water is much warmer than the land.

19. One portion flows northward between Great Britain and Northern Europe, the other moves south along Europe and northern Africa. These warm waters raise temperatures in the North Sea, which raises air temperatures over land between 3 to 6oC
Because air traveling over the warm water in the Gulf Stream picks up a lot of water, London gets a lot of rain.

20. Other ocean currents

21. Factor # 6 - Altitude Mountains affect climate by Lowering temperature
Temperature decreases with altitude in the troposphere
Rainshadow Effect
Air is dry after it has been forced over mountains  no precipitation
e.g. California compared to Nevada
Gravity pulls air molecules closer together at sea level than at higher altitudes. The closer molecules are packed together, the more likely they are to collide. Collisions between molecules give off heat, which warms the air. At higher altitudes, the air is less dense and air molecules are more spread out and less likely to collide.