1. Atmosphere and Climate ChangeSection 1 Climate average weather conditions in an area over a long period of time. determined by factors that include: latitude, atmospheric circulation patterns, oceanic circulation patterns, the local geography of an area, solar activity, and volcanic activity. most important factor: distance from the equator

2. Atmosphere and Climate ChangeSection 1 Latitude: distance north or south from the equator, is expressed in degrees Equator at 0° latitude, most northerly latitude is the North Pole, at 90° north; most southerly latitude is the South Pole, at 90° south affects climate because the amount of solar energy an area of the Earth receives depends on its latitude.

3. Atmosphere and Climate ChangeSection 1 Low Latitudes (near equator) more solar energy falls on these areas night and day both about 12 hours year-round temperatures high year-round, no summers or winters

4. Atmosphere and Climate ChangeSection 1 High Latitudes (closer to poles) sun is lower in the sky, reducing the amount of energy arriving at the surface sunlight hits the Earth at an oblique angle and spreads over a larger surface area than it does at the equator temperatures lower than they are at the equator

5. Atmosphere and Climate ChangeSection 1 hours of daylight vary 45° N and S, as much as 16 hours of daylight during the summer ; 8 hours of sunlight in the winter Near poles, sun sets for only a few hours during the summer, rises for only a few hours during the winter –yearly temperature range very large

6. Atmosphere and Climate ChangeSection 1 Atmospheric Circulation Air circulation affects climate Cold air (denser than warm ) sinks, compresses and warms Warm air rises, expands and cools Warm air can hold more water vapor than cold air can. When warm air cools, the water vapor it contains may condense to form rain, snow, or fog.

7. Atmosphere and Climate ChangeSection 1 Solar energy heats the ground, warms the air above Warm air rises, cooler air moves in to replace it. This movement is called wind. Earth’s rotatation, energy differences N & S create pattern of global atmospheric circulation –circulation pattern determines precipitation pattern

8. Atmosphere and Climate ChangeSection 1 Ex: intense solar energy at the equator causes the surface and air above to become very warm –warm air can hold large amounts of water vapor –as it rises and cools, its ability to hold water is reduced, producing large amounts of rain

9. Atmosphere and Climate ChangeSection 1 Global Circulation Patterns Cool air over the equator cannot descend because hot air is rising up below it. Forced away, accumulates at about 30º N & S –Some sinks becomes warmer. This warm, dry air then moves across the land, causes water to evaporate from the land, creating dry conditions.

10. Atmosphere and Climate ChangeSection 1 At about 60º N & S air from equator air collides with cold air from the poles –the warm air rises, most forced toward the poles –cold, dry air descends –poles essentially very cold deserts

11. Atmosphere and Climate ChangeSection 1 Prevailing Winds, (Belts) Winds that blow predominantly in one direction throughout the year Because of the Earth’s rotation not directly northward or southward –deflected right, from northeast, Northern Hemisphere –deflected left, from southeast, Southern Hemisphere

12. Atmosphere and Climate ChangeSection 1 Belts produced between 30º N & S latitude and the equator, trade winds Belts produced between 30º and 60º N & S, westerlies Belts produced between poles to 60º N & S, easterlies

13. Atmosphere and Climate ChangeSection 1 Oceanic Circulation Ocean currents have a great effect on climate because water holds large amounts of heat. –surface currents caused mostly by winds, Earth’s rotation –redistribute warm and cool masses of water around the world

14. Atmosphere and Climate ChangeSection 1 El Niño–Southern Oscillation (ENSO) El Niño: warm phase periodic occurrence in eastern Pacific Ocean when surface-water temperature becomes unusually warm winds in the western Pacific Ocean, strengthen, push warm water eastward rainfall increased southern half of U.S., drought in Australia.

15. Atmosphere and Climate ChangeSection 1 La Niña: cool phase periodic occurrence in the eastern Pacific Ocean when surface water temperature becomes unusually cool El Niño and La Niña are opposite phases of cycle.

16. Atmosphere and Climate ChangeSection 1 Pacific Decadal Oscillation (PDO) Long-term, (20 to 30 year) change in location of warm and cold water masses in the Pacific Ocean –influences climate in the northern Pacific Ocean, N.A. –affects ocean surface temperatures, air temperatures, and precipitation patterns

17. Atmosphere and Climate ChangeSection 1 Topography Height above sea level (elevation) has an important effect on climate. Temperatures fall by about 6°C (about 11°F) for every 1,000 m increase in elevation. Mountain ranges also influence the distribution of precipitation. –rain on the western side, eastern side dry –effect known as a rain shadow.

18. Atmosphere and Climate ChangeSection 1 At a solar maximum, increased amount of ultraviolet (UV) radiation –produces more ozone, which warms the stratosphere –can also warm the lower atmosphere, surface a little Large-scale volcanic eruptions produce sulfur dioxide gas that can reach the upper atmosphere. –can remain in the atmosphere for up to 3 years –reacts with water vapor and dust to form a bright layer of haze that reflects enough sunlight to cause a global temperature decrease Other Influences on Earth’s Climate

19. Atmosphere and Climate ChangeSection 1 Seasonal Changes in Climate The seasons result from the tilt of the Earth’s axis, about 23.5° relative to the plane of its orbit –the sun’s rays strike the Earth at different angles as the Earth orbits the sun

20. Atmosphere and Climate ChangeSection 1 Seasonal Changes in Climate Summer, Northern Hemisphere, earth tilts toward the sun and receives direct sunlight. –hours of daylight greatest –Southern Hemisphere tilts away from the sun, receives less direct sunlight (their winter)