Atmospheric pressure is greatest near the Earth ’ s surface because

1. Solar Radiation CHECK YOUR NEIGHBOR Atmospheric pressure is greatest near the Earth’s surface because of the weight of all the air above. 90% of Earth’s atmosphere is in the troposphere. of warmer temperatures. of water vapor.

2. Solar Radiation CHECK YOUR ANSWER Atmospheric pressure is greatest near the Earth’s surface because of the weight of all the air above. 90% of Earth’s atmosphere is in the troposphere. of warmer temperatures. of water vapor.

3. Solar Radiation CHECK YOUR NEIGHBOR The “ozone hole” is considered to be a problem, because ozone is a pollutant that creates smog. depleted from the stratosphere contributes to an increase of harmful UV rays at Earth’s surface. is detrimental to life on Earth. at the troposphere contributes to skin cancer.

4. Solar Radiation CHECK YOUR ANSWER The “ozone hole” is considered to be a problem, because ozone is a pollutant that creates smog. depleted from the stratosphere contributes to an increase of harmful UV rays at Earth’s surface. is detrimental to life on Earth. at the troposphere contributes to skin cancer.

5. Climate Zones The world is divided into different climate zones. Temperatures are: • Highest in the tropics, near the equator • Lower nearer the poles • Moderate and variable in the temperate zone

6. Temperature Depends on Latitude Why does the temperature depend on latitude? Latitude affects temperature because the Sun’s rays strike different latitudes at different angles.

7. Temperature Depends on Latitude When the Sun’s rays strike a surface at right angles, the rays strike the smallest possible area. They are the most concentrated at this angle and have maximum solar intensity. Solar intensity – solar radiation per area.

8. Temperature Depends on Latitude Which climate zone would have the highest solar intensity? Tropical

9. Temperature Depends on Latitude Which climate zone would have the lowest solar intensity? Polar

10. Temperature Depends on Latitude Temperate climate zones have a moderate solar intensity. Tropical Temperate Polar

11. Days and Years Earth’s revolution (orbit) around the Sun determines the length of a year (365 days). • Earth’s rotation on its axis determines day length—24 hours in each day. • The number of daylight hours varies during the year depending on latitude.

12. Why Are There Seasons? When the Sun’s rays are closest to perpendicular at any spot on the Earth, that region’s season is summer. Six months later, as the rays fall upon the same region more obliquely, the season is winter. In between are the seasons fall and spring.

13. Why Are There Seasons? Variation in solar intensity with latitude and the tilt of the Earth’s axis helps to explain the different seasons. • The combination of more direct rays and longer days creates the warmth of summer.

14. Why are There Seasons? At the summer solstice (June 21st),locations north of the Arctic Circle in the Northern Hemisphere have ~24 hours of daylight. At the winter solstice (December 22nd), locations north of the Arctic Circle have ~24 hours of night. In the Southern Hemisphere, the Antarctic Circle, the seasons are reversed (summer solstice is in December).

16. CHECK YOUR NEIGHBOR On the fourth of July in Kansas City, Missouri, the season is _________. On the fourth of July in Perth, Australia, the season is ___________. • winter; spring • summer; fall • summer; winter • winter; summer

17. CHECK YOUR ANSWER On the fourth of July in Kansas City, Missouri, the season is _________. On the fourth of July in Perth, Australia, the season is ___________. • winter; spring • summer; fall • summer; winter • winter; summer

18. Flow of the Atmosphere - Wind If you puncture a tire or a balloon, you can hear and feel the air escaping. Why does the air rush out of the balloon and tires? • Air moves naturally from a region of high pressure to a region of low pressure. Wind is air that flows horizontally from higher pressure to lower pressure. Larger differences in air pressure produce stronger, faster winds.

19. Flow of the Atmosphere - Wind

20. What Causes Differences in Air Pressure? • Pressure differences are caused by uneven heating of the Earth’s surface. Warm air characteristics: • Warm air expands • Warm air has lower density and lower pressure • Cool air characteristics: • Cool air contracts • Cool air has higher density and higher pressure

21. Local Winds • Not all surfaces are heated equally. Example: Land heats and cools more rapidly than water. • Unequal heating results in pressure differences. And pressure differences result in wind. • Remember: Wind is air that flows horizontally from higher pressure to lower pressure. Which way to does the sea breeze blow and why? Animation of Sea Breeze

22. Global Winds • Global Winds: • Planet-scale differences occur because of solar intensity variations—equatorial regions have greater solar intensity than polar regions. • Differences contribute to global wind patterns—prevailing winds.

23. The Coriolis Effect Earth’s rotation greatly affects the path of moving air. • Coriolis effect: moving bodies (such as air) deflect to the right in the Northern Hemisphere, to the left in the Southern Hemisphere. • Deflection of wind varies according to speed and latitude. • Faster wind, greater deflection • Deflection greatest at poles, decreases to zero at equator

25. CHECK YOUR NEIGHBOR The prevailing westerly winds are affected by the Coriolis effect by the deflection of winds to the right in the Northern Hemisphere and left in the Southern Hemisphere. to the left in the Northern Hemisphere and right in the Southern Hemisphere. laterally toward the poles. westward.

26. CHECK YOUR ANSWER The prevailing westerly winds are affected by the Coriolis effect by the deflection of winds to the right in the Northern Hemisphere and left in the Southern Hemisphere. to the left in the Northern Hemisphere and right in the Southern Hemisphere. laterally toward the poles. westward. Explanation: Winds are named for the direction from which they blow. Westerlies blow from the west to the east.

27. Circulation of the Atmosphere Summary Factors that affect wind: • The pressure gradient force: air moves from high pressure to low pressure • The Coriolis effect: apparent deflection of winds due to Earth’s rotation • Frictional force: air moving close to ground encounters friction • Surface friction reduces wind speed, which reduces the effect of Coriolis.

28. Oceanic Circulation: Currents • Ocean currents are streams of water that move, relative to the larger ocean. • Surface currents are created by wind. • Surface ocean currents correspond to the directions of the prevailing winds.

29. Oceanic Circulation: Currents Factors that influence ocean currents: • For short distances, wind is strongest factor • For longer distances, Coriolis effect comes into play: • Coriolis causes surface currents to turn and twist into semicircular whirls called gyres. • Northern Hemisphere gyres rotate clockwise. • Southern Hemisphere gyres rotate counterclockwise.

30. Oceanic Circulation: Currents • Surface currents redistribute Earth’s heat. • The Gulf Stream current carries vast quantities of warm tropical water into higher latitudes. • Great Britain and Norway have warmer winter temperatures (for their latitude) because of the Gulf Stream.

32. Water in the Atmosphere • Water vapor is water in the gaseous phase. • Water vapor in the atmosphere produces humidity, clouds, and precipitation.

33. Humidity • Humidity is the mass of water vapor a given volume of air contains. • There is always some water vapor in the air.

34. Humidity • Air that contains as much water vapor as it possibly can is saturated. • Warm air holds more water vapor than cold air. • As air cools, it holds less and less water vapor. • Saturation can occur when air temperature drops, causing water vapor to condense. • Saturation and condensation are more likely in cold air—slower-moving molecules.

35. Humidity • Dew point is the temperature at which saturation occurs. • Condensation occurs when the dew point is reached. • Water vapor condenses high in the atmosphere and forms clouds. • Water vapor condenses close to the ground surface to form dew, frost, and/or fog.

36. Clouds • Cloud - visible aggregate of minute water droplets or tiny ice crystals. • How do clouds form? • Clouds form as moist, warm air rises, then cools to its dew point and water vapor condenses. • Solid particles must be present for the water molecules to condense on.

37. Precipitation • Precipitation – water in the liquid or solid phase that returns to Earth’s surface from the atmosphere. • Rain, snow, sleet, hail, and mist.