Chapter: Weather and Climate

2. Table of Contents Chapter: Weather and Climate Section 1: Earth’s Atmosphere Section 2: Weather Section 3: Climate Section 4: Earth’s Changing Climates

3. Earth’s Atmosphere 1 Atmospheric Composition • Air is a mixture of gases. Nitrogen is the largest component with 78 percent and oxygen is next with 21 percent by volume. Most of the remaining one percent is the inactive gas argon and water vapor. • The remaining portion is a mixture of trace gases, so called because they are present in such small, barely detectable amounts.

4. Earth’s Atmosphere 1 Biological Processes • Cellular respiration by organisms produces water vapor and carbon dioxide (CO2). • Photosynthetic organisms use carbon dioxide and produce almost all the oxygen in the atmosphere.

5. Earth’s Atmosphere 1 Biological Processes • Microorganisms in swamps, rice paddies, and soil produce nitrogen and methane. • The microorganisms in the digestive tracts of animals such as termites, cows, and sheep produce methane.

6. Earth’s Atmosphere 1 Formation of the Atmosphere • Earth’s early atmosphere contained mostly hydrogen and helium. • These gases were lost and were replaced by gases from volcanic eruptions. • Oxygen from photosynthetic marine organisms accumulated in the atmosphere and intense solar radiation converted some of it into ozone.

7. Earth’s Atmosphere 1 Atmospheric Structure • Earth’s atmosphere extends more than 1,000 km above earth’s surface. • Most of our weather takes place within the troposphere, a layer extending 30 km above Earth’s surface. • In this layer temperature normally decreases with height. • Sometimes, however, temperature increases with height. This is called a temperature inversion.

8. Earth’s Atmosphere 1 Atmospheric Structure • Above the troposphere is the stratosphere, which is extremely dry and rich in ozone. • Here, temperature always increases with height, creating a permanent temperature inversion.

9. Earth’s Atmosphere 1 Atmospheric Structure • The place where this temperature inversion begins is called the tropopause.

10. Earth’s Atmosphere 1 Heating the Atmosphere • The energy that heats the atmosphere ultimately comes from the Sun. • Ozone absorbs nearly all of the sun’s ultraviolet radiation. • As Earth’s surface is heated, it emits long-wave, infrared radiation.

11. Earth’s Atmosphere 1 Heating the Atmosphere • Trace gases, such as carbon dioxide and water vapor, absorb long wavelengths and re-emit some of them back to Earth’s surface. • The term greenhouse effect refers to this re-emission of infrared radiation back to Earth’s surface.

12. Earth’s Atmosphere 1 Heating the Atmosphere • Latent heat is heat energy released or absorbed during the phase changes of water, such as evaporating water or melting snow.

13. Earth’s Atmosphere 1 Water in the Atmosphere • Cloud formation is the first step in the precipitation process. • Cumulus clouds form from rising air parcels. • Stratus-type clouds form mainly when layers of air rise gently.

14. Earth’s Atmosphere 1 Water in the Atmosphere • For precipitation to occur, droplets must grow large. • Growth can occur when droplets collide and combine.

15. Earth’s Atmosphere 1 Global Water Cycle • Precipitation, runoff, storage, and evaporation make up the global water cycle.

16. Section Check 1 Question 1 Air can be described as a _______. A. combination of elements B. compound C. mixture D. solution

17. Section Check 1 Answer The answer is C. Air is a mixture of gases; including nitrogen, oxygen, and water vapor.

18. Section Check 1 Question 2 Temperature _______ with height in the troposphere. A. decreases B. doubles C. increases D. stays the same

19. Section Check 1 Answer The answer is A, decreases.

20. Section Check 1 Question 3 Which cloud type is an example of a low cloud? A. altostratus B. cirrocumulus C. cirrostratus D. cumulus

21. Section Check 1 Answer The answer is D. Cumulus clouds form from rising air parcels. If they produce rain, it is usually only brief showers.

22. Weather 2 Atmospheric Pressure Global Winds and Pressure Systems • Weather patterns result from complex global patterns of wind and pressure. • The most important of these are the westerlies—winds that blow from the west in the middle latitudes—and the trade winds, which blow from the east, in the tropics.

23. Weather 2 Global Winds and Pressure Systems • Two factors produce these global patterns—unequal heating between the equator and poles and the rotation of Earth.

24. Weather 2 Global Winds and Pressure Systems • Imbedded in these wind systems are fast and powerful jet streams.

25. Weather 2 High and Low Pressure Systems • Subtropical highs are relatively stable belts of high pressure near latitudes of 30°. • Sub-polar lows and the westerlies tend to meander as smaller cells of high and low pressure develop. • The lows generally develop from a disturbance in the polar front jet and move eastward with the jet stream.

26. Weather 2 Air Masses and Weather Fronts • Air masses can be polar or tropical and continental or maritime. • Air masses interact in zones called weather fronts. • Warm and cold fronts create different types of precipitation.

27. Weather 2

28. Weather 2 Severe–Weather Thunderstorms • A typical cumulonimbus cloud has ice crystals near its top.

29. Weather 2 Severe–Weather Thunderstorms • Sometimes these ice crystals act as nuclei to trigger further growth of cloud droplets. • This forms hail.

30. Weather 2 Downdrafts and Squalls • The force of the falling precipitation in a thunderstorm may pull with it cold air bursts from higher in the cloud. • This sinking current of cold air is called a downdraft. • When a downdraft hits the surface with particularly strong force, it spreads out in a series of windy gusts called squalls.

31. Weather 2 Downbursts • Cold air descends from a thunderstorm and hits the ground. • When it hits the ground, it bursts outward like the spokes on a wheel.

32. Weather 2 Tornadoes and Hurricanes • Tornadoes are intense, short-lived localized storms in the mid-latitudes. • This map shows where tornadoes frequently occur.

33. Weather 2 Tornadoes and Hurricanes • A twisting, funnel-shaped tornado cloud can move across land at a speed of around 50 km/h. • Intense, circular winds in the funnel can reach speeds up to 400 km/h.

34. Weather 2 Tornadoes and Hurricanes • Hurricanes are tropical storms that cover vast areas and last for days. • When winds exceed 118 km/h, the storms are called hurricanes.

35. Section Check 2 Question 1 What causes the atmospheric pressure on your body? A. air pockets B. gas molecules moving and colliding C. gravity D. Earth’s rotation

36. Section Check 2 Answer The answer is B. The number of air molecules decreases as altitude increases so pressure always decreases with altitude.

37. Section Check 2 Question 2 Which produces showers and thunderstorms? A. cold front B. occluded front C. stationary front D. warm front

38. Section Check 2 Answer The answer is A. In a cold front, air pushes the warm air aloft in a random and chaotic fashion, forming cumulus clouds.

39. Section Check 2 Question 3 Where would you be least likely to experience a tornado? A. Kansas B. New York C. Oklahoma D. Texas

40. Section Check 2 Answer The answer is B. Tornadoes are more common in the Great Plains, lower Midwest, and parts of the south.

41. Climate 3 Climate and Weather • Climate means the long-term average of weather conditions—wind, temperature, precipitation, moisture, and other aspects of weather.

42. Climate 3 Climate System • This biogeophysical system can be visualized as five spheres that interact to create the environments in which we live.

43. Climate 3 Climate System • The biosphere is everything organic. • The hydrosphere is liquid water. • The cryosphere is frozen water in snow, ice, and glaciers. • The lithosphere is the solid Earth.

44. Climate 3 What causes climate? • Latitude is the primary factor that determines climate at a given location. • The amount of radiation received from the Sun and the prevailing circulation features depend on latitude.

45. Climate 3 Causes of Mean Temperature • In the winter, the amount of solar radiation varies, because of the low angle at which it strikes Earth.

46. Climate 3 Causes of Mean Temperature • In summer, sunlight strikes at a higher angle and periods of daylight are longer.

47. Climate 3 Causes of Mean Temperature • The strong temperature gradients in winter and spring help to create storms and severe weather.

48. Climate 3 Ocean and Land Influence • Areas with little direct ocean influence are called continental climates and have steep temperature gradients. • A climate with strong ocean influence is called a maritime climate.

49. Climate 3 Precipitation • Wind and pressure patterns determine precipitation.

50. Climate 3 Influence of Mountains • Mountains act as barriers in the wind, blocking weather systems and altering patterns of precipitation. • When the wind blows perpendicular to one side of a mountain range, a lee rain shadow forms on the opposite side.