Weather and Climate

1. Weather and Climate Chapter 17 and sections of Chapter 9

2. Atmosphere Composition • Mixture of gases- 78% Nitrogen, 21% oxygen, 1% other gases. • The biggest component of the other gases is carbon dioxide-.3%. • Oxygen and carbon dioxide are exchanged by photosynthesis and respiration.

3. Atmosphere Formation • The early atmosphere had mostly hydrogen and helium. NO OXYGEN! • Volcanoes blew those gases from the atmosphere and replaced with different gases which included carbon dioxide. • Photosynthesis began to convert carbon dioxide into oxygen.

4. Atmosphere Structure • The atmosphere is in 4 layers: troposphere, stratosphere, mesosphere, and exosphere • In the troposphere, the temperature decreases with altitude and all weather occurs here. • In the stratosphere, temperature increases with altitude and the ozone layer is in this layer.

6. atmosphere

7. The atmosphere is heated three ways: radiation, conduction, and convection Radiation- heating using electromagnetic waves. This is how the sun heats the atmosphere. Heating of the Atmosphere

8. Water in the Atmosphere • Water is present in all three states of matter: solid (ice), liquid (rain), and gas (vapor). • Water is transferred around the globe by the water cycle. • The water is controlled by the sun and gravity.

9. Precipitation Condensation Evaporation

10. Evaporation • The process where water is changed into a gas. • This process is a cooling process where the temperature will drop. • This puts water into the atmosphere. • Transpiration is how plants put water into the atmosphere.

11. Condensation • This process converts water vapor into a liquid. • This is a heating process. It gives off heat to the atmosphere. • This process makes clouds.

12. Precipitation • The joining of the condensed water molecules in the clouds to form drops. • When the drops get large enough, it rains, sleets, snows, hails, or a combination of these.

13. Cloud formation • There are 3 main types of clouds: • Cirrus- high clouds- wispy and feathery looking. Composed of ice • Cumulus- puffy clouds- usually form when warm air is forced upward. • Stratus- layered- form where warm and cool air meet.

14. Weather • Weather patterns result from global patterns of wind and pressure. • Global winds are caused by the heating and cooling of air. • The most important to the US are the westerlies (winds from the west) and the trade winds (winds from the east).

15. Westerlies bring weather from the Pacific side to the Atlantic side. • Trade winds move hurricane systems from east to west. • As part of these winds, high speed jet streams control much of the storm movement.

16. High and Low Pressure • Earth’s heating controls the pressure. • The areas of low pressure have a rainy climate, like the equator. • Areas of high pressure have dry climates like deserts.

17. Air Masses and Fronts • There are large masses of air above the land and the water. • North American Air Masses • These masses meet along front lines. • Each type of front has different weather patterns associated with it.

18. Types of Fronts • Cold- cold air pushes warm air up violently- Causes severe weather.

19. Warm front- warm air advances and gently moves over cold air- causes rain showers

20. Stationary- neither warm nor cold push past each other. Causes heavy rains.

21. Occluded- Where 2 cold air masses meet with warm air above. Causes rain.

22. Tornadoes

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

25. Causes of Climate • Latitude- distance from the equator helps determine temperature and amount of light • Temperature- average temp determines the types of plants that can survive • Distance from ocean- the closer to the water the more constant the climate. Affected by global winds

26. Precipitation- determines types of plants. Highest amounts at equator. • Mountains- most rain on side of the mountain that faces the wind. Air rises, cools and rains on that side.

27. Types of climates • Three major types: cold, semi-arid (dry), and arid

28. Climate Changes • Cycles of glaciations, called ice ages, represent long-term climatic change • Last ice age-18,000-22,000 years ago • Changes in Earth’s orbit are the most important factors, producing changes that determine the rhythmic cycles of glaciation.

29. Human Influences • Humans may be speeding up the process by releasing pollution that changes the climate faster than the cycle. • The excess carbon is from burning fossil fuels and removing vegetation. • Other gases like methane and nitrogen oxides are also released by humans.

30. Affects of human activities • Global warming- proposed theory that humans are increasing the natural rate of temperature change. Main cause carbon dioxide. • Ozone thinning- pollutants that destroyed ozone. These pollutants are now banned and the ozone layer is slowly recovering.

31. Explore Weather