1. Pressure, Winds, and Precipitation

2. Heating the Earth Weather is the daily conditions of the atmosphere Weather is caused by the unequal heating of the Earth The factors that interact to cause weather are heat energy, air pressure, winds, and moisture

3. Heat Energy and the Atmosphere The Sun’s energy that is absorbed by the Earth is spread throughout the atmosphere, some is reflected back into space

4. Heat Transfer Radiation is the transfer of energy by waves such as light, UV rays hit the surface of the Earth and heat it up. Conduction is the direct transfer of heat energy from one substance to another, UV is changed into IR Convection is the transfer of heat energy in a fluid, hot air rises causing currents

5. The Greenhouse Effect Infrared light is absorbed by carbon dioxide, water vapor, and other gases in the atmosphere and forms a blanket that traps heat around the Earth.

6. Unequal heating of the Earth’s surface

7. Air Pressure Air pressure depends on the density of the air in a particular place Density is affected by temperature, water vapor, and elevation As temperature increases density decreases As water vapor increases density decreases As elevation increases density decreases

8. Measuring Air Pressure A barometer measures the pressure of the air

9. Air Pressure and Weather Low air pressure usually means stormy weather and high air pressure usually means fair weather

12. Winds Both local winds and global winds are caused by differences in air pressure due to unequal heating of the atmosphere Isobars that are closer together indicate stronger winds Winds travel from areas of high pressure to areas of low pressure

13. Measuring Wind Wind is measured by an anemometer for speed and a weather vane for direction

14. Local Winds Land and sea breezes

15. How they form…

16. Global Winds draw a big circle on your paper and fill in what we talk about each time.

17. Unequal heating of the Earth’s surface causes the global wind pattern Winds do not blow in a straight N to S or S to N pattern, they curve to the right in the Northern hemisphere and to the left in the Southern hemisphere due to the Coriolis effect, which is caused by the Earth’s rotation.

18. Doldrums are located at the equator where the winds are very calm because the air is warm and rises producing a low pressure belt (Low pressure means precipitation, what biome is found around the world at the equator?) Trade winds are from the equator to 30 degrees N and S where the warm equatorial winds cool and sink, winds are warm and steady high pressure

19. Horse latitudes are located about 30 degrees N and S, winds are calm with little precipitation (High pressure means no precipitation, what biome is found ar 30 around the world?) Prevailing westerlies are located between 30 and 60 degrees latitude Caused by cool sinking air moving toward the poles These westerly winds are usually strong

20. 60 degrees is a zone of low pressure Polar easterlies are cold, but weak winds caused by the rising and sinking of the westerlies N and S poles are high pressure

21. Jet Stream The jet stream is a narrow belt of strong, high speed, high pressure air that flows across, from west to east, the Earth

22. Moisture in the Air Water vapor or moisture in the air is called humidity Humidity can vary from place to place and time to time Water condenses at a point called the dew point

23. Relative humidity is the percent of moisture the air holds relative to the amount it could hold at a particular temperature Measuring humidity using a psychrometer that consists of 2 thermometers, one wet and one dry

24. Clouds Clouds form when moisture in the air condenses on small particles of dust or other solids in the air They are classified as to where they are found in the atmosphere

25. Cumulus clouds are white and puffy and indicate fair weather Cumulonimbus or thunderheads indicate thunderstorms with lightning and possibly tornadoes if the conditions are just right

26. Stratus are gray clouds that cover the whole sky. Day is mostly cloudy and can drizzle. Nimbostratus are gray clouds that cover the sky but are associated with drizzle and rain. Usually form in a warm front

27. Cirrus clouds are feathery clouds that are found very high in the atmosphere They are associated with fair weather, but rain or snow could come within the next 12-24 hours

28. Fog is formed when the temperature and the dew point temperature are the same.

29. Weather Patterns: Air Masses Changes in the weather are caused by very large areas of air with specific temperature and humidity called air masses There are four main air masses that affect the weather in the United States They are named for the regions they originate in

31. Maritime masses Maritime tropical air mass originates near the equator over the ocean, it brings warm moist air onto the continent Maritime polar air mass forms over the Pacific Ocean in both winter and summer, it forms over the North Atlantic and brings cold winter weather in the winter and cooler temperatures during the summer to the east coast

32. Continental masses The continental tropical forms over land in the Southwestern US it brings dry hot air The continental polar mass forms over the land in Canada and brings very cold dry air into the US

33. Fronts Fronts form when large air masses meet that have different temperatures and humidity The weather at a front is can be very unstable and stormy There are four different types of fronts: cold front, warm front, occluded front, and stationary front

35. Cold Front A cold front forms when a mass of cold air pushes over a mass of warm air The cold air pushes its way below the warm air Violent storms, even tornadoes can be associated with these front Fair, cooler, and drier air usually follows

36. Cold Front

37. Warm Front A warm front forms when a mass of warm air overrides a mass of cooler air Rain showers can accompany a warm front Hot and humid weather follows

39. Occluded Front When a very fast moving cold air mass overtakes a slower moving warmer air mass, an occluded front forms It produces less severe weather than a warm or cold front can

40. Stationary Front A stationary front is formed when a cold air mass and a warm air mass meet and do not move This produces several days of rain

41. High and Low Pressure Systems

42. High Pressure Some high pressure systems are associated with cold air systems that move in and change the weather Subtropical high pressure systems are slow moving, usually bring very warm conditions

43. Low Pressure Systems Low pressure systems are associated with precipitation and a change to the weather for an extended time Low pressure systems can bring rain or snow Low pressure systems can bring a sudden dramatic drop in temperatures

44. Predicting the Weather and Climates Just think the end is near!!!!

45. Predicting the Weather Meteorologist is a person who studies and predicts the weather They interpret weather information from local weather observers, balloons, satellites, and weather stations around the world

46. Weather Maps Data from stations around the country is gathered and put on weather maps This includes temperature, air pressure, precipitation, and the wind speed and direction Information about cloud cover, air masses, and fronts may be included The information is recorded by a number of symbols and numbers

47. Recording Weather Data

48. Isotherms and Isobars Isotherms connect points of equal temperatures Isobars connect points of equal pressure

49. Symbols

50. Controlling the Weather At the present time, weather control is limited to seeding of clouds This is done by placing dry ice or silver iodine crystals into the super cooled layers of the stratosphere These cause large ice crystals to form that eventually fall as rain