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# Understanding Weather

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### Understanding Weather

1. 1. Observe two glasses of water. One filled with ice water, and one filled with warm water. Why do water droplets form on the outside of the cold container? Where do the water beads come from? Why don’t the water beads form on the warm container?
2. 2.  Explain how water moves through the water cycle.  Describe how relative humidity is affected by temperature and levels of water vapor.  Describe the relationship between dew point and condensation.  List three types of cloud forms.  Identify four kinds of precipitation.
3. 3.  Weather is the condition of the atmosphere at a certain time and place.  The condition of the atmosphere depends on how much water is in the air.  Understanding weather starts with understanding how water cycles through the atmosphere.
4. 4.  The condition of the atmosphere is affected by the amount of water in the air. Water in liquid, solid, and gaseous states is constantly being recycled through the water cycle.  The water cycle is the continuous movement of water from sources on Earth’s surface into the air, onto and over land, into the ground, and back to the surface.
5. 5.  Humidity is the amount of water vapor in the air.  The air’s ability to hold water vapor changes as the temperature of the air changes.
6. 6.  Relative Humidity is the amount of water vapor in the air compared to the maximum amount of water vapor that the air can hold at a certain temperature.  Calculate the relative humidity by using the formula: actual water vapor content (g/m3) relative humidity (%) saturation water vapor content (g/m3)
7. 7.  Suppose that 1 m3 of air at a certain temp. can hold 24 g of water vapor. However you know that the air is currently holding 18 g of water vapor. What is the relative humidity?
8. 8.  Assume that 1 m3 of air at 25°C contains 11 g of H20(g). At this temperature, the air can hold 24 g/m3 of H20(g). Calculate the relative humidity.
9. 9.  A psychrometer is an instrument that is used to measure relative humidity. A psychrometer consists of two thermometers, one of which is a wet-bulb thermometer. The difference in temperature readings between the thermometers indicates the amount of water vapor in the air.
10. 10.  Condensation is the process by which a gas, such as water vapor, becomes a liquid.  The dew point is the temperature at which a gas condenses into a liquid.
11. 11.  A cloud is a collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs.
12. 12. 1. Warm air rises and cools 2. Relative humidity of the air increases 3. Air eventually becomes saturated 4. Water vapor condenses on small particles in the air 5. Millions of tiny water droplets collect to form a cloud.
13. 13.  Clouds are classified by form and altitude.  Cumulus clouds are puffy, white clouds that tend to have flat bottoms.  Stratus clouds are clouds that form in layers.  Cirrus clouds are thin, feathery, white clouds found at high altitudes.
14. 14.  Rain is the most common form of precipitation.  Sleet forms when rain falls through a layer of freezing air. Snow forms when temperatures are so cold that water vapor changes directly to a solid.  Hail are balls or lumps of ice that fall from clouds.
15. 15.  What is the water cycle?  How are humidity and temperature related?  How do clouds form and what are the different types?
16. 16.  Identify the four kinds of air masses that influence weather in the United States.  Describe the four major types of fronts.  Explain how fronts cause weather changes.  Explain how cyclones and anticyclones affect the weather.
17. 17.  Mr. Long will pour cooking oil (warm air mass) and water (cold air mass) into the container.  Make a prediction about what will happen when the two try to mix.  What happens when the liquids meet?  Was your prediction correct?  Using your results, hypothesize what would happen if a warm air mass met a cold air mass.
18. 18.  Changes in weather are caused by the movement and interaction of air masses.  An air mass is a large body of air where temperature and moisture content are constant throughout.  Air masses get their characteristics from where they form.
19. 19.  The characteristics of air masses are represent by two letter symbols on maps.
20. 20.  The area in which two types of air masses meet is called a front.  Cold Fronts A cold front forms where cold air moves under warm air, which is less dense, and pushes the warm air up.  Warm Fronts A warm front forms where warm air moves over cold, denser air.
21. 21.  Occluded Fronts An occluded front forms when a warm air mass is caught between two colder air masses. Normally brings cold weather and large amounts of rain or snow.  StationaryFronts A stationary front forms when cold and warm air masses meet. The air masses don’t have enough force to lift as normal. Usually this produces many days of cloudy, wet weather.
22. 22.  Cyclones are areas that have lower pressure than the surrounding areas do.  Anticyclones are areas that have high pressure.
23. 23.  What are 3 places in the US you would like to visit? What air masses commonly affect the weather there?  What type of weather is normally associated with each type of front?
24. 24.  Write a one-paragraph description of a thunderstorm. Describe the weather conditions immediately before, during, and after the storm. How does the storm affect each of your senses?
25. 25.  Describe how lightning forms.  Describe the formation of thunderstorms, tornadoes, and hurricanes.  Describe the characteristics of thunderstorms, tornadoes, and hurricanes.  Explain how to stay safe during severe weather.
26. 26.  Thunderstorms are small, intense weather systems that produce strong winds, heavy rain, lightning, and thunder.  They most often occur along cold fronts but only two atmospheric conditions are required to produce them  Warm moist air near Earth’s surface  Unstable atmosphere
27. 27.  Lightning is an electric discharge that occurs between a positively charged area and a negatively charged area. Thunderstorms are very active electrically.  Thunder is the sound that results from the rapid expansion of air along the lightning strike.
28. 28.  A tornado is a small, spinning column of air that has high wind speeds and low central pressure and that touches the ground.  A tornado starts out as a funnel cloud that pokes through the bottom of a cumulonimbus cloud and hangs in the air. The funnel cloud becomes a tornado when it makes contact with Earth’s surface.
29. 29.  Only about 1% of all thunderstorms produce tornadoes.  The US is home to about 75% of the world’s tornadoes.  They are most likely to occur during spring and early summer.
30. 30.  A hurricane begins as a group of thunderstorms moving over tropical ocean waters. Winds traveling in two different directions meet and cause the storm to spin.  Hurricanes can cause a lot of damage when they move near or onto land. Wind speeds of most hurricanes range from 120 to 150 km/h.
31. 31.  Thunderstorm Safety Lightning is one of the most dangerous parts of a thunderstorm. If you are outside, stay away from trees, which can get struck down. If you are in the open, crouch down.  Tornado Safety If there is a tornado warning for your area, find shelter quickly. The best place to go is a basement or cellar.
32. 32.  Flood Safety The best thing to do during a flood is to find a high place to wait out the flood.  Hurricane Safety If you live in an area where hurricanes strike, your family should have a disaster supply kit that includes enough water and food to last several days.
33. 33.  What is the relationship between lightning and thunder?  Why do hurricanes not form over land?  Tornadoes form from what type of cloud?
34. 34.  If you did not have the benefit of the weather forecast on the news, radio, or television, how would you forecast the weather?
35. 35.  Describe the different types of instruments used to take weather measurements.  Explain how radar and weather satellites help meteorologists forecast the weather.  Explain how to interpret a weather map.
36. 36.  Weather balloons carry electronic equipment that can measure weather conditions as high as 30 km above Earth’s surface.  Measuring Air Temperature and Pressure A tool used to measure air temperature is called a thermometer. An instrument used to measure air pressure is a barometer.
37. 37.  Wind direction can be measured by using a windsock or a wind vane.  An instrument used to measure wind speed is called an anemometer.  Radar is used to find the location, movement, and amount of precipitation. Weather satellites that orbit Earth provide images of weather systems.
38. 38.  The National Weather Service produces weather maps based on information gathered from about 1,000 weather stations across the United States.
39. 39.  Weather maps that you see on TV include lines called isobars. Isobars are lines that identify areas of equal, high, or low air pressure.
40. 40.  Whatdo each of the following instruments measure?  Anemometer  Windsock  Barometer  Thermometer
41. 41.  Allimages and content were taken from Holt, Rinehart, and Winston materials.