Atmosphere and Weather Unit Study Guide

1. What is the most abundant gas in the atmosphere? Nitrogen (78%) 2. List the layers of the atmosphere. Troposphere, Stratosphere, Mesosphere, Thermosphere 3. Most important weather phenomena occur in the ____. Troposphere 4. Fifty percent of the gases that make up the atmosphere are found below ____ km. 5.8 5. Which gas is most important for understanding atmospheric processes? Water vapor 6. Rain, snow, sleet, and hail are all examples of ____. Precipitation 7. Which substance can change from one state of matter to another at the temperatures and pressures experienced at Earth’s surface? Water 8. The change of state from a gas to a liquid is called ____. Condensation 9. Air that has reached its water-vapor capacity is said to be ____. Saturated 10. Which type of air can hold more water vapor? 11. The ratio of air’s water-vapor content to its capacity to hold water vapor at that same temperature is the ____. Relative humidity 12. ____ the temperature to which air would have to be cooled to reach saturation. Dew point 13. The force exerted by the weight of the air above is called ____. Air pressure 14. Which instrument is used to measure air pressure? Barometer 15. What is the ultimate energy source for most wind? Solar radiation 16. The lines on the weather map that connect points of equal pressure are ____. Isobars 17. Closely spaced lines of pressure indicate ____. Widely spaced isobars indicate ____. High wind; low wind 18. Variations in air pressure from place to place are the principal cause of ____. Wind 19. The Coriolis effect influences wind ____. Direction 20. In the Northern Hemisphere, winds associated with a low-pressure system blow ____. Counterclockwise 21. In the Northern Hemisphere, winds associated with a high-pressure system blow ____. Clockwise 22. Fair weather can usually be expected with the approach of a _____ pressure system. High 23. The general movement of low-pressure centers across the United States is from ____. West to East 24. Which instrument is used to measure wind speed? Anemometer 25. Which two properties characterize an air mass? Temperature and moisture 26. An air mass gets its characteristic properties from an area known as the ____. region 27. Which type of air mass originates in northern Canada? Continental polar 28. Maritime air masses form over ____. Water 29. An mT air mass is best described as ____. Warm and moist 30. Which air masses have the greatest effect on weather conditions in much of the United States? Continental polar and maritime tropical 31. Which air mass is the source of much of the precipitation in the central and eastern United States? mT 32. The boundary that separates different air masses is called a(n) ____. Front 33. On a weather map, which type of front is shown by a line with triangular points on one side? Cold front 34. What type of front forms when the surface position of the front does not move? Stationary front 35. Along a front, which type of air is always forced upwards? Warm air 36. The weather behind a cold front is dominated by what? Strong thunderstorms 37. What type of front usually produces several hours of light-to-moderate precipitation over a large region? Warm front 38. Thunderstorms form when warm, humid air rises in a(n) ____. Unstable environment 39. The center of a tornado is characterized by its ____. Rotating column of air (vortex) 40. Tornadoes are most frequent from ____.June - Sept 41. What causes a hurricane to lose energy when it moves onto land? Lack of warm water to fuel it.

Essay (You will be asked to choose two of the four essay questions to answer on the test. Be prepared!)

45. Describe the formation of the four types of fronts and the weather associated with each. A warm front occurs when warm air moves into an area previously occuplied by cold air. Warm fronts bring gentle rains. A cold front forms when cold air moves into an area previously covered by warm air. Cold fronts bring heavy rain. An occluded front occurs when two cold air masses meet and push the warm air upward off the ground. Strong rain can occur at occluded fronts. A stationary front happened when a warm front and a cold front meet and neith has the energy to push the other out of the way.

46. Describe the life cycle of a thunderstorm. Warm moist air rises and cumulus clouds begin to form. As the cloud builds, the moisture increases until a cold heavy rain begins to fall. Once most of the moisture has fallen, the rain subsides to a light rain even as the cloud gets taller and develops an anvil-shaped top. 47. Explain how cloud cover can influence temperature in the lower atmosphere. Increased cloud cover can cause lower temperatures on the surface because less solar radiation is able to get through to warm the surface. On the other hand, at night, increased clouds help keep the day’s heat trapped near the surface. On a clear night, the temperature will drop more than it will on a cloudy night. 48. Define the Coriolis effect and describe how it influences objects or fluids in each hemisphere. The Coriolis Effect is the apparent shifting to the right (in the Northern hemisphere) of free-flowing matertials (air, water) due to the rotation of the Earth.