FORCASTING WEATHER MAP ANSWER KEY LINK: http://tdedrick.cmswiki.wikispaces.net/file/view/Weather+Forecasting+Packet+ANSWERS.pdf
Atmospheric(Air)Pressure
•Pressure caused by the weight of air above an area •Pressure decreases with increasing height above Earth •A 1 square inch column of air measured from sea level to the top of the atmosphere weighs approximately 14.7 pounds Air Pressure •Measured with a barometer in millibars. •Average barometric pressure at sea level is 1013.25 millibars or 29.92 Hg (inches of mercury) •High pressure –creates greater pressure on the barometer •Low pressure - creates less pressure on the barometer High pressure H As air cools, it becomes more dense and sinks toward the Earth’s surface spinning clockwise. Low pressure L As air warms, it becomes less dense and rises above the Earth’s surface spinning counterclockwise. High Pressure •Sunny, clear skies •Calm winds, spiral clockwise •Cool, dry air •Higher than normal - 30.5 Hg Low Pressure •Cloudy, stormy skies •Strong winds, spiral counterclockwise •Warm, moist air Lower than normal - 28.9Hg Isobars • A line connecting points of equal atmospheric pressure. •Measured in millibars - mb •One millibars is equal to about .02953 inches of mercury. Low Pressure in Storms Tornados Hurricanes 850 mb, 25.17 Hg 882 mb, 26.05 Hg Possibly lowest ever recorded Lowest U.S. storm measured Air Masses •A large body of air that has relatively uniform temperature and humidity. •Originate •over land (Continental) •over water (Maritime). •Cold air masses tend to approach from N, NW or W. •Warm air masses tend to approach from S, SE or E. Frontal Movement •Cooler air masses (H) are more dense and flows toward areas that are less dense, warm, and moist. (L). = High pressure areas move into low pressure areas Front •The boundary between two air masses. •Classified by which type of air mass (cold or warm) is replacing the other. •Map symbols point in direction front is moving. Cold Front •A cold air mass is replacing a warm air mass. •Air behind the front is colder and drier. •Pressure increases (H) •Moist air is pushed up over the cold air. •Showers and thunderstorms form along leading edge of front. Warm Front •A warm air mass is replacing a cold air mass. •Air behind the front is warm and moist. •Pressure goes down (L) •Slow moving, gradual rise of warm air over cold air. •Widespread, continuous precipitation occurs along and ahead of the front. Stationary Front •A boundary between two different air masses, neither of which is strong enough to replace the other. •Light rain over several days Occluded Front •Two cold air masses converge on a warm air mass. •Occurs when a fast moving cold front overtakes a warm front pushing it up and over cold air. •Thundershowers form along the front. •After frontal passage the sky is usually clear and dry. Back Door Cold Front •Approaches from the east or northeast. •The term “back door” is most commonly used in the northeast U.S. when cool Atlantic maritime air moves in from the east and replaces warmer continental air. Weather Instruments •Barometer (A) - measures atmospheric pressure in mb & Hg •Anemometer (B) - measures wind speed in mph •Thermometer (C) - measures temperature in oC & oF •Weather Balloon (A) - carry instruments to high altitudes to measure pressure, temperature, humidity, and wind speed •Compass Rose (B) - helps determine wind direction when reading weather maps •Wind Vane (C) - measures wind direction as N,S,E,W
STUDY JAMS: ATMOSPHERE VIDEO:
studyjams.scholastic.com/studyjams/jams/science/weather-and-climate/earths-atmosphere.htm Science 8: Completed Lesson 1 & 2 packets on the Atmosphere and had time to study during the hour for the test on 2/9/18. Packets may be used as a resource during the test.
Science 7: Completed Lesson 1 Packet on the Cell Cycle & Cell Division and Lesson 3 Packet on Plant Processes & Reproduction and had time during the class period to study for the test on 2/9/18. Packets may be used as a resource during the test.
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Erik E. Mason
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