Weather Test Study Guide
Weather - Weather is the condition of the air around the Earth. Weather changes from day to
day and even from hour to hour.
Climate describes average weather conditions in an area for a long period of time (many years).
Meteorologists are scientists who use special tools to measure, predict, and study weather.
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Weather satellites provide almost all of our weather data.
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Iso?
Measuring Weather Conditions
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A thermometer measures temperature, or how hot or cold the air is. Temperature is
measured in degrees Celsius (◦C).
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A rain gauge measures how much precipitation has fallen in either mm or cm.
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A wind vane shows which direction the wind is blowing. Wind is measured in compass
directions.
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An anemometer measures how fast the wind is blowing in km/hr.
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A barometer measures air pressure. Air pressure is measured in millibars (mb).
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A hygrometer measures humidity using percentages. Humidity is the amount of
moisture in the air.
Wind - movement of air due to differences in air pressure
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Weather in the United States is affected by a global wind pattern called the westerlies.
Air pressure - weight of gas molecules pressing down; measured using a barometer
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When barometric pressure increases, fair weather is approaching.
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When barometric pressure decreases, stormy weather is approaching
H - high pressure - brings dry weather and clear skies
L - low pressure - brings clouds and rainy weather
Thermal energy - moved through the atmosphere and the oceans by radiation and convection
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Radiation - electromagnetic waves from the sun
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Convection - current caused by warm air or liquid rising and cool air or liquid sinking
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Warm molecules move faster and farther apart, causing them to rise.
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When water absorbs heat from the sun, its temperature will increase more slowly than
the temperature of the land nearby.
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The temperatures near large bodies of water in the summer will be cooler than areas
without large bodies of water.
Precipitation
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Sleet is rain that leaves a cloud, falls through air below 0oC, and freezes.
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Hail forms in cumulonimbus clouds as round ice pellets.
Severe Weather
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Hurricanes form over warm oceans and are the most powerful storms on Earth.
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Tornadoes form over land when winds spiral inward toward a center of low pressure.
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Some thunderstorms form over land that is strongly heated.
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Droughts are long periods of unusually low precipitation. A drought could cause plants
and animals to die and bodies of water to dry up.
Air mass - large body of air that has same properties of the surface under it
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Continental air masses form over the continent.
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Maritime air masses form over an ocean.
Front- the place where two air masses come together but do not easily mix
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Cold front - cold air pushing up warm air
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Warm front - warm air mass moves into an area replacing a cold air mass
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Stationary front-
Understand how to read a weather map to determine types of fronts and pressure systems.