water and weather chapter six: weather and climate 6.1 introduction to weather 6.2 weather patterns...
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Water and Weather
Chapter Six: Weather and Climate6.1 Introduction to Weather6.2 Weather Patterns6.3 Climates and Biomes
Investigation 6BHow does Doppler radar work?
6.2 MeteorologyA meteorologist is a person who uses scientific principles to explain, understand, observe, or forecast Earths weather.
6.2 MeteorologyMany meteorologists have college degrees in physics, chemistry, or mathematics.
6.2 MeteorologyMeteorologists use satellite and computer technology to inform people about the weather.
6.2 Water in the atmosphereHigher temperatures cause liquid water molecules to move faster.These water molecules become water vapor in the atmosphere.
6.2 Cloud formationDifferent conditions cause different clouds.Cumuliform clouds include:cirrocumulusaltocumuluscumuluscumulonimbus
6.2 Cloud formationStratiform clouds form when a large mass of stable air gradually rises, expands, and cools.Stratiform clouds include:cirrostratusaltostratusstratusnimbostratus
6.2 Cloud formationSometimes a cloud formation combines aspects of both cumuliform and stratiform clouds. We call these clouds stratocumulus clouds.
6.2 Cloud formationCirrus clouds are thin lines of ice crystals high in the sky, above 6,000 meters.They are just a thin streak of white across a blue sky.
6.2 RainRain is the result of a cooling air mass.Cooling an air mass is like wringing out a wet sponge.Tiny droplets form a cloud or fog. Larger droplets fall as rain.
6.2 SnowSnow usually forms when both ice crystals and water droplets are present in the sky. The water droplets attach to ice crystals and freeze. When the ice crystals are large enough, they will fall to the ground as snow.
6.2 Air masses and frontsAn air mass is a large body of air with consistent temperature and moisture characteristics throughout.Two air masses that affect the United States are the continental polar air mass and the maritime tropical air mass.
Changing conditions and global winds cause these air masses to move.
6.2 FrontsA cold front occurs when cold air moves in and replaces warm air.
6.2 FrontsA warm front occurs when warm air moves in and replaces cold air.
6.2 FrontsOn a weather map, a cold front is shown using a line marked with triangles. The triangles point in the direction the front is moving.A warm front is shown using a line marked with semicircles.
6.2 Low- and high-pressure areasWhen a cold front moves into a region and warm air is forced upward, an area of low pressure is created near Earths surface at the boundary between the two air masses.A center of high pressure tends to be found where a stable cold air mass has settled in a region.
6.2 ThunderstormsThunderstorms occur because of convection in the atmosphere.The downdraft and updraft form a type of convection cell called a storm cell within the cloud.
6.2 LightningLightning is a bright spark of light that occurs within a storm cloud, between a cloud and Earths surface, or between two storm clouds.
6.2 HurricanesA hurricane is a tropical cyclone with wind speeds of at least 74 miles (119 km) per hour. The Saffir-Simpson Hurricane Scale is one scale used for rating hurricanes.
6.2 TornadoesA tornado, like a hurricane, is a system of rotating winds around a low-pressure center.As the rotating wind pattern narrows and lengthens, it forms a funnel cloud.
6.2 El Nino Southern OscillationsStorm patterns across the globe can happen in cycles.Usually the trade winds blow warm water from east to west across the Pacific Ocean.Every so often the trade winds weaken and the warm water reverses direction.
6.2 El Nino Southern OscillationsAlong with warm water comes greater thunderstorm activity across the Pacific.This change in wind flow, air pressure, and thunderstorm activity is known as the El Nio Southern Oscillation.