Water and Weather

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Water and Weather
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Chapter Six Weather and Climate

• 6.1 Introduction to Weather
• 6.2 Weather Patterns
• 6.3 Climates and Biomes

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Investigation 6B
Storms

• How does Doppler radar work?

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6.2 Meteorology

• A meteorologist is a person who uses scientific
  principles to explain, understand, observe, or
  forecast Earths weather.

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6.2 Meteorology

• Many meteorologists have college degrees in
  physics, chemistry, or mathematics.

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6.2 Meteorology

• Meteorologists use satellite and computer
  technology to inform people about the weather.

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6.2 Water in the atmosphere

• Higher temperatures cause liquid water molecules
  to move faster.
• These water molecules become water vapor in the
  atmosphere.

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6.2 Cloud formation

• Different conditions cause different clouds.
• Cumuliform clouds include
• cirrocumulus
• altocumulus
• cumulus
• cumulonimbus

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6.2 Cloud formation

• Stratiform clouds form when a large mass of
  stable air gradually rises, expands, and cools.
• Stratiform clouds include
• cirrostratus
• altostratus
• stratus
• nimbostratus

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6.2 Cloud formation

• Sometimes a cloud formation combines aspects of
  both cumuliform and stratiform clouds.
• We call these clouds stratocumulus clouds.

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6.2 Cloud formation

• Cirrus 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.

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6.2 Rain

• Rain 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.

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6.2 Snow

• Snow 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.

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6.2 Air masses and fronts

• An 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.
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6.2 Fronts

• A cold front occurs when cold air moves in and
  replaces warm air.

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6.2 Fronts

• A warm front occurs when warm air moves in and
  replaces cold air.

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6.2 Fronts

• On 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.

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6.2 Low- and high-pressure areas

• When 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.

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6.2 Thunderstorms

• Thunderstorms occur because of convection in the
  atmosphere.
• The downdraft and updraft form a type of
  convection cell called a storm cell within the
  cloud.

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6.2 Lightning

• Lightning is a bright spark of light that occurs
  within a storm cloud, between a cloud and Earths
  surface, or between two storm clouds.

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6.2 Hurricanes

• A 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.

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6.2 Tornadoes

• A 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.

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6.2 El Nino Southern Oscillations

• Storm 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.

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6.2 El Nino Southern Oscillations

• Along 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 Niño
  Southern Oscillation.