Topic VI

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Topic VI Meteorology

• Weather Studies

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I. Moisture in the Atmosphere the primary source
of energy for the water cycle is the Sun. It
unevenly heats Earths surface.

• A. Phases of the Water Cycle
• 1. Evaporation liquid to gas. Requires energy
  making it a cooling process.
• 2. Condensation gas (water vapor) to a liquid.
  Releases energy into the air.

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3. Transpiration the releasing of water in the
air by plants.

• 4. Precipitation the falling of liquid or solid
  water from clouds.
• Ex. Rain, sleet, snow and hail.

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B. Factors Affecting Evaporation Rate

• 1. Temp. as temp. inc. evap. rate inc.
• 2. Humidity as humidity inc. evap. rate
  decreases.
• 3. Wind as wind inc. evap. rate inc.
• 4. Surface Area as surface area inc. evap. rate
  increases.

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C. Relative Humidity a comparison between the
amount of moisture in the air with the amount
that the air can hold at that temp.

• Dewpoint Temp. the temp. at which condensation
  occurs.
• dew drops of water forming on a cool surface.
• frost water vapor freezes (sublimates) on a
  frozen surface.

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2. Sling Psychrometer instrument used to
determine the dewpoint temp. and relative
humidity.

• 3. Steps to determine Dewpoint
• a. Find dry bulb temp.
• b. Find the diff. Between the wet and dry bulb
  temps.
• c. Use the chart on page 12 of the ref. Table.

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D. Clouds collection of tiny water droplets or
ice crystals suspended in the atmosphere.

• 1. Cloud Formation
• a. Warm moist air rises.
• b. Air cools below dewpoint temp. and droplets
  form around condensation nuclei (dust/salts).

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2. Cloud Types

• a. Cumulus big puffy white clouds.
• b. Cirrus whispy ice crystals high in the
  atmosphere.
• c. Stratus low clouds that blanket the sky.

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II. Air Pressure the force/weight of air pushing
on a surface. Air pressure pushes in all
directions equally. Pg. 13 ref. Table.

• A. Barometer instrument used to measure air
  pressure.
• As air pressure increases, the barometer rises.

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B. Factors Affecting Air Pressure

• 1. Temperature as temp. increases, air pressure
  decreases.
• 2. Altitude as altitude increases, air pressure
  decreases.
• 3. Humidity as humidity increases, air pressure
  decreases.

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C. Winds caused by differences in air pressure.
The greater the difference (gradient) the
stronger the winds.

• 1. Isobars connect points of equal air pressure.
• the closer the isobars the stronger the winds.

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D. Local Breezes smaller horizontal movement of
air .

• 1. Sea breeze air flows from the sea to the
  land.
• cooler air (high pressure) over the sea, flows
  towards warmer air (low pressure) over the land.

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2. Land breeze air flows from the land to the
sea.

• Air over the land cools at night and flows
  towards the warmer air over the water.

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E. Wind Direction flow from regions of high to
low pressure and named for the direction they
come from.

• 1. Cyclone (low pressure) winds blow
  counterclockwise towards the middle.
• 2. Anticyclone (high pressure) winds blow
  clockwise and out.

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F. Global Winds caused by the unequal heating of
earths surface. Page 14 ref. Table.

• 1. Diverging zones cool, dry high pressure air
  sinks at the poles and 300 lat.
• 2. Converging zones warm, moist low pressure air
  rises at the equator and 600 lat.

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III. Air Masses large masses of air that have a
characteristic temp. and moisture of their source
region. Page 13 ref. table.

• A. Source Regions
• 1. Maritime formed over water. (moist)
• 2. Continental formed over land. (dry)
• 3. Polar cool air from high latitudes
• 4. Tropical warm air from low latitudes.

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IV. Front the boundary that separates two
different air masses. Pg. 13 ref.

• A. Types of Fronts
• 1. Cold Front dense cold air forces warm moist
  air upward creating heavy precipitation for short
  periods of time at the frontal boundary.

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2. Warm Front warm air slowly rises over cold
air producing long periods of light precipitation
ahead of the frontal boundary.
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3. Occluded Front a fast moving cold front over
takes a slower warm front causing clouds and
precipitation.
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4. Stationary Front cold and warm air masses
near each other with neither advancing causing
long periods of light precipitation.
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B. Synoptic Weather Maps show weather conditions
on a national or global basis.

• 1. Storm Tracks most storm systems move from
  west to east across the U.S.

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V. Severe Weather

• A. Hurricanes a large rotating storm of tropical
  origin.
• they get their energy from warm water. Once
  they hit land they lose energy.

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Hurricane Eye
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B Tornadoes caused by the collision of warm,
moist air with cold, dry air. Winds can exceed
370 mph.

• C. Storm Safety
• 1. Stay indoors
• 2. Store food/water
• 3. Have batteries/flashlights
• 4. Have a radio