Download Energy Exchanges in the Atmosphere: Meteorology

Earth Science
Mr. Butz
Meteorology
I.
The Atmosphere - the thin envelope of gas that surrounds the
earth.
A. Atmospheric Structure - the atmosphere is divided into five
distinct layers that are based on their unique characteristics.
1.
The Troposphere - this is the layer that lies closest to
the earth’s surface and is approximately 7 miles thick.
All weather on earth takes place in the troposphere,
which also contains over 90% of all of the
atmospheres gases.
Earth Science
Mr. Butz
2.
The atmosphere contains approximately 78%
Nitrogen, 21% Oxygen, and trace amounts of other
gases like carbon dioxide, argon, and, water vapor.
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Mr. Butz
II.
Weather - The present condition of the atmosphere at any
location. It can also be described as a description of specific
atmospheric weather variables during a short period of time.
A.
Temperature - temperature in the earth’s atmosphere is
dependent on the intensity and duration of the sun’s
insolation.
1.
Adiabatic Temperature Change – Temperature
decreases with altitude in the troposphere as a result
of the expansion of air.
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Mr. Butz
B.
Atmospheric Pressure - Atmospheric air pressure is the
weight of a column of air pushing down on the surface of
the earth at one given point. In general:
cooler air = high pressure
warm air = low pressure
1.
Atmospheric or Barometric pressure is measured
using a barometer, and is recorded as inches of
mercury or millibars
2.
Air Pressure and Air Temperature - In general terms,
the higher the air temperature, the lower the air
pressure.
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Mr. Butz
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Mr. Butz
C.
Humidity - Humidity is the amount of water vapor present
in the atmosphere. In general the cooler the air, the less
amount of moisture it can hold; therefore, warmer air has
higher humidity.
1.
Relative Humidity - this is the most common form of
measuring the amount of moisture in the air as a
percentage.
2.
Dew Point Temperature - The dew point is the
temperature of the air at which it would be saturated
at its current water vapor content. The dew point can
be calculated by using a pyschrometer.
3.
Humidity and Air pressure - in general, humid air
masses have lower air pressure than drier air
masses, this is due to the water molecules taking up
more space than air molecules do in that particular air
mass. Water
molecules weigh
less than oxygen or nitrogen molecules.
4.
Sources of Atmospheric Moisture - Moisture enters
the atmosphere by evaporation (liquid to water vapor),
transpiration (evaporation of liquid water off a leaf
surface), and sublimation (ice to water vapor).
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Mr. Butz
D.
Wind - The horizontal movement of air across the earth’s
surface is called wind. Air moves across the Earth’s
surface from areas of high pressure to areas of low
pressure.
1.
Convection Cells - The unequal distribution of solar
energy striking the Earth’s surface results in the
formation of large convection cells, also called Hadley
Cells.
2.
Planetary Winds - large scale planetary winds form as
an air moves from areas high pressure to areas of low
pressure. Because of the Coriolis effect caused by
the Earth's rotation, planetary winds are deflected to
the right in the Northern Hemisphere.
Earth Science
Mr. Butz
a.
3.
Planetary winds are responsible for the
movement of weather across the planet, and also
drive many major ocean currents.
Mesoscale Winds - Air masses often have well
defined pressure centers. Low pressure centers are
called Lows, or Cyclones. Cyclones move in a
counter-clockwise rotation in the Northern
Hemisphere due to the Coriolis effect.
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Mr. Butz
4.
Air Masses - A large body of air in the troposphere
with similar characteristics of temperature, pressure,
and moisture.
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Mr. Butz
3.
Land and Sea Breeze
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Mr. Butz
E.
Formation of Clouds and Precipitation - Clouds and
precipitation form when air rises and air is cooled
below its dew point, and water vapor condenses into
tiny water droplets or ice crystals.
1.
Conditions that Cause Air to Rise:
A.
Air is warmed by sunlight heating the surface
of the earth, expands and rises.
B.
Warm air is forced to rise upwards by
topography (mountains).
C.
Dense, cold air masses wedge under warm
air masses and force them to rise.
Earth Science
Mr. Butz
2.
Cloud types - Low clouds: cumulus, medium
height clouds: stratus, high clouds: cirrus.
3.
Forms of Precipitation - The common forms of
precipitation include: rain, drizzle, sleet (ice
pellets), hail, freezing rain, and snow.
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Orographic Precipitation
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Mr. Butz
II.
Air Masses and Fronts
A.
Fronts - Areas where two different air masses come
together.
1.
Cold Front - A cold front occurs when a cold air mass
advances towards a warm air mass.
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Mr. Butz
2.
Warm Fronts - A warm front occurs when a warm air
mass slowly overtakes a colder air mass.
3.
Stationary Fronts - When a cold air mass lines up with
a warm air mass, and there is no movement.
4.
Occluded Front - Fast moving cold fronts can
overtake a slow moving warm air mass, causing it to
rise off the ground.
VI. Storm Systems - Hazardous weather conditions can endanger
life and property, and are an important aspect of
understanding weather.
A.
Thunderstorms - thunderstorms form when warm air
begins to rapidly rise up into the atmosphere creating
cumulonimbus clouds.
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B.
Tornadoes - the most unpredictable form of severe weather
occurs when extremely intense thunderstorms develop over a
region and form extreme areas of low pressure within the
cloud.
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C.
Hurricanes -warm, humid air masses forming over the
ocean often create large, intense areas of low pressure at
the equator.
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Mr. Butz
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Mr. Butz