Download 7.1 Meterology - Northside Middle School

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Weather includes short term changes in temperature,
precipitation, pressure, volume and density of the air. Long term
weather, defined as 30 years, is called climate.
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Weather occurs in the troposphere.
This part of the atmosphere has
75% of the atmosphere's mass and
most of the water vapor to form
clouds, thunderstorms, tornadoes,
hurricanes, and blizzards.
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Charles' Law says there is a direct relationship
between temperature and volume.
Temperature is the result of
variations in solar energy
unevenly heating the
atmosphere and the tilt of
Earth on its axis, that
provides seasons.
With a fixed amount of gas, when the temperature
is increased, the volume is increased.
Simply put,
gases expand
when heated.
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Warm air rises and expands
carrying more water vapor.
The air becomes less
dense and creates low
pressure.
Asair
airrises
risesititcools.
cools. Cold
Coldair
airholds
holdsless
lesswater
watervapor
vaporthan
thanwarm
warm
As
air,so
sowater
wateris
isreleased
releasedas
asprecipitation
precipitation.and giant convection cells
air,
circulate air currents in the atmosphere.
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The rotation of the earth gives air masses their properties.
Because air doesn’t heat evenly, wind is created.
Winds create climate, circulate
heat, moisture and nutrients
across the earth, but they also
transport pollution.
Winds are moved around the earth by the daily rotation and
the yearly revolution around the sun.
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As temperature increase, the evaporation rate increases and the
volume of water contained in the air increases.
Relative humidity is a term used to
describe the amount of water vapor
that exists in the atmosphere. It is
“relative “ to 100% saturation.
As water vapor it rises
to form clouds.
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Clouds will form when the dew point of water is reached in the
presence of any small non-gaseous particle – water droplet, ice
crystals, dust, soot, salt, or pollution. Cloud seeding artificially
add particles as cloud condensation nuclei.
Dew point is the temperature when atmospheric humidity
reaches 100% and the air is fully saturated.
Clouds usually look white because they reflect the same amount of
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all of the colors of visible light.
Thick, low-lying clouds appear gray because sunlight does not
fully penetrate and the amount of water vapor scatters the short
blue-gray wavelengths.
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At sunrise and sunset clouds may appear reddish because
long, low energy, wavelengths of sunlight are scattered and
reflected in low clouds.
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There are basically four types
of clouds. However, dozens of
combinations define very
specific cloud formations at
various altitudes.
The names, derived from
Latin, describe the way
clouds look.
1. Cumulus - heap, puffy
2. Stratus - layered
3. Cirrus - curls, wispy
4. Nimbus – cloud, rain storm
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Cloud are grouped by their altitude of the bottom section.
Family A. - Prefix Cirrus
High altitude clouds occur above
20,000 ft. They appear white, thin
and wispy and indicate good
weather.
Family B. - Prefix Alto
Middle altitude clouds appear
between 6,500 to 20,000 ft. and
are more gray from increased
water vapor. Rain may develop.
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Family C. – Prefix Cumulo or Strato
Low altitude cloud that form on the
ground up to 6,500 ft
Clouds can be more accurately
described by combining the
descriptive names such as
Stratocumulus or
Cumulonimbus. Sometimes
cloud form vertically.
Altostratus
Cumulonimbus
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Contrails are condensation
trails left behind jet aircrafts.
Contrails form when hot humid air from jet exhaust mixes with
air of low vapor pressure and low temperature.
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The forms of precipitation:
•Rain - condensation of atmospheric water vapor
•Hail - Thunderstorm updrafts carry water droplets high into the
atmosphere where they can freeze multiple times.
•Snow - Water droplets form and then freezing occurs slowly.
•Sleet - Rain freezes somewhere between the clouds and the ground.
•Frost - Dew forms and then it freezes.
•Ice - Rain freezes on contact with the ground.
•Fog - Temperature equals the dew point.
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