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LACEMOP
Factors that Shape Weather
Some Definitions
Weather: a condition of the
atmosphere in one place during a
short period of time
Climate: weather patterns typical for
an area over a long period of time
Latitude
Earth-Sun Relationships — seasons and
atmospheric scattering and energy spreading.
Air Masses
Air masses take on the “weather” of the
place from which they came.
Convectional Precipitation:Typical of
hot climates; convection occurs after
morning sunshine heats warm moist air.
Clouds form in the afternoon and the
rain falls.
Convectional Precipitation
Near Equator
Fontal Precipitation — when 2 fronts of
different temperatures meet.
Warm air forced upward by heavier, cool air.
Rising warm air cools = precipitation
Most common type
Continentality
Large bodies of water have moderating
effect on land temperatures.
Why? Land and water absorb and store
energy at different rates. Land changes
quickly — water more slowly. Opposite air
blows off the water and moderates land
temperature.
Mid-Latitudes
a) summer—warm masses of air from
the Tropics
b) winter– cold masses of air from the
high latitudes
Elevation
a) Height above sea level
b) Temperature decreases
as elevation increases
Mountain Barriers
• Can block air masses and cause
precipitation.
• Orographic Precipitation: warm moist
air forced
upward when passing over a mountain.
Warm winds cool as they rise over the
mountains and clouds form
• Air is warm and dry on the other side
• Windward: mountain side which faces
the ocean
• Leeward: mountain side which is in a
“rain shadow” (no precipitation received)
Ocean Currents
• Help to distribute heat
• Carry warm water from tropics to poles and
return cold water to the Equator
• Winds affect
current
movement
• Air masses take
on water
temperature
Pressure & Wind
•Rising warm air = low pressure
•Falling cool air = high pressure
•Wind moves high to low
•Movement from equator to poles and back
•Coriolis Effect: rotation of
the earth bends the patterns
of the wind
Winds blow in constant patterns and are
called prevailing winds.
Historical Fact: Many were named for the
direction they blew…some were even
given names because they were used by
trading ships through the region…
Trade winds -- blow from the northeast
toward the Equator and from the
southeast toward the equator
Westerlies – prevailing winds in the midlatitudes blow diagonally west to east
Polar Easterlies – blow diagonally in the
high latitudes east to west—pushing the
cold air toward the mid latitudes
Doldrums: windless
area near the equator
Horse Latitudes: Historically, ships would lighten
their loads in order to take advantage of the
slightest wind such as cargo, excess supplies
and livestock…this also included horse.
Greenhouse Effect
Earth’s atmosphere acts a a greenhouse
trapping 50% of the sun’s heat radiation.
Clouds, water vapor and carbon dioxide
absorbs the heat reflected by the earth and
radiates it back
again to keep
the balance
Global Warming
Global Warming: Scientists claim that
there has been a rise in CO2 levels and that
has caused a rise in global temperatures.
• Burning of coal, oil and natural gas has
caused the CO2 levels to rise—increased
burning will trap more heat in the
atmosphere
• Some scientists predict it will cause
more extreme global weather patterns
such as rapid water evaporation causing
drier soils between rain and humidity
might increase due to rapid evaporation
in the oceans
• Not all scientists agree on the nature of
global warming…hmmmmm!