Transcript Weather Power Point for Weather Foldable

Weather
Weather
Weather is the term used to
describe the conditions that exist
in a certain place for a short time.
The Force Behind Weather
• The Sun
provides the
energy that
forms weather.
• Solar energy
heats the
equator more
than the poles.
The Force Behind Weather
As land or the ocean
warms, it heats the
air next to it and this
air begins rising. As
the heated air rises,
air from elsewhere
flows in to replace it.
What is this type of heat transfer called?
Convection causes pressure changes
• Low pressure
– caused by rising air
– counterclockwise rotation
– associated with storms
• High pressure
– caused by sinking air
– clockwise rotation
– associated with sunny
days and calm weather
What causes winds?
• Wind is a horizontal
movement of air from
an area of high
pressure to an area of
low pressure
• It is this difference in
pressure that makes
the air move=wind
• Winds are measured by
direction and speed
• Wind speed is
measured with an
anemometer.
Local Winds
• Winds that blow over short distances
• Caused by unequal heating of Earth’s
surface over a small area
• Often occurs near a large body of water
because land heats and cools faster
than water
Sea Breeze
• Land warms up faster than water.
• The air over the land becomes warmer
than the air over the water.
• The warmer air rises and cooler air
blows inland from the water.
Land Breeze
• Land cools faster than water.
• The air over the land becomes cooler than
the air over the water.
• The warmer air rises and cooler air blows
towards the water.
Sea Breeze vs. Land Breeze
Monsoons
• Sea and land breezes over a large region that
change direction with the seasons
• In the summer in South and Southeast Asia,
the land gradually gets warmer than the
ocean.
– A large “sea breeze” blows steadily inland from
the ocean all summer, even at night.
• In the winter, the land cools and becomes
colder than the ocean.
– A “land breeze” blows steadily from the land to
the ocean.
Global Winds
• Winds that blow
steadily from
specific directions
over long distances
• created by
convection currents
in the atmosphere
Coriolis Effect
• Because Earth is rotating, global
•
•
•
winds do not follow a straight path.
As the winds move, Earth rotates
from west to east underneath them,
making it seem as if the winds have
curved. This is called the Coriolis
effect.
Northern Hemisphere- winds turn
toward right.
Southern Hemisphere, winds curve
toward left.
Global Wind Belts
• Doldrums
– Regions near the
equator with little
or no wind.
• Horse Latitudes
– belt of calm air at
about 30° north and
south latitudes where
the air stops moving
toward the poles and
sinks
Global Wind Belts
• Trade Winds
– steady easterly winds
– From the equator to 30° north latitude and 30° south latitude
• Prevailing Westerlies
– blow generally from the southwest between 30° and 60° north
latitudes and from the northwest between 30° and 60° south
latitudes.
– play an important part in the weather of the United States.
• Polar Easterlies
– meet the prevailing westerlies at about 60° north and 60° south
latitudes, along a region called the polar front.
– has a major effect on weather changes in the United States.
Air Masses
• huge body of air that has similar
temperature, humidity, and air pressure
throughout it
• has the same characteristics of the surface
over which it develops
• Classified by
– Humidity—Continental (dry) or Maritime (humid)
– Temperature—Tropical (warm, low pressure) or
Polar (cold, high pressure)
• generally move west to east in N. America
Air Masses in N. America
Fronts
• the boundary between air masses
• Caused when air masses collide
• Four types—
– warm
– cold
– stationary
– occluded
Warm Front
• warm air slides over departing
cold air- large bands of
precipitation form
This is the
symbol on
a map for
a warm
front
Cold Fronts
• Cold air pushes under a warm
air mass. Warm air rises
quickly=narrow bands of
violent storms form
This is
the
symbol
for a cold
front
Occluded Front
• 2 cold air masses merge and force
warm air between them to rise
quickly. Strong winds and heavy
precipitation will occur
This is the
weather
map
symbol for
an occluded
front
Stationary Front
• Warm or cold front stops
moving. Light wind and
precipitation may occur across
the front boundary
This is the
weather map
symbol for a
stationary
front
Currents Also Affect Weather
• streams of water within the oceans that
move in regular patterns
• Warm currents carry warm water from
tropics toward the poles.
• Cold currents bring cold water from polar
zones toward the equator.
• The surface of the water warms or cools the
air above it. The warmed or cooled air then
moves over the nearby land.
Weather Maps
• Show locations of
fronts,
precipitation, air
masses and other
data
• Can be used to
help predict
weather