Transcript Weather

Earth Systems, Structure and
Processes
Introduction to Weather and
Weather Stations
Vocabulary
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What do these words mean?
Atmosphere
Weather
Weather forecasting
Meteorology
Meteorologist
Climate
Weather station
Weather Vocabulary – take 1
• Atmosphere
– The air surrounding the
earth
• Weather
– The condition or state of
atmosphere at a given
time and place
• Weather
Forecasting
– Predicting of future
weather conditions
Meteorology and Meteorologists
• Meteorology –
– The study of
atmosphere and its
weather
• Meteorologist
– A person who studies
the atmosphere and
its weather
• Climate
– The average
temperature over a
long period of time
• Weather Station
– A place for recording and
displaying data that has
been collected.
Forecast
• a scientifically derived
prediction of the upcoming
weather at any given time.
Weather Instruments
• What is air pressure?
– When air pushed down on the Earth’s surface
What is a Barometer?
– An instrument that measures air pressure.
What is convection?
– Differences in air pressure causes convection. Energy
moves through troposphere because of the rising and
sinking of air. Warm air rises and cold air moves in to
takes its place. This moving air is called WIND.
• What is a wind vane?
• A wind vane shows wind direction. The wind
vain points in the direction the wind is
blowing from.
• What is an Anemometer?
• An anemometer measures wind speed. There
are little cups on the top and the faster they
spin the faster the wind is blowing.
• Why is there water vapor in the atmosphere?
– The water on the Earth is heated and it evaporates
and forms a gas in the air.
• Describe humidity.
– It is the amount of water vapor in the air.
• What is a hygrometer?
– It is a weather instrument that measures
humidity.
• Describe Relative Humidity?
– It compares the amount of water vapor in the air
with the greatest amount that could be in the air
at that temperature and pressure. It the
hygrometer reads 50%, then that means there is
half of the mount of water vapor in the air that
could be there.
• What is precipitation?
– It is any form of water falling from the clouds to
the Earth.
What is a weather balloon used for?
• Weather balloons collect information from
high in the atmosphere. The balloons rise
through the air and has an instrument panel
hanging from it. It holds weather instruments
which measures temperature, air pressure,
wind speed and humidity.
Collecting Weather Data
• Beaufort Scale – Is a scale used to rate the force
and speed of the wind on a scale from 0-12 and
relates to the observable effects. For example:
The more intense the wind – indicates a storm is
approaching. The decreasing speed of the wind
indicates calmer weather is approaching.
• Rain Gauge – an instrument that collects rain to
determine the amount of rain that has fallen to
the Earth.
Air Pressure
• Air Pressure – is measured in terms of weight
of air per unit of area. The air pressure on an
object is equal to the amount of pressure
exerted on an object in all directions.
• A vacuum is a space that has no air pressure.
What does air pressure have to do
with the weather?
• Temperature and air pressure are related. Cold
air is dense, so, when it pushes down on the
earth, it creates high air pressure. Warm air is
less dense and does not exert as much
pressure. In areas with warm air, the air
pressure is lower.
What do you think causes wind?
• Air moves from areas of higher pressure to
areas of lower pressure. The greater the
difference in air pressure, the stronger the
movement of air; consequently, the stronger
the wind blows.
How does the change in barometric
pressure change the weather?
• A falling barometer reading and warm temperatures
precede stormy weather and some sort precipitation.
• A rising barometer reading and cooler temperatures
indicate fairer weather and probably dry conditions.
• Typically, areas of high pressure press down on warm,
moisture-filled air, preventing it from rising and
forming clouds, so the weather is usually dry.
• Areas of low pressure allow the moisture-filled air to
rise, forming clouds and then precipitation. There are
always exceptions.
Vocabulary
• Barometer- an instrument to measure
barometric pressure or air pressure.
• Aneroid barometer – uses mercury to
measure air pressure instead of liquid.
• Millibars – The inner scale that gives the
metric equivalent of inches of barometric
pressure. A millibar is a unit of pressure that is
related to the actual weight of air pressing on
a 1 square centimeter area.
Look at a weather map
• http://www.weather.com/map
s/maptype/currentweatherusn
ational/uscurrentweather_larg
e.html
Station Model
Weather Fronts
• Air mass –a term used to describe a vast
body of air in which temperature /
humidity is basically the same.
• Front – is the boundary where air masses
of different temperatures and humidities
collide. ( they are called weather
changers)
Four different types of Fronts
• Cold Front – Forms when a cold air mass
advances to display masses of warm air.
• Warm front - Forms when a warm air mass
advances and rises over a retreating mass of
cold air. *As it rises, the warm air cools. If the
warm air is also moist, layered clouds and
precipitation may form. Hot, humid weather
usually follows.
Fronts - continued
• Occluded Front – Occurs when a cold front,
closely following a warm front, finally overtakes
the warm front. The dense, cool airlifts the lessdense warm air off the ground. As the warm air is
pushed upward, it also cools, producing clouds
and precipitation. Occluded fronts produce less
extreme weather than cold or warm fronts.
• Stationary Front – If a warm air mass encounters
a cold air mass and no movement occurs, a
stationary front forms.
Fronts
• What would happen if the warm air contained a lot of
moisture? (As the moist, warm air rose up higher into
the atmosphere, any water vapor would be cooled,
causing it to condense and turn into a liquid.)
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• What kind of weather does a warm front bring? Why?
(Clouds and rain. Warm fronts slide slowly above the
cold air, so more air cools, causing condensation and
precipitation. Because the warm air is the mass that
moves in, storms, are usually followed by hot and
humid weather.)
Fronts
• What kinds of weather does a cold front bring? Why?
(The denser the cold air dives under the warm air,
pushing it upward. Again, the warm air cools, and any
water vapor condenses. This time, however, it is the
cold front that is moving in, so rain is followed by
cooler weather.)
• What kinds of weather does occluded fronts bring?
Why? (In an occluded front, the warm air mass, being
lighter, is pushed above the two cold masses. Up high,
the air becomes cooler and its water vapor condenses.
So occluded fronts usually bring clouds and rain, but
less extreme conditions than cold fronts bring. )
Fronts
• What kind of weather does a stationary front
bring? Why? (With a stationary front, neither the
cold nor the warm air is advancing, and
widespread clouds can form on both sides of the
frontal boundary. Since the clouds are barely
moving, a stationary front often brings lengthy
periods of precipitation.)
• What direction do weather fronts typically
move? ( they move typically from west to east;
however, some will push down from the north or
up from the south)
Isobars – areas of same atmospheric pressure
can be connected on a weather map by lines
called isobars
Isotherms – are lines drawn to connect areas of
the same atmospheric temperature at a given
time.
What happens when the sun heats the
earth and water condenses?
• Convection – As the sun heats the surface of the
earth, whether it be land or a body of water,
water at the surface evaporates as water vapor.
This water vapor is carried up from the surface by
rising warm air is a process called convection.
• Condense - Water vapor goes higher and higher
and it gets cooler and cooler. The cool air cannot
hold as much water as warm air so water vapor
condenses to form droplets of liquid water.
How do clouds form?
• For clouds to form, more is needed that just
air and water vapor. The water vapor needs
tiny particles around which to condense. We
call these tiny particles nuclei. They can be any
type of small airborne materials, including
dust and smoke particles. Then the water
molecules attach. If enough water vapor
condenses round the nuclei, a cloud forms.
Cirrus Clouds
Cirrus – clouds appear wispy and
form at very HIGH altitudes.
• Since they form where the
temperature is always far below
freezing they are almost always
complete made up of ice crystals.
Cumulus - billowing white or dark grey
cloud associated with rising air currents
• Clouds appear
puffy or piled
up and form
throughout
much of the
cloud layer
Cumulonimbus• tall and dense and
usually dark.
• A Cumulonimbus forms
if a cumulous cloud
produces precipitation.
Nimbus - they are typically gray and heavy
and present just before and during a storm.
Nimbostratus• dark, low-level clouds with
precipitation
• Nimbostratus are dark, low
level clouds accompanied
by light to moderately
falling precipitation.
• A stratus cloud that forms
precipitation. Nimbus is
Latin for “rainstorm”
Stratus – clouds appear layered form
at levels below 6500 feet
• Stratus clouds are low-lying,
uniform clouds that blanket
the sky. They are often a
dullish white to gray in color,
and they are generally the
sort of clouds that appear
when people talk about a
cloudy day. Stratus clouds are
not generally associated with
poor weather, although they
can be accompanied by
drizzle, and at higher
altitudes, they can be an
indicator that rain is on the
way.
Fog- stratus clouds that are formed on
the surface of the Earth.
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Tornado
• Tornado- Tornados can be
even more destructive than
hurricanes; however, they
follow a narrower path. It
does not last as long but has
violent rotating , narrow
columns of air. The wind
speeds are between 50-300
mph. They usually develop
in cumulonimbus clouds but
is not officially called a
tornado unless it looks like a
funnel.
Hurricanes
• Hurricane- are largest storm
on the earth for the sheer
size. It is a rotating wind
system that originates over
warm ocean water in low
pressure areas. Hurricanes
extend for several
miles/kilometers and can
last for days. They have
severe winds that can be up
to 200 mph. The eye of the
hurricane is the calm center
(the eye of the storm). The
eye averages about 20 miles
wide.
Other Severe Weather
• What causes a thunderstorm? (warm moist air
quickly rising along a cold front)
• What type of air pressure do you find in a
tornado? (very low)
• How can you tell a thunderstorm is
approaching? (anvil shape cloud with a dark
bottom is approaching)
Jet Streams
• The jet stream is a fast flowing, river of air found
in the atmosphere at around 12 km above the
surface of the Earth just under the tropopause.
• They form at the boundaries of adjacent air
masses with significant differences in
temperature, such as of the polar region and the
warmer air to the south.
• Because of the effect of the Earth's rotation the
streams flow west to east, in a serpentine or
wave-like manner at lower speeds than that of
the actual wind within the flow.
Jet stream
What are the global wind patterns?
• The equator receives the Sun's direct rays.
• Here, air is heated and rises, leaving low pressure
areas behind.
• Moving to about thirty degrees north and south
of the equator, the warm air from the equator
begins to cool and sink.
• Between thirty degrees latitude and the equator,
most of the cooling sinking air moves back to the
equator. The rest of the air flows toward the
poles.
Global Wind Patterns
What are the trade winds?
• What are the trade winds?
The trade winds are just air movements
toward the equator.
• They are warm, steady breezes that blow
almost continuously.
• The Coriolis Effect makes the trade winds
appear to be curving to the west, whether
they are traveling to the equator from the
south or north.
What are the doldrums?
• The doldrums is an area of calm weather.
• The trade winds coming from the south and
the north meet near the equator.
• These converging trade winds produce general
upward winds as they are heated, so there are
no steady surface winds
What are the prevailing westerlies?
• Between thirty and sixty degrees latitude, the
winds that move toward the poles appear to
curve to the east.
• Because winds are named from the direction in
which they originate, these winds are called
prevailing westerlies.
• Prevailing westerlies in the Northern Hemisphere
are responsible for many of the weather
movements across the United States and Canada.
What are the polar easterlies?
• At about sixty degrees latitude in both
hemispheres, the prevailing westerlies join with
the polar easterlies to reduce upward motion.
• The polar easterlies form when the atmosphere
over the poles cools.
• This cool air then sinks and spreads over the
surface.
• As the air flows away from the poles, it is turned
to the west by the Coriolis effect. Again, because
these winds begin in the east, they are called
easterlies.
El Nino
Introduction
• El Niño refers to the irregular warming in the sea
surface temperatures from the coasts of Peru and
Ecuador to the equatorial central Pacific.
• This causes a disruption of the ocean-atmosphere
system in the tropical Pacific having important
consequences for weather around the globe.
• This phenomenon is not totally predictable but on
average occurs once every four years. It usually
lasts for about 18 months after it begins.
What are the effects of El Nino?
• Effects show up most clearly during wintertime
• Linked with drought not just in parts of Latin
America but in southeastern Africa, South Asia,
Indonesia and Australia.
• El Niño usually brings a warm winter to the
northern USA from the Pacific Northwest across
to the Midwest and sometimes the Northeast
• Reduction in the number of hurricanes that
form over the Atlantic Ocean, especially strong
ones
La Nina
• La Nina is the name given to the slight cooling
of the surface waters of the Pacific Ocean.
• As the ocean is one of the biggest influences
on our weather, this change in the surface
temperature has a dramatic effect on the
weather around the world.
Causes of La Nina
• What is known is that during a La Nina event
the prevailing winds strengthen.
• These winds blow towards the west, so the
warm surface waters are blown away from the
coast of South America, towards Indonesia.
• This causes cold waters from the depth of the
ocean to well-up along the coast of Peru and
Ecuador.
Affects of La Nina
• La Nina - as the water near the coast of Peru and
Ecuador is cooler than usual, it makes sense that
the weather in the region is also cooler than
usual.
• If the waters around Indonesia are warmer than
usual, then this part of the world will be wetter
than usual.
• As the warmer water will heat the air, and
warmer air can hold more moisture than cooler
air.