Download What is Weather

Weather
Definition: the meteorological conditions- temperature, wind, clouds,
precipitation...
Compiled by Rocio Munoz
TEKS 8.10 A recognize that the Sun provides the energy that
drives convection within the atmosphere and oceans, producing
winds and ocean currents
Deconstruct the TEKS
Recognize
Sun provides energy
drives convection in the atmosphere to produce wind
Recognize
Sun provides energy
drives convection in the ocean to produce ocean currents
What is
Weather ?
Weather
• Weather Refers to temperature, amount of
moisture, air pressure, wind direction, and
wind velocity.
• Local weather is affected by movement of
air masses into the local area.
Weather Factors
The day to day changes in the atmosphere.
Air Pressure
Wind
Temperature
Moisture
Tools to Study Weather
Thermometer: instrument that measures the temperature
Barometer: instrument that measures atmospheric
pressure (pressure from the weight of the air)
Hygrometer: instrument used to measure the relative
humidity of the atmosphere (ratio of the amount of
water in the air at a given temperature to the
maximum it can hold at that temperature)
More Weather Tools
Psychrometer: A special type of
hygrometer with two thermometers
Rain Gauge: An instrument used to
measure the amount of rain that has
fallen. Measurement is done in
hundredths of inches (0.01").
Anemometer: An instrument
used to measure wind speed
In a psychrometer, one thermometer is ordinary and the
other has a cloth wick over its bulb and is called a wet-bulb
thermometer. When a reading is to be taken, the wick is
first dipped in water. The water evaporates from the wick,
cooling the wet-bulb thermometer. Then the temperatures
of both thermometers are read.
If the surrounding air is dry, more moisture evaporates from
the wick, cooling the wet-bulb thermometer more so there
is a greater difference between the temperatures of the two
thermometers. If the surrounding air is holding as much
moisture as possible - if the relative humidity is 100% there is no difference between the two temperatures.
Under Pressure
• As we know, the air in the atmosphere is made
up of a number of gases. These gases press
down on the Earth’s surface, exerting a force that
we call atmospheric pressure or air pressure.
Although we are usually unaware of this
pressure, it actually presses down very hard –
roughly equivalent to the force of an elephant
balancing on a desk!
• Each layer of air presses down on the layers
below, and so the greatest pressure is at ground
level where we have the maximum amount of air
above.
• In the stratosphere air pressure decreases until it
reaches about zero.
Changes in Air Pressure
Changes in air pressure are caused by the difference in air
temperature above the earth. Land masses and areas of water
change the temperature of the air above them. These changes
create wind and cause pressure patterns to develop. The wind
moves these pressure patterns that change as they pass over
mountains, oceans, and other areas.
Heat Energy and the Atmosphere
The Sun
The Sun’s Energy also powers the water cycle
Radiant energy from the sun is transformed into heat by
absorption at the earth’s surface.
The angle of the sun’s rays affect the
heating of Earth’s Surface
• The uneven distribution of heat energy in the
atmosphere is the cause of weather.
Wind
Changes in air pressure bring changes in
the weather and make winds blow. Air
usually moves from areas of high pressure
to areas of low pressure, and this
produces winds. This can be easily
remembered with the phrase:
"Winds blow, from high to low!"
Wind Facts:
• Winds move from high to low pressure
areas.
• High pressure is associated with cold air,
low pressure with warm air.
• Warm air rises because it is less dense
than cold air
• Both local and global winds are caused by
differences in air pressure due to unequal
heating of the air.
Air Circulation Pattern
,
•
•
•
When air is heated, it becomes lighter (less dense) than the surrounding air.
Therefore, warm air rises.
Cool air is heavier (more dense), so it tends to sink. As air rises or falls, the
surrounding air rushes in to replace it, causing air to circulate. This
circulation, brings about changes in the weather.
The heating of Earth's surface depends on the nature of the surface
Local Winds
Sea Breeze, Land Breeze, and Monsoon
Land Breeze
Occur on warm sunny days
Air over the land heats faster than the air
over the cool ocean
Warmer air rises
Cool air flows in under it to fill the area over
the land
This air warms and the cycle continues
Sea Breeze
Occur at night and on cool days
Air over water maintains an even
temperature
Air over land cools faster
Cooler air flows from the land out
under the warmer ocean air
This air warms and the cycle
continues
Global Winds
Coriolis Force (effect)
The original circulation of air
caused by convection is in a north
–south direction. But because the
earth turns toward the east, all
winds veer from this north-south
direction.
The Coriolis force is caused by
the differences in velocity of
rotation at different latitudes. At
the equator the velocity of rotation
is at its maximum (1,000 mi/hr).
At the poles the velocity of
rotation is at its minimum (0mi/hr).
The velocity of rotation gradually
decreases from the equator to the
poles.
• Rotation of the
earth, distribution
of land and water
areas, and the
exchange of heat
between warm
and cold areas
causes the
circulation
patterns of the
atmosphere.
Major Wind Systems
Trade Winds or Easterlies - An area
of calm found at the equator.
When warm air from the equator
rises, it cools, and flows back toward
the equator. It appears to flow to the
west because of the Coriolis Effect.
Prevailing Westerlies - When air
moves toward the poles, it flows from
west to east.
clouds, rain , or snow may occur
when highs and lows overtake one
another
Polar Easterlies - Air over the poles
cools and sinks back down, it
eventually returns to the equator.
The Jet Stream
• The Polar
Front at the
Tropopause
• Recall that
winds aloft are
faster than
surface winds
Climate
• Climate is the general character of the weather that prevails in an
area from season to season and from year to year. It can be
thought of as the average weather of an area over a long period of
time.
• Factors that combine to produce different climates:
• A- latitude
B- altitude
• C- Large bodies of water D- Mountain barriers
8.10 B identify how global patterns of atmospheric
movement influence local weather using weather maps that
show high and low pressure and fronts.
Deconstruct the TEKS
•
•
•
•
Identify
Global patterns of atmospheric movement
Influence weather
Using weather maps that show H and L and fronts
Air masses are classified based on their
and amount of
Air masses get their characteristics based
on
The abbreviations used to classify air masses
use the following letters: c, m, T, P, and A.
For each letter, describe its property:
Word
c
continental
m maritime
T Tropical
P Polar
A Arctic
Means
dry
moist
warm
cold
very cold
warm and moist
cold and dry
http://www.classzone.com/books/earth_science/terc/content/visualizations/es2001/es2001page01.cfm?chapter_no=20
cP air mass
mT air mass
dry, cool air
warm, moist air
High Pressure
Area
Low Pressure
Center
cP air mass
mT air mass
dry, cool air
warm, moist air
High Pressure
Area
Low Pressure
Center
cP air mass
mT air mass
dry, cool air
warm, moist air
High Pressure
Area
Low Pressure
Center
cP air mass
mT air mass
dry, cool air
warm, moist air
High Pressure
Area
Low Pressure
Center
cP air mass
mT air mass
dry, cool air
warm, moist air
High Pressure
Area
Low Pressure
Center
Air Masses
Facts:
•
•
•
•
•
•
Air mass is a region of air with similar properties in the atmosphere
Air mass typically move from the west to the east in the Northern Hemisphere under
the influence of the prevailing westerlies.
Example: Hot, dry air from the continental tropical air mass will bring hot, dry weather
to Texas when it moves in from Arizona.
Masses of air that stay in place for some length of time take on the characteristics of
temperature and humidity from the surface of the earth over which the air stands.
Masses of air that originate over the ocean tend to be moist
There are four major types of air masses that affect the weather in the United States:
Maritime Tropical
Maritime Polar
Continental Tropical
Continental Polar
Characteristics
Name
Characteristics
Maritime Tropical
•Forms near the equator.
•Warm, moist air
•Summer- very hot, humid weather
•Winter - rain or snow
Maritime Polar
•Forms over the Pacific Ocean in both the
winter and the summer.
•Summer – cooler temperatures to the
eastern states and fog to California and
other western states.
•Winter- Heavy snow and very cold
temperatures
Continental Tropical
•Forms over land in Mexico.
•Brings dry, hot air to the southwestern
states.
Continental Polar
•Forms over land in northern Canada.
•Winter- very cold temperatures in the
United States
High and Low Pressure Systems
High Pressure Areas (H) – air
tends to sink, winds blow
outward from the center,
turning clockwise. High
pressure area usually brings
clear skies, dry weather, and
gentle winds.
Low Pressure Areas (L) – the
air tends to rise, and winds
spiral in toward the center in
a counterclockwise direction.
The low pressure areas
usually brings cloudy, wet
weather, often with strong,
gusty winds.
High and Low Pressure Systems
• Areas of high pressure can be caused when cool air is
sinking and pressing on the ground. When warm air
rises, however, it causes a region of low pressure.
• Regions of sinking air are called highs, high pressure
regions, or anticyclones. Clear skies and fair, dry
weather usually occur in these regions.
• Regions of rising air are called lows, low pressure
regions, depressions, or cyclones. Clouds, rain, and
strong winds often occur in these regions.
High vs. Low
• High pressure areas are generally larger
and move slower than low pressure.
• The winds are generally weaker than
those around a low pressure, especially
in the center.
• High pressure does not necessarily
mean warm weather, a 'cold anticyclone'
has cold air near the ground. These cold
anticyclones are common in Siberia and
Canada.
Cold Front
If cold air is moving toward warm air, then it is a “cold front”.
Definition: a warm-cold air boundary with the colder air replacing the warmer.
A typical cold front
plows into warmer,
lighter air forming
towering clouds,
rain, and often
thunderstorms.
Air Movement- Cold Front
Symbol for Cold Front
• The weather map symbol for
a cold front is a blue line with
triangles pointing the
direction the cold air is
moving.
• As a cold front moves into an
area, the heavier, cool air
pushes under the lighter,
warm air it's replacing. The
warm air cools as it rises. If
the rising air is humid
enough, water vapor in it will
condense into clouds and
maybe precipitation.
Weather Associated with Cold Fronts
In the summer, an arriving cold front can trigger thunderstormssometimes severe with large hail, dangerous winds, and even tornadoes!
Warm Front
If warm air is moving toward cold air, it is a “warm front”.
Definition: boundary where a warm air mass replaces a cool air
mass. Warmer tropical air is forced over the cooler polar air.
Heavier, denser cold
air retreats slowly as
warm air rises over
cold air, bringing
widespread clouds
and precipitation.
Air Movement- Warm Front
Symbol for Warm Front
The weather map symbol for a
warm front is a red line with
half-circles on it. The circles on
the red line point in the
direction the warm air is
moving.
As the warm air advances
northward it rides over the cold
air ahead of it, which is heavier.
Sometimes the cold air slows
the warm front down and can
lead to several days of wet
weather.
Weather Associated with Warm Fronts
When a warm front passes through, the air becomes noticeably
warmer and more humid than it was before. As the warm air rises
over the cold air the water vapor in it condenses into clouds that can
produce rain, snow, or sleet. A slow-moving warm front can mean
hours, if not days, of cloudy, wet weather before the warm air finally
arrives.
Stationary Front
When a warm or cold front stops
moving, it becomes a stationary
front. Once this boundary resumes
its forward motion, it once again
becomes a warm front or cold
front.
A stationary front is represented
by alternating blue and red lines
with blue triangles pointing
towards the warmer air and red
semicircles pointing towards the
colder air.
Occluded Front
When a cold and warm front
merge into one front, it is known
as an occluded front, or
occlusion. The warm air mass
becomes trapped between two
colder air masses, one from the
west and one from the east, and
is forced up. Occluded means
"closed in." A large area of bad
weather accompanies the
occluded front.
Warm front weather will be
followed by cold front weather in
all occlusions.
Which types of fronts can you
find on this map?
Predicting the Weather
Weather forecasting takes time and research. Here are just a few tips on
scientific weather forecasting …
– Watch for a steadily falling barometer with winds from the
east/northeast. This usually indicates the arrival of a storm from the south
or southwest within 24 hours.
–
Expect fair weather if the barometric pressure is steady and winds are
coming from the southwest to northwest.
– Look for the presence of cirrocumulus clouds that are in patches or in
widespread layers. This is usually a sign of an advancing, large, unstable
weather system.
– Watch for the formation of cumulonimbus clouds early in the day. As they
become more active, the likelihood of severe weather increases.
– Expect nice weather the following day if the night sky is clear.
Weather Maps
• Blue book page 71
• TEKS 8.10 A recognize that the Sun provides the energy
that drives convection within the atmosphere and
oceans, producing winds and ocean currents.
• 8.10 C Identify the role of the oceans in the formation of
weather systems such as hurricanes
Deconstruct the TEKS 8.10 C
• Identify
• Role of the oceans
• Formation of weather systems
• Hurricanes
Ocean Currents
The patterns of ocean surface currents are determined by the force and direction of
the winds and by land masses that act as barriers.
Ocean Currents
• Surface currents are cause by winds, and they have
circulation similar to those in the atmosphere. For example,
surface currents in the tropics are set in motion by the trade
winds that drive the ocean water before them.
• Density Currents formed by the movement of more dense
seawater toward an area of less dense seawater.
Temperature and salinity affect the density of seawater.
• Ocean currents traveling away from the equator are warmwater currents
• Ocean currents traveling toward the equator are cold- water
currents.
Ocean Currents
•
Examples of warm currents:
–
–
–
–
–
–
–
–
•
Gulf Stream
Alaska
Brazil
Norwegian
Agulhas
Mozambique
Kuroshio (Japan current)
East Australia
Examples of cold currents:
•
•
•
•
•
•
•
•
California current
Peru current
Canary
East Greenland
Labrador
Benguela
West Australia
Oyashio
How Do Hurricanes Form?
Hurricanes need four conditions to
form:
1. low air pressure
2. warm temperatures
3. moist ocean air
4. tropics winds (near the equator).
•It starts as a tropical wave, a westward-moving area of low air pressure.
•As the warm, moist air over the ocean rises cold air from above replaces it producing strong
gusty winds, heavy rain, and thunderclouds (tropical disturbance).
•As the air pressure drops and there are winds up to 38 mph, it is a tropical depression.
•When the cyclonic winds speeds from 39 to 73 mph, it is a tropical storm.
•The storm becomes a hurricane when there are winds of 73 mph or more.
Hurricane Safety
If a hurricane watch is issued:
•Listen to a battery-operated radio or
television
•Check emergency supplies and fuel
your car
•Bring in outdoor objects and anchor
objects that cannot be brought inside.
•Secure buildings by closing and
boarding up windows
•Store drinking water
•Review evacuation plan
•If at home, stay inside, away from
windows, skylights, and glass doors.
El Nino and La Nina
What are El Nino and La Nina?
El Nino - (El Nee-nyo) is the warming of water in the Pacific Ocean.
La Nina - (Lah Nee-Nyah) is the cooling of water in the Pacific Ocean.
El Nino Weather
La Nina Weather
•Rain and flooding along the
Pacific coast
•Warm water disrupts food
chain of fish, birds, and sea
mammals
•Tornadoes and thunderstorms
in southern US
•Fewer than normal hurricanes
in the Atlantic
•Snow and rain on the west coast
•Unusually cold weather in Alaska
•Unusually warm weather in the rest of the USA
•Drought in the southwest
•Higher than normal number of hurricanes in the
Atlantic
Bibliography
•
Front. [Online image] Available http://www.abdn.ac.uk/physics/meteo/metoh12_files/frame.htm, August 2004.
•
Cold Front. [Online image] Available http://www.usatoday.com/weather/tg/wcfront/wcfront.htm, August 2004.
•
Warm Front. [Online image] Available http://www.whyy.org/tv12/franklinfacts/dec1400_5.jpg, August 2004.
•
Cold and Warm Front Animation. [Online image] Available http://earthsci.org/weather/weaimages/weaimages.html, August 2004.
•
Air Masses. [Online image] Available http://www.weatherquestions.com/air_masses_AMSU.jpg, August 2004.
•
Satellite Image of Cold Front. [Online image] Available http://www.whyy.org/tv12/franklinfacts/dec1400_4.jpg, August 2004.
•
Thunderstorm. [Online image] Available http://home.online.no/~g-murray/bilder/ytd2003/images/19-Thunderstorm.jpg, August 2004.
•
Tornado. [Online image] Available http://www.scottandrew.com/img/storm.jpg, August 2004.
•
Weather Cartoon. [Online image] Available http://www.learnenglish.org.uk/magazine/apimages/cartoon_big31.gif, August 2004.
•
Walking in the Rain. [Online image] Available http://wwwru.kodak.com/RU/images/en/consumer/pictureTaking/lighting/lightNoDirectManUmbrella.jpg, August
2004.
•
Thermometer. [Online image] Available http://lamar.colostate.edu/~hillger/images/thermometer_small.jpg, August 2004.
•
Barometer. [Online image] Available http://www.steamertrunkmerchants.com/ps/barometer.jpg, August 2004.
•
Hygrometer. [Online image] Available http://www.csdm.qc.ca/edurocher/meteo/images%20aide.jpg/Brass%20Hygrometer.jpg, August 2004.
•
Rain Gauge Detailed. [Online image] Available http://images.encarta.msn.com/xrefmedia/zencmed/targets/illus/ilt/T240116A.gif, August 2004.
•
Psychrometer. [Online image] Available http://home.wanadoo.nl/crijkee/images/psychro.jpg, August 2004.
•
Substitute Weatherman. [Online image] Available http://www.betsystreeter.com/assets/images/158_sub_weatherman.gif, August 2004.
Weather Unit