chapter 9: weather patterns and climate
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Chapter 9: Weather Patterns and Climate. Aim: How do air masses affect weather?. Air Masses. An air mass is a large region of the atmosphere where the air has similar properties throughout Gets its properties from the region it is from Are named for the region they come from - PowerPoint PPT PresentationTRANSCRIPT
Chapter 9: Weather Patterns and
Climate
Aim: How do air masses affect weather?
An air mass is a large region of the atmosphere where the air has similar properties throughout
Gets its properties from the region it is from
Are named for the region they come from
When an air mass moves it brings the conditions with them
Air Masses
4 types:1. Continental polar: cold, dry air2. Maritime polar: cool, moist air3. Continental tropical: hot, dry air4. Maritime tropical: warm, moist air
When 2 air masses meet, they form a boundary called a front
Weather changes rapidly at fronts because you are passing from one kind of air mass into another
Aim: How do fronts affect weather?
4 types:1. Cold Front Cold air moves in under a warm air
mass Brings brief, heavy storms Can cause strong winds and
thunderstorms After the storm, the weather is cooler
and drier
Types of Fronts
2. Warm Front Warm air moves in over a cold air mass
It brings light, steady rain or snow Precipitation can last for days Can bring fog After the rain, the weather is warmer and more humid
3. Occluded Front Occurs when a cold front and warm
front meet 2 ways this can happen
1. Cold front occlusion Air behind the front is cold Air ahead of the warm front is cool Cold air is moving in on cool air and
the warm is pushed up in between them
Weather is like that of a cold front2. Warm front occlusion Air behind front is cool not cold Air ahead of warm front is cold Weather is like that of a warm front
4. Stationary Front Stays over an area for days without
moving Have calm weather
Aim: How do thunderstorms form?
Most common kind of severe storm Form in cumulonimbus clouds called thunderheads
Usually have heavy rains, strong winds, thunder and lightning
Some can even produce hail There are 3 stages during a thunderstorm
Stages of Thunderstorms
1. First Stage Intense heat causes air to rise very
quickly Updrafts form and the cloud grows
bigger and bigger Water droplets and ice crystals grow
larger too2. Second Stage When the rain starts falling air moves
downward Static electricity forms from the rubbing
of upward air and downward air
Lightning occurs when static electricity builds up
Lightning is unpredictable3. Third Stage The storm dies when the downdraft
becomes stronger than the updraft Heavy rains subside and finally stop
Thunderstorms usually form in the warm air just ahead of a cold front
Aim: How do tornadoes happen?
A tornado is a violent whirling wind that moves across the ground in a narrow path
Form when dry, cold air masses mix with warm, moist air masses.
When the updraft is really strong air rushes in from all sides causing the air to curve into a spin
This spin lowers the air pressure even more, causing air to rush in even faster
Tornadoes
As the tornado gets stronger a funnel forms that touches the ground
Winds can reach up to 300 mph in the center of a tornado
The direction of a tornado can continually change
Most tornadoes occur in the Midwest of the United States
They mostly likely occur where there are big differences in the air masses
Aim: How do hurricanes form?
Are very large, swirling storms with very low pressure at their center
They form over tropical oceans Strong heating and lots of evaporation cause a large low pressure center to form
The Coriolis effect causes winds to spiral counterclockwise and clusters of thunderstorms are pulled into the spiral
The thunderstorms merge forming the storm
Hurricanes
The lower the pressure, the stronger the winds blow
In order for the storm to be considered a hurricane, the winds need to reach 75 mph or higher
Hurricanes have an eye at the center of the storm
The eye is an area of light winds and clear skies
Hurricanes can grow 400 miles in diameter
Aim: How do hurricanes affect ocean waves?
Hurricane winds cause large waves in the ocean
These waves pound the shore for days before the hurricane hits
The storm surge causes the most damage
Storm surges are caused by low air pressure
It causes the sea to rise, along with heavy rain from the hurricane
Storm surges cause flooding, which destroys homes and wears away beaches
Hurricanes begin to die when they move onto land because it has no water to replace what falls as rain
Aim: How can you be safe in a storm?
Aim: How can radar track storms?
Doppler radar is used to find storms as they form
Radar stands for radio detection and ranging
Radar sends out radio waves and records their echoes
The change in echoes gives scientists clues
It is used to track storms because radio waves reflect off storm clouds
Radar
With the radar, scientists can tell if rain is moving toward or away from an area, and spot spinning motions of clouds
Spotting motions of clouds can help warn scientists of tornadoes or hurricanes
Doppler radar helps scientists find and track thunderstorms, tornadoes and hurricanes
Aim: What is climate?
Is the average weather pattern of a region Climate can be described by the following factors: temperature, precipitation, winds, distance from coast, mountain ranges and ocean currents
We can also describe climate by the plants that live their b/c plants require their own conditions for growth, such as amount of sunlight, precipitation and temperature
Climate
Examples: 1. Alaska has a climate of long, cold
winters and short cool summers2. Florida has a climate of long, hot
summers and short, cool winters
Aim: What affects climate?
1. Latitude is the measure of how far north or
south a place is from the equator Temperatures are different at different
latitudes due to the angle of insolation 3 different zones: Tropical Zone Temperate Zone Polar Zone
Factors that Affect Climate
2. Bodies of Water Most of Earth is covered with water Land and water cool and heat at
different rates Land heats up faster in sunlight and
cools off faster Air temperatures over land are
warmer in the summer and cooler in the winter than over oceans at the same latitude
3. Winds and Ocean Currents The westerlies blow in the middle
latitudes They bring warm, moist air to the west
coast and push air masses and fronts Ocean Currents are also moved by
winds Gulf stream is a warm current that
flows up the east coast California current is a cool current that
moves down along the west coast
4. Altitude Is the measure of how high a place is
above sea level The higher a place the cooler it is
Aim: How does the Greenhouse Effect affect Earth?
Earth absorbs heat from the sun It also gives off heat into space Radiative balance is when the amount of energy gained equals the energy lost
Average temperature of Earth = 59˚F The atmosphere protects Earth from getting too hot or too cold
Only about ½ of incoming sunlight reaches Earth
Earth’s Energy
30% reflects off of particles and clouds back to space
The atmosphere absorbs 15- 20% of the heat
This keeps temperatures from rising too high
At night clouds aid in keeping the night from getting too cold
The atmosphere keeps Earth warmer than it would be
Earth’s atmosphere acts like the glass in a greenhouse by letting in sunlight, but not letting heat escape
2 main greenhouse gases are water vapor and CO2
Methane, nitrous oxide and chlorofluorocarbons (CFC’s) have a small effect
The Greenhouse Effect
These greenhouse gases are increasing due to human activity
With this increase Earth’s climate can change and make our planet warmer
The increase in these gases have a great effect on our environment
Aim: What causes climate change?
Over time Earth has undergone changes, which caused periods of cooling and heating
Shifts in the radiative balance is caused by changes in sunlight, currents and landmasses and volcanoes
1. Sunlight the amount of energy the sun sends
out changes These changes are due to sunspots
Causes of Climate Change
Sunspots are dark areas that appear on the surface of the sun
These spots are cooler than other parts of the sun
They are not permanent Sunspot maximum-large count of sunspots, which happens about every 11 years
Around the time of a sunspot maximum, earth’s temperature goes up
2. Ocean Currents They move heat from the equator to
the poles Change in speed and direction of
currents can explain sudden and long term climate changes
3. Landmasses Continents have changed positions
and continue to move climate will change with their
locations
4. Volcanoes Eruption of volcanoes send dust and
gases into the atmosphere The dust and gases could block out
the sun and cause cooling In the past volcanic eruptions were
very common and could have caused the ice ages
They are less common today, but still cause cooling, just not long term changes