Transcript chapter 14 pages 359-363 and 370-377

Geo D Unit 6 Lecture
Chapter 11 pages 271-282, all of
Chapter 12, and Chapter 14 pages
559-363 and pages 370-377
CHAPTER 11
PAGES 271-282
Key Atmospheric Gases
• The atmosphere is made up of many gases
• 99% nitrogen and oxygen
• Water vapor and carbon dioxide determine
temperature
• Particulates are solids floating around in the
air that water vapor can condense on
Ozone
3 oxygen molecules bonded together
• Located in the stratosphere
• Absorbs UV rays and protect us from the sun
Layers of the Atmosphere
• Troposphere- closest to Earth, where most of
the weather occurs, gets colder as your go
higher
• Stratosphere- contains ozone, gets warmer as
you go higher
• Mesosphere- very few molecules, coldest
layer, gets colder as you go higher
• Thermosphere- hottest layer, gets hotter as
you go higher
• Beyond the thermosphere is the exosphere
which leads us into space
Solar Fundamentals
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Radiation:
The sun radiates onto Earth
50% absorbed by the surface
15% absorbed by atmosphere
25% reflected from clouds back into space
4% reflected by surface back into space
6% reflected by atmosphere back into space
• Conduction:
• Transfer of heat to
solids
• Done by contact
• Convection:
• Transfer of heat to
liquids and gases
• Creates convection cells
in the atmosphere
Temperature verses Heat
• Temperature
• Measure of the average
kinetic energy of
molecules
• Heat
• Transfer of energy
because of a difference
in temperature
• Moves from high to low
Measuring Temperature
• In the United States we use Fahrenheit
• For science class we will use Celsius or Kelvin
• To convert from Celsius to Kelvin, simply add
273
• 0 C = 273 K (freezing point of water)
• 100 C = 373 K (boiling point of water)
Dew Point
• Dew point is the temperature when air
reaches saturation
• Once dew point is reached, condensation
happens (water vapor forms into water drops)
Vertical Temperature Changes
• In the troposphere, temperature decreases as
elevation increases
• Cooling of 10 C for every 1000m increase
• This is the dry adiabatic lapse rate
• The height at which condensation occurs is
called the lifted condensation level (LCL)
• Above the LCL, air cools more slowly
Air Pressure and Density
• The density of air is proportional to the
number of particles present
• The density of air decreases as you move from
the crust out into the atmosphere
Pressure Temperature Density
Relationship
• Temperature is directly proportional to
pressure
• Temperature decreases=pressure decreases
• Ex: Moving higher up Mt. Everest
• Pressure and density also directly proportional
• Pressure decreases=density decreases
Temperature Inversions
• An exception to the rule
that pressure and
temperature decrease
with height in the
troposphere is an
inversion
• Commonly happens
when cities are in a
basin and pollution
becomes trapped there
Wind
• Caused by unequal heating of the earth’s
surface
• Cool air sinks, warm air rises and allow for
areas with differences in air pressure
• Wind speeds increase with altitude because
there is less friction with objects and the earth
CHAPTER 12
Meteorology
• Meteorology is the study of atmospheric
phenomena
• Hydrometeors are the items that contain
water like clouds, rain, fog, etc
• Lithometeors are condensation nuclei like
smoke and dust
• Electrometeors are the items that are a visible
or audible manifestation of electricity like
thunder and lightning
Weather verses Climate
• Weather
• Current state of the
atmosphere
• Short term
• Climate
• Long term variations in
weather for a particular
area
• The continual motion of air and water
reallocates heat energy among Earth’s surface,
oceans, and atmosphere and helps keep
balance
Air Masses
• Air masses are large bodies of air over a
certain area
• Those that form over land are drier than those
over water
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Warm and dry = cT continental tropical
Warm and humid= mT maritime tropical
Cold and dry =cP continental polar
Cold and humid=mP maritime polar
Arctic A
All 5 air masses can be found in N America
Modification happens when they move away
from their source regions
Weather Systems
• The Coriolis Effect is the deflection of air to
the right in the N Hemisphere and to the left
in Southern
• Caused by the rotation of the earth
Global Wind Systems
• At the equator are the doldrums where ships
would become stranded due to weak winds
• Trade winds occur above and below the
equator
• Moves to the west
• Also known as the Hadley cell
• Between the trades and the westerlies is a
calm belt with weak winds called the horse
latitudes
• Boats become stranded here
• The prevailing westerlies blow to the east
• The polar easterlies blow to the west
Jet Streams
• Jet streams are narrow bands of fast, high
altitude winds
• Move up to 185 km/h
• Two main jet streams:
• 1. polar jet stream
• 2. subtropical jet stream
Fronts
• A front is a narrow region separating two air
masses of different densities
• Their interaction brings dramatic changes in
the weather
• 4 types of fronts:
• 1. cold front
• 2. warm front
• 3. stationary front
• 4. occluded front
Cold Front
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Cold, dense air displaces warm air
Forces the air up along a steep front
Clouds, showers, sometimes thunderstorms
Drawn as a solid blue line with solid blue
triangles
Warm Front
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Advancing warm air displaces cold air
Develops a gradual frontal slope
Extensive cloudiness and precipitation
Drawn as a solid red line with solid red
semicircles
Stationary Front
• Small temperature and pressure difference
between two air masses
• The boundary between them stalls
• Mild weather patterns
• Drawn as a combo of warm and cold front
symbols
Occluded Front
• Cold air moves so fast that it wedges warm air
upward
• That cold air collides with an advancing cold
front
• Precipitation is common
• Drawn as alternating purple triangles and
semi circles
Pressure Systems
• High Pressure
• Air moves outward in a
clockwise direction in N
Hemisphere
• Fair weather
• Low Pressure
• Moves inward in a
counter-clockwise
direction in N
Hemisphere
• Clouds and
precipitation
Gathering Weather Data
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Thermometers measure temperature
Barometers measure air pressure
Anemometers measure wind speed
Hygrometer measures humidity
Ceilometer measures the height of the clouds
• Radiosonde measures temperature, air
pressure, and humidity
• Sends radio signals back to the ground station
from heights of 30,000m
Doppler Radar
• The Doppler effect is the change in frequency
based on movement towards or away from
the observer
• Doppler radar plots the speed that raindrops
moved toward or away due to wind
Weather Satellites
• Weather satellites use both visible light and
other forms of radiation to observe the
atmosphere
• Infrared satellites detect changes in thermal
energy
• Allow scientists to determine the temperature
of a cloud to determine its type and height
Weather Analysis
• A station model is a record of weather data for
a particular site at a particular time
• Isopleths are lines that connect points of
equal values
• Temperature= isotherms
• Pressure= isobars, closer together are stronger
winds
Forecasts
• Short term
• Digital forecasts
• Done by high speed
computers
• Uses numerical data
• Analog forecasts
• Use past events
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Long term
Less accurate
Less detailed
Vague
Used more for seasonal
forecasts
CHAPTER 14
PAGES 359-363 AND 370-377
Climate
• Climate describes the long term weather
patterns of an area
• Variations in temperature, precipitation, wind,
etc
• Data is such as daily high and low temps,
rainfall, wind speed and direction, humidity,
and air pressure is collected
• Averaged on a monthly or annual basis for 30
years
• This determines the normals (standard value)
Causes of Climate
• 1. latitude
• The closer to the equator, the more direct the
sun’s rays hit and therefore receives more
solar radiation
• 2. topography
• Closeness to lakes and oceans
• Warmer in winter and cooler in summer than
inland areas
• Mountain climates cooler than sea level
• Windward side of mountains are wet and cool,
leeward side is dry and warm
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3. air masses
Warm and dry = cT continental tropical
Warm and humid= mT maritime tropical
Cold and dry =cP continental polar
Cold and humid=mP maritime polar
Arctic A
Short term climate changes
• Seasons are short term periods of climate
change caused by variations in daylight,
temperature, and weather patterns
El Nino
• El Niño is a warm ocean current that develops
off the western coast of S America
• When the high pressure system and its trade
winds weaken, changes in weather occur
• Causes stormy weather to normally dry places
and drought conditions to normally wet
Natural Changes to Climate
• 1. solar activity
• The sun’s sunspot cycles last about 11 years
• A period of low sunspot activity is called a
Maunder Minimum, causes colder
temperatures
• 2. Earth’s orbit
• Earth’s orbit becomes more elliptical then
more circular and so on back and forth
• When the orbit elongates, the earth is closer
to the sun, and temperatures become warmer
• 3. Earth’s tilt
• Angle varies from 22.2 degrees to 24.5 every
41,000 years
• Differences in angle could cause seasons to
become more severe
• 4. Earth’s wobble
• By the year 14,000 Earth’s axis will point
toward the star Vega instead of Polaris
• This will cause more extreme seasons
• 5. volcanic activity
• When volcanoes erupt, they send out
immense quantities of dust into the
atmosphere which blocks incoming solar
radiation
The Human Factor
• The greenhouse effect allows for life to survive
on earth, because a small portion of radiation
is not allowed to reflect back into space
• This effect is impacted by the amount of
greenhouse gases in the atmosphere
• These include carbon dioxide, methane, and
water vapor
Global Warming
• Temperatures have increased over the past
200 years
• This warming is causes a melting of the polar
ice caps
• This would then causes a rise in sea level
• Scientists are not all in agreement about what
is causing global warming
• Most blame our carbon dioxide output due to
burning fossil fuels