Transcript weather ≠ climate - Leuzinger High School

The Atmosphere
Atmospheric Composition
Component
% of
atm.
Information:
Nitrogen (N2)
78
Fundamental Nutrient for living organisms
Oxygen (O2)
21
Enter atm. in photosynthesis; removed in
cellular respiration.
Water Vapor
(H2O)
0-4
Varies depending on region: more over oceans
and at equator; less over deserts and near
poles
Carbon
Dioxide (CO2)
<<1
Taken up in photosynthesis; release in cellular
respiration; increased 25% in past 300 years
Methane
(CH4)
<<<1 Contributes to green house effect; increased
150% since 1750
Nitrous Oxide
(N2O)
<<<1 Comes from burning fossil fuels and
deforestation
Ozone (O3)
<<<1 97% in stratosphere (ozone layer); absorbs UV
radiation
Structure of Atmosphere
Layers
Height
above
Earth’s
Surface
Information:
Troposphere
0-11km
75% of atmospheric mass; Temperature
decreases with altitude; weather occurs
here
Stratosphere
11 – 50
km
Temperature increases with altitude due
to absorption of heat by ozone layer;
ozone layer here
Mesosphere
50 – 80
km
Temperature decreases with altitude;
coldest layer; meteors burn up in this
layer; ice clouds here
Thermosphere
(Ionosphere)
80+ km
Temperature increase with altitude due to
gamma and x-rays and UV radiation;
auroa borealis and auroa australis here
Structure of Atmosphere
Weather and Climate
WEATHER ≠
CLIMATE
Weather
• The short-term conditions of the atmosphere in
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a given place
Influenced by the movement or transfer of heat
energy
Influences:
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Temperature
Air pressure
Humidity
Precipitation
Available sunshine (lack of cloud cover)
Wind speed
Wind direction
She is reporting weather
Climate
• The total of all weather occurring over a
period of years in a given place
• Energy transfered through:
– Radiation
– Conduction
– Convection
Factors that influence climate
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Air Mass
Air Pressure
Albedo
Altitude
Angle of sunlight
Carbon Cycle
Clouds
Distance to Oceans
Fronts
Greenhouse Effect
Heat (convection)
Land Changes
Land mass distribution
• Latitude
• Location
• Moisture content of the
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air
Mountain ranges
Plate Tectonics
Pollution
Precession
Rotation
Solar Output
Volcanoes
Wind Patterns
Human Activity
Air Mass
• Large Body of air that has similar temperature
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and moisture content
Categorized by:
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Equatorial
Tropical
Polar
Arctic
Continental
Maritime
Air Pressure
• Decreases with altitude (99% within 20 mi
of earths surface)
• Low Pressure Masses: produces cloudy
and stormy weather
• High Pressure masses: contain cool dense
air; drops to Earth’s surface and becomes
warmer
– Associated with fair (nice) weather
Albedo
• Reflectivity
– Oceans – low
– Land masses – moderate
– Snow and Ice – high
• Positive feedback mechanism
• Dust in air can form a high albedo layer in
the atmosphere and reflects sunlight back
– Temporarily cooling the atmosphere
Altitude
• Every 1000 feet (300m) rise in elevation =
3°F drop in temperature
• Every 300 feet (90m) rise in elevation =
62mi (100 km) shift north in latitude and
biome similarities
Altitude changes
Angle of sunlight
• Areas of the earth closest to the sun receive
more sunlight and have a higher temperature
Carbon Cycle
Clouds
• Collections of water droplets or ice crystals
suspended in the atmosphere
Distance to Oceans
• Oceans are thermally more stable than
land
– Changes in temperature are more extreme in
center of land masses than near the oceans
Fronts
• Boundary between two air masses
• Vary by
– Temperature
– Dew point
– Wind direction
• Cold fronts – leading edge of an
advancing cold air mass
– Associated with thunderstorms
Greenhouse effect
• Water, carbon dioxide, and methane trap
solar radiation
– Too much = Earth too hot to live on
– Too little = Earth too cold to live on
Heat (Convection)
Convection:
• Primary way energy is
transferred from
hotter to colder
regions in the Earth’s
atmosphere
• Primary determinant
of weather patterns
Conduction:
• Involves the heat
transfer through a
substance heat
results from different
temperatures in
different parts of that
substance
Atmospheric Convection Cell
Land Mass Distribution
• Oceans absorb more solar heat than land
masses
• Earth receives more solar radiation at low
latitudes (near the equator) than at high
latitudes
• More landmasses near the equator leads
to a cooler planet
Latitude
• High latitude = less solar radiation = cooler climate
Land Changes
• Deforestation
• Urbanization
Moisture Content (Humidity)
• Atmospheric water vapor:
– Provides moisture for clouds and rain
– Acts as a green house gas keeping the Earth
warm
• A primary determinant of plant growth
– Determines type of biome
• Dew point – temperature at which
condensation takes place
Mountain Ranges
• Force air masses from a low elevation to a high
elevation
– Air mass expands and cools as it rises
– Relative humidity is raised
– Clouds form (sometimes get rain)
• Windward side of the range gets the most rain
• The leeward side gets the least rain creating a
rain shadow effect and producing a different
biome
Rain shadow effect
Plate Tectonics
• Stable plate tectonics leads to less
volcanism
• Less volcanism means less carbon dioxide
in the atmosphere  cooler planet
• More plate movement  more volcanism
 more greenhouse gasses  hotter
planet
Pollution
• Greenhouse gasses from human sources
 increase in global temperature
• CFC’s damage the ozone layer
• Excess sulfur  acid rain
Precession
• Precession – the wobble of the Earth on
it’s axis
• Changes in precession  changes in the
amount of sunlight the earth receives 
atmospheric changes
Rotation
• Daily temperature changes are affected by
the Earth’s 24 hour rotation cycle (1 day)
• Solar radiation warms the planet during
the day
• Heat escapes the planet at night
Solar Output
Radiation
• Flow of electromagnetic radiation from the sun
• Adds energy to the Earth’s systems
Volcanoes
• Volcano aerosols:
– Sulfur ejected into the stratosphere warms
the stratosphere and cools the troposphere.
– Can destroy ozone
– Carbon dioxide – green house gas
• Increased iron  increased biological
activity  take up carbon dioxide and cool
the atmosphere
• Large eruptions may trigger El Niño events
Wind Patterns
• Influenced by:
– Temperature
– Pressure differences
– Coriolis effect
Wind Patterns
1. Sun heats the atmosphere unevenly
2. Air closest to the surface warms and
rises
3. Air at high elevations cools and sinks
4. Rising and falling sets up a convection
process  wind
Global Air Circulation
• Caused and affected by:
– Uneven heating of the Earth’s surface
– Seasons
– The Coriolis effect
– The amount of solar radiation reaching the
earth’s surface over a given period of time
– Convection cells created by areas of warm
ocean water
Coriolis Effect
• Once an air mass is
set in motion (by
pressure gradients)
it undergoes an
apparent deflection
from it’s path due
to the rotation of
the earth
– Coriolis force at
Equator is zero
Trade Winds
• Caused by Coriolis effect
• Determined shipping routes during the Age of Sail
Human Activity
• Human activities that affect the climate:
– Deforestation
– Urbanization
– Heat island effects
– Release of pollutants
– Burning fossil fuels
– Produce acid rain
Major Climate Periods
Time
period
Events
2,000,000
– 12,000
BCE
Pleistocene Ice Age: Characterized by large advancing and
retreating glaciers over North America, Europe, and Asia;
Global temperatures 7°F – 9°F cooler than today
12,000 –
Gradual warming trend began
3,000 BCE 10,000 – 8,500 BCE: cooling period believed to be caused by
fresh water draining into the North Atlantic and changing
ocean currents
5,000 – 3,000 BCE: Climate Optimum, warmest period; Many
ancient civilizations flourished here.
3,000 750 BCE
Cooling period, caused sea levels to drop 6 – 10 feet (many
islands formed) and high latitude and altitude glaciers to
form
Brief warming period from 2000 – 1500 BCE
Major Climate Periods
Time
period
Events
750 BCE – Warming up to 150 BCE
900 CE
Cooling began during Roman Empire
-Nile River and Black Sea froze
900 –
1550 CE
Little Climate Optimum: (to 1200 CE) warm period – Viking
Expansion
Followed by cooling period with record floods, droughts,
extreme season fluctuations up to 1400’s
1550 –
1850 CE
Little Ice Age: coldest global temperatures
Temperatures in the northern hemisphere were about 2°F
colder
1850 –
Present
General warming trend – due largely to humans
Atmosphere Circulation Cells
• Hadley Air Circulation Cells
• Ferrel Air Circulation Cells
• Polar Air Circulation Cells
Help
determine
biomes and
biogeography
of the Earth
Winds
• Isobar Map – shows wind speeds over a
geographic area
– The closer the bars are the greater the wind speed
Hadley Air Circulation Cells
• Air is heated at the equator, rises and expands
north and south
Ferral Air Circulation Cells
• Develop between 30N and 30S latitude
• Mid-latitude climates have servere winters and
cool summers, defined seasons
Polar Air Circulation Cells
• Icy dry air from poles meets moist tropical air from mid-
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latitudes
Air returns to the poles, cooling and sinking, causing
precipitation
Very little liquid water – most is ice or snow
The whole picture…
Hurricanes, Cyclones, Typhoons
• Same thing different place
– Hurricanes – Atlantic and NE Pacific
– Cyclones – S Pacific and Indian Oceans
– Typhoons – NW Pacific
• Most severe weather on planet
– Begin with collision of warm ocean areas
where trade winds converge
• Cyclonic flow is initiated by Coriolis effect
Tornado
• Swirling air masses with wind speeds up to 300mph
• Occur primarily over land
• Require vertical shear of the horizontal winds (change in
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wind speed and direction with height)
Last less than one hour – typically
Monsoons
• Strong violent winds that change direction
with the seasons
• Blow from land to sea in winter
• Blow from sea to land in summer
• Summer monsoons provide large
quantities of rain
Normal State
• Walker circulation – easterly trade winds move
water and air warmed by the sun toward the
west
El Niño
• Air Pressure in the S Pacific Changes direction,
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trade winds reverse direction  pushes
thermocline deeper and decreases upwelling
Results in a shift of prevailing rain pattern
La Niña
• Trade winds are stronger than normal 
•
increased upwelling
Brings opposite effects of El Niño, warmer and
drier weather.