Transcript Atmosphere And Climate

Atmosphere And Climate
Atmosphere
• Invisible layer of gases that surround the
earth
– 78% nitrogen
– 21% oxygen
– 0-4% water vapor (major non anthropogenic
greenhouse gas)
– 1% carbon dioxide, methane, nitrous oxide,
ozone
• Atmosphere becomes less dense as you move
upwards into space
Carbon Dioxide
• -produced by cellular respiration and
organic decay
• **major greenhouse gas
• Avg time a molecule stays in
atmosphere=100 yrs.
• Volume has increased ~25% in last 300
yrs. Due to burning of fossil fuels and
deforestation
Methane
• Major greenhouse gas
• Since 1750 has increased 150% due to :
– Use of fossil fuels
– Coal mining
– Landfills
– Grazers (cattle)
**stays about 10 yrs in atmosphere
Nitrous Oxide
• Contributor to greenhouse effect
• Increasing about .3% per year due to:
– Burning of fossil fuels
– Fertilizers
– Burning biomass
– Deforestation
**lasts about 170 yrs in atmosphere
Atmosphere Origin
• Gases were released from the planet itself
• Functions:
– Protects earth from uv rays, x-rays, cosmic
rays
– Allows visible light and infrared (heat) to
penetrate, warming the earth
– 2.3-2.7 billion years ago evolution of
photosynthetic organisms
Layers of the Atmosphere
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Troposphere
Stratosphere
Mesosphere
Thermosphere (Ionosphere)
Exosphere
Memory technique: Troy smiled more than
Ed
Layers of the
Atmosphere
Layers of the Atmosphere
Troposphere
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0-7 miles (0-11km) above surface
75% of atmosphere mass
Temp. decreases with increasing altitude
Weather occurs in this layer
Stratosphere
• Extends 12-50 km up
• Temperature increases with altitude
because of heat absorption by ozone
• **contains ozone layer**
Mesosphere
• 51-80 km
• Lowest temperature in atmosphere
(-138oC)
• Meteors burn up here
Thermosphere (Ionosphere)
• 81-120 km
• Temp. rises steadily with increasing
altitude due to gamma rays, x-rays, and uv
rays
• Gases absorb x-rays and short wave uv
radiation
• Aurora borealis and aurora australis
(southern hemisphere) occur here
Aurora borealis-sept-oct, marchapril
Heat Transfer
• Heat always move from a warmer
substance to something that is cooler
• Heat moves in 3 ways:
– Radiation
– Conduction
– Convection
Radiation
• Transfer of energy through space as
waves or particles (no direct contact
between objects)
– Ex. When your car door handle gets hot on a
sunny day
– Dark objects absorb more radiation than light
objects
Conduction
• Transfer of heat between 2 objects that
are in contact with each other (when
molecules collide)
– Ex. When your hand touches the hot car
handle
Convection
• The transfer of heat by the movements of
the currents in gases and liquids
• Related to DENSITY
– Convection currents: warm air is less dense
than cooler air
– Convection currents cause winds and move
heat through the atmosphere
Heat Transfer
Weather vs. Climate
• Weather-day to day
• Climate-total of all weather occurring a
long period of time (includes avg temp and
avg precipitation)
Factors that Influence Climate
• Air mass-a large body of air that has
similar temps and moisture
• Can be equatorial, tropical, polar, arctic,
continental, or marine
Factors that Influence Climate
• Air pressure-gravity on an air mass,
measured in millibars, inches of mercury,
hectopascals (hPa), decreases with
altitude
low pressure=usually cloudy and
stormy weather
high pressure=usually fair weather
Factors that Influence Climate
• Albedo-reflectivity
– oceans=low albedo
– Land masses=moderate
– Snow & ice=high
More ice=more cooling (positive feedback loop)
Factors that Influence Climate
• Altitude-for every 1000 ft (300m) rise in
elevation, there is a 3F (1.5 C) drop in
temp
– Every 300 ft (90m) rise in elevation=62 mile
(100km) north latitude
Factors that Influence Climateangle of the sunlight
Factors that Influence ClimateCarbon Cycle
• Consumption of carbon results in cooling
• The production of carbon results in
warming
Factors that Influence Climate
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Clouds
Fronts
Greenhouse effect
Convection currents (atmosphere &
ocean)
• Land changes-urbanization/deforestation
• Landmass distribution
• Latitude
Factors that Influence Climate
• Humidity-water vapor a greenhouse gas
• Mountain ranges
• Plate tectonics and volcanoes: plate
instability=more volcanic activity
• Volcanoes-can cause tropospheric cooling
when a lot of ash is ejected into
atmosphere, also increased amount of ash
in oceans, increases biotic activity,
lowering carbon dioxide content of water,
which leads to cooling
Factors that Influence Climate
• Solar output-sunspots=decrease in solar
radiation, solar flare=increased radiation
• Pollution
• Precession (earth wobbles on its axis and
its orientation in space (tilt) can change
periodically)
• Wind patterns (global air circulation)
Major Climatic Periods
• Pleistocene Ice Age (2,000,000 B.C.E to
12,000 B.C.E)
– Large glaciers covered much of N. America,
Europe, and Asia
– Average temps. 7-9 F (4-5 C) colder than
today
Major Climatic Periods
• 12,000 B.C.E to 3000 B.C.E
– Gradual period of warming and glacial retreat
– Brief cooling period occurred between 10,0008500 B.C.E perhaps caused by a large influx
of fresh water shifting ocean currents
– By 3000 B.C.E average global temps = 2-4 F
(1-2 C) warmer than today
– Known as the Climatic Optimum (many great
ancient civilizations flourished during this
time)
Major Climatic Periods
• 3000 B.C.E. to 750 B.C.E
– Period of overall cooling
– Glaciers grew and sea level dropped
Major Climatic Periods
• 750 B.C.E to 900 C.E
– In general a warming trend except
• Roman Empire (150 B.C. E to 300 C.E) saw a
cooling trend when the Nile River and Black Sea
would freeze
Major Climatic Periods
• 900 C.E to 1200 C.E
• Little Climatic Optimum
– A warming period
– Vikings established settlements on Greenland
and Iceland
– Records of flood, droughts, and extreme
seasonal fluctuations
Major Climatic Periods
• 1550 C.E to 1850 C.E.
• Little Ice Age
• Average temp. of northern hemisphere=
2F (1 C) colder than today
Major Climatic Periods
• 1850 C.E to present
• General period of warming
Atmospheric Dynamics
• Atmospheric circulation
– Transfers heat from equator to the poles
(warm air near equator rises, then cools and
sinks again)
– Moderates earth’s temperature
– The atmosphere circulation AND the ocean
currents determine climate
• Climate=avg. temp. and avg. precipitation
Surface Winds
• Influenced by:
– Temperature and pressure differences
(gradients)
• Caused by:
– Uneven heating of earth’s surface
– Seasons
– Coriolis Effect
– Amount of solar radiation reaching earth
– Convection cells in the ocean
Differences in Atmospheric
Pressure
• Winds blow from high pressure to low
pressure (the greater the difference
between the high and low, the stronger the
wind
Earth’s Rotation
• Earth rotates from west to east
– Coriolis Effect: earth’s rotation causes the
winds to be deflected to the right in the
northern hemisphere and to the left in the
southern hemisphere
Three Prevailing Winds
• Winds are named for the direction they
come FROM
– Polar easterlies (north and south poles)
– Westerlies (mid-latitudes)
– Trade winds (tropics)
Three Prevailing Winds
3 Types of Air Circulation Cells
Associated with Latitude
• Hadley-tropics
• Ferrel-temperate regions
• Polar
Hadley Air Circulation Cells
• Warm air rises at the equator and moves
toward the temperate latitudes with air
there cooling and sinking to return to the
equator
• Equatorial regions are characterized by
high humidity, high clouds, and heavy
rains (tropical rainforest)
• Subtropical regions characterized by low
relative humidity, few clouds, high ocean
evaporation (deserts, savanna)
Ferrel Air Circulation Cells
• Develop between 30-60 north and south
latitude
• Climate goverend by both tropical and
polar air masses
• Defined seasons with strong annual cyles
of temp and precip.
• Broadleaf deciduous and taiga
Polar Air Circulation Cells
• Originate as icy-cold, dry dense air that
descends from the troposphere to the
ground
• Sinking air suppresses precipitation,
hence the polar regions are deserts
• Tundra and some taiga
The Ocean
• Salt water covers ¾ of the earth’s surface
(continuous body of water, but divided into
4 sections-Pacific, Atlantic, Indian, Arctic)
– Pacific covers 1/3 of earth and contains more
than ½ of earth’s water
Ocean Currents
• Caused by prevailing winds
– Gyres: circular ocean currents
• Influenced by Coriolis Effect
• Varying density-warm water is less dense
than cold water
Gyres
Weather
• Short term properties of the troposphere
such as:
– Temperature
– Pressure
– Humidity
– Precipitation
– Cloud cover
– Wind direction and speed
Fronts
• Boundary between 2 air masses with
different temps and densities
– Warm front
– Cold front
Warm Front
• Boundary between an advancing warm air
mass and the cooler one it’s replacing
• Warm air is less dense, so it rises up over
the mass of cooler air
• First signs: high, wispy clouds
– A moist warm front can bring days of cloudy
skies and drizzle
Warm Front
Warm Front
Warm Front
Cold Front
• Leading edge of an advancing mass of
cold air
• Wedges underneath (more dense) the
warmer air mass
• Produces thunderstorms
Cold Front
Cold Front
Cold Front
Air Pressure
• Caused by tiny molecules bouncing off of
each other; affected by gravity
– Air pressure at the earth’s surface is greatest
because of the weight of all of the other air
particles being pulled by gravity
• High pressure
• Low pressure
High Pressure
• High, dry, cool
• Winds are clockwise and out
• Usually associated with fair weather
Low Pressure
• Low, moist warm
• Winds move counterclockwise and inward
• Usually associated with stormy weather
High Pressure/Low Pressure
Extreme Weather
• Tornados (form over land)-each year more
than 800 touch down in the US
• Tropical Cyclones (form over water)
– Form over Atlantic Ocean=hurricanes
– Form over Pacific Ocean=typhoons
• The warmer the water where the storm tracks, the
more energy the storm has and the more
damaging it will be
• Monsoons
Hurricane/Typhoon
Hurricanes
• Most severe weather phenomenon
• Katrina=$75 billion in damage and 1,830
deaths
• Separate thunderstorms that develop over
tropical oceans, coriolis effect initiates
cyclonic flow
• Can be hundreds of kilometers
Typhoons/Hurricanes
• Negative Impacts-deaths, property
damage
• Ecological Benefits:
– Flushes out excessive nutrients, dead and
rotting sea grass from coastal bays and
marshes. This flushing out in turn:
• Reduced brown tides
• Increased growth of sea grasses
• Increased the number of shrimp, crabs, fish
Tornadoes
• Swirling masses of air with wind speeds
close to 300 mph
• Tornado alley in the U.S
• Hundreds of meters, one storm (not many)
Tornado
Monsoons
• Very strong winds that change direction
with season (blow from land to sea in
winter and sea toward land in summer)
• India (hot dry winters), wet heavy rains in
summer, because the monsoons bring
moisture from the ocean
• Farmers rely on this water for irrigation
and a large amount of India’s power is
generated by water received from
monsoons
El Nińo-Southern Oscillation
(ENSO)
• Air pressure patterns in south Pacific reverse
direction, so trade winds can weaken or even
reverse (so ocean water piles up in S. America
pushing thermocline deeper and causing many
changes)
• Prevailing westerly winds weaken or cease
• Surface water along the S. and N. American
coasts becomes warmer
• Suppresses upwellings(colder, more oxygenated
water that cycle nutrients)
El Nińo-Southern Oscillation
• Productivity decreases, sharp decline in
some fish populations
• Can trigger extreme weather changes
(mild winters on east coast, stronger
storms in the west)
• Shift in prevailing rain pattern
La Nińa
• Cooling of ocean surface water
• Shifts prevailing rain patterns
• More hurricanes b/c of temperature
increase in SE U.S
• Heavier than normal monsoons in India
and SE Asia
• Almost causes the opposite effect of El
Nino to the U.S.:
– Winter temps. warmer than usual in SE U.S
– Cooler than normal in NW
El Nińo-Southern Oscillation/ La
Nińa
Ozone Layer
• Located in Stratosphere
• O2 is continuously converted into O3
(ozone) by uv radiation
• Keeps 95% of harmful uv rays from
reaching the earth
• Provides a thermal cap so warm, churning
gases do not leave the troposphere
Microclimates
• Local climatic conditions
• Caused by:
– Mountains
– Cities
– Land to ocean interactions
Microclimates-Mountains
• (Seattle) Moist air blowing inland from the ocean
is forced to rise up over the mountains
• Rising air expands, cools, and condenses
(RECC) so precipitation occurs
• As the drier air mass flows down the other side
of the mountain it draws moisture from plants
and soil
• Rain Shadow Effect-the term for the low
precipitation and semi-arid conditions on the
leeward side of mountains
Rise, Expand, Cool, Condense
Microclimates-Mountains
Microclimates-Mountains
Microclimates-Cities
• Concrete, asphalt, brick, and building
materials absorb and hold heat and block
wind flow
• Haze and smog from pollutants released
from vehicles create higher temps.
Microclimates-Cities
Microclimates-Land-Ocean
Interactions
• Ocean to land breezes during the day (sea
breezes)
• Land to ocean breezes at night (land
breezes)
Sea Breeze
Land Breeze
Other wind types
• Anabatic winds- a warm wind which blows
up a steep slope or mountain side, driven
by heating of the slope through insolation,
• Katabatic winds- down-slope winds,
frequently produced at night by the
opposite effect, the air near to the ground
losing heat to it faster than air at a similar
altitude over adjacent low-lying land.