Transcript The Atmosphere (Abridged)

The Atmosphere (Abridged)
Purpose: The purpose of
this presentation is to
provide APES students with
important information on
the atmosphere.
Objective: At the end of
this presentation students
will have generated notes
necessary to understand
key processes in the
Earth’s atmosphere.
The Atmosphere-history
• 3.2 billion years ago (bya) atmosphere mostly
steam and CO2 (Life begins in sea)
• 2.3-2.7 bya photosynthetic bacteria
(cyanobacteria) began producing oxygen
• 400-500 mya ozone levels in stratosphere
sufficient to protect land plants from UV
radiation.
The Atmosphere-current
composition
•
•
•
•
•
78 % N2
21 % O2
Around 1% Ar2
0.01-4% H2O
0.037 CO2
The Atmosphere-current composition
• The Greenhouse Effect
- Natural warming effect of the troposphere
1. sunlight hits the Earth’s surface turning
into infrared (heat) radiation
2. heat risessome escapes into space
some heats greenhouse gases
emitting infrared radiation
which warm the troposphere
+
The Atmosphere-current composition
• Major greenhouse gases:
-
water vapor (primary)
CO2
O3 (ozone)
CH4 (methane)
N2O (nitrous oxide)
CFCs (chlorofluorocarbons)
The Atmosphere-current composition
• Mean global temperature
14.53oC or 58.14oF (2000-2008)
14.0oC or 57.2oF (1951-1980)
(Source http://data.giss.nasa.gov)
-18oC
or 0oF without greenhouse effect
The Atmosphere-Climate
• Climate: Regional patterns of atmospheric
conditions
-mainly influenced by average temperature
and precipitation
-globally follows a cyclic pattern
+ glacial periods lasting around 100,000 yrs
+ interglacial periods lasting around
10,000 yrs
+ Holocene epoch—nearing end of
interglacial period
The Atmosphere-climate
Factors that affect global climate
 shape of the Earth’s orbit (eccentricity)
 “wobble” of the Earth’s axis (precession)
 changes in the tilt of the Earth’s axis
(obliquity)
 volcanic activity
 changes in solar output
 atmospheric composition
The Atmosphere-climate
Factors that affect regional climate
 uneven heating of the Earth’s surface
(varies by latitude and season)
 rotation of the Earth
 ocean currents
 mountains
 altitude
 tilt of the Earth
The Atmosphere-factors that affect
regional climate
Uneven heating of the Earth’s surface
 Consistent, year-round heating at equator
 More seasonal variation as latitude increases
 Uneven heating produces atmospheric areas
of low pressure (less dense, rising air) and
high pressure (more dense, falling air.)
 Pattern alternates about every 30 degree
change in latitude (p. 125)
The Atmosphere-factors that affect
regional climate: Earth’s rotation
Coriolis Effect—The apparent deflection of a
moving object due to the motion of the Earth
underneath it
The Atmosphere-factors that affect
regional climate: ocean currents
• Water’s high specific heat causes it to gain and
lose heat slower than land masses
• Oceans produce milder climates
• Changes in density due to temperature
differences and the Earth’s rotation produce
ocean circulation patterns
• Europe is warmer than it should be due to
warm ocean currents
The Atmosphere-factors that affect
regional climate: ocean currents
The Atmosphere-factors that affect
regional climate: mountains
• Mountains force air masses to rise as they
pass across them
• Rising air cools and moisture condenses
producing precipitation on the “windward’
side
• Descending air on the “leeward” side has less
moisture producing areas of lower
precipitation
• Rain shadow effect
The Atmosphere-factors that affect
regional climate: mountains
The Atmosphere-factors that affect
regional climate: altitude
Average temperature decreases about 3oF for
every 1000 feet in altitude
Barrons p. 117
The Atmosphere-factors that affect
regional climate: tilt of the Earth
• The Seasons!
The Atmosphere-weather
• Weather-The short-term conditions in the
troposphere at a location.
• Includes atmospheric conditions such as
- temperature
- pressure
- relative humidity
- sunshine
- cloud cover
- wind direction and speed
The Atmosphere-weather:
temperature
• Measure of kinetic energy
• Differences produced by uneven heating of
Earth’s surface
• Maps of areas with the same temperatures
are called isotherms
The Atmosphere-weather:
temperature
The Atmosphere-weather: temperature
• Normally troposphere gets cooler with
altitude
• Temperature inversion--a layer or warmer air
above cooler surface air
- subsidence inversionlarge mass of warmer
air moves into a region, floats over top of
stationary cooler air
- radiation inversionat night air near the
ground cools faster than air above
The Atmosphere-weather: temperature
The Atmosphere-weather: temperature
• Cold Front—leading edge of advancing mass
of cold air
-more dense so slides under warmer air lifting
it
-rising warm air produces thunderheads and
rainstorms
The Atmosphere-weather: temperatureCold Front
The Atmosphere-weather: temperature
• Warm Front—leading edge of advancing mass
of warm air
-less dense so rises up over colder air
-more gradual lifting produces thickening
clouds and longer periods of rain
The Atmosphere-weather: temperatureWarm Front
The Atmosphere-weather: temperature
(note symbols)
The Atmosphere-weather:
clouds
• Condensation of water vapor in rising air due
to lower temperatures.
• Atmospheric conditions determine cloud type
• Cloud names indicate appearance and altitude
The Atmosphere-weather:
Clouds
Cirrus Clouds:
-High altitude
-Thin and wispy
The Atmosphere-weather:
Clouds
Stratus Clouds
-lower altitude
-layered and
sheetlike
The Atmosphere-weather:
Clouds
Cumulus Clouds
-Low to medium
altitude
-Flat bottom and fair
weather
-Cumulonimbus are
thunderstorm clouds
The Atmosphere-weather:
Pressure
 Earth’s gravity pulling down on molecules in
the atmosphere creates atmospheric pressure
Atmospheric pressure at sea level is:
- 760 mm of Hg
- 29.9 in. of Hg
- 14.7 psi
- 1013.25 millibar
The Atmosphere-weather:
Pressure
• Maps of areas with the same barometric
pressure are called isobars
• Areas of low pressure bring cloudy rainy
weather. Counterclockwise (NH) (cyclone)
• Areas of high pressure usually indicate clear
weather. Clockwise (NH) (anticyclone)
• Air moves from areas of high pressure into
areas of low pressure—wind!
The Atmosphere-weather:
Pressure
The Atmosphere-weather:
Pressure
The Atmosphere-weather:
Jet Stream
• Narrow, fast-moving wind current in the upper
troposphere
• Position usually coincides in part with the
regions of greatest storminess in the lower
troposphere
• Also called polar jet stream, because of the
importance in moving cold, polar air.
The Atmosphere-weather:
Jet Stream
Atmospheric-Oceanic Interactions: El NinoSouthern Oscillation (ENSO)
• Normal conditions in eastern equatorial
Pacific Ocean
Atmospheric-Oceanic Interactions: ENSO
Atmospheric-Oceanic Interactions: ENSO
• El Nino-A warming of the surface water of the
eastern and central Pacific Ocean, occurring
every 4 to 12 years and causing unusual global
weather patterns.
• trade winds that usually push warm surface
water westward weaken, allowing the warm
water to pool as far eastward as the western
coast of South America.
Atmospheric-Oceanic Interactions: ENSO
Atmospheric-Oceanic Interactions: ENSO
Atmospheric-Oceanic Interactions:
La Nina
• Cooling of the surface water of the eastern
and central Pacific Ocean, causing similar,
generally opposite disruptions to global
weather patterns.
• Trade winds blow more strongly than usual,
pushing the sun-warmed surface water farther
west and increasing the upwelling of cold
water in the eastern regions.
Atmospheric-Oceanic Interactions: El Nino vs. La Nina
Typical vs. El Nino vs. La Nina
• Typical
• Winds off the western coast of equatorial South America blow
east to west, pushing surface waters west.
• Cooler deeper waters rise (upwelling) to replace moving
surface water, bringing nutrients to the surface, increasing fish
populations.
• El Nino
• Winds off the western coast of equatorial South America
lessen, stop or start to blow west to east.
• Warmer surface waters deepen as they “run into” western
South America. Deep nutrients do not rise, decreasing fish
populations.
• La Nina
• Winds off the western coast of equatorial South America
strengthen, blowing east to west, pushing surface waters
west.
• Surface waters off of the west coast of equatorial South
America cool due to increased upwelling. Increased fish
populations.
Typical vs. El Nino vs. La Nina
• Typical
• Normal rainfall in western South America, southeastern Asia,
eastern Africa, southeastern South America and southeastern
U.S.
• Normal rainfall in southern Africa, Australia, eastern South
America, northwestern and northeastern Canada and U.S.
• El Nino
• Increased rainfall in western South America, southeastern
Asia, eastern Africa, southeastern South America and
southeastern U.S.
• Less rainfall/drought in southern Africa, Australia, eastern
South America, northwestern and northeastern Canada and
U.S.
• La Nina
• Decreased rainfall in western South America, southeastern
Asia, eastern Africa, southeastern South America and
southeastern U.S. Increased tornadoes in the U.S.
• More rainfall in southern Africa, Australia, eastern South
America, northwestern and northeastern Canada and U.S.
Typical vs. El Nino vs. La Nina
• Typical
• Normal number of Atlantic and Pacific hurricanes
• Normal temperatures in eastern Asia, northwestern
Canada and U.S. and northeastern Canada and U.S.
• El Nino
• Fewer Atlantic and more Pacific hurricanes
• Warmer temperatures in eastern Asia, northwestern
Canada and U.S. and northeastern Canada and U.S.
• La Nina
• “Sometimes” more Atlantic and fewer Pacific hurricanes
• Cooler winter temperatures in southeastern and
southwestern U.S.
• Warmer winter temperatures in north central U.S.
Don’t Forget the 5-Question Quick
Quiz on Tuesday