the atmosphere (abridged) purpose: the purpose of this presentation is to provide apes students with...

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 troposphere1. sunlight hits the Earth’s surface turning

into infrared (heat) radiation2. heat risessome escapes into space

some heats greenhouse gases emitting infrared radiation

which warm the troposphere

+


• Major greenhouse gases:- water vapor (primary)- CO2

- O3 (ozone)

- CH4 (methane)

- N2O (nitrous oxide)- CFCs (chlorofluorocarbons)


• 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• Normally troposphere gets cooler with

altitude• Temperature inversion--a layer or warmer air

above cooler surface air- subsidence inversionlarge mass of warmer air moves into a region, floats over top of stationary cooler air- radiation inversionat night air near the ground cools faster than air above


• 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: temperature-Cold Front


• 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: temperature-Warm 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


Stratus Clouds-lower altitude-layered and sheetlike


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


• 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: 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 Nino-Southern Oscillation (ENSO)

• Normal conditions in eastern equatorial Pacific Ocean

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: 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

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