Air, Weather, and Climate - PowerPoint PPT Presentation

1 / 41
About This Presentation
Title:

Air, Weather, and Climate

Description:

Air, Weather, and Climate Current Evidence of Climate Change Global average surface temperature rose 0.6o C during 20th century. Droughts are more frequent and ... – PowerPoint PPT presentation

Number of Views:129
Avg rating:3.0/5.0
Slides: 42
Provided by: ccsN5
Category:

less

Transcript and Presenter's Notes

Title: Air, Weather, and Climate


1
Air, Weather, and Climate
2
Outline
  • The Atmosphere and Climate
  • Greenhouse Effect
  • Convection Currents
  • Weather
  • Coriolis Effect
  • Cyclonic Storms
  • Climate
  • El Nino
  • Climate Change

3
THE ATMOSPHERE AND CLIMATE
  • Weather - A description of physical conditions of
    the atmosphere.
  • Climate - A description of the long-term weather
    pattern in a particular area.
  • Weather and climate are primary determinants of
    biomes and ecosystem distribution.

4
The Atmosphere and Climate
  • Troposphere
  • Ranges in depth from 18 km over the equator to
    8.0 km over the poles.
  • All weather occurs here.
  • Composition is relatively uniform.
  • Air temperature drops rapidly with increasing
    altitude.
  • Tropopause - Transition boundary that limits
    mixing between the troposphere and upper zones.

5
The Atmosphere and Climate
  • Stratosphere
  • Extends from troposphere to about 50 km.
  • Air temperature is stable, or increases with
    altitude.
  • Has almost no water vapor and ozone is 1000x more
    than in the troposphere.
  • Relatively calm

6
The Atmosphere and Climate
  • Mesosphere
  • Middle Layer
  • Thermosphere
  • Begins at 80 km.
  • Ionized gases and high temperatures.
  • Lower Thermosphere
  • Aurora borealis (northern lights)

7
(No Transcript)
8
Energy and the Greenhouse Effect
  • Of the solar energy that reaches the outer
    atmosphere
  • About one-quarter is reflected by clouds and the
    atmosphere.
  • Another quarter is absorbed by carbon dioxide,
    water vapor, ozone and a few other gases.
  • About half reaches the earths surface.

9
Energy Balance
10
Energy and the Greenhouse Effect
  • Surfaces that reflect energy have a high albedo
    (Reflectivity).
  • Fresh clean snow 80-85
  • Dark soil 3
  • Net average of earth 30

11
Energy and the Greenhouse Effect
  • Most solar energy reaching the earth is visible
    light.
  • Energy reemitted by the earth is mainly infrared
    radiation (heat energy).
  • Longer wavelengths are absorbed in the lower
    atmosphere, trapping heat close to the earths
    surface.
  • Greenhouse Effect
  • Increasing atmospheric CO2 due to human
    activities appears to be causing global warming.

12
Convection and Atmospheric Pressure
  • Lighter air rises and is replaced by cooler,
    heavier air, resulting in vertical convection
    currents.
  • Transport energy and redistribute heat.
  • Much of solar energy absorbed by the earth is
    used to evaporate water.
  • Energy stored in water vapor as latent heat.
  • If condensation nuclei are present, or if
    temperatures are low enough, condensation will
    lead to precipitation.

13
Convection Currents
  • Releasing latent heat causes air to rise, cool,
    and lose more water vapor.
  • Rising, expanding air creates an area of
    relatively high pressure at the top of the
    convection column.
  • Air flows out of high-pressure zone towards areas
    of low-pressure, where cool, dry air is subsiding.

14
Convection Currents
  • Subsiding air is compressed as it approaches the
    earths surface where it piles up and creates an
    area of high pressure at the surface.
  • Air flows out of this region back towards low
    pressure, closing the cycle.

15
(No Transcript)
16
Coriolis Effect
  • As air warms at the equator, rises, and moves
    northward, it sinks and rises in several
    intermediate bands, forming circulation cells.
  • Surface flows do not move straight North and
    South, but are deflected due to Coriolis Effect.

17
Coriolis Effect
  • Major zones of subsidence occur at about 30o
    north and south latitude.
  • Where dry, subsiding air falls on continents, it
    creates broad, subtropical desert regions.
  • Winds directly under regions of subsiding air are
    often light and variable.

18
Jet Streams
  • Jet Streams - Large-scale upper air flows.
  • Generally follow undulating paths where Hadley
    and Ferrell cells meet.

19
Ocean Currents
  • Warm and cold ocean currents strongly influence
    climate conditions on land.
  • As surface water moves, deep water wells up to
    replace it.
  • Ocean circulation also driven by differences in
    water density.
  • Gyres

20
Seasonal Winds and Monsoons
  • Monsoon - Seasonal reversal of wind patterns
    caused by differential heating and cooling rates
    of oceans and continents.
  • Most prevalent in tropical countries where large
    land area is cut off from continental air masses
    by mountain ranges and surrounded by a large
    volume of water.

21
Frontal Weather
  • Cold Front - Boundary formed when cooler air
    displaces warmer air.
  • Cold air is more dense, thus hugs ground and
    pushes under warm air.
  • Warm air cooled adiabatically.
  • Warm Front - Boundary formed when warm air
    displaces cooler air.
  • Warm air is less dense and slides over cool air,
    creating a long wedge-shaped band of clouds.

22
(No Transcript)
23
Cyclonic Storms
  • When rising air is laden with water vapor, latent
    energy released by condensation intensifies
    convection currents and draws up more warm air
    and water vapor.
  • Storm cell will exist as long as temperature
    differential exists.
  • Hurricanes (Atlantic)
  • Typhoons (Western Pacific)
  • Cyclones (Indian Ocean)

24
Cyclonic Storms
  • Tornadoes - Swirling funnel clouds.
  • Rotation not generated by Coriolis forces.
  • Generated by supercell frontal systems where
    strong dry cold fronts collide with warm humid
    air.
  • Greater air temperature differences in Spring
    thus more tornadoes.
  • Spinning - Rolling vortex tubes.
  • Downbursts - Disorganized supercells.

25
Tornadoes
26
CLIMATE
  • Driving Forces and Patterns
  • Periodic weather cycles detected.
  • Solar magnetic cycles
  • Milankovitch Cycles - Periodic shifts in earths
    orbit and tilt.
  • Change distribution and intensity of sunlight
    reaching the earth.
  • Ice cores show drastic changes may have occurred
    over short periods of time (decades).

27
El Nino Southern Oscillation
  • Large pool of warm surface water in Pacific Ocean
    moves back and forth between Indonesia and South
    America.
  • Most years, the pool is held in western Pacific
    by steady equatorial trade winds.
  • Every three-five years the Indonesian low
    collapses and the mass of warm surface water
    surges back east.

28
El Nino Southern Oscillation
  • During an El Nino year, the northern jet stream
    pulls moist air from the Pacific over the U.S..
  • Intense storms and heavy rains.
  • During intervening La Nina years, hot, dry
    weather is often present.
  • Pacific Decadal Oscillation - Very large pool of
    warm water moving back and forth across the North
    Pacific every 30 years.

29
(No Transcript)
30
Human-Caused Global Climate Change
  • In 1988, the Intergovernmental Panel on Climate
    Change (IPCC) was formed.
  • Released third climate report in February 2001.
  • Recent changes in worlds climate have had
    discernable impacts on physical and biological
    systems.
  • Human activities must be at least partially
    responsible.

31
CO2 Concentrations on Mauna Loa
32
Sources of Greenhouse Gases
  • Carbon Dioxide - Fossil-fuel burning.
  • Atmospheric levels increasing steadily.
  • Methane - Ruminants, Coal-mines.
  • Absorbs more infrared than CO2.
  • Chlorofluorocarbons (CFCs) - Refrigerants
  • Declined in recent years.
  • Nitrous Oxide - Burning organic material.

33
Aerosol Effects
  • Aerosols have a tendency to reflect sunlight and
    cool surface air temperatures.
  • Short-lived, thus effects are temporary.
  • Mt. Pinatubo erupted in 1991 and ejected enough
    ash and sulfate particles to cool global climate
    about 1o C for nearly a year.

34
Current Evidence of Climate Change
  • Global average surface temperature rose 0.6o C
    during 20th century.
  • Droughts are more frequent and widespread.
  • Severe weather events have increased
    dramatically.
  • Polar regions have warmed much faster than the
    rest of the world.
  • Ice shelves on Arctic peninsula are disappearing.
  • Many animals breeding earlier and extending their
    ranges.
  • Amphibians disappearing.

35
Current Evidence of Climate Change
  • Retreating alpine glaciers.
  • Mt. Kilimanjaro
  • Glacier National Park
  • Coral reefs are bleaching.
  • Northern growing seasons are longer.
  • Sea level has risen.
  • Arctic sea ice is 40 thinner.

36
Winners and Losers
  • Residents of extreme northern areas would enjoy
    warmer temperatures and longer growing-seasons.
  • Plant growth patterns may be altered.
  • One-third of population living in areas likely
    flooded by rising seas.
  • More evaporation may cause severe storms.
  • Infectious disease likely to spread faster.
  • Circulation patterns may cause more snowfall at
    poles - New ice age ?

37
Predicted Warming for CO2 Doubling in 2100
38
International Climate Negotiations
  • Kyoto Protocol (1997)
  • 160 nations agreed to roll back carbon dioxide,
    methane, and nitrous oxide emissions about 5
    below 1990 levels by 2012.
  • Sets different limits for different countries,
    depending on prior output.
  • Developing countries exempted.
  • 126 countries have ratified the Protocol. U.S.
    has not.

39
Controlling Greenhouse Emissions
  • Reducing carbon dioxide levels.
  • Renewable energy sources may offer a better
    solution to climate problems.
  • Capturing and storing carbon dioxide.
  • Carbon Management
  • Planting vegetation
  • Emissions trading system
  • Deep water injection

40
Summary
  • The Atmosphere and Climate
  • Greenhouse Effect
  • Convection Currents
  • Weather
  • Coriolis Effect
  • Cyclonic Storms
  • Climate
  • El Nino
  • Climate Change

41
(No Transcript)
Write a Comment
User Comments (0)
About PowerShow.com