Download Climate System

Climate System
Sophie Zechmeister-Boltenstern
Reference:
Chapin F. St., Matson P., Mooney Harold A. 2002
Principles of Terrestrial Ecosystem Ecology. Springer, Berlin, 490 p.
Structure of this lecture
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The Atmospheric System
The Oceans
Landform effects on Climate
Vegetation Influences on Climate
Climate Variability
Climate and Ecosystems
Climate is the state factor that most strongly governs the global pattern
of ecosystem structure and function
Climate is a key mechanism by which ecosystems interact with
the total Earth System
Energy Budget
Energy in = energy out
Half of solar radiation
reaches Earth
The atmosphere is
transparent to
shortwave but absorbs
longwave radiation
(greenhouse effect)
The atmosphere is
heated from the bottom
by longwave radiation
and convection
Energy Budget
The temperature of a body determines
wavelengths of energy emitted
Solar radiation has high energy
(shortwave) that readily penetrates
the atmosphere
Earth emits low-energy (longwave)
radiation that is absorbed by the
atmosphere
Atmospheric
Structure
The atmosphere is heated from the
bottom
Therefore it is warmest near the
and gets colder with increasing
elevation
Atmospheric Circulation
Uneven heating of Earth’s surface causes atmospheric circulation
Greater heating at equator than poles
1. sun’s rays hit more directly
2. less atmosphere to penetrate
Therefore
1. Net gain of energy at equator
2. Net loss of energy at poles
Air rises at equator and subsides at poles
(vertical circulation)
Circulation cells explain
global distribution of rainfall
Earth’s rotation determines
wind direction
(horizontal circulation)
(Coriolis force)
tropical easterlies
temperate westerlies
At 30º N & S, air descends more strongly over cold ocean than over land
At 60 º N & S, air descends over cold land (high pressure) and rises over
warm ocean (low pressure)
Pressure gradients create geographic variation in prevailing winds
In summer at 60 º N & S, air descends over cold ocean (high pressure)
and rises over warm land (low pressure)
1. Cool equator-ward flow of air on W coast of continents
2. Warm poleward flow of air on E coasts of continents
Creates planetary waves
Uneven heating of Earth’s surface causes atmospheric circulation
60% of heat transport is carried by atmosphere through storms that
Move along pressure gradients
40% is carried by ocean currents (conveyor belt)
surface (warm) currents move poleward
deep (cold) currents move equatorward
Ocean
Circulation
Ocean currents are similar to wind patterns:
1. Driven by Coriolis forces
2. Driven by winds
Ocean currents move 40% of “excess heat” from equator to poles
Driven by circulation of deep ocean waters
Deepwater formation occurs near Greenland and in Antarctic
Landform effects on climate
• Land-water interactions
– Monsoons
– Land-sea breezes
• Mountain effects
– Rain shadow
– Effects of aspect
– Air drainage (inversion)
Vegetation effects on climate
Amazonasgebiet
How can the atmosphere warm?
1. More solar radiation
variation in Earth’s orbit
2. Less reflected shortwave
less sulfate aerosols
darker surface of Earth
(land-cover change)
3. More absorbed longwave
more “greenhouse gases”
Temporal Variability
in Climate
1. Long-Term Changes
Changes in solar orbit causes long-term variations in solar input to Earth
Climate effects on vegetation
Earth’s climate is now warmer than at any time in the last 1000 years
1. increased solar input (small warming effect)
2. Increased sulfate aerosols reflects radiation (small cooling effect)
3. Increased greenhouse gas concentrations (large warming effect)
4. Land-cover change creates a darker surface (large warming effect)
Inerannual Climate Variability
The Pacific Ocean strongly influences the climate system becauseIt is the largest
ocean basin.
Normal ocean current and wind direction in central Pacific is easterly
Interannual climate variation
ENSO events
Teleconnections carry these
climate effects throughout
the globe
(e.g., El Niño creates warm
winters in AK and Calif)
Weltweite Folgen von El Niňo
Seasonal and Daily Variations
Seasonal variation in climate results from tilt in Earth’s axis
Changes sun angle and day length
Climate and Ecosystem Distribution and Structure
Climate gives rise to predictable types of ecosystems
Summary
• Climate is a complex system determined
by radiation in- and output, atmospheric
circulations and oceans
• Milankowich cycles induce ice ages
• Landforms and landcover affect climate
• Interannual variability include ENSO (El
Nino) and NAO events
• Vegetation depends on climate but it also
affects climate