Download - APES – Earth’s Heat Engine
APES – Earth’s Heat Engine
How heat is transported through Earth’s atmosphere and oceans
Lecture Overview
• How is heat redistributed around our planet?• What creates distinct patterns of rainforests
and deserts?
Answer:
• The sun!• Well… it’s not quite that
simple.
Where do winds come from?• What happens when you heat molecules?• Heated fluids and gases become less dense and rise• Cooled fluid/gases become more dense and sink
heat
Less dense fluid rises
More dense fluid sinks
coolingAir moves because at one place less dense air rises, while in another place denser air sinks toward Earth
A convection cell is formed in the atmosphere when air is warmed at one location and cooled at another
Where do winds come from?
• Idealized Earth with no rotation, no land– Unequal heating like real
Earth• Around equator, the air
warmed from below rises• Flows toward poles,
where it is cooled and sinks back toward the equator
• Go to Moving Heat Animation
Fig. 7.16
air rises
air cools and sinks
What factors determine the density of air?
• Heating and cooling of air and gains and losses of water vapor in the air are related to:– Unequal distribution solar energy over Earth’s surface– Presence or absence of water– Variation in temperature of earth’s surface materials in response to
heating• These act to affect the density of air
– Temperature - warmer air, less dense– Water vapor – moist air less dense (water has lower molecular
weight than dry air)– Altitude – less dense with increasing altitude
• Warm moist air is less dense than cool, dry air
What is atmospheric pressure?
• Atmospheric pressure is the force of a column of air on an area of earth’s surface
• High pressure – density of air is more dense than average
• Low pressure – density of air is less dense than average
• Winds blow from high to low pressure
• Winds named from direction they come from
low pressure
high pressure
Is this a North or South wind?
N
S
How are vegetation patterns related to atmospheric circulation?
http://www.esa.int/Our_Activities/Observing_the_Earth/ESA_global_land_cover_map_available_online
Comment: Better legend for previous map
The water cycle is driven by solar energy too
• We often think of the water cycle as a local phenomenon
• Important globally• Return to
Moving Heat Animation
How can disrupting the water cycle, change climate?
How can disrupting the water cycle, change climate?
• The rainforests (and all forests) ‘make’ their own clouds
• Transpiration video• Transpiration in Amazon
creates rainfall in:– Peru– Bolivia– Argentina– Uraguay– Paraguay and S. Brazil
http://www.guardian.co.uk/environment/2009/apr/01/prince-charles-rainforest-funding
Energy in Evaporation and Condensation
• Energy is transported through atmosphere with the molecules, especially water!
• The transfer of energy from surface to atmosphere disrupted.
Summarize so far…
• How are the water cycle and atmospheric circulation related?
• What impacts does deforestation have to both cycles?
Tomorrow
• Examine the atmosphere in more detail– Normal function of greenhouse gases– Heat trapping properties of certain gases