Transcript Document

CLIMATE
After the surface of
the earth cooled and
surface crust
(lithosphere)
formed, the planet
surface took on
something of the
“look” it has today
– land, air, oceans
(lithosphere,
atmosphere,
hydrosphere)
The temperature at
the ______ of the
earth is
determined, not by
geology of the core
but primarily by
energy coming
from outside – the
_____.
NASA
What is energy?
The capacity to do work (move mass) and transfer heat
Two main forms:
1. ________ – a mass moving
2. _________ – “stored” in a structure,
molecule, nucleus - able to become kinetic
under right conditions
Where does the sun get it’s energy? Nuclear fusion
Atoms of hydrogen fuse to form __________ – releases large
amounts of energy
Nuclear fusion
Reaction
conditions
Fuel
Proton
Neutron
Hydrogen-2
(deuterium nucleus)
100
million °C
Hydrogen-3
(tritium nucleus)
Products
Helium-4 nucleus
Energy
9-18/10-19
Neutron
Requires extremely high pressure & temperature conditions,
such as exist in the sun. Fusion reactions further _______ these
temperatures.
How does the sun supply energy to the earth?
The sun is a “hot body”. Hot bodies emit
___________ waves (EM), as a function of
their temperature.
What are electromagnetic waves? Light.
Physicists tell us that light has both ____ and particle
properties. The particles are called “photons”, the
wavelength measures their energy level.
The energy of light is determined by ___________
hc
E = -----
E = energy
h = Planck’s constant
c = speed of light
 = wavelength
There is a broad spectrum of wavelengths and energies
Shorter waves = _______ energy
Visible light is a small segment of the electromagnetic spectrum
The sun emits electromagnetic waves as a function of its
temperature. Its heat results from nuclear fusion (H to He)
Peak (intensity) wavelength of a radiating body (Wein’s law)
Max  = 2.88 x 106 / T (oK) T = temp
Sun’s max  = (2.88 x 106)/5750
= 500 nm (__________)
Peak Wavelength
Sun temperature 5750
oK
1200
1000
800
600
400
200
0
3000
4000
5000
6000
Temperature (K)
Interestingly, at planet formation,
sun 25% ________; max  = 670nm – orange
Stars heat up as they age (why?)
7000
Total light
energy is
distributed
around this
peak
wavelength
2-6
Much of the energy hitting the earth is in the ______ spectrum
Is this just a lucky coincidence?
The density (#photons/m2) _________ with distance from the sun
The energy density
intercepted by the
earth is determined
by the distance to
the sun.
“Solar _________” = 2 cal/cm2/min
1 cal/cm2/min reaches surface
Varies through the year
– orbit an _________.
The total energy intercepted by the earth a
function of area of the “profile”.
(earth radius = 6378km)
Solar constant x area =
2.495 x 1018 cal/min
This energy input
creates a surface
temperature, a
“dynamic
equilibrium” – a
balance of inputs
and outputs
2-10
What is a dynamic equilibrium?
“Equilibrium” describes an entity that appears
_____________ over time, a “steady state”.
For example, a tub of water half full.
There are at least two ways that tub could stay half full.
1. Turn off the tap - it sits there unchanging.
2. Leave the tap on, but open the drain.
#2 is a “dynamic equilibrium”
Obviously, a key relationship for a dynamic equilibrium is
________ = __________
What happens to an equilibrium if you increase inputs?
Does the water level go up, down, stay the same?
What did you assume to decide on your answer?
We can easily imagine at least three ways to get a
dynamic equilibrium in our bathtub
1. ________ output, ________ input – adjust input to
match output. Total amount in tub is irrelevant.
(could also have fixed input, match output)
2. Output __________ as input increases.
a. tub is fixed size, overflow = input, tub full.
b. output increases as amount in tub increases,
output eventually matches input
What kind of dynamic equilibrium is earth surface temperature?
Surface temperature is a balance of solar inputs,
reflectance, _________ and re-radiation (into space).
Re-radiation is also EM
waves, at _____ wavelength
If no re-radiation, no heat
loss, earth ____________.
As the earth heats up, it
re-radiates more (output
increases)
Type 2b dynamic equilibrium
Higher input, _________ equilibrium temperature.
If sun was cooler in past, earth was __________, yes?
Maybe, but this ignores the “greenhouse effect”
Components of
atmosphere absorb
outgoing wavelengths,
re-radiate back to _____,
increase heat before
leaving at lower energy.
Depends on composition of the atmosphere.
Carbon dioxide, ________, __________, and nitrous oxide are
strong “greenhouse gases”. Early earth atmosphere was _____ in
these, so may have been as warm as or warmer than today (est. 23oC).
Question: what would be an equivalent of the
greenhouse effect in the bathtub analogy?
Estimates of global
temperature indicate
lots of changes
during the history of
the planet.
Barry Saltzman, Dynamical Paleoclimatology: Generalized Theory of
Global Climate Change, Academic Press, New York, 2002, fig. 1-3.
Including “_________” that lasted many thousands of years
NOAA
Much of the earth was covered with ice packs miles
deep, that altered the landscape and created lakes and
rivers when they melted.
The most recent glacial period began about 70,000
years ago, and ended about _________ years ago.
These changes in ice pack directly affect the amount of
liquid water and therefore ocean levels.
12-16/12-15
12-17/12-16
Greenhouse gas composition
is one factor affecting this
temperature variation
12-17/12-16
Dynamical systems like surface temperature can be
difficult to understand and predict because of the
interconnectedness of the component processes.
These connections create feedback loops, or causal cycles
rather than simple causal chains like A affects B affects C.
For example, two simple feedbacks
1. ________ feedback – increase
in A increases B, which decreases
A. “homeostatic”, “stable”
2. _________ feedback – increase in A
increases B, which further increases A.
“Blowup” or “collapse”.
+
A
_
B
+
A
B
+
In earth temperature regulation, we have already
seen an example of each
1. Re-radiation: _________
feedback. Increasing solar input
(heating) results in increased
radiation to space (cooling)
2. Water Vapor: __________
feedback. Increased temperature
increases evaporation, increased
water vapor in atmosphere
increases greenhouse effect.
Earth
temp.
+
Re-radiation
_
+
Earth
temp.
Water vapor
+
But also, increased water vapor in the
atmosphere tends to increase cloud cover,
which increases ________ and thereby
decreases earth temperature
Earth
temp.
_
+
Water vapor
+
What would
you call this??
+
Cloud cover
In the bathtub analogy,
what is equivalent to
cloud cover?
Predicting cloud cover is an important
source of _________ in climate modeling.
Solar energy density is not even across the earth or
through the year – climate varies from place to place.
_____ in winter,
_____ at poles.
Opposite seasons
in the northern
and southern
hemispheres
Three basic ways heat is transferred:
1. Convection – movement of heated fluid due to density
2. Conduction – direct contact – molecular collisions
3. Radiation – EM waves from hot body
Wind and ocean currents move heat around
_________ cells – warm moist air
rises at equator, cools, rains; high
dry air moves toward poles, cools
and sinks.
12-3
Six “Hadley cells” in earth
redistribute heat and moisture
Wind and ocean currents move heat around
_____ winds form due to earth’s rotation –
faster at equator than at poles
Which way does the earth turn?
Wind and ocean currents move heat around
Similar forces generate ocean currents: differences in
temperature, wind, topography, _______, earth’s rotation
These currents can alter ________ on land in coastal areas
http://earth.usc.edu/~stott/Catalina/Oceans.html
Cold, salty water in the North Atlantic sinks and flows south into
the Pacific, eventually warms, rises and returns.
Topography can also alter climate
1. High altitude air is ________
– lower pressure
2. The “rain shadow effect”
– ______ on the “lee” side
Weather – large air masses generally moving and
interacting – local climate conditions frequently change
Fronts – where different
air masses contact, energy
is transferred.
______ front – moving
warm air mass contacts a
cold mass, it rises up,
widespread clouds.
______ front – moving cold
mass drives under a warm
air mass, sudden cooling,
strong winds and rain.
Tornadoes
High energy
concentration can result
in special storms with
spiraling high velocity
winds
Hurricanes (Typhoons)
___________ cycle
_____ driven evaporation of water into air begins a cycle as
the warm moist air rises, condenses to clouds and rain,
which returns directly to surface water (lakes, oceans) via
rivers and underground (ground water flow), and so on.
2-19/2-25
Energy flow and material cycles
The water cycle is an example of a general natural pattern on earth
the linkage of the flow of energy and cycling of materials
EM (Space)
Energy
flows
Water vapor
Water
cycles
Liquid Water
EM (Solar)
12-2
These multiple forces drive variation in climate across the world
Conclusions
earth a dynamic process, has history
geologically active – rock cycle
temperature a balance of factors
solar energy drives climate patterns
water cycles through its states
flows of energy and cycles of materials
interaction of geological and solar energy
NOAA