Week 2: Systems and Energy

•Systems science

•Energy: forms and transformations

•Radiation

Reading: Chapter 2 of your textAssignment 2 (Due Friday)

Today –Change in Complex Systems

•Systems

•Earth Climate System

•Couplings and Feedbacks

Earth’s Atmosphere•Gases and some condensedphases

•Extends from Earth’s surface toabout 100 Km.

•Primary components % by volume•N2 (78%)•O2 (21%)•Argon (0.9%)•H2O vapor (0.00001 – 4%)•CO2 (0.038%)

•Many trace and ultra-tracecomponents that are important

Earth’s Hydrosphere

Earth’s Lithosphere

Continental Drift: Mechanism for ClimateChange

Movie downloadable from plates@ig.utexas.edu

Earth’s Biosphere

Microbes: most abundant lifeform. Phytoplankton, bacteria,etc.

Vegetation

????

Other life forms?

Earth as a Coupled System

Fig 1-1 fromtext

Couplings

If a change in onesubsystem is “felt” byanother—these partsare coupled

Couplings can give riseto feedbacks

An increase in the population of wolves would causethe population of bunnies to decrease. Is this a

positive or negative coupling?

Pos

itive

Neg

ativ

e

100%

0%

1. Positive2. Negative

But wait, a decrease in the number of bunnieswould cause a decrease in the wolves, so shouldn’t

it be a positive coupling?

Yes

No

83%

17%

1. Yes2. No

Feedbacks

X Y

Somethingincreases X

Positive coupling causes Y toincrease when X increases

Positive coupling causes X toincrease further when Y increases

+

+

Air T increases, sea surface T increases,causing stronger winds.

Pos

itive

feed

back

loop

Neg

ativ

e fe

edba

ck lo

op

Not

a fe

edba

ck lo

op

31%

63%

6%

1. Positive feedback loop2. Negative feedback loop3. Not a feedback loop

Today –Climate Stability and Energy

•Equilibrium – Stable and Unstable

•Perturbations and Forcings

•Energy: Work + Heat

Today –Announcements

•Please take online poll for office hours!

•Homework 2 link should be working now•DUE TUESDAY 22nd of JAN

Steady-State and EquilibriumSteady-state some property does not change in time.

Equilibrium implies steady state, but is more specific to asystem’s energy.

2nd Law of Thermodynamics: The equilibrium state of asystem has maximum disorder and minimum free energy

Energy “landscape” andequilibrium states.

“Local” equilibrium

unstable equilibrium

“Global” equilibrium

Changes in Climate Time Series

Fluctuations aroundstationary long-term trend

Fluctuations aroundnon-stationarylong-term trend

step change betweentwo mean states

(e.g. Internal readjustments)

(e.g. external forcings orperturbations)

Vostok Ice Core Record

T based on waterisotope proxy

ΔE = ΔW + ΔQ

• 1st Law of Thermodynamics

Pred > PATM

PATM

Pred = PATM

PATM

Plunger atrest afterexpansion

Connection toatmospheric motions

Release plunger

Expansion Work: Happens in Atmosphere

Something Else Involved

Something Else Involved

No mechanical or electrical work doneon the system, and yet, the system’sability to do work was increased.

Heat

system

surroundings

Energysystem

surroundings

Energy

Heat transport through Earth components isa fundamental aspect of climate and weather

For Prof. Thornton’s office hours, I prefer

Tu 1

1:3

0

Th 1

1:3

0

Tu 4

Th 4

38%

13%

30%

19%

1. Tu 11:302. Th 11:303. Tu 44. Th 4

For Brian’s 1st office hour set at 9 –10 AM, I prefer

M Tu

W Th

25% 25%

36%

15%

1. M2. Tu3. W4. Th

For Brian’s 2nd set of office hours, I prefer

Tu 5

Th 5

47%

53%

1. Tu 52. Th 5

Today –Announcements

•Please set your preferences fordiscussion page.

•Homework link should be working now•DUE TUESDAY 22nd of JAN•Brian will take questions about it onFri.

Summary

• 1st Law of Thermodynamics– ΔE = ΔW + ΔQ

• Equilibrium – minimum in energy/order

• Forcings, perturbations, and feedbacks– Induce natural variability around stable

equilibrium– or destabilize a system causing a state

change.

Thermochemistry

C HH

H

H + 2O2 CO2 + 2H2O ΔE ~ 5.6x104 KJ/kg

H2O(s) H2O(liq) requires 333 KJ/kg of heat

H2O(liq) H2O(gas) requires 2260 KJ/kg of heat

Consider the amount of heat released when reversed!

Heats of Fusion and Vaporization

Heats of Combustion

I put a glass of water in a dry, insulated containerand record the water temperature which

initi

ally

dec

reas

es

initi

ally

incr

ease

s

sta

ys c

onst

ant

14%

67%

19%

1. initially decreases2. initially increases3. stays constant

How much energy is required to operate a100-Watt light bulb for 24 hrs (86400 s).

1W = 1J/s

~8.6

x106 k

J

~8.6

x103 k

J

~2400 J

52%

8%

41%

1. ~8.6x106 kJ2. ~8.6x103 kJ3. ~2400 J

A coal fired power plant can produce 3x107 J per1 kg of coal burned. How much coal is required to

operate a 100 W light bulb for a day?

~ 3

kg

~ 0

.3 k

g

~ 3

00 k

g

21%25%

54%1. ~ 3 kg2. ~ 0.3 kg3. ~ 300 kg

Summary

•Heat flow into or out of a substance changesits temperature (heat capacity)

•Land-sea T differences•Energy required to increase sea surface T

•Phase changes require or release heat•Energy required to melt a glacier•Energy released during cloud formation

•Evaporative cooling: liquid itself supplies heatfor vaporization

•A form of T regulation

Announcements

• Device ID check• What’s recorded• Seminars: www.atmos.washington.edu

– ATMS colloquium Fridays 3:30pm here– Program on Climate Change– ESS

Towards a Climate Model

• The energy of a gas is a function of itstemperature only (vice versa).

• Thus, if the atmosphere’s T changes, itsenergy balance has changed.

• If we can describe the sources and sinksof energy, we can predict T.

Earth’s Primary Energy Source

• Light is energy?• How much energy does the Earth receive?

Charged Particle Motion

- +

Electromagnetic field disturbance

Charged Particle Motion

-

+

Electromagnetic field disturbance

Charged Particle Motion

-

+

Electromagnetic field disturbance

Charged Particle Motion

-+

Oscillations in the electric and magnetic fieldsmove, “radiate”, through space.

Such oscillations are known as electromagneticradiation (which encompasses light)

The chair you are sitting on is emittingelectromagnetic radiation

Tru

e

Fals

e

52%

48%

1. True2. False

Electromagnetic Radiation

Wavelength (λ): distance between peaks: m,cm,µm

Frequency (ν): # of full cycles passing a point per second: Hz

λ and ν related by speed of light (c): ν = c/λ

Energy Carried by Electromagnetic Radiation

The energy a photon carries is directly proportionalto its frequency

Ephoton = hν

h is Plank’s constant6.636x10-34 Js

The intensity (brightness) of radiation is related to thenumber of photons of a particular frequency

List the wavelengths of light in order ofincreasing energy

220

nm

, 530

nm

, 50.

.

500

0 nm

, 530

nm

, 2..

72%

28%

1. 220 nm, 530 nm, 5000 nm2. 5000 nm, 530 nm, 220 nm

Electromagnetic SpectrumEnergy increases this way

Wavelengthincreases this way

The sun emits the most photons as green light (~ 500 nm6x1014 s-1). Our bodies intercept ~200 W during a sunnysummer day (very rough). Estimate, or guess, roughly how

many green photons your body intercepts per second.

100

0 ph

oton

s/s

1x1

07 p

hoto

ns/s

1x1

020

phot

ons/

s

2%

19%

79%

1. 1000 photons/s2. 1x107 photons/s3. 1x1020 photons/s

Electromagnetic SpectrumEnergy increases this way

Wavelengthincreases this way