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 condensed phases

•Extends from Earth’s surface to about 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-trace components that are important

Earth’s Hydrosphere

Earth’s Lithosphere

Continental Drift: Mechanism for Climate Change

Movie downloadable from plates@ig.utexas.edu

Earth’s Biosphere

Microbes: most abundant life form. Phytoplankton, bacteria, etc.

Vegetation

????

Other life forms?

Earth as a Coupled System

Fig 1-1 from text

Couplings

If a change in one subsystem is “felt” by another—these parts are coupled

Couplings can give rise to feedbacks

An increase in the population of wolves would cause the population of bunnies to

decrease. Is this a positive or negative coupling?

Posi

tive

Neg

ativ

e

100%

0%

1. Positive2. Negative

But wait, a decrease in the number of bunnies would cause a decrease in the

wolves, so shouldn’t it be a positive coupling?

Yes N

o

83%

17%

1. Yes2. No

Feedbacks

X Y

Something increases X

Positive coupling causes Y to increase when X increases

Positive coupling causes X to increase further when Y increases

+

+

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

Posi

tive

feed

back

loop

Neg

ativ

e fe

edbac

k lo

op

Not a

feed

back

loop

31%

63%

6%

1. Positive feedback loop

2. Negative feedback loop

3. 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 a system’s energy.

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

Energy “landscape” and equilibrium states.

“Local” equilibrium

unstable equilibrium

“Global” equilibrium

Changes in Climate Time Series

Fluctuations around stationary long-term trend

Fluctuations around non-stationary long-term trend

step change between two mean states

(e.g. Internal readjustments)

(e.g. external forcings or perturbations)

Vostok Ice Core Record

T based on water isotope proxy

E = W + Q

• 1st Law of Thermodynamics

Pred > PATM

PATM

Pred = PATM

PATM

Plunger at rest after expansion

Connection to atmospheric motions

Release plunger

Expansion Work: Happens in Atmosphere

Something Else Involved

Something Else Involved

No mechanical or electrical work done on the system, and yet, the system’s ability to do work was increased.

Heat

system

surroundings

Energy

system

surroundings

Energy

Heat transport through Earth components is a fundamental aspect of climate and weather

For Prof. Thornton’s office hours, I prefer

Tu 1

1:30

Th 1

1:30

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 T

h

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 for discussion page.

•Homework link should be working now

•DUE TUESDAY 22nd of JAN•Brian will take questions about it on Fri.

Summary

• 1st Law of Thermodynamics E = W + Q

• 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 H

H

H

H + 2O2 CO2 + 2H2O E ~ 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 container and 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 decreases

2. initially increases3. stays constant

How much energy is required to operate a 100-Watt light bulb for 24

hrs (86400 s). 1W = 1J/s

~8.

6x10

6 kJ

~8.

6x10

3 kJ

~24

00 J

52%

8%

41%

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

A coal fired power plant can produce 3x107 J per 1 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 changes its 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 heat for 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 its temperature only (vice versa).

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

• If we can describe the sources and sinks of 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 fields move, “radiate”, through space.

Such oscillations are known as electromagnetic radiation (which encompasses light)

The chair you are sitting on is emitting electromagnetic radiation

Tru

e

Fal

se

52%

48%

1. True2. False

Electromagnetic Radiation

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

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

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

Energy Carried by Electromagnetic Radiation

The energy a photon carries is directly proportional to its frequency

Ephoton = h

h is Plank’s constant6.636x10-34 Js

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

List the wavelengths of light in order of increasing energy

220

nm

, 530

nm

, 50.

.

500

0 nm

, 530

nm

, 2..

72%

28%

1. 220 nm, 530 nm, 5000 nm

2. 5000 nm, 530 nm, 220 nm

Electromagnetic SpectrumEnergy increases this way

Wavelength increases this way

The sun emits the most photons as green light (~ 500 nm6x1014 s-1). Our bodies intercept ~200 W

during a sunny summer day (very rough). Estimate, or guess, roughly how many green photons your

body intercepts per second.

100

0 photo

ns/s

1x1

07 p

hotons

/s

1x1

020

photon

s/s

2%

19%

79%1. 1000 photons/s2. 1x107 photons/s3. 1x1020

photons/s

Electromagnetic SpectrumEnergy increases this way

Wavelength increases this way