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Overview of Chapter 1-4: October 17. Chapter 1 Overview. Dx dy = [R*cos  * d  ][Rd  ]. Application to Atmospheric flow, e.g., Exercise 1.20. N 2 , O 2 dissociation. P=mg P ~ p o exp(-z/H). O 3 dissociation. Rad. + conv. Main gases + greenhouse gases (Table 1.1).

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Presentation Transcript
slide2

Chapter 1 Overview

Dx dy =

[R*cos* d][Rd]

Application to

Atmospheric flow, e.g.,

Exercise 1.20

slide3

N2, O2 dissociation

P=mg

P ~ po exp(-z/H)

O3 dissociation

Rad. + conv.

Main gases + greenhouse gases (Table 1.1)

slide4

Cyclonic: low pressure in

both hemispheres, CCW

In NH

SP NP

Think: right-hand-rule. explains

Flow around a low in NH

slide6

Surface winds + SLP, NCEP

January

Understand (simply) what are the

Major meteorological regimes

And why they are there.

July

July rainfall

slide7

Chapter 2: The Earth System

Thermohaline circulation

Cryosphere budget (table 2.1)

Carbon Cycle

Oxygen

Earth History:hothouse period, glacial cycles

Exercises: know how to do all of them, will provide

numbers for calc.

slide12

Euphotic zone takes up carbon dioxide, decaying matter

Sinks it deeper.

2nd

Carbon

Cycle:

The Ocean

slide13

Carbon in the Oceans:

CO2 + H2O -> H2CO3 carbonic acid. Equilibrate w/atmos.

H2CO3 -> H+ + HCO3 bicarbonate ion

HCO3 -> H+ + CO32-

Net: CO2 + CO32- + H2O -> 2HCO3

This is connected to Calcium from the Earth’s mantle:

Ca + 2HCO3 -> CaCO3 + H2CO3coral. 3rd carbon cycle

Where the Ca derived from the weathering of

Rocks containing Ca-Si.

slide15

Oxygen:

Unique component of Earth’s atmosphere

Increasing with time:

Photosynthesis creates oxygen

- and -

Reduction of water (H2O -> H2 + O) via mineralization,

with hydrogen escaping to space.

slide16

Early Earth’s History, in brief:

~ 4.5 billion years ago (bya): accretion from

planetesimals, evidence is lack of noble gases relative

to cosmos.

2. 1st ~750 millions years, named Hadean Epoch: more

bombardment, early atmosphere, moon

3. 1st production of O2, 3.0-3.8 bya.

Low atmos. conc., but ozone layer

4. Increased O2, 2 bya. -> 1st glaciation

slide17

Sun’s luminosity increases w/ time as core contracts.

Why wasn’t Earth’s surface frozen ?

slide19

2nd glaciation: ~ 2.5 million years ago.

  • Reduced plate tectonics -> reduced volcanic
  • emission of CO2. +
  • Increased sink of CO2 in oceans through increased
  • Atmospheric carbon
  • Movement of Antarctica to SP -> increased albedo
  • Drake Passage opens, Panama Isthmus closes
  • -> Changing thermohaline circulation
  • -> less poleward heat transport ->colder Arctic
slide20

3rd glaciation mechanism: orbital mechanics

primarily northern

hemisphere summertime

solar insolation changes

that matter

slide21

Last glacial maximum 20,000 years ago

Global sea level ~ 125 m lower

CO2 levels ~ 180 ppm

Snow/ice extent preceeds CO2 changes

slide22

Venus Mars Jupiter

Cold & small:

No (liquid) water

No vulcanism

No atmosphere

Hot:

No oceans:

No hydrogen or water

Atmosphere all carbon

“runaway greenhouse

Effect”

WHY LIFE ON EARTH ?

ROLE OF OCEANS:

ROLE OF CHEMICAL PHYSICS:

ROLE OF TECTONICS

ROLE OF OTHER PLANETS:

slide23

Chapter 3: Thermodynamics

Of the W&H questions: ex. 3:18-3.24,3.26-3.36,3.39-3.44, understand

Ideas behind 3.53,3.54,3.55.

Nothing on Carnot Cycle. Will probably include a sounding plotted

On a skewT-lnp diagram & ask some questions about it.

Know: gas law p=RT. Applies separately to dry air, vapor

Connecting to observed p, where p = pdry air + pwater vapor; same

For  = dry air + water vapor)

p = RdTv where Tv ~ T(1+0.61w) ; w=mvapor/mdry air

Know:

hydrostatic eqn., geopotential height and thickness; scale height

slide24

1st law of thermo: dq -dw = du

dw=p* dV

Specific heats cv = dq/dT|V constant= du/dT

cp = cv + R

Enthalpy = cpT ; dry static energy =h+

Stays constant if dq=0

Adiabatic; diabatic

Know the “dry” and “moist” variables,

What is conserved when, e,w,q,e,wsat,esat

Td,LCL,latent heating

slide25

Understand what happens to these variables as

An air parcel moves over a mountain (3.5.7)

Static stability (z > 0 condition);

Concept behind brunt-vaisala f oscillations;

Conditional instability;

convective instability (ez > 0 condition);

Entropy dS=dQrev/T => s=cpln

Adiabatic transformations are isentropic

Concept behind Clasius-Clapeyron eqn.

slide26

Chapter 4: Radiative Transfer

Exercises: 4.11-4.44,4.51,4.55,4.56

Know the various units

  • Integrated over all wavelengths: E=T4 ;
  • x 10-8 W m-2 K-4;
  • E is called irradiance, flux density. W/m^2
slide27

Sun

Earth

visible

slide28

Sahara

Mediterranean

slide29

Energy absorbed from Sun establishes Earth’s mean T

Energy in=energy out

Fsun*pi*R2earth = 4*pi*R2earth*(1.-albedo)*(sigma*T4earth)

global albedo ~ 0.3

=> Tearth = 255 K

Fsun= 1368 W m-2

@ earth

This + Wien’s law explains why earth’s radiation is in the infrared

slide30

High solar transmissivity + low IR transmissivity =

Greenhouse effect

1.

2.

Consider multiple isothermal layers, each in radiative equilibrium. Each layer, opaque in

the infrared, emits IR both up and down, while solar is only down

Top of atmosphere: Fin = Fout incoming solar flux = outgoing IR flux

At surface, incoming solar flux + downwelling IR = outgoing IR

=> Outgoing IR at surface, with absorbing atmosphere > outgoing IR with no atmosphere

slide31

Manabe&Strickler, 1964:

Note ozone, surface T

slide32

Whether/how solar radiation scatters when it impacts

gases,aerosols,clouds,the ocean surface depends on

1. ratio of scatterer size to wavelength:

Size parameter x = 2*pi*scatterer radius/wavelength

Sunlight on a flat ocean

Sunlight on raindrops

X large

X small

Scattering neglected

IR scattering off of air, aerosol

Microwave scattering off of clouds

Microwave

(cm)

slide33

Rayleigh scattering: solar scattering off of gases

proportional to (1/

R=0.1m

R=10-4 m

Gas (air)

aerosol

Solar scattering

Cloud drops

Mie scattering:

1 < x < 50

R=1m

slide34

Clouds.

As a first approximation, infrared emissivity and

Cloud albedo can be parameterized as a function of

Liquid water path.

Note dependence on LWP (and optical depth) becomes

unimportant for thick clouds

A further improvement is drop size

slide35

Radiation transmits through an atmospheric layer

According to:

  • I = intensity
  • = air density

r = absorbing gas amount

k =mass extinction coeff.

rk = volume extinction coeff.

Path length ds

Inverse length unit

Extinction=scattering+absorption

slide36

Radiative heating rate profiles:

-or-

Cooling to space approximation:

Ignore all intervening layers

Manabe & Strickler, 1965

Rodgers & Walshaw, 1966, QJRMS

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