overview of chapter 1-4: october 17. chapter 1 overview dx dy = [r*cos * d ][rd ] application to...
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Overview of Chapter 1-4: October 17
Chapter 1 Overview
Dx dy =
[R*cos* d][Rd]
Application toAtmospheric flow, e.g.,Exercise 1.20
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O3 dissociation
N2, O2 dissociation
P=mgP ~ po exp(-z/H)
Rad. + conv.
Main gases + greenhouse gases (Table 1.1)
SP NP
Think: right-hand-rule. explainsFlow around a low in NH
Cyclonic: low pressure inboth hemispheres, CCWIn NH
Horizontal heating gradients:aquaplanet simulation
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January
July
Surface winds + SLP, NCEP
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July rainfall
Understand (simply) what are theMajor meteorological regimesAnd why they are there.
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 providenumbers for calc.
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Thermohaline Driver: Heating @ Equator, Cooling andFreezing at High Latitude
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Mass units of 103 kg m-2; equivalent to meters of wateraveraged over surface of earth
CO2 + H2O CH2O +O2
3 Carbon Cycles: The Quickest is
Euphotic zone takes up carbon dioxide, decaying matterSinks it deeper.
2nd CarbonCycle:The Ocean
Carbon in the Oceans:
1. CO2 + H2O -> H2CO3 carbonic acid. Equilibrate w/atmos.2. H2CO3 -> H+ + HCO3 bicarbonate ion3. HCO3 -> H+ + CO3
2-
Net: CO2 + CO32- + H2O -> 2HCO3
This is connected to Calcium from the Earth’s mantle:
Ca + 2HCO3 -> CaCO3 + H2CO3 coral. 3rd carbon cycle
Where the Ca derived from the weathering ofRocks containing Ca-Si.
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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.
Early Earth’s History, in brief:
1. ~ 4.5 billion years ago (bya): accretion fromplanetesimals, evidence is lack of noble gases relativeto cosmos.
2. 1st ~750 millions years, named Hadean Epoch: morebombardment, 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
Sun’s luminosity increases w/ time as core contracts.
Why wasn’t Earth’s surface frozen ?
Initial high methane conc. gives way to oxygen ->
3 major glaciations. First is ~ 2.3 bya
2nd glaciation: ~ 2.5 million years ago.•Reduced plate tectonics -> reduced volcanic emission of CO2. +•Increased sink of CO2 in oceans through increasedAtmospheric carbon
•Movement of Antarctica to SP -> increased albedo
• Drake Passage opens, Panama Isthmus closes-> Changing thermohaline circulation -> less poleward heat transport ->colder Arctic
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3rd glaciation mechanism: orbital mechanics
primarily northernhemisphere summertimesolar insolation changesthat matter
Last glacial maximum 20,000 years ago
Global sea level ~ 125 m lower
CO2 levels ~ 180 ppm
Snow/ice extent preceeds CO2 changes
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Venus Mars JupiterHot: No oceans:No hydrogen or waterAtmosphere all carbon“runaway greenhouseEffect”
Cold & small:No (liquid) waterNo vulcanismNo atmosphere
WHY LIFE ON EARTH ?
ROLE OF OCEANS:ROLE OF CHEMICAL PHYSICS:ROLE OF TECTONICSROLE OF OTHER PLANETS:
Chapter 3: Thermodynamics
Of the W&H questions: ex. 3:18-3.24,3.26-3.36,3.39-3.44, understandIdeas behind 3.53,3.54,3.55.
Nothing on Carnot Cycle. Will probably include a sounding plottedOn 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; sameFor = 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
1st law of thermo: dq -dw = du
dw=p* dV
Specific heats cv = dq/dT|V constant= du/dTcp = cv + R
Enthalpy = cpT ; dry static energy =h+Stays constant if dq=0
Adiabatic; diabaticKnow the “dry” and “moist” variables,What is conserved when, e,w,q,e,wsat,esat
Td,LCL,latent heating
Understand what happens to these variables asAn air parcel moves over a mountain (3.5.7)
Static stability z > 0 condition) Concept behind brunt-vaisala f oscillations;Conditional instability; convective instability ez > 0 condition);
Entropy dS=dQrev/T => s=cplnAdiabatic transformations are isentropic
Concept behind Clasius-Clapeyron eqn.
Chapter 4: Radiative Transfer
Exercises: 4.11-4.44,4.51,4.55,4.56Know 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
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Sun Earth
visible
Sahara
Mediterranean
Energy absorbed from Sun establishes Earth’s mean T
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Fsun= 1368 W m-2
@ earth
Energy in=energy outFsun*pi*R2
earth = 4*pi*R2earth*(1.-albedo)*(sigma*T4
earth) global albedo ~ 0.3=> Tearth = 255 K
This + Wien’s law explains why earth’s radiation is in the infrared
High solar transmissivity + low IR transmissivity =Greenhouse effect
Consider multiple isothermal layers, each in radiative equilibrium. Each layer, opaque inthe infrared, emits IR both up and down, while solar is only downTop of atmosphere: Fin = Fout incoming solar flux = outgoing IR fluxAt surface, incoming solar flux + downwelling IR = outgoing IR
=> Outgoing IR at surface, with absorbing atmosphere > outgoing IR with no atmosphere
1.
2.
Manabe&Strickler, 1964:
Note ozone, surface T
Whether/how solar radiation scatters when it impactsgases,aerosols,clouds,the ocean surface depends on
1. ratio of scatterer size to wavelength:
Size parameter x = 2*pi*scatterer radius/wavelength
X large
X small
Sunlight on a flat oceanSunlight on raindrops
IR scattering off of air, aerosolMicrowave scattering off of clouds
Microwave(cm)
Scattering neglected
Rayleigh scattering: solar scattering off of gasesproportional to (1/
aerosol
Cloud drops
R=10-4 m
R=1 m
R=0.1 m
Solar scattering
Gas (air)
Mie scattering:1 < x < 50
Clouds. As a first approximation, infrared emissivity and Cloud albedo can be parameterized as a function ofLiquid water path.
Note dependence on LWP (and optical depth) becomesunimportant for thick clouds
A further improvement is drop size
Radiation transmits through an atmospheric layerAccording to:
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I = intensity= air densityr = absorbing gas amountk =mass extinction coeff.
rk = volume extinction coeff.Inverse length unit
Extinction=scattering+absorption
Path length ds
Radiative heating rate profiles:
Manabe & Strickler, 1965
-or-
Cooling to space approximation:Ignore all intervening layers
Rodgers & Walshaw, 1966, QJRMS