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Overview of Chapter 1-4: October 17

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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Overview of Chapter 1-4: October 17

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  1. Overview of Chapter 1-4: October 17

  2. Chapter 1 Overview Dx dy = [R*cos* d][Rd] Application to Atmospheric flow, e.g., Exercise 1.20

  3. N2, O2 dissociation P=mg P ~ po exp(-z/H) O3 dissociation Rad. + conv. Main gases + greenhouse gases (Table 1.1)

  4. Cyclonic: low pressure in both hemispheres, CCW In NH SP NP Think: right-hand-rule. explains Flow around a low in NH

  5. Horizontal heating gradients:aquaplanet simulation

  6. Surface winds + SLP, NCEP January Understand (simply) what are the Major meteorological regimes And why they are there. July July rainfall

  7. 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.

  8. Thermohaline Driver: Heating @ Equator, Cooling and Freezing at High Latitude

  9. Mass units of 103 kg m-2; equivalent to meters of water averaged over surface of earth

  10. 3 Carbon Cycles: The Quickest is CO2 + H2O CH2O +O2

  11. Euphotic zone takes up carbon dioxide, decaying matter Sinks it deeper. 2nd Carbon Cycle: The Ocean

  12. 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.

  13. 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.

  14. 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

  15. Sun’s luminosity increases w/ time as core contracts. Why wasn’t Earth’s surface frozen ?

  16. 3 major glaciations. First is ~ 2.3 bya Initial high methane conc. gives way to oxygen ->

  17. 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

  18. 3rd glaciation mechanism: orbital mechanics primarily northern hemisphere summertime solar insolation changes that matter

  19. Last glacial maximum 20,000 years ago Global sea level ~ 125 m lower CO2 levels ~ 180 ppm Snow/ice extent preceeds CO2 changes

  20. 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:

  21. 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

  22. 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

  23. 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.

  24. 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

  25. Sun Earth visible

  26. Sahara Mediterranean

  27. 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

  28. 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

  29. Manabe&Strickler, 1964: Note ozone, surface T

  30. 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)

  31. 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

  32. 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

  33. 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

  34. Radiative heating rate profiles: -or- Cooling to space approximation: Ignore all intervening layers Manabe & Strickler, 1965 Rodgers & Walshaw, 1966, QJRMS

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