New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here


by: Guiseppe Bednar


Guiseppe Bednar

GPA 3.93

Margaret Tolbert

Almost Ready


These notes were just uploaded, and will be ready to view shortly.

Purchase these notes here, or revisit this page.

Either way, we'll remind you when they're ready :)

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Margaret Tolbert
Class Notes
25 ?




Popular in Course

Popular in Chemistry

This 92 page Class Notes was uploaded by Guiseppe Bednar on Friday October 30, 2015. The Class Notes belongs to CHEM 5151 at University of Colorado at Boulder taught by Margaret Tolbert in Fall. Since its upload, it has received 12 views. For similar materials see /class/232185/chem-5151-university-of-colorado-at-boulder in Chemistry at University of Colorado at Boulder.




Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 10/30/15
Lecture 5 Spectroscopy and Photochemistry 1 Required Reading FP Chapter 3 Suggested Reading SP Chapter 3 Atmospheric Chemistry CHEM5151 ATOC5151 Spring 2005 Maggie Tolbert amp JoseLuis Jimenez Outline of Next Two Lectures Today Importance of spectroscopy amp photochemistry Nature of light EM spectrum Molecular spectroscopy Thursday The Sun as a radiation source Light absorption Atmospheric photochemistry Importance of Spectroscopy and Photochemistry l Most chemical processes in the atmosphere are initiated by photons 7 Photolysis of O3 generates OH 7 the most important atmospheric oxidizer 03 hv 7 02 01D 01D HZO 7 2 OH 7 Solar photodissociation of many atmospheric molecules is often much faster than any other chemical reactions involving them CFZCIZ hv 7gt CFZC1 C1 photolysis of CFCs in the stratosphere HONO hv 7gt OH NO source of OH in the troposphere NOZ hv 7gt O NO source ofO3 in the troposphere NO3 hv 7gt 02 NO or O NOZ removal ofNO3 generated at night Clz hv 7gt C1 C1 source of C1 atoms HZCO hv 7gt HZ CO or H HCO important step of hydrocarbon oxidation etc Importance of Spectroscopy and Photochemistry ll Absorption of solar and earth radiation by atmospheric molecules directly in uences the energy balance of the planet 7 Greenhouse effect C02 H20 N20 CFCs 7 Stratospheric temperature inversion O3 photochemistry Spectroscopy of atmospheric molecules is used to detect them in situ 7 OH is detected Via its electronic transition at 310 nm 7 NH3 is detected Via its fundamental Vibrational transition at 1065 cm39l etc Solar Radiation Initiator of Atmos Reactions Average thermal energy of collisions RT 83 J mol391 K391 X T RT 25 kJ mol391 300 K Energy of photons E hv 300 nm photon 380 kJ mol391 600 nm photon 190 kJ mol391 Typical bond strengths D002 495 kJ mol391 D0C12 243 kJ mol391 CH OH CO 400 kJ mol391 Atmospheric Chemistry on Earth is driven by photolysis not by thermal excitation From S Nidkorodov What is light Dual nature Direction of propagation gt Photon as particle 0 Energy but no r mass a 1 Disthce 39 H I I As wave electrIC l J J and magnetic FIGURE 310 The instantaneous electric By and magnetic Hz flelds OSClllatlng 1n eld strength vectors of a planepolarized light wave as a function of 39 position along the axis of propagation x from Calvert and Pitts Space and tlme 1966 Wavelength frequency 0 c 3 X 109 ms Discuss in class at a fundamental physical level why are molecules capable of absorbng light The Electromagnetic Spectrum The Electromagnetic Spectrum m umva 11147111quot 3 7 swimquot minquot W39u gt Will g sharia animation mum emu Amlcnuclsl Malcculc Alums Units used for photon energies and mvelengths 7 1 eV 7 8065 54 cmquot 7 96 4853 kJmol 7 23 0605 kealmol 7 11604 4 K 1130 1nrn lU39mm mlcron 106m lUUUnm Solve in class Calculate the energy frequency and v urnber ofa green photon A 7 530 nm Types of radiation important in lower atmosphere I Ultraviolet and visible radiation A 100800 nm 7 Excites bonding electrons in molecules 7 Capable orbreuking bonds in molecules 2 photoolissociatio 7 Ultraviolet photons A 7 100300 nm have most energy can break more and stronger bonds We will pay special attention to them I Infmred radiation A 08 300 pm 7 Excites vibrational motions in molecules 7 with avery few exceptions infraredradiation is not energetic enough to break molecules or initiate photochernical processes I Microwave radiation A 05 300 mm 7 Excites rotational motions in molecules Fundamentals of Spectroscopy Molecules have energy in translation vibration rotation and electronic state Translation T cannot be changed directly with light We will focus on the other 3 energy types W H Molecule can absorb radiation efficiently if The photon energy matches the energy spacing between molecule s quantum levels Ephoton vquotJquot Optical transition between these quantum levels is allowed by selection rules Forbidden transitions can occur but are weaker Vibrational Energy amp Transitions Bonds can be a A viewed as H H H K amp springs H H gt 2 Energy levels are Symmetric Stretch Asymmetric Stretch Bend 39 v1 3652 cm 1 v3 3756 cm391 v2 1595 cm391 quantlzeda EV hvwbvl2 vwb is constant dependent on molecule v0 12 is vibrational quantum number FIGURE 31 a Internal vibrations of the bonds in the water molecule b rotational motion of water and c translation of the water molecule From FPampP re a WED Vibrational Energy Levels 09000000 o W a o Ideally Harmonic Oscillator b Restoration force of spring vibm onmanmm We follows Hooke s law F k Ax 3 EV hvwbvl2 v O l 2 Energy levels are equally spaced 0 Really Anharmonic oscillator Restauration force rises sharply at small r bond breaks at large r Em hvv hwczvz hw2vl Vibrational quantum levels are more closely spaced as v increases molecule HCl b polen tquotl of an Ideal harmonl r and c an anha rrrr nic From FPampP Id energy oscillator described by the Morse function Potential energy Energy Inlernuclear distance r FIGURE 32 a Vibration of diatomic Vibrational Selection Rules For ideal harmonic oscillator Av irl For anharmonic oscillator Av i2 i3 weaker overtone transitions can occur At room T most molecules at v O Energy spacing of levels is large lOOO cm39l vquot O gt v l is by far strongest For purely vibrational transition Absorption of light can occur if dipole moment changes during vibration E g HCl CO NO Homonuclear diatomics e g 02 N2 don t have vt Infrared Active and Inactive Modes V1 o C O nfrared Inactive e d Only vibrational modes that change the dipole moment can interact V O l O with light and lead to 2 Infrared Active t C T absorptlon CO2 is infrared active but not all of its modes V3 0 C O are Infrared Active Figure 32 Illustration of the infrared active and 139nact139ve Vibrational modes of 002 Modes 12 and 13 lead to a Change in the dipole moment and are thus infrared active Rotational Energy and Transitions If molecule has permanent dipole Rotation in space produces oscillating electric eld Can interact with light s elds and result in absorption Only heteronuclear molecules Rigid rotor EM 2 BJ J 1 cm391 No simultaneous vibration 2 B h where MR2 Allowed energy levels 87 21 m1 m2 Nonrigid rotor EM 2 BJJ1 DJ2J12 Spacing increases with J Spacing between levels small many levels are populated Example Ground Electronic State of HF v4 v3 v2 vl v0 14000 Elam Eral Evil 12000 Em H BJ J 1 Evib H hVV 10000 FIT E 8000 E 6000 Rotational level manifolds for Possible 2 different vibrational quanta rovibrational m overlap with each other transition 4000 V0 V1 J14 gt J15 HF molecular constants 2000 B F0 20557 cm391 rotational constant v 413832 cm391 harmonic frequency 0 vxe 8988 cm l anharmonicity Vibrationrotation of HCl 0 Molecules Vibrate and rotate simultaneously v l Energy Absorbance o39 io39lt llgt39oibgt39ioo 24 L L Llli 411 3050 2950 2850 2750 2650 Wavenumbers cm l FIGURE 34 Vibrationerotation spectrum of 018 Torr HCl at I 2 5 room temperature using a path length of 192 m Resolution is 025 cm The rotational transitions are shown as initial J nal J m cm39l from B J FinlaysonPitts and S N Johnson unpublished data FIGURE 33 Schematic diagram of energy levels involved in HCl vibratiunerotation transitions at room temperature from Herzbcrg From FPampP 1950 Electronic Energy and Transitions Several additional quantum numbers A related to electronic angular momentum S spin number Multiplicity 2s 1 Mu1t 1 2 3 are referred to as singlet doublet triplet Most stable molecules have singlet ground states 02 has triplet ground state important exception Q 2 TABLE 3 Allowed Electronic Transitions of l l Diatomic Molecules Having Light Nucleib 39 Z Sy S lD D S Homunuclear diatomic Heteronuclear diatomic equal nuclear charge unequal nuclear charge 7 4 77 g or u states 2 2 2 2 g T u 9 L 77 L 77 27 quot 2u 279 or stateson Hieguo uezg 92 ir ezj 11 H2 1192 o More com leX selection WW 39er l lglt gtA l Iult gtAg HQA A e A A H A g rules involving these numbers Presuming that the rule AS 0 is obcycd b Source Herzbcrg 1950 p 243 Electronic Transitions ETs Molecules can undergo an a 4 ET upon absorption of an m appropriate photon U er Simultaneous vibrational 32 and rotational transitions No restriction on Av many vib trans can occur A 1 0 1 P Q and R branches FrankCondon principle gigggg Time for ET so short 103915 my electronic s that internuclear distance State cannot change Namk vertlcal tranSItlonS FIGURE 35 Schematic of some possible rotational and Vibra tional transitions involved during an electronic transition of a di From FPampP atomic molecule from the ground electronic state Potential Energy Curves for an ET At room T vquot0 Prob of transition proportional to product of vib wavefucntions Transition to v394 11 1 upper electronic state most Intense From FPampP Intensity Convergence limit Potential energy re Internuclear distance r FIGURE 36 Potential energy curves for the ground state and an electronically excited state of a hypothetical diatomic molecule Righthand side shows relative intensities expected for absorption bands from Calvert and Pitts 1966 VS 139 CUI39VCS Dissociation occurs From FPampP No minima in PE immediately after absorption of light Repulsive States b Potential energy FIGURE 37 Potential energy curves for a hypothetical diatomic molecule showing electronic transitions to two repulsive excited states having no minima A is an electronically excited atom 10 More complex case amp Predissociation Some repulsive and some nonrepulsive upper elec states Example Trans to R causes immediate dissociation Trans to E can lead to dissociation if cross over to state R occurs Predissociation If high enough energy r trans to E can yield AB ll Potential energy FIGURE 38 Potential energy curves for the ground state and tWO electronically excited states in a hypothetical diatomic molecule Predissociation may occur when the molecule is excited into higher vibrational levels of the state E and crosses over to repulsive state R at the point C from Okabe 1978 l From S Nidkorodov Polyatomic Molecules Number of vibrations increases to s 3N 6 s 3N 5 for linear molecules where N is the number of atoms in the molecule H20 N 3 CeHe N 12 060 N 60 gts3 2330 yquot H quotgtltquot gtS174 Symmetric Stretch Asymmetric Stretch v 3552 cmquot v3 3756 cm39 v2 1595 cm 2 Three independent axes of rotation each characterized by its own rotational constant A B C Asymmetric tops A at B t C H20 molecule meat grinder Prolate symmetric tops A lt B C Oblate symmetric tops A B lt C CHSF molecule a pencil CH3 radical planet Earth b 3 Complexity of the absorption spectrum increases very quickly with N New types of bands become possible V Seguence bands one vibration excited while maintaining excita ion in another vibration allowed V Combination bands two different vibrations excited simultaneously forbidden in harmonic approxima ion V Overtone bands are also possible just like for diatomic molecules forbidden in harmonic approximation ll 5000 Energy cmquot 5 8 2000 moo Sequences Overtanes Example Vibrational Spectrum of H20 V1V2V3 Combinations 000 002 1 mt 39Water has S 3 Vibrations n is a strongly asymmetric top A 279 cmquot B 145 cmquot 0 93 cmquot 0venone and combination bands are relatively intense only selected bands shown in the graph ham 5 maimmduv No obVIou 7000 v1v3 combination band shown a ure vibrational transition 6 lt Q lt typical for asymmetric tops 7100 7200 7300 Photon Energy cm39l Sample NearIR Spectrum of H20 7400 mes Nldkumduv Pathways for Loss of e39 Excitation Photophysical processes 7 Lead to emission of radiation ABM Wm WM EF 7 Energy converted to eat 7 Read details in book Photochemical ionization 1 reactioH Fig 31 Pathways for lass a electrunic excurallon that are uhmpnrtance m amospharic Charmstwine use allhe symbols ana lllustraleslhe presence With me exception 0 pathways x and 1m excited atoms can pamclpale ax wet as excited molecules Photochemical processes Can produce new chemical species Photodissociation 7 most important by far 7 Eg sole source of O3 in troposphere NOZX2A1 hv 290 lt A lt 430 nm NOX2P 03P Others intramolecular rearrangments photoisomerization photodimerization Hatom abstraction and photosensitized reactions Reminder photochemistry drives the chemistry of the atmosphere Quantum Yields 25 Relative efficiency of various photophysical and photochemical processes by processi I 7 Numberofr nim quot 39 Total number of photons absorbed Eg2 NO hvaNOZ 3 N03 gtNOZ 0 4a gt NO 02 4b gt NO3 hv 4c 7 W A Total number of photons absorbed and 50 on l Are wavelength dependent all important at different i Quantum Yields II Quantum Weld 02 1 I I u I I 590 600 610 620 630 640 7 nm FIGURE 418 Quantum yields for N03 photolysis dotted line NO3 a NO2 0 solid line N03 4 NO 0 dashed line uo rescence quantum yields adapted from Johnston et all 1996 CoUmn Mass 3 km rquot r W ij iyic2lt 3 90 H T m5 23 ma a iii Qasomp xcmag Such 06 VP 722 9 E39ng M Z S 39 L C Q 03 393w adlabatlc eannsIon annude altltude adlabatlc comEresslon Figure 41 Schemati of a thought experiment concerning expansion and compression of an airparce due to vertical displacement Tis tln initial temperature inside the parcel and T is the temperature after vertical displacement See the text for an explanation ofan adiabatic process QQCUV UB ILU GSAlag Z J K at 7 of 9 39 dle J 151 39 LCM L 40 mm W433 07xma 13704 Or can bodkwrm W 0L1 r m f Ck O 1th ACWC dw W N Oi CC I 4 jug 7 p0 V Uz bumCf b azALQr taqc Ag g 397 Elm OklaL 19 L9fq 61 M01 gt In 4 f 4 41 Qa L L W L r dad quot 1749 may Eek 1 d7 ELTdTi p a 2272 CvdTa Paw GQ39Q vid 0 44 d Pv paw MP PVmET n dT Paw anT LET a P RdT m 1amp7 QIF EQVVQnsi n3 P g n Cy d7 n R d a d7 Z F lt m T Assuvu mule Q w use mohr CV JV 0 7 394 Mquot 9 gg d T Q I 77quot ZQtEQ I X Laps 2 g 3 T o 42 quot 3 a n V Cmm qumeMc Gim un dvaa Hon MM 2851 jlmula 3M 3 MI GC2 11111111111111 11111111111111 m 1111111111111 1 MAB 11 111m 3 111111111111 nRM tnn III III 1 1111111111111 1111111111111 1111111111111 11111111111 1111111111 1111111110 F1111 0111111111111111111111111111111111111111111111111111111111111111111111111111111 111111111111111111111111113911111111111 511111111111111111111 111 A avor about the main problems London smog Primary pollutants Photochemical LA smog Global tropospheric pollution Particles Health Visibility Acid deposition Stratospheric ozone depletion Global climate change Air Pollution amp Excess Deaths 40 30 20 Particles mg m3 075 050 802 ppm 025 quotPar1icesquot 39 l I l39 a 39 7quot LO quot 39 4 l39n I I I 39ll quotIquot 12 34 5 6 7 8 9101112131415 December 1000 750 500 TABLE 11 Some Incidents of Excess Deaths Associated with Smog Number of Year Place excess deaths 1930 Meuse Valley Belgium 63 1948 Donora Pennsylvania 20 1952 London 4000 1962 London 700 From Firket 1936 Wilkins 1954 Rouech 1965 and Cochran er a 1992 FIGURE 12 Concentrations of SO2 and smoke as well as the death rate during the 1952 smog episode adapted from Wilkins 1954 From FP amp P Cold days strong inversions foggy Smoke Fog Smog Governments industry amp scientists start to recognize importance of AP Chemical and From FP amp P Allied Products 3 ueI Combustion Other 39 All Other 4 NonRoad Engines Metals and lel i icles Processing Primar1i 10 were 51 0 Waste Disposal 17 300 240 180 120 7 Lead emissions thousand short tons l 60 l O 1960 1970 1980 1990 Year FIGURE 216 a Contribution of various sources to total anthro pogenic Pb emissions in the United States in 1996 b Trend in lead emissions in the United States from EPA 1995 1997 Primary Pollutants Primary emitted directly e g Pb You reduce emission to reduce concentrations Secondary formed in the atmosphere eg O3 Pb was easy Almost all from gasoline vehicles Added to gasoline as antiknock agent Did without it after regulation required its removal Many countries still use leaded gasoline l4 of gasoline in Spain most in Africa Photochemical LA Smog Sharp contrast to London sunny hot days Q40 Eye irritation plant 036 Oxidam damage g 032 1950 s HaagenSmit g 03928 Organics NOX sunlight gt g 03924 03 other products 8 020 o g 016 Now w1despread problem 0121 39 throughout the world 008 004 00039 39 0 500 1000 1500 2000 2500 Time hours FIGURE 13 Diurnal variation of NO N02 and total oxidant in Pasadena California on July 25 1973 adapted from FinlaysonPitts and Pitts 1977 From FP amp P In photochemical smog what is a primary pollutant A 048 044 040 036 032 A NO B N02 C 03 0121 D all of the above 008 004 028 024 020 Concentration ppm 016 000 39 39 0 500 1000 1500 2000 2500 Time hours FIGURE 13 Diurnal variation of NO N02 and total oxidant in Pasadena California on July 25 1973 adapted from FinlaysonPitts and Pitts 1977 Background 03 Concentrations 003 FromFPampP g 002 3 D C S 001 o o I I I I I 1850 1875 1900 1925 1950 1975 2000 Year FIGURE 16 Typical tropospheric ozone concentrations in the 1800 s and present values adapted from V012 and Kley 1988 Tropospheric O3 Bad ozone effects on humans plants materials Roughly same chemistry as LA smog Globally increasing trend Thought to be due to shift in chemical regime as NOX has increased Stratospheric Ozone 350 From FPampP l 397 v 300 2quot v Vvv Stratospherrc 03 V W V o g 250 V v39 V GOOd OZOHC nothrng W V 39 to be damaged up there C CS 200 39vv protects us from hard a W UV radiation E 150 v v39 100 l l I I 1950 1960 1970 1980 1990 2000 Year FIGURE 17 Average total column ozone measured in October at Halley Bay Antarctica from 1957 to 1994 adapted from Jones and Shanklin 1995 0 Discovered from ground measurements even though there were satellite measurements Acid Depositic Figure 132 Regions of North America with low soil alkalinity to neutralize acid rain pH of rain decreases mostly due to HZSO4 Dire effects if soil cannot neutralize acids What is the pH or natural rainwater A 46 B 56 C 70 D 92 Health Effects of Particles I Nasopharynx Nasooropharyngo laryngeal region Turbinates D Oral Pharynx 0398 39 N Tracheobronchial region Vestibule Epiglottis 8 Larynx 395 E Trachea g 9 Lun 9 Lung 8 Pulmonary region Q Bronchus Conducting Bronchiole 00 I I I 4 Terminal Bronchiole 0001 001 01 10 10 Respiratory Bronchioli Panide diameter Hm FIGURE 213 Calculated deposition of particles in various regions of the lung for Alveolar Duct polydisperse aerosol crg 25 see Chapter 9A2 adapted from Yeh et al 1996 Al San 3 3quot 3 Subm1cron and ultra ne Alveolus FIGURE 212 Schematic diagram of human respiratory tract p art39 penetrate most deep From Hinds W C Aerosol Technology Copyright 1982 John Wiley amp Sons Inc Reprinted by permission of John Wiley amp Sons Inc Health Effects of Particles II I I I I 0 5101520253035 FquotV3925 HQ m3 FIGURE 214 Estimated adjusted mortality rate ratios taking the least polluted city Portage Wisconsin P as 10 T Topeka Kansas W Watertown Massachusetts L St Louis Missouri H Harriman Tennessee S Steubenville Ohio Adapted from Dockery et al 1993 From FPampP Sulfate Hg m3 g 2 4 6 8 10 12 14 14 I I I I I I D E g 13 E S O E 12 13 H 9 L U 3 11 E W 390 o D a 10 PT T5 UJ Harvard six city study 1993 Mortality increases with ne particle concentration Disputed for a decade now considered proven Mechanism still uncertain Visibility Degradation I Particles can scatter A and absorb radiation B These effect limit C atmospheric D Figure 83 Scattering of a radiation beam processes of reflection A refraction B refraction and internal reflection C and diffraction D SOLAR RADIATION 4 object 1 2 background 3 V Figure 85 Reduction of visibility by aerosols The visibility of an object is determined by its contrast with the background 2 vs 3 This contrast is reduced by aerosol scattering of solar radiation into the line of sight 1 and by scattering of radiation from the object out of the line of sight 4 Visibility Degradation II Scattering efficiency is very strong function of particle size For a given wavelength Visible A 05 urn Particles 052 urn are g E E lt3 O W 35 3 25 2 15 l 05 most efficient scatterers Scattering Efficiency dimensionless IIIIIIIIIIIIIIIIIIFIIIIIIIIIIIII l 0 l l 10 100 Particle Diameter pm 5 O Figure 84 Scattering efficiency of green light it 05 pm by a liquid water sphere as a function of the diameter of the sphere Scattering efficiencies can be larger than unity because of diffraction Adapted from Jacobson MZ Fundamentals of Atmospheric Modeling Cambridge University Press Cambridge 1998 Earth s Radiation Balance F mm F PampP b Incoming Solar Radiation 1368 342 w 4 m2 NW Re ection in Surface Reflection Atmosphere 77 Absorption at Surface 1 68 235 w C Outgoing Radiation m2 Absorption by H20 C02 03 etc Release of Latent Heat of and clouds 350 Direct Surface Evaporation Radiation 40 Heat Transfer by 78 Thermals 24 Condensation I O of Water l t l Radiation From Surface Blackbody at 288K FIGURE 19 Global average mean radiation and energy balance per unit of earth s surface adapted gt Absorption in Atmosphere by 002 03 H20 and 02 67 Upward Emission from H20 002 O3 clouds etc 195 Downward Emission from H20 C02 03 etc 324 Surface with permission from IPCC 1996 with numbers from Kiehl and Trenberth 1997 Climate average weather Driven by solar radiation Depends on complex balance of many terms Current small perturbations in gas absorption causing heating Greenhouse gas concentrations 360 1800 E CARBON DIOXIDE E METHANE a 3 1600 3 34 V Z 9 I400 320 2 95 I200 300 E U 2 I000 280 8 000 I 0 260 uuu I I I I 17m 1800 1050 1900 1950 20 0 I760 1800 I050 1900 1050 20 0 YEAR YEAR 310 E J NITROUS OXIDE g CFC11 z 9 300 F 02 E Z LU 2 290 O 0 I o 6 IL 280 O 1750 1800 I050 20 0 V50 1300 I I I I I I I I 1850 1900 1850 IQUO 1950 20 0 YEAR YEAR Figure 71 Rise in the concentrations of greenhouse gases since the 18th century Midlatitude air temperature Warm Cold Warm Cold Warm Cold Warm Cold Earth s Temperature History l l 1900 1950 2000 Date l l 600 1000 1500 2000 Date A A V l l l l 30 20 10 0 Date kw BP I l I 150 100 50 0 Dale IQr EPl GquotC 60 Surface T as surrogate of climate Very large changes in past Current consensus is that recent changes are due to human activity 0 Forcing system in unknown domain danger of abrupt large changes in future not quite like in the day after tomorrow Figure 72 Trend in the surface temperature of the Earth at northern midlatitudes over the past 150000 years Each panel from the top down shows the trend over an increasingly longer time span with the shaded area corresponding to the time span for the panel directly above The record for the past 300 years is from direct temperature measurements and the longerterm record is from various proxies From Graedel TE and PJ Crutzen Atmospheric Change an Earth System Perspective New York Freeman 1993 Problems are often linked TABLE 14 Atmospheric Effects of Trace Gases Decreased Urban SelfCleaning of Air Acid Visibility Greenhouse Stratospheric Atmosphere Gas Pollution Deposition Impairment Effect 03 Depletion Decreases OH C02 CH4 C0 N20 NO NO N02 SO2 CFCs 03 Plus signs indicate a contribution to the effect minus signs indicate amelioration Dual signs indicate that the effect of the gas can vary For example C02 N20 and NOX can either enhance or deplete stratospheric 03 de pending on altitude CH4 generally ameliorates stratospheric O3 depletion except in the polar ozone hole The ten dency of CH4 to diminish the selfcleaning of the atmosphere by reducing OH abundance is different in the Northern NH and Southern Hemispheres SH CH4 diminishes selfcleaning in the SH but has the opposite ef fect in the NH Source Graedel and Crutzen 1989 Lecture 13 Gas Phase Organic NOX UV Reactions II Reguired Reading FPampP Chapter 6 except as noted next Additional Reading SampP Chapter 5 CatchingUp Reading Jacob Chapters 11 amp I2 aree online Atmospheric Chemistry CHEM5151 ATOC5151 Spring 2005 Prof JoseLuis Jimenez Outline of Lecture The big picture of atmospheric oxidation A OXidants B Lifetimes of Organics Last Lecture C Reactions of Alkanes D of R R0 and R02 Radicals E of Alkenes amp Biogenics 13 F A 11 14 n i or i wires 1 C C AF A t39 H cc cc 2 n V L 39 39 r vu39 n 11 UL U U ULEQLLLUD I Vf f 4 39 39 rnnvu39 n J Chemistry of Remote Regions K Atm Chem amp Biomass Burning Summary of Alkane Oxidation RCH3 OH gt RCH2 H20 02 M minor RCHZONOZ NO H02 F CH202 gt RCH200H02 RCHZO No2 I major R 02 02 Products RCHO HO2 Decomposition lsomenzation FIGURE 62 Summary of alkane oxidation by OH in airl 39 Chemistry is all about electrons Species with unpaired electrons radical doing most of the work Big Picture of Organic Oxidation 1 generation 2m generation Parent primary species stabie products stabie products VDCoXidant VDCoXidant VDCoXidant ernistry ernistry ernistry on 03 on 03 on 03 N03 no No3 hv No3 hv Peroxy R02 Peroxy R02 Peroxy R02 is chemistry cnernistry Decomc nmmi i nNMNvmh mam Pn nnt Oxidation of CH4 High NOX Case k 11X10 e WM k298 K 10x10 13 cm3s CImax 104 illcm3 Consumed 1 OH 21 NO row kC1 32 years Produced g 1 N02 g 3 H02 C Followed by NO2hv 02 gt NOO3 HCI A CH4 CH H20 k 245mor12 e477 CHZO k298 K 63x1015 cm3s 0mm 106 lcm3 WV tom kOH 1 5 years O 0 H02 2 HCO H 2 HO2 CO or M meS Nizkorodov H2 CO Oxidation of CH4 Low NOX Case O O CH302 CH30H CHZO 02 CH4 CH3 z CH302 or 39 H2 39V39 CH30 CH30 02 HO2 CHZO HZO 02 02 or CHBO CHZO CHgooH 02 H02 We already know what happens to CHZO it is converted to H2 H02 and CO How about CH3OOH and CH30H HZO OH H2 OH droplets H2O CHSOZ droplets H20 CH30 hv OH CHgooH CHgo OH CH30H m CHon 2 O O2i39 H02 H2O CHZOOH CH2O OH CH2O From S Nizkorodov Lifetimes of Organics 0 As always enormous number of possibilities but what is important Org X gt Products X is an oxidant dOrgdt kX Org lifetime I maxi TABLE 61 Estimated Lifetimes of Representative Drganics in the Troposp here OH o No H0 Cl Organic 1 1 x 10 cmdi mm mm 50 pth u x ill cm 3 pm I x 10 cmquot n Bnlune 5 days 2 1300 yr Eili day39s 5 clays immZBmenc 43 h 3f min 35 min 41 days Aculylcnc 14 days 2 4m days 2 133 days 2 d quot133quot Toluene 2 days a 4ll39li days 133 darys i 2 days HCHO 12 day a ii13 days Iii days 1341quot 1 days r ifkpl xltlill39ill time for the organic to fall lo lv of its initial value except as shown here ram mnslams are found in tch h Note This is only or the forward reaction Since the adduct decomposes back to reactanls under most atmospheric conditions lhi effective atmospheric lifetime is much longer V 7 I quot Based on k Cl Cgli 53 X lquot 1 cm1 moleculequot 5quot mm kl 57 x lli cm molecule s39x k1 23 t it cm molecuir l 539 and FE iAlkinson N at 9971 From FPampP quot39 Using k 18 X 10 ll cm moleculequot 5 quot lAtkinsou Willi ll Reactions of Alkenes 0 Eg HC3CHCHCH3 2butene 0 Double bond adds reactivity For alkanes OH could abstract any H No strong preference for reaction site The double bond has extra electron density Attacked by electrophilic radicals OH 03 N03 Cl The double bond gets the Whole molecule in trouble Alkenes are more reactive than alkanes oH Q OHC C C C 32 32 OH lOH i M C C gt C C 33 iAlkenes OH TABLE M5 Rule Constants and Temperature Dependence or the Reunions of DH Radicals Will l Allaneg I l mm Tami Prcisurc of Airquot lquotllll cm3 Armquotcm 133 Mkmc l39llIsl d llll L 5 mtvlcrulrquot 5 mil 39 Remember Hawquot 552 mm 43gt Pmpcnc 3b IlhlV colhswn rate 25 x it 12 1010 2E513 2113 3931 22 Hrl cillngnc 35 Very fast reactlons EZLETELZEM f f 1 L39gclupcnILnc 17 a H 3 L w l1uLne 343 532 L 0r 2ici2539iLlmiwlc M H 0 3921u cm quot19 1 J l alkenes 25233 l l 2397 39 L39y clumxc nu 1 7 39 Pressure dep39a i f i ipmx i 39 1 I c one 74 negatlve T dep film 345 44 ZMclhyll3 hu11di4nu liwprcncl VII 254 am Suports Importance of 3552 addition to double b f fl i mw i hc lzmdrcne lbs 39 Compare OH 332225 3 2 Propane l X 103912 I39liffi39lf i f 39i39crpinolene 325 3912 1 w vim L39lnm 7 X 1012 Acquot quotH valid ui39liy for I m 5 25 K rangt Heptel lel X 1 012 39J mustanls LII except for Ell14 and L391ll l rom A kinmn WM 39 Stu F39iglh2 1m momma of hingcnirs E Wh th ft OH dd39t39 9 o Hydroxy group OH CH3CHCH2 a CH3CH CH20H 343 alkyl radical a CH3CHOH CH2 34b Alkyl radical gt oo39 Peroxy radical CH3CH CHZOH 02 gt CH3CH CH20H 35 OO39 0 Peroxy rad1cal gt I CH CH CH OH NO Alkoxy rad1cal or 3 2 O39 stable n1trate I gt CH3CH CHZOH NO2 36a 0N02 Alkoxy radical gt gt CHSCH CHZOH 36b reaction with 02 decomposition isomerization O l CH3CH CH20H gt CH3CHO CHZOH 37 Example of Bhydroxyalkyl Isomerization As for alkanes larger alkoxy radicals isomerize OH 0 CHSCHZCHCH2 OH 72 CH3CH2CH CH20039 N0 39 t N02 EH OH Isomerimtion CHZCHZCH CHZOH CH3CH2CH CHZO halo 0 Decomposition IDH 39OOCHZCHZCH CHZOH N0 1 N02 OH 02v H02 OCHZCHZCH CH20H gt C CH2CHOHCH20H o 34 Dihydroxybutanal TAHLE 69 Rana Cmsmnrs md TemperMum E Dependencequot or The Gastlmsc Reunions of 0 3 I S with Some Alkunwquot Jarl quot rmquot Atlll cm39 an quot1 K Minrte mulecule39 5 J moleculequot 5 0 Remember that c0111s1on rate Enhcnu Ib ll1 END I mpcnc I I 55 131 s X 10 rnurcnc um 33r 1m ZNICEITIPHIPCDE I 2U 1132 39fi 39 mum 39 122 968 0 Much slower reactlons than Wyclmwm run a m M amen mu 393clnpcnicm 57H Lh39 350 for EMclhyLZhncnc 4113 ms 32 IHuxcnu Ilrt L39Mnhcmn EH 4 Z H HIM compare fir3431ulhyTZ pcmem win rmnr McrhylZpcmenu Sntl 23Dim1ll ry 2hulunc IFIH 11L1 I M Propene X 11 13rmmuwnc M m 2sz E MHILVIiJI39Jllladitl h ilh39 736 913 O Pro we 1 X 103917 W 739 3 p 39 EL39LIILnl 2344 3C39urrrnc 3T Limunem 3m 0 But remember m Phcl unndmnc J Iquot h I l 39 w ll39l39 39r ll 7 dOrgdt kOX1dantOrg 34 u IFLrpinlum 3 lt NI4 O 1 va39l urpincnu 110 39 39 quotI39mminnlcnc mm Mclhyl vinyl kelnnc in O3 Miclhucmrum 121 Mk r Rik so ozonOIYSIS Of alkenes Is a Slow From Atkinson J NTMJ md lkmwn Lquot m 1100ai or sunr process It Is Important In the atmosphere because mm ol hi gcrlicmsee mm 39 wcr gc of Gmsjuam am irmjtrm 1199an and Neck 4 at ofthe large concentrations of 03 mm E Mechanism of 03 Alkenes First steps O O3 adds across 0 O the double 0 R1CCR3 a Rxl lR3 3 bond R2 R4 R2 Primary R4 ozonide 42 The primary ozonide is not stable and breaks a b ELOPJ R1R2CO R3R4COO 7 a R 1 I R 3 Criegee intermediate C R2 c R4 R3R4CO Rle39Coo lt gt Criegee intermediate 43 c breaks a or b break E Fate of Excited Criegee Intermediates Contain excess energy from broken bonds Stabilized by collision Decompose in various ways 0 Some to radicals and some to stable products Example of Criegee from lpropene 03 HcHoo M g HCHoo M 45a Stablllz d Cflegee 012 Intermedlate gt HCO OH 45b C0 H20 45c 3 02 H2 45d coZ 2H 45c igt HCOOH 45f E Fate of Stabilized Criegee Intermediates React with H20 802 NO NOZ CO aldehydes and ketones All reactions lead to stable products Reaction with H20 dominates RlHCOO H20 6 R1COOH H20 4820 l1 3 RlCOOH RCOOH H20 3m RICHO H202 48b 48c Others more uncertain SO2 amp NO may be important in urban atmospheres aPinenc all incnl Tcrpmolcnc Camplmrm LEBuiadxene lmprcnc Rem 0 yield tlhene 012quot DDSquot Pmpcm 033 8quot l Bulcnc 141 1 l PcnanL 137 I Huxcm 032 l HL plan 027 1 Guam NHLb mZButcnc 04L 0 mmil liulcxlc um LL14quot yclopcmcnc 011 l39 Q Cluhcxcm 008 lMclhylcyclohcxcnc It ll Muhylpmpmc 184quot IMuzhyllhulcnc 083quot ZMulhylZhulcnc 089quot ISdimelliylEvbnlnnc 0 Si l 1 ansquot 0 w nllzvllfl39 Importance of OH generation OH can react with all organics not just alkenesl TABLE 611 Yields Di OH mm Gayl hasu 0 Alkcn Reactions al 1 arm Pressurequot quot as 39m w E 25 Tom in 2 g 20 E quot E v x to 15 9 thud 5 1o l 392 iHCHgohvii i111 E 5 33 11 x quot ltC C area 0 Wu 1 H I 5 1o 5 Time EST FIGURE 66 Calculated tales of HOI radical generation from LIS39quot various sources for a rural forested 39 n the southcm lern United 704139 Slams adapted from Paulson an w 1996 Specially important at night because no photolytic OH sources NO3 Alkenes N03 adds to CH3 CH3 CH3 0N0 CH3 double bond cc N057 cl CH CH EXCited CHG CH3 3 3 adduct can 7 Form epoxide CHCI N 2 CH3 CH3 0 CH3 C C gt C C 7 Stabilize GHQO CH3 CH3 CH3 2 form peroxy CH3N09 I B39CHa quot02 radical C 5 blah blah CH3 CH3 FIGURE 68 Mechanism of the NO reaction wih 237dimethyl7 Zrbulene adapted from Sknv ct KL 1994 39 TABLE 613 R T Ra Cu d N03 Reaction Rates cziiasiz ie arm k cm mnlmle All 539 293K Remember that colliSion quot Ja Em ll X 1quot rate 25 x 103910 MES v5 x 1an IBmcnc l 4 X I 39 Reactions are quite fast for 7335quot iiiquot biogenic alkenes 43 quot 33 37 57 X ID H 7 Comparable rates to OH 0 X In 1 as X m dOrgdt 7 kOxidant Org gg g1 7H N03 50 ppt mght ifil lrw 7 OH 01pptday limr X ID NO3 reactions With 5V W X biogenic alkenes night 1331 I 14 1quot are very important 9 4 97 X H l 6 X 1quot Mcmncmlcin 33 x m4 F GHI Aromatics OHaddition Aldehydes aldehydic Habstraction Ketones and alcohols alkyl chain Habstraction Carboxylic acids OHaddition or Habstraction 0 Similar types of downstream chemistries What about other organics 0 Similar types of radical chemistries Gets really complicated quickly You should be able to understand it from what we have covered If need to know for your research 0 See the book for introduction 0 Then search the literature J Biogenic VOCs TABLE 624 Estimated Global Annual Biogenic VOC Emissions Tg yr 1 Other Source Isoprene Mnnnterpenes VOCs Canopy foliage 460 115 500 Terrestrial ground cover 40 13 50 and soils Flowers 0 2 2 Ocean and freshwater 1 lt 0001 10 Animals humans and insects 0003 lt 0001 0003 Anthropogenic including 00 1 93 biomass burning Total 500 130 650 139 Fm999 and references therein b Other 39 u u nclude all volatile organic compounds other than methane isoprene and monoterpenes Biogenic VOCs dominate globally Lots of double bonds Large gt products to aerosols I lsopvene W lennene H reminoiana RH Myrcene FIGURE 622 hydrmzlrbons 8 lt3 uPmene 5Pmene Ki uTevpmene y Terpinene Camphena gt kQ uPhellandlene BP nellsndrene Q Ocnmene A3 Carene prmene m 39hcmiml slruclurcs uI some lviugcnically emillud Mechanisms of VOC emission from plants new many mm EYHVLENE K FHWOHDRMGNES chlamlam MEYHANOL 394 2Mzmueummm NE lsowa Iasm mus m glands loosol vocs cumswsuss leaves sum yams cs ALDEHVDES c5 ALCOHOLS omen c r c Mmaamss n mm mamaquot m mum macawquot mum vats Ray Fall in CU Biochemistry JIsoprene vs T amp Light ugm an all on on on Very strong functlon of both 1 l i l i 4 E Not stored emltted as 1t IS made 2007 5 ma Enzyme precursor g D 7 Both depend on light a an 20 WW 7 Enzyme more active as Tl b degrades if TM 5 we Lea E 5 so EmlsslaF E g so Q s E 40 3 a 20 E K I I v l l l 0m 20 30 m 50 60 209 600 mm 300 Immzmumvm We mmmmwnmmucm mam lnmclm s l FIGURE 525 Em at mow lam mmpmmm on women i V a u I uquot M mm 0 mm mmme from ml m wlmcmmm m m m 35715i ml li u39 in 5W n 1w ww mm Biogenic Emissions of Oxygenates m quotm Many dlfferent spec1es mum mm w fi fa 3333 Can be a large fractlon of a WNWW H total emltted C 39 39 on niniu umcs ervc M39YL39V o m amia nlmfc d K mummy WW7quot W Command Clnwer quot39W Wm ELAN flquot if W on a KSELTW 312 3 39quotquot W W 1 mm x 2 ltm a st MWMme W Mum I lt m m mm uum l gm 39139 3 W quot1quot 33 CW WW 0 351133212quot n H x Z 13 ml 4 lt u an Wm dMcmwZpcmnnunc 57 In g l o quotm mm M m lt m Emmi quot l 339 WK Adapted mm mm M H mm mm m M W Chemlstry of Remote Reglons a c 2 Wm WWW 323333323quot quot swap w WWW M M W my a w we WW m nnuuimv WWW m MW an W m WWW MWquot w W W mm 617 an mm mm Binmms Eurmng mm mow Emmmm w mm 3 human mum m nu mm mm m awnm W V cmquot mm W m mmymm mm m m m MinnowINmMWWW mm m 2 8 m um mm 35quot mm 1 mm 322 um m m vmmnmWNW 24 m 4 A mt u n n g u i a g m 1 g 0 m mm u u l2 s m mum MM 0 n u h wquot quotmm s no 1 m quot1 mm m V 4 y Kth amk us 11 1 w m 75 CW umm WW 42H 11 mi mm m mnlm m4 mn uLuc ulymvc urban M w E N CAquot xumml mum W q V g Q A Imm Mum H WIW u l u z Fxlmlmg wpmk a my meul hum mum mmrdui mhmmn hurnmg r 2 w cm M g e q 51 Very Important source of many speCIes X n 1 Being studied intensively NCAR mm Kiwi General Circulation TRANSPORT AND TRANSFORMATION GENERAL GOAL TO UNDERSTAND THE INTERPLAY BETWEEN ATMOSPHERIC MOTIONS AND ATMOSPHERIC CHEMISTRY EXAMPLE FOR A RELATIVELY INERT MATERIAL THE DISTRIBUTION OF THE GAS IS CONTROLLED BY TRANSPORT GIVEN ENOUGH TIME THE MATERIAL WILL BE UNIFORMLY MIXED THROUGH THE ATMOSPHERE Midlatitude Chlorine release Antarctic Ozone Hole H EXAMPLE FOR A SHORT LIVED MATERIAL THE DISTRIBUTION IS CONTROLLED BY CHEMISTRY CFCIB F11 Altitude km 1oquot7 103916 103915 10quot 103913 103912 1039 103910 10399 Volume mixing ratio SPECIFIC GOALS 1 DETERMINE THE TRANSPORT TIMES IN VARIOUS PORTIONS OF THE ATMOSPHERE FOR COMPARISON WITH CHEMICAL LIFETIMES A OBSERVED WINDS B BOX MODELS 2 UNDERSTAND HOW TO LINK CHEMISTRY AND DYNAMICS A CONTINUITY EQUATIONS B METEOROLOGICAL TRACERS 3 FIND WAYS TO SIMPLIFY THE DYNAMICS SO WE CAN CONCENTRATE ON THE CHEMISTRY TRANSPORT TIME SCALES SOME COMMON TRANSPORT TERMS 1 ZONAL MEAN CIRCULATION TIME AVERAGED WIND PARALLEL TO LATITUDE CIRCLES A FASTEST TRANSPORT SINCE ANGULAR MOMENTUM ACCELERATES WINDS zero km per day 40000 km per day WHAT DRIVES THE ZONAL WINDS ANGULAR MOMENTUM CONSERVATION WE CAN EASILY WORK OUT THE VELOCITY OF THE AIR PARCEL IF THE PARCEL IS INITIALLY AT REST AT A PARTICULAR PLACE WHERE THE DISTANCE TO THE EARTH S AXIS IS R THEN IT HAS ANGULAR MOMENTUM PER UNIT MASS Jg2R2 QANGULAR ROTATION RATE OF EARTH 7310 5 RADIANSSEC IF WE MOVE TO ANOTHER PLACE WHERE THE DISTANCE TO THE CENTER OF THE EARTH IS RdR THE ANGULAR MOMENTUM IS QdURdR RdR2 9R2 HERE dU IS THE VELOCITY THE AIR PARCEL HAS OBTAINED EXPAND OUT AND DROP THE SMALL TERMS deU AND deR LEAVES dU2 2dR EXAMPLE MOVE AN AIR PARCEL FROM THE EQUATOR TO 30N dRRearth 1cos30 dU273X10395 13464X106mS1 25 mS Jet Streams Hadley Cell Divergence Coriolis force 30 N 3005 equator wwwweizmannaciESERPeopleYinonRudich coursesLectureS Circulationpdf B TYPICAL ZONAL WINDS TRADE WINDS LIGHT WINDS THAT BLOW FROM THE EAST EASTERLIES IN THE TROPICS WESTERLIES NEAR SURFACE WINDS THAT BLOW FROM THE WEST WESTERLIES IN MIDLATITUDES SUBTROPICAL lET A HIGH SPEED NARROW REGION OF WESTERLY WIND WELL ABOVE THE SURFACE THAT MARKS THE POLEWARD EXTENSION OF THE HADLEY CIRCULATION POLAR NIGHT IET A HIGH SPEED NARROW REGION OF WESTERLY WIND WELL ABOVE THE SURFACE THAT MARKS THE BEGINNING OF THE POLAR REGIONS H H H H H H H ii1 I Li aw i The Surface Winds aa N Lalitude U g n v R iLH H if I H H 7 HIHIHiH i i iquot e anuary an uly averaged surface winds 0 BITE m E Qu E IZITE ISO E Im I mlw IZITW 11 5mm XTW Longitude W Arrows depict the monthly 1 averaged wind vector in m v 39 2 3 a s 7 a g m amplliude mfs i i i i s see arrow scale below picture The colors depict the vector magnitude in m g 5 according to the colorscale 2 below Note the seasonal 33 differences clue both to the Eb shift in the location of the 3 maximum in tropical heating and the heating and cooling of the continents 9039s 30 s Cquot ED E SO39EI 3990 IWE ISUE iaml SD39V wwwweizmannaoilESERPeopl n mgme eYinonRudich 2 4 coursesLeotureSCirculationpdf I i i i i 39 izo39w 90w eo w atrw w s a m 2 14 amnlimde imis39i Trade winds wwwweizmannaciVESERPeopIeYinonRudich coursesLecture5Circulationpdf r C cgt mSe lardv S N r Io unwnc an N Bind Mthp can39t3 HEIGHY my 10 0 3 lt y M D waEw HEMISPHERE a39 A mg A 30 SUMMER NEMISPHEHE TIME SCALES TO CIRCLE THE EARTH IN THE MEAN ZONAL WIND NAME OF WIND TYPICAL TYPICAL TIME TO WIND CIRCLE EARTH SPEED TRADE WINDS ltltIO ms gtone month NEAR SURFACE WESTERLIES lt 1 0 ms gtone month NEAR SURFACE SUBTROPICAL 10 1115 33 days 450130 J ET SUMMER SUBTROPICAL 4Q mS 8 days 4501at J ET WINTER NOAANESDIS EDGE IMAGE DISPLAY OPT THK 7 7 LAT 1 KM GLOBAL ANALYSIS NOAAls 3918 179 LON QSQSQB QOQ 515Q3 QIQQ 169 HOURS 39 a 39 z quot A View of aerosol transport There were large res in Russia prior to this time period and dust storms in Africa Can you tell the source and sink regions just by glancing at the distributions and knowing the Winds General Circulation CONT 2 MERIDIONAL MEAN CIRCULATION TIMELONGITUDE AVERAGED WIND PARALLEL TO LONGITUDE CIRCLES A WHAT DRIVES THE MEAN NORTH SOUTH MOTION THE EQUATOR TO POLE HEATING IMBALANCE HOWEVER SUCH MOTIONS ARE DIFFICULT TO ACHIEVE DUE TO ANGULAR MOMENTUM CONSERVATION SO THE MEAN MOTION IS VERY SLUGGISH Latitudinal Radiation Imbalance EXCESS 300 lt deficit Laulude ar39 e 4 iuRudichl mm a ll 39 39 quot pdf B TYPICAL MERIDIONAL WINDS HADLEY CELL A CIRCULATION WITH RISING MOTIONS IN THE TROPICS AND DESCENT IN THE SUBTROPICS INTERTROPICAL CONVERGENCE ZONE THE REGION OF RISING AIR USUALLY FULL OF CONVECTIVE CLOUDS NEAR THE EQUATOR FERRELL CELL POLAR CELLSOVERTURNING CIRCULATIONS WHICH ARE SO WEAK THAT THEY PLAY LITTLE ROLE IN TRANSPORT LITTLE TRANSPORT ON EARTH OCCURS BY THE MERIDIONAL CIRCULATION The Ferrel Cell and the Meridional Mass Circulation The Hadley Cell ends at about 30 north and south of the equator because it becomes dynamically unstable creating eddies that are the reason for the weather disturbances of the midlatitude belts see Lecture lV These eddies force a downward p l rnithjel W f l l motion just south of the jet axis JE 39 22331 Jul f summeron and an upward motion between WWW gin IR g 40 and 60 north and south of the all fl equator forming the Ferrel Cell The eddies are also responsible i for spreading the westerlies down j to the surface Ferrel ce39ll J subtropical mag 1 high wmu lx l i 994 Enngciupama Erilannmay lrm wwwweizmannaciESERPeopleYinonRudich coursesLeoture5Circulationpdf gt 5 o o i gt O N The Zonally Averaged Mass Circulation 200 amp frith 3m mm 0 Latitude The annuallyaveraged atmospheric mass circulation in the latitude pressure plane the meridional plan The arrows depict the direction of air movement in the meridional plane The contour interval is 2x10 l0 Kgsec this is the amount of mass that is circulating between every two contours The total amount of mass circulating around each quotcellquot is given by the largest value in that cell Data based on the NCEP NCAR reanalysis project l958 l998 wwwweizmannaciESERPeopleYinonRudich coursesLeotureSCiroulationpdf General CirculationCONT 3 WAVE TRANSPORT TIME DEPENDENT WINDS HAVE BOTH NORTH SOUTH AND EAST WEST COMPONENTS NORTHSOUTH TRANSPORT ON EARTH IS DOMINATED BY WAVES TIME SCALES ARE SIMILAR TO THOSE FOR ZONAL FLOW 2 n k a 00 OCT w Nmember 1904 1113 and endln a 12 GC 39 T 2 are labeled m cns ormezm g o Nmmhquot 196 39 5 COMM A w 39 9 xx 12 6 Signs 50mm Chan CM 90 GCT 0 Nmember 1964 in geopoltmm hmghx conmun m and labeled In men of meters kw lymhcrmx labeled m LILgram Cglqus Wind SDcedlt are m knots dawn al mervals of 60 Baroclinic eddies on EaIth from Clementine April 1994 Fig 66 Schematic cfmc slmamlmcs solid and isommns dashed associamd Mm a largescale 39 39 439 A I m 39 rmws along m 39 ind vclccily 39 39 pressum quot 2 Ward mm momenmm rampon and m wesmud phase shin of m empermure wave rclauv o m prcssum Wave gives a nunhward heal umspon PD00 UJ m f r 1 um pole SOME COMMON TRANSPORT TERMS CONT 4 STRATOSPHERIC TRANSPORT A THE BASIC STRATOSPHERIC TRANSPORT IS SIMILAR TO THAT IN THE TROPOSPHERE WITH HIGH ALTITUDE JETS THE EQUATOR TO POLE TEMPERATURE GRADIENT IS SOMETIMES REVERSED IN THE STRATOSPHERE CLOSING THE JETS THERMAL WIND EQUATION UTOP OF LAYER UpBOTTOM OF LAYER IS PROPORTIONAL TO MINUSHORIZONTAL GRADIENT OF MEAN TEMPERATURE OF LAYER Z i E dz RTdPEg P so T2gtT1 y1 32 Equator Schematic derivation of the thermal wind r C cgt mSe lardv S N r Io unwnc an N Bind Mthp can39t3 HEIGHY my 10 0 3 lt y M D waEw HEMISPHERE a39 A mg A 30 SUMMER NEMISPHEHE B TYPICAL STRATOSPHERIC WINDS ZONAL FLOW DOMINATES TIME SCALES TO CIRCLE THE EARTH IN THE STRATOSPHERIC ZONAL WIND NAME OF VOLCANO TYPICAL TIME TO CIRCLE EARTH Mt St HelensUS 15 days May 18 1980 12 15 moving eastward km 46N E1 ChiChon Mexico three weeks April 4 1983 25 30 moving westward km17 N Pinatubo three weeks Philippines June 15 moving westward 1991 20 25 km 15N QUASI BIENNIAL OSCILLATION A ROUGHLY TWO YEAR VARIATION IN THE WIND DIRECTION IN THE TROPICAL STRATOSPHERE GLZ n 4 4 a a 2 E 4336 22m 33 a 3g 333 N31 gam 35 a gala mag 0ng 33 m 23 a 55mm 5139533333wcw EQs 5 a2 as 5392133333 ES 3 as gt2 3 mggep 50 ES 2 a MERIDIONAL FLOW IS STILL IN THE HADLEY SENSE IN THE LOWER STRATOSPHERE DURING WINTER HOWEVER IT IS LARGELY DRIVEN BY DYNAMICS RATHER THAN SOLAR HEATING WINTER POLAR VORTEX A REGION ROUGHLY CONCENTRIC WITH THE POLAR CAPS IN WHICH DESCENT OCCURS FROM ALOFT AND LITTLE EXCHANGE OCCURS WITH THE REST OF THE STRATOSPHERE TROPICAL PIPE A REGION OF THE TROPICAL LOWER STRATOSPHERE IN WHICH LITTLE EXCHANGE OCCURS WITH THE REST OF THE LOWER STRATOSPHERE The Ferrel Cell and the Meridional Mass Circulation The Hadley Cell ends at about 30 north and south of the equator because it becomes dynamically unstable creating eddies that are the reason for the weather disturbances of the midlatitude belts see Lecture lV These eddies force a downward p l rnithjel W f l l motion just south of the jet axis JE 39 22331 Jul f summeron and an upward motion between WWW gin IR g 40 and 60 north and south of the all fl equator forming the Ferrel Cell The eddies are also responsible i for spreading the westerlies down j to the surface Ferrel ce39ll J subtropical mag 1 high wmu lx l i 994 Enngciupama Erilannmay lrm SAGE 11 Optical depths after Pinatubo Eruption SUMMARY FROM EXAMINING WINDS 1 THERE ARE SYSTEMATIC WIND SYSTEMS THAT CONTROL WHERE MATERIALS ARE DISTRIBUTED ON AN AVERAGE BASIS ZONAL WINDS TRADE WINDS HADLEY CELL SUBTROPICAL JET ETC 2 THE WINDS ARE FUNDAMENTALLY DRIVEN BY THE TEMPERATURE PRESSURE GRADIENT AND ANGULAR MOMENTUM CONSERVATION 3 WINDS BECOME SO LARGE DUE TO ANGULAR MOMENTUM CONSERVATION THAT THEY FORM JETS WHICH ARE UNSTABLE AND MAKE WAVES 4 WAVES ACTUALLY DO MOST OF THE TRANSPORT 5 WE CAN GET USEFUL TIMES TO CIRCLE THE EARTH FROM THE MEAN ZONAL WINDS ON THE ORDER OF A FEW WEEKS TO MONTHS DEPENDING ON ALTITUDE AND LATITUDE AND SEASON 6 WE CAN T GET USEFUL VERTICAL TRANSPORT TIMES FROM THE WINDS CONVECTION IS VERY RAPID BUT ISOLATED MEAN VERTICAL VELOCITY IS VERY SLOW 7 WE CAN T GET USEFUL MERIDIONAL TRANSPORT TIMES FROM THE MEAN MERIDIONAL CIRCULATION TRANSPORT IS BY WAVES SOLUTION LOOK AT DISTRIBUTIONS OF TRACERS TO UNDERSTAND TRANSPORT TIMES BOX MODELS A BOX MODEL IS AN IDEALIZED VOLUME IN WHICH THE CONCENTRATION IS ASSUMED TO BE UNIFORM WITHIN THE BOX AND IN WHICH THE TRANSPORT ACROSS THE WALLS OF THE BOX IS REPRESENTED AS SIMPLY AS POSSIBLE Earth39s Atmosphere b Lb Mb P b A BOX MODEL FOR THE RESIDENCE TIME OF A MATERIAL OF MASS M IN THE ATMOSPHERE Mb IS THE TOTAL MASS OF THE MATERIAL OF INTEREST WITHIN THE BOX Pb IS THE FLUX OF THE MATERIAL INTO THE BOX SOMETIMES CALLED THE PRODUCTION RATE OR SOURCE STRENGTH GIVEN THE HUGE MASS OF MOST MATERIALS IN THE ATMOSPHERE Mb USUALLY HAS UNITS OF TERRAGRAMS Tg AND Pb HAS UNITS OF Tg YRl A TERRAGRAM Tg IS 1012 g OR EQUIVALENTLY 106 METRIC TONS THE WEIGHT OF ALL THE PEOPLE ON EARTH IS ABOUT 250 Tg LB WHICH HAS UNITS OF INVERSE TIME IS THE LOSS RATE THEREFORE WE CAN WRITE THE FOLLOWING EQUATION FOR THE RATE OF CHANGE OF Mb de dt Pb Lbe IF Mb IS IN STEADY STATE OR IN OTHER WORDS IF Mb IS NOT CHANGING IN TIME THE SIMPLE STEADY STATE SOLUTION IS Lb PbMb EQUATION 1 HAS THE TIME DEPENDENT SOLUTION ASSUMING Pb AND Lb ARE NOT VARYING IN TIME Pb pb Mb E Mbt0 L exp39th IMAGINE THAT PRODUCTION OF THE MATERIAL SUDDENLY STOPPED SO THAT PO IN HQ 2 THEN THE TIME quotCC 1Lb IS THE TIME THAT WOULD BE REQUIRED FOR Mb TO DECLINE BY A FACTOR OF e39l FOR THIS REASON 1 IS CALLED THE LIFETIME OF MATERIAL Mb LIFETIMES OF SOME INTERESTING MATERIALS Material H20 CH4 COS 802 N20 CFC1 1 CFC12 CH3C1 NaCl Mb Abundance Tg 13x107 5x103 52 0609 25x103 62 103 5 36 Pb Source 1c Tg yr 5x108 515 12 200 1221 025 037 35 1300 Lifetime yr 0025 10 43 003005 120 50 100 15 0003 Altitude Km mquot in in ms in in3 inquot inquot volume mining lane An example of how uxes can be misleading when comparing species with differing lifetimes BOX MODELS CAN BE EXTENDED TO PROVIDE INFORMATION ABOUT THE RATES AT WHICH MATERIALS MOVE BETWEEN VARIOUS REGIONS OF THE ATMOSPHERE Northern Hemisphere Southern Hemisphere Ke Mn Mn KeMS Ms Pn f PS The exchange rate of air between the two hemispheres is Ke We can write the following two equations for the budgets of the tropospheres in the two hemispheres dMn Pn KeltMn Msgt dt dMS P5 KEltMS Mngt dt Subtracting the Southern Hemisphere equation from the Northern Hemisphere equation yields dMn MS dt The solution of this equation when the production rate and loss rate are not changing in time is Pu R ZKJMH Ms P P P P M M n 5 M M n 5 ex 2Kt n s n st4 2K6 e If we allow a time to pass which is much longer than 12Ke then we can find the exchange rate using 21lte Pu P5 M M If we assume that the production of the material of interest were to suddenly cease the difference in the masses of the material in the two hemispheres will decay by a factor of e391 in a time 1 quotCe 2Ke However it is usual to consider the transport time just in terms of a single hemisphere Then the time for the mass of material in a given hemisphere to be reduced by a factor of e391 due to transport to the other hemisphere is 1 L e Ke 028 I I I I I I I I I I I I I I I I 032 I 39 Production I 39 030 03926 Rate I a 39 a 024 I 03928 239 a 39 I O D I 026 g 022 I 3 E O 20 Northern I 03924 a g 39 Hemisphere 022 9 0 18 39 l 39 539 E 39 l 020 I Southern I lt 016 Hemisphere 39 018 quot I 014 39 I I l I I I I I I I I I I I I 39 016 1975 1980 1985 1990 1995 year The mixing ratio of CFC11 in the Northern and Southern Hemisphere and the rate of production of CFC11 Mn Ms013 Tg P26 Tg yr So 1 Te K is about lyr


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."

Jennifer McGill UCSF Med School

"Selling my MCAT study guides and notes has been a great source of side revenue while I'm in school. Some months I'm making over $500! Plus, it makes me happy knowing that I'm helping future med students with their MCAT."

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.