Principles of Environmental Physics Fourth Edition Principles of Environmental Physics Plants, Animals, and the Atmosphere Fourth Edition John L. Monteith† and Mike H. Unsworth AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK OXFORD • PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE SYDNEY • TOKYO Academic Press is an imprint of Elsevier †Deceased. Academic Press is an imprint of Elsevier The Boulevard, Langford Lane, Kidlington, Oxford OX51GB, UK Radarweg 29, PO Box 211, 1000 AE Amsterdam, The Netherlands 225 Wyman Street, Waltham, MA 02451, USA 525 B Street, Suite 1900, San Diego, CA 92101-4495, USA Fourth Edition Copyright © 2013, 2008 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher. Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: permissions@ elsevier.com. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material. Previous Editions 1990, 1975 Edward Arnold Publishers Ltd. Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress For information on all Academic Press publications visit our web site at store.elsevier.com Printed and bound in Poland 13 14 15 16 17 10 9 8 7 6 5 4 3 2 1 ISBN: 978-0-12-386910-4 Preface to the Fourth Edition Sadly,JohnMonteith,mycolleague,mentorandfriend,diedinJuly2012beforethis editionwascomplete.Formorethan50yearshepioneeredtheapplicationofphysics to the study and analysis of biological processes. He began his career in the Physics DepartmentofRothamstedExperimentalStation,wherehiscollaborationwithHoward PenmanledtothePenman-Monteithequationthathasbeensoinfluentialinecophys- iologyandhydrologyforestimatingevaporationandtranspiration.AtRothamstedhe alsocollaboratedwithGezaSzeiczandothersindesigningandbuildingsomeofthe firstinstrumentsforEnvironmentalPhysics,includingearlyversionsoftubesolarime- ters and porometers that became much-used tools for investigating canopy and leaf environments.Hewasalsoamongthefirsttouseinfraredgasanalyzersformicrome- teorologicalmeasurementsofthecarbondioxideexchangeofcropcanopies. In1967hemovedtotheUniversityofNottinghamSchoolofAgriculturewherehe builtupthefirstacademicdepartmentwithafocusonEnvironmentalPhysics.Thefirst editionofthisbookin1973wasderivedfromthecoursethathedevelopedtherefor seniorundergraduates,whichwasuniqueincoveringbothplantandanimalinteractions withtheenvironment.Thetextquicklybecameessentialreadingforresearchersinthe expanding fieldofEnvironmental Physicsworldwideandwastranslatedintoseveral languages.WhenIjoinedJohnasco-authorforthesecondedition(1990),weupdated thebook,expandedseveralchapters,andaddednewsectionsonnon-steady-stateheat balances and on particle and pollutant gas transfer in recognition of the emerging disciplinethatwouldeventuallybetermedbiogeochemistry. Bythetimeofthethirdedition(2008),EnvironmentalPhysicshadexpandedrapidly, drivenbyconcernsoverincreasingglobalcarbondioxideconcentrationsandchanging climate.Inparticular,researchonthecarbonandwaterbudgetsofforestsandnatural vegetationhadgreatlyincreased.Availabilityofnewfast-responseinstrumentationfor trace gas measurement allowed the previously esoteric micrometeorological method ofeddycovariancemeasurementtobewidelyapplied.Consequentlyweaddedmore materialabouteddycovarianceandincludedmoreexamplesofapplicationsinforest science.Wealsorespondedtorequeststoincludemoreworkedexamplesandproblem sets for student use. The Preface to the Third Edition, which is reproduced below, capturesmanyofJohn’sinsightsintothedevelopmentofEnvironmentalPhysics,and reveals some of the thinking behind how this book is structured and the conventions wehavechosentoadopt. Thisfourtheditionprovidesanopportunitytoimproveonthepresentationofmate- rial,updatethecorechapters,andsummarizesomeofthehighlightsofthehugeexpan- sioninpublishedworkinEnvironmentalPhysicsoverthepastdecade.Inkeepingwith thetitle,wehavechosentofocusonprinciples;readersseekingmoreadvancedtreat- viii PrefacetotheFourthEdition mentsoftopicsareencouragedtoexploresomeofthetextsmentionedintheBibliog- raphy.Inchoosingexamplesfrompublishedresearchwehavecontinuedourpractice of focusing on work that presents new insights and applies principles from the text; this becomes increasingly challenging as Environmental Physics grows, so we have includedmanynewreferencesaimedtohelpreadersfollowuponemergingtopics. It has always been our aim to keep the mathematics in this book at a level acces- sible to readers competent in algebra but not necessarily familiar with calculus. We have responded to suggestions from our students and others by expanding many of thealgebraicderivationstoshowintermediatesteps,andwehaveplacedsomeofthe morecomplexmathematicsintextboxeswhichcouldbeomittedbythegeneralreader. MorehasbeenincludedaboutthePenman-Monteithequationanditsapplications,and about coupling of vegetation to the atmosphere. And we have increased the material oneddycovarianceandmodifiedthepresentationofgradientmethodsinmicromete- orologysothatmuchofthediscussionofnon-neutralstabilitycouldbebypassed. Wearegratefultoourmanystudentsandcolleagueswhohavegivenusfeedback on their use of this book and have provided many of the research examples that are mentionedinthetext.Comments(bothpositiveandnegative!)onthiseditionwillbe [email protected]. MikeUnsworth,2013. Companion Website Visitthisbook’scompanionwebsitetoaccessadditionalcontent. http://booksite.elsevier.com/9780123869104 Preface to the Third Edition InthetimesincethefirsteditionofPrinciplesofEnvironmentalPhysicswaspublished in 1973 the subject has developed substantially; indeed, many users of the first and secondeditionshavecontributedtothebodyofresearchthatmakesthisthirdedition larger than the first. From the start, this text has been aimed at two audiences: first, undergraduateandgraduatestudentsseekingtolearnhowtheprinciplesofphysicscan beappliedtostudytheinteractionsbetweenplantsandanimalsandtheirenvironments; andsecond,theresearchcommunity,particularlythoseinvolvedinmultidisciplinary environmentalresearch.Inmanyways,environmentalphysicshasbecomemorethor- oughlyembeddedinenvironmentalresearchoverthedecades.Forexample,inecology andhydrology,conceptsofatmosphericexchangeofgasesandenergybetweenorgan- isms and the atmosphere, and the resistances (or conductances) controlling them are commonly applied. And in atmospheric science, soil-vegetation-atmosphere transfer schemes (SVATS) are an integral part of general circulation, mesoscale, and climate models.This“unionofideas”acrossthedisciplineshasmadeitchallengingtodefine the scope of this third edition and to keep the size manageable. In doing so we have beenguidedbytheword“Principles”inthetitle,sohavefocused,asinpreviousedi- tions, on describing the critical principles of energy, mass, and momentum transfer, and illustrating them with a number of examples of their applications, taken from a rangeofclassicandmorerecentpublications. Severalthemeshavewaxedandwanedovertheeditions.Atthetimeofthefirstedi- tion,agriculturalcropmicrometeorologywasadominantapplicationofenvironmental physics,beginningwiththedesiretoquantifythewateruseandirrigationrequirements of crops, and extending, as new instrumentation became available, to the analysis of carbondioxideexchangeineffortstoidentifytheenvironmentalcontrolsofcroppro- ductivity.Therehasbeenmuchlessnewworkonagriculturalcropmicrometeorology in the last decade or two, but applications of environmental physics to the study of managed and natural forests and other ecosystems gathered pace through the 1970s and1980s,andprobablycurrentlyaccountforalargerfractionoftheannualreviewed publicationsinenvironmentalphysicsthanagriculturalapplications.Alsointhe1970s and1980s,concerns over human influences onairquality(particularlyacidrainand ozone)grew,leadingtotheapplicationofenvironmentalphysicstostudyfluxesofpol- lutantgases,acidicparticles,andmisttocropsandforests.Additionally,thetechnology forremotesensingfromsatellitesdevelopedconsiderably. The second edition of Principles of Environmental Physics, published in 1990, reflectedthesedevelopmentsbyaddinganewchapteronparticletransfer,newmate- rial on radiative transfer, and expanding the sections on micrometeorological meth- ods. It also expanded treatment of the environmental physics of animals and their x PrefacetotheThirdEdition environments,influencedbytheworkofanumberofresearchersstudyingtheheatbal- anceoflivestockandwildanimals,whobegantousetheterminologyofenvironmental physics,thusestablishingparallelswiththeintegrationofenvironmentalphysicsinto plant science. The identification of the ozone hole above Antarctica in 1985, and its influenceonultravioletradiationatthesurfacereceivedashortmentioninthesecond edition,butemergingresearchondepositionofnitrogen-containinggasestovegetation wasnotcovered;bothtopicsreceivemoreattentioninthisedition. Throughthe1980s,extendingtothepresenttime,concernoverrisingconcentrations ofcarbondioxideandothergreenhousegasesintheatmosphereandconsequentlikely effectsonclimatehasbeenadominanttopic,leadingtoanexplosionofmeasurement andmodelingresearchprogramsthatmakeuseofprinciplesdescribedinthisbook.Two developments have been particularly important: improved instrumentation allowing theeddycovariancetechniqueinmicrometeorologytobeappliedforstudiesofland- atmosphereexchangeofcarbondioxide,watervapor,andsomeothertracegasesover seasonalandmulti-annualperiods;andtheoreticaladvancestoenablemodelsofplant- atmosphereexchangetobescaledupfromtheleafscaletolandscape,regionalandeven globalscales,creatinglinksbetweentheprinciplesdescribedinthisbookatorganism andcanopylevelswiththetypeofregionalandglobalmodelingnecessarytoaddress climate-changeconcerns.Thiseditioncontainstwosubstantiallyrevisedchapterson micrometeorologywithexpandedtreatmentoftheeddycovariancemethod,andwhich contain several new case studies to illustrate the application of micrometeorological methodsoverforestsandnaturallandscapes.Wehavealsoexpandedthematerialon solar and terrestrial radiation with new discussion of the roles of radiatively active greenhousegasesandaerosols. Althougheddycovariancehasbecomethemethodofchoiceformicrometeorologyin manysituations,wehaveretainedthematerialdescribingprofile(similarity)techniques for deducing fluxes, because an understanding of similarity methods is essential for large-scalemodelsandbecauseprofilemethodshaveadvantagesintermsofsimplicity ofinstrumentationwhendesigningstudentprojectsorworkingwithlimitedresources. Anumberofotherchangesinthiseditionhaveresultedfromourownexperience andfeedbackfromothersusingthisbookasateachingtext:severalsectionsthatwere particularlycondensedinearliereditionshavebeenexpandedtoaidclarity,andsome sectionshavebeenrearrangedtoimprovetheflow;moreworkedexampleshavebeen includedinthetext;somespecializedmaterial(forexample,detailsofthephysicsof radiative emission and of radiation interaction with aerosols) has been added in text boxes that can be omitted by readers seeking a briefer treatment of the subject; and numericalproblemshavebeenaddedattheendofeachchapter.Manyofthenumerical problemsaremoreextensivethantypicallyfoundintextbooks.Thisreflectsrequestswe havehadovertheyearsfromteacherswhowouldliketoexplorerealisticapplications of the subject; many of the problems have been used in our own undergraduate and graduate teaching at Nottingham and Oregon State Universities, and we thank many studentsfortheirfeedbackandsuggestionsforimprovementstotheproblems. In planning this third edition we debated whether to change nomenclature in flux equationsfromresistancestoconductances,andwhethertoexpressquantitiesin“mole” unitsratherthan“m-kg-s”units.Biologistsincreasinglyuseconductancesandmoles PrefacetotheThirdEdition xi intheiranalyses,andtherearesomegoodtheoreticalanddidacticargumentsforthis. But,onbalance,wepreferredtoretainthe“resistance”termsand“s m−1”unitsused inearliereditions:theanalogywithOhm’sLawemphasizestheunderlyingphysicsof manyanalysesusedinthisbook,andunitsofsm−1 forresistancesaremoreintuitive forheatandmasstransfercalculationsinenergybalanceandhydrologicalapplications. Nevertheless, werecognize thatmany readers willbefamiliarwithconductance and mol units, so we have discussed conversions of units at several appropriate points inthetext.Therearemanyadvantagesinenvironmentalphysiciststryingtobecome comfortableinworkingwithbothsystemsofunitstofacilitatecommunicationacross thedisciplines. Weintendthistexttobeusefulforteachingundergraduatesandgraduatestudents specializing in physics, biology, and the environmental sciences. The mathematical treatmentisdeliberatelykeptrelativelysimple,withlittleuseofcalculus;thebiology isalsostrictlylimited,consistingprincipallyofmaterialessentialforunderstandingthe physicalapplications.Thereisabibliographydirectingreaderstomoredetailedtexts ifnecessary.Forourothercategoryofreaders,researchscientists,wehavecontinued the approach of previous editions by including a large number of references to the peer-reviewed literature, identifying a mix of papers that we consider classics and ground-breakingresearchapplications;morethan30ofthereferencesinthisedition havebeenpublishedsince1990. In the preface to the second edition we expressed the hope that our book would encourage more university physics departments to expose their students to environ- mental physics. Our impression is that progress has been slow. This surely cannot be because of a lack of career opportunities—current environmental concerns open many possibilities for environmental physicists in the atmospheric sciences, hydrol- ogy,ecology,andbiology,particularlyiftheyenjoythechallengesofmultidisciplinary work. Nor does it seem to be because physics students lack interest in environmen- talsubjects.Perhaps itisinevitable thatthecrowded physics curriculumleaves little roomforoptionssuchasenvironmentalphysics,butitwouldbesatisfyingif,bythe timethefourtheditionofthisbookappears,environmentalphysicswasascommonas astronomyormeteorologyasanoptionalcourseinphysicsdepartments. JohnMonteithandMikeUnsworth,2006. Acknowledgments We thank the following for allowing us to use diagrams, photographs, and original data: Drs R. Keeling and P. Tans, and the database provided by the US Department of Energy through its Carbon Dioxide Information Analysis Center (Figure 2.2); Dr. G. Kopp for providing the data used in Figure 5.1; Dr. S.T. Henderson and Adam Hilger Publishers (Figure 5.2); Dr. J.A. Coakley (Figure 5.3); The British Antarctic Survey (Figure 5.4); The Solar Energy Research Institute for the computer models used to construct Figure 5.5; Dr. M.D. Steven and the Royal Meteorological Society (Figure 5.6) from the Quarterly Journal of the Royal Meteorological Society; Dr. F. Vignola for providing the data used in Figure 5.8; Dr. J.V. Lake for providing the data used in Figure 5.9; Mr. F.E. Lumb and the Royal Meteorological Society (Figure 5.10) from the Quarterly Journal of the Royal Meteorological Society; Dr. R. von Fleischer and the Deutschern Wetterdienstes (Figure 5.15); Dr. R. Nakamura for providing the data used in Figure 5.17; Dr. K. Bible for providing the data used in Figure 5.18; Dr. E.L. Deacon and Elsevier Publishing Co. (Figures 6.1 and 15.7); Dr. S.A. Bowers and Lippincott Williams and Wilkins Co. (Figure 6.3) from Soil Science; Dr. K.J. McCree and Elsevier Publishing Co. (Figure 6.4) from Agricultural Meteorology; Dr. G. Stanhill and Pergamon Press (Figure 6.6) from Solar Energy; Professor L.E. Mount and Edward Arnold (Figures 6.7, 14.3, and 14.4); Dr. J.C.D. Hutchinson and Pergamon Press (Figure 6.8) from Comparative Biochemistry and Physiology; Dr. W. Porter for providing data used in Figure 6.9; Dr. C.R. Underwood and Taylor and Francis Ltd (Figure 7.5) from Ergonomics; Dr. G.S. Campbell and Nottingham University Press (Figure 8.3) Dr. K. Cena and the Royal Society of London (Figure 8.6) from the Proceedings of the Royal Society; Dr. J. Grace and Oxford University Press (Figure 9.3) from Journal of Experimental Botany; The Royal Meteorological Society (Figures 9.4, 9.5, 13.6, 13.7, 13.8, 13.9, 15.3, 17.13, and 17.14) from the Quarterly Journal of the Royal Meteorological Society; Dr. W.C. Hinds and John Wiley & Sons Inc. (Figures 9.6, 12.7, 12.8, 12.9, 12.10); Dr. D. Aylor and the American Society of Plant Physiologists (Figure 9.7) from Plant Physiology; Dr. A Stokes and Cambridge University Press (Figure 9.8); Drs C.J. Wood and R. Belcher and D. Reidel Publishing Co. (Figure 9.10) from Boundary Layer Meteorology; Dr. J.A. Clark and D. Reidel Publishing Co. (Figure 10.3) from Boundary Layer Meteorology; Dr. B.J. Bailey and the International Society for Horticultural Science (Figure 10.4) from Acta Horticulturae; Dr. S. Vogel and Clarendon Press (Figure 10.5); Dr. A.J. McArthur and the Royal Society of London (Figures 10.7 and 10.8) from the Proceedings of the Royal Society; Dr. R.P. Clark and The Lancet (Figures 10.9 and 10.11), and Cambridge University Press (Figure 10.8) xiv Acknowledgments from Journal of Physiology; Dr. P.F. Scholander and the Marine Biological Laboratory (Figure 10.12); Dr. I. Impens allowed us to use unpublished measurements in Figure 11.1. Dr. T. Haseba and the Society of Agricultural Meteorology in Japan (Figure 11.3) from Journal of Agricultural Meteorology; Dr. H.G. Jones and Cambridge University Press (Figure 11.7); Dr. D. Aylor and Pergamon Press (Figure 12.5) from Atmospheric Environment; Professor N.A. Fuchs and Pergamon Press (Figure 12.1); Dr. A.C. Chamberlain and Academic Press (Figure 12.3), and D. Reidel Publishing Co. (Figure 17.1) from Boundary Layer Meteorology; Dr. D. Fowler and Springer (Figure 12.6) from Water, Air, and Soil Pollution; Dr. K. Raschke and Springer (Figure 13.5) from Planta; R. Milstein (Figure 13.10); Elsevier Publishing Co. (Figures 13.11 and 13.12) from the Journal of Hydrology and (Figure 17.11) from Agricultural and Forest Meteorology; Dr. A.M. Hemmingsen (Figure 14.2); Dr. D.M. Gates and Springer-Verlag (Figure 15.2); Dr. J. van Eimern and the Deutschern Wetterdienstes (Figure 15.5); Dr. W.R. van Wijk and North Holland Publishing Co. (Figure 15.6); D. Vickers and Dr. L. Mahrt (Figure 16.3); Dr. J. Finnigan and D. Reidel Publishing Co. (Figure 16.4) from Boundary Layer Meteorology and (Figures 17.16 and 17.17); Dr. R.H. Shaw and Elsevier Publishing Co. (Figure 16.8) from Agricultural Meteorology; Academic Press (Figures 16.9 and 16.10); Dr. M.R. Raupach and Annual Reviews Inc. (Figure 16.11) from Annual Review of Fluid Mechanics; Dr. T.A. Black and Blackwell Scientific (Figures 17.9 and 17.10) from Global Change Biology; Dr. D. Baldocchi (Figure 17.7) and D. Reidel Publishing Co. (Figure 17.19) from Boundary Layer Meteorology; Dr. M. Sutton and the Royal Society (Figure 17.15) from the Philosophical Transactions of the Royal Society of London.