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时间:2019-08-09
《Chapter 3- Simple Models》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、22CHAPTER3.SIMPLEMODELSTheconcentrationsofchemicalspeciesintheatmospherearecontrolledbyfourtypesofprocesses:•Emissions.Chemicalspeciesareemittedtotheatmospherebyavarietyofsources.Someofthesesources,suchasfossilfuelcombustion,originatefromhumanactivityandarecalledant
2、hropogenic.Others,suchasphotosynthesisofoxygen,originatefromnaturalfunctionsofbiologicalorganismsandarecalledbiogenic.Stillothers,suchasvolcanoes,originatefromnon-biogenicnaturalprocesses.•Chemistry.Reactionsintheatmospherecanleadtotheformationandremovalofspecies.•T
3、ransport.Windstransportatmosphericspeciesawayfromtheirpointoforigin.•Deposition.AllmaterialintheatmosphereiseventuallydepositedbacktotheEarth’ssurface.EscapefromtheatmospheretoouterspaceisnegligiblebecauseoftheEarth’sgravitationalpull.Depositiontakestwoforms:“drydep
4、osition”involvingdirectreactionorabsorptionattheEarth’ssurface,suchastheuptakeofCO2byphotosynthesis;and“wetdeposition”involvingscavengingbyprecipitation.Ageneralmathematicalapproachtodescribehowtheaboveprocessesdeterminetheatmosphericconcentrationsofspecieswillbegiv
5、eninchapter5intheformofthecontinuityequation.Becauseofthecomplexityandvariabilityoftheprocessesinvolved,thecontinuityequationcannotbesolvedexactly.Animportantskilloftheatmosphericchemististomakethejudiciousapproximationsnecessarytoconvertthereal,complexatmosphereint
6、oamodelsystemwhichlendsitselftoanalyticalornumericalsolution.Wedescribeinthischapterthetwosimplesttypesofmodelsusedinatmosphericchemistryresearch:boxmodelsandpuffmodels.Aswewillseeinchapter5,thesetwomodelsrepresentrespectivelythesimplestapplicationsoftheEulerianandL
7、agrangianapproachestoobtainapproximatesolutionsofthecontinuityequation.Wewillalsouseboxmodelsinchapter6toinvestigatethegeochemicalcyclingofelements.233.1ONE-BOXMODELAone-boxmodelforanatmosphericspeciesXisshowninFigure3-1.ItdescribestheabundanceofXinsideaboxrepresent
8、ingaselectedatmosphericdomain(whichcouldbeforexampleanurbanarea,theUnitedStates,ortheglobalatmosphere).TransportistreatedasaflowofXintothe
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