简介：

简介：TheuniquegeographicallocationandhighaltitudeoftheTibetanPlateaucangreatlyinfluenceregionalweatherandclimate.Inparticular,theAsiansummermonsoon(ASM)anticyclonecirculationsystemovertheTibetanPlateauisrecognizedtobeasignificanttransportpathwayforwatervaporandpollutantstoenterthestratosphere.Toimproveunderstandingofthesephysicalprocesses,amulti-locationjointatmosphericexperimentwasperformedovertheTibetanPlateaufromlateJulytoAugustin2018,fundedbythefiveyear(2018–2022)STEAM(stratosphereandtroposphereexchangeexperimentduringASM)project,duringwhichmultipleplatforms/instruments—includinglong-durationstratosphericballoons,dropsondes,unmannedaerialvehicles,specialsoundingsystems,andground-basedandsatellite-borneinstruments—willbedeployed.Thesecomplementarymethodsofdataacquisitionareexpectedtoprovidecomprehensiveatmosphericparameters(aerosol,ozone,watervapor,CO2,CH4,CO,temperature,pressure,turbulence,radiation,lightningandwind);therichnessofthisapproachisexpectedtoadvanceourcomprehensionofkeymechanismsassociatedwiththermal,dynamical,radiative,andchemicaltransportsovertheTibetanPlateauduringASMactivity.

简介：Irregularsurfaceflattening,whichisbasedonaboundaryconforminggridandthetransformationbetweencurvilinearandCartesiancoordinatesystems,isamathematicalmethodthatcanelegantlyhandleirregularsurfaces,buthasbeenlimitedtoobtainingfirstarrivalsonly.Bycombiningamultistageschemewiththefast-sweepingmethod(FSM,themethodtoobtainfirst-arrivaltraveltimeincurvilinearcoordinates),thereflectedwavesfromacrustalinterfacecanbetracedinatopographicmodel,inwhichthereflectedwavefrontisobtainedbyreinitializingtraveltimesintheinterfaceforupwindbranches.Alocaltriangulationisappliedtomakeaconnectionbetweenvelocityandinterfacenodes.Thenajointinversionoffirst-arrivalandreflectiontraveltimesforimagingseismicvelocitystructuresincomplexterrainsispresented.Numericalexamplesallperformwellwithdifferentseismicvelocitymodels.Theincreasingtopographiccomplexityandevenuseofahighcurvaturereflectorinthesemodelsdemonstratethereliability,accuracyandrobustnessofthenewworkingscheme;checkerboardtestingillustratesthemethod’shighresolution.Noisetolerancetestingindicatesthemethod’sabilitytoyieldpracticaltraveltimetomography.Furtherdevelopmentofthemultistageschemewillallowotherlaterarrivalstobetracedandusedinthetraveltimeinversion.