简介:Amplitudemodulationofnear-wallturbulencebylarge-scalestructuresintheouterlayerisinvestigatedbydirectnumericalsimulationofturbulentchannelflowsatReynoldsnumberReτ=540,1000,2000.Theeffectofmodulationisobviousinthetwo-pointcross-sectioncorrelationmap,andthecorrelationcoefficientsincreasesignificantlywiththeReynoldsnumber.Theinfluenceofmodulationisreflectedinthetailoftheprobabilitydensityfunctionofthenear-wallflowsignals,whichexpandsastheReynoldsnumberincreases.Theflatnessfactorprovidesaquantitativedescriptionofthehighfluctuationeventsduetomodulation.Vorticalstructuresassociatedwithmodulationarerevealedbyconditionallyaveragingtheflowfieldofthenear-wallextremeevents,providingadepictionofhowtheinfluenceofthelarge-scalestructurespenetratetowardsthenear-wallregion.
简介:Telluriumisasortofscatteredrareelementontheearth.Itsconcentrationisverylowinearth'scrust,only1.0ng/g.However,ithasextremelyhighabundanceinCo-richcrusts,marinepolymetallicnodules,deep-seasedimentsandaerolites.Tofindouttheoriginoftelluriumenrichmentindeep-seasediments,weanalyzedandcomparedtelluriumconcentrationsandheliumisotopecompositionsinthemagneticpartsandthoseinthebulkpartsofdeep-seasediments.Theresultindicatesthattheheliumcontent,3He/4Heratioandtelluriumconcentrationareobviouslyhigherinthemagneticpartsthanthoseinthebulkparts.The3Heabundancevariessynchronouslywiththetelluriumconcentration.3HeandTehaveadistinctpositivecorrelationwitheachother.Itisthefirsttimethatthepaperbringsforwardthattheextremeenrichmentoftelluriumindeep-seasediments,likeheliumisotopeanomalies,probablyresultsfromtheinputofinterplanetarydustparticles(IDPs).Similarly,theextremeenrichmentoftelluriuminmarinepolymetallicnodulesandCo-richcrustsispossiblyrelatedtoIDPs.
简介:WesternChinaexperiencedanextremehotsummerin2015,breakinganumberoftemperaturerecords.Thesummermeansurfaceairtemperature(SAT)anomalywastwicetheinterannualvariability.Thehottestdaytimetemperature(TXx)andwarmestnight-timetemperature(TNx)werethehighestinChinasince1964.Thisextremehotsummeroccurredinthecontextofsteadilyincreasingtemperaturesinrecentdecades.Wecarriedoutasetofexperimentstoevaluatetheextenttowhichthechangesinseasurfacetemperature(SST)/seaiceextent(SIE)andanthropogenicforcingdrovetheseverityoftheextremesummerof2015inwesternChina.Ourresultsindicatethatabout65%-72%oftheobservedchangesintheseasonalmeanSATandthedailymaximum(Tmax)anddailyminimum(Tmin)temperaturesoverwesternChinaresultedfromchangesinboundaryforcings,includingtheSST/SIEandanthropogenicforcing.Fortherelativeroleofindividualforcing,thedirectimpactofchangesinanthropogenicforcingexplainabout42%oftheSATwarmingand60%(40%)oftheincreaseinTNxandTmin(TXxandTmax)inthemodelresponse.ThechangesinSST/SIEcontributedtotheremainingsurfacewarmingandtheincreaseinhotextremes,whicharemainlytheresultofchangesintheSSToverthePacificOcean,whereasuperElNi?oeventoccurred.OurstudyindicatesaprominentroleforthedirectimpactofanthropogenicforcingintheseverityoftheextremehotsummerinwesternChinain2015,althoughthechangesinSST/SIE,aswellastheinternalvariabilityoftheatmosphere,alsomadeacontribution.
简介:NumericalsimulationsofextremewavegenerationarecarriedoutbyusingtheVolumeOfFluid(VOF)method.Extremewavesaregeneratedbasedonwavefocusingina2-Dnumericalmodel.TovalidatethecapabilityoftheVOF-basedmodeldescribedinthisarticle,thepropagationofregularwavesiscomputedandcomparedwiththetheoreticalresults.Byadjustingthephasesofwavecomponents,extremewavesareformedatgiventimeandgivenpositioninthecomputation.Thenumericalresultsarecomparedwiththeoreticalsolutionsandexperimentaldata.ItisconcludedthatthepresentmodelbasedontheVOFtechniquecanprovideacceptablyaccuratenumericalresultstoservepracticalpurposes.
简介:第五产生的宾夕法尼亚州的University/NCARMesoscaleModelVersion3(MM5V3)被用来在1999年6月在长江盆上模仿极端重降雨事件。模型极端气候事件上的水平、垂直的决定的效果详细被调查。原则上,模型能描绘每月重的降水的空间分发。结果显示水平分辨率的增加能减少建模的大雨的偏爱并且相当在学习时期期间模仿每日的降水的变化。导致的一个更好的垂直决定显然与更小的偏爱改进降雨模拟,并且因此,更好解决重降雨事件。在水平、垂直的分辨率的Theincrease能生产重降雨事件的更好的预言。在不同水平、垂直的格子间距的情况中改变的不仅降雨模拟,而且另外的气象学的领域在模型以决定变化表明了多样的变化。在模仿的海平面气压的明显的改进源于水平分辨率的增加,但是模拟对垂直格子间距感觉迟钝。垂直分辨率的增加能在底层提高地面温度以及大气循环的模拟,当在中间、上面的层次的循环的模拟在改变分辨率上被发现是少得多依赖时。另外,积云parameterization计划显示出高敏感到水平分辨率。Differentconvective计划关于改变分辨率在降雨模拟展出了大差异。在Grell计划的对流降水的百分比与增加水平分辨率增加了。相反,Kain-Pritsch计划引起了对流降水的减少的比率总计相应于增加水平分辨率的降雨累积。
简介:Inrecentyears,theredtideeruptedfrequently,andcausedagreateconomicloss.Atpresent,mostliteraturesemphasizetheacademicresearchonthegrowthmechanismofredtidealga.Inordertofindoutthecharactersofredtideindetailandimprovetheprecisionofforecast,thispapergivessomenewapproachestodealingwiththeredtide.Bytheextremevalues,wedealwiththeredtidefrequencyanalysisandgettheestimationofT-timesredtidelevelU(T),whichistheleveloncetheconsistenceofredtidealgaexceedsontheaverageinaperiodofTtimes.
简介:Forpredictionoftheextremesignificantwaveheightintheoceanareaswherelongtermwavedataarenotavailable,theempiricalmethodofextrapolatingshorttermdata(1~3years)isusedindesignpractice.Inthispapertwomethodsareproposedtopredictextremesignificantwaveheightbasedonshort-termdailymaxima.AccordingtothedaarecordedbytheOceanographicStationofLiaodongBayattheBohaiSea,itissupposedthatdailymaximumwaveheightsarestatisticallyindependent.Thedatashowthatdailymaximumwaveheightsobeylog-normaldistribution,andthatthenumbersofdailymaximavaryfromyeartoyear,obeyingbinomialdistribution.Basedonthesestatisticalcharacteristics,thebinomial-log-normalcompoundextremumdistributionisderivedforpredictionofextremesignificantwaveheights(50~100years).Forexaminationofitsaccuracyandvalidity,thepredictionofextremewaveheightsisbasedon12years′dataatthisstation,andbasedoneach3years′datarespectively.Theresultsshowthatwithconsiderationofconfidenceintervals,thepredictedwaveheightsbasedon3years′dataareveryclosetothosebasedon12years′data.TheobserveddatainsomeoceanareasintheAtlanticOceanandtheNorthSeashowitisnotcorrecttoassumethatdailymaximumwaveheightsarestatisticallyindependent;theyaresubjecttoMarkovchaincondition,obeyinglog-normaldistribution.Inthispaperananalyticalmethodisderivedtopredictextremewaveheightsinthesecases.AcomparisonofthecomputationsshowsthatthedifferencebetweentheextremewaveheightsbasedontheassumptionthatdailymaximaarestatisticallyindependentandthattheyaresubjecttoMarkovChainconditionissmallerthan10%.