专业英语2-new

专业英语南京信息工程大学段明铿UnitII:Frontogenesisandfrontalcharacteristics第二课锋生和锋的特征NewWordsfront锋，锋面frontolysis锋消frontogenesis(frontogeneses)锋生frontal锋面的mid-latitude中纬度low-latitude低纬度high-latitude高纬度day-to-day逐日的daily逐日的mass气团，质量humidity湿度specifichumidity比湿discontinuity不连续性meteorologist气象学家integral整数的，积分的，完整的integration积分interface交界面，接口interactioninternetinterannual(年际的）medium(media)介质mediumrangeforecasts中期预报numerical数值的numericalweatherprediction(NWP)数值天气预报model模式baroclinic斜压的barotropic正压的barotropicprimitiveequationmodel正压原始方程模式cyclone气旋anticyclone反气旋cyclogenesis气旋生成depression低压low低压isobaric等压的isothermal等温的iso+..等。。synoptic天气的PrincipleofSynopticMeteorology天气学原理convergence辐合divergence辐散apex顶点，峰尖peak峰zone区域regioncirrus(cirri)卷云ana-front上滑锋kata-front下滑锋slope坡度order量级multi-layered多层的multi-cell多单体的stratus(strati)层云cirrostratus卷层云altostratus高层云nimbostratus雨层云stratocumulus层积云drizzle毛毛雨precipitation降水rainfall降水量saturate使饱和descend下降ascend上升medium-level中层high-level高层low-level低层mid-tropospheric对流层中部的coalescence（雨滴的）合并airflow气流large-scale大尺度的meso-scale中尺度的broad-scale大范围的momentum(momenta)动量convective对流性的convection对流advective平流性的advection平流potential位势，潜在的potentialheat潜热geopotentialmeter位势米rainband雨带rainbeltorographic地形的topographicdown-wind在下风方向upwindana-type上滑型kata-typecumulonimbus积雨云downpour倾盆大雨thunder雷duration持续时间occlusion锢囚occlude锢囚trowal(troughofwarmairaloft)高空暖舌aloft高的，上面的stratiform层状的stratification层结poleward向极地的phase相位，阶段，方面squall飑jet急流lowleveljet低空急流geostrophic地转的greenhouse温室效应albedo反照率evaporate蒸发v.evaporation蒸发n.oceanic海洋的lee背风面trough槽ridge脊气团：气象要素（主要指温度和湿度）水平分布比较均匀的大范围空气团。气团的形成：下垫面加热气团的变性：移动气团的地理分类：极地、赤道；大陆性、海洋性气团的热力分类：相对性FrontFrontogensis锋生Thefirstrealadvanceinourdetailedunderstandingofmid-latitudeweathervariationswasmadewiththediscoverthatmanyoftheday-to-daychangesareassociatedwiththeformationandmovementofboundaries,orfronts,betweendifferentairmasses.Observationsofthetemperature,winddirections,humidityandotherphysicalphenomenaduringunsettledperiodsshowedthatdiscontinuitiesoftenpersistbetweenimpingingairmassesofdifferingcharacteristics.Theterm“front”,forthesesurfacesofairmassconflict,wasalogicaloneproposedduringtheFirstWorldWarbyagroupofmeteorologistsworkinginNorway,andtheirideasarestillanintegralpartofmostweatheranalysisandforecastingparticularlyinmiddleandhighlatitudes.在对中纬度天气变化详细深入理解的过程中，第一次真正意义上的进步就是发现很多逐日天气变化是与不同气团边界或者说锋的形成和移动有关的。对不稳定期内温度、风向、湿度和其它物理现象的观测表明，紧密接触的不同特征气团之间通常表现为持续的不连续性。气团之间的交界面“锋”，这个在第一次世界大战时由一群挪威气象学家提出的。这一思想仍然是目前大多数天气分析和预报（特别是在中纬度地区）不可或缺的一部分。FrontalwavesItwasobservedthatthetypicalgeometryoftheairmassinterface,orfront,resemblesawaveform.Similarwavepatternsare,infact,foundtooccurontheinterfacebetweenmanydifferentmedia,forexample,wavesonseasurface,ripplesonbeachsand,aeoliansanddunes,etc.Unlikethesewaveforms,however,thefrontalwavesintheatmospherearecommonlyunstable:thatis,theysuddenlyoriginate,increaseinsize,andthengraduallydissipate.Numericalmodelcalculationsshowthat,inmiddlelatitudeswavesinabaroclinicatmosphereareunstableiftheirwavelengthexceedsafewthousandkilometers.Frontalwavecyclonesaretypically1500-3000kminwavelength.锋面波观测表明，气团交界面（锋）的典型几何形状如同波动一样。事实上，类似的波动形态还可以在很多不同介质间的交界面上找到，例如海面上的波动、沙滩上的波痕以及风吹形成的沙丘。但是，不同于这些波动形式，大气中的锋面波通常都是不稳定的，也就是说，锋面波会突然出现，尺度增加，然后又慢慢消失。数值模式的计算表明，若干波长超过几千千米，在中纬度地区的斜压大气中，波动是不稳定的。锋面气旋的波长一般在1500-3000千米。Similarwavepatternsare,infact,foundtooccurontheinterfacebetweenmanydifferentmedia,forexample,wavesonseasurface,ripplesonbeachsand,aeoliansanddunes,etc.Itwasobservedthatthetypicalgeometryoftheair-massinterface,orfront,resemblesawaveform.1500-3000kminwavelength.Unlikethesewaveforms,however,thefrontalwavesintheatmospherearecommonlyunstable:thatis,theysuddenlyoriginate,increaseinsize,andthengraduallydissipate.Theinitiallyattractiveanalogybetweenatmosphericwavesystemsandwavesformedoninterfaceofothermediais,therefore,aninsufficient-basisonwhichtodevelopexplanationsoffrontalwaves.Inparticular,thecirculationoftheuppertroposphereplaysakeyroleinprovidingappropriateconditionsfortheirdevelopmentandgrowth,aswillbeshownbelow.Adepression(alsotermedaloworcyclone)isanareaofrelativelylowpressure,withamoreorlesscircularisobaricpattern.Itcoversanarea100-3000kmindiameterandusuallyhasalife-spanof4-7days.Systemswiththesecharacteristics,whichareprominentondailyweathermaps,arereferredtoassynopticscalefeatures.Thedepression,inmid-latitudesatleast,isusuallyassociatedwithaconvergenceofcontrastingairmasses.ThefrontalwavedepressionTheinterfacebetweentheseairmassesdevelopsintoawaveformwithitsapexlocatedatthecentreofthelow-pressurearea.Thewaveenclosesamassofwarmairbetweenmodifiedcoldairinfrontandfreshcoldairintherear.Theformationofthewavealsocreatesadistinctionbetweenthetwosectionsoftheoriginalairmassdiscontinuityfor,althougheachsectionstillmarkstheboundarybetweencoldandwarmair,theweathercharacteristicsfoundintheneighborhoodofeachsectionareverydifferent.Thetwosectionsofthefrontalsurfacearedistinguishedbythenameswarmfrontforthe