《航海英语二三副》-Unit 2 Marine Weather

Lesson1MarineMeteorology

FactorsⅠ.Wind Windmakesthewaves,whichcanforcetheshipoffcourse,inresultofdelaysoractualhazardsincoastalwaters. Winddirectionisreportedbythedirectionfromwhichitoriginates. Ashortburstofhighspeedwindistermedawindgust. Strongwindsofintermediateduration(aroundoneminute)aretermedsqualls. Long-durationwindshavevariousnamesassociatedwiththeiraveragestrength,suchasbreeze,gale,storm,hurricane,andtyphoon.1.WindForce Theforceofthewindisproportionaltothesquareofthewindspeed. TheBeaufortwindforcescaleprovidesanempiricaldescriptionofwindspeedbasedonobservedseaconditions. WithintheBeaufortscale,gale-forcewindsliebetween28knots(52km/h)and47knots(88km/h)withprecedingadjectivessuchasmoderate,fresh,strong,andwholeusedtodifferentiatethewind'sstrengthwithinthegalecategory. Astormhaswindsof48knots(89km/h)to63knots(117km/h).Warningsofwinds,namelyGaleWarning,StormWarning,Hurricane/TyphoonWarning(≥64kts)areissuedintextinweatherforecastwhenthewindsareexpectedtoreachcorrespondingcategories.2.

PrevailingWinds PrevailingwindsarewindsthatblowpredominantlyfromasinglegeneraldirectionoveraparticularpointontheEarth'ssurface.(1)Doldrums

(2)Tradewinds(3)Horselatitudes(4)Theprevailingwesterlies

(5)Thepolareasterlies

(6)Monsoons

(7)Landandseabreeze

PrevailingWindsⅡ.Waves Wind-drivenwaves,orsurfacewaves,arecreatedbythefrictionbetweenwindandsurfacewater. Awave’shighestpointiscalleditscrest. Thelowpointbetweentwowavesiscalledatrough. Theverticaldistancebetweencrestandtroughiscalledthewaveheight. Thedistancetwowavesiscalledthewavelengthanditisusuallymeasuredeitherfromonecresttothenextorfromonetroughtothenext. Thetimeittakesforwavestopassiscalledthewaveperiod.Forweatherreportingandforscientificanalysisofwindwavestatistics,theircharacteristicheightoveraperiodoftimeisusuallyexpressedassignificantwaveheight.SignificantWaveHeightⅢ.Current Oceancurrentsaretheverticalorhorizontalmovementofbothsurfaceanddeepwaterthroughouttheworld’soceans.

Surfaceoceancurrentsaregenerallywinddrivenanddeveloptheirtypicalclockwisespiralsinthenorthernhemisphereandcounter-clockwiserotationinthesouthernhemispherebecauseoftheimposedwindstresses. Oceaniccirculationpattern,alongwithotherweatherstatisticsvitaltonavigation,isavailableinCoastPilots,PlanningGuideandSailingDirections.

Seafloortopographyandtheshapeoftheocean’sbasinsimpactbothsurfaceanddeepwatercurrentsastheyrestrictareaswherewatercanmoveand"funnel"itintoanother.Ⅳ.

Fog FogisacollectionofliquidwaterdropletsoricecrystalssuspendedintheairatorneartheEarth‘ssurface.Fogdevelopswhentheairatgroundleveliscooledenoughtocausesaturation(relativehumidityequals100%).Fogcanforminanumberofways,dependingonhowthecoolingthatcausedthe

condensation

occurred.1.

FogandHumidity Relativehumidityistheratiooftheactualamountofwatervaporintheair,atacertaintemperature,tothemaximumamountofwatervaporthatitcouldholdatthattemperature. TheDewpointisthetemperatureatwhichtheairbecomes100%saturated. Anytemperatureabovethedewpointwillhaverelativehumiditylowerthan100%,andanypointbelowthedewpointwillhaverelativehumidityof100%.2.

FourMainTypesofFog(1)AdvectionFog

(2)RadiationFog(3)FrontalFog(4)SteamFog(ArcticSeaSmoke)3.

Fog,MistandHaze Fogisasuspensionofverysmallwaterdropletsintheairreducingthevisibilityattheearth’ssurface. Mistisasuspensionintheairofmicroscopicwaterdropletsorwethygroscopicparticles,reducingthevisibilityattheearth’ssurface. Hazeisasuspensionintheairofextremelysmalldryparticlesinvisibletothenakedeyeandsufficientlynumeroustogivetheairanopalescent(milkyorpearly)appearance.Ⅴ.Clouds1.

HighClouds ThehighcloudgroupconsistsofCirrus,Cirrostratus,andcirrocumulusclouds. Thebaseofahighcloudabovethesurfacecanbeanywherefrom6000-18000minthetropicsto3000-8000minthepolarregion.2.

MiddleClouds ThemiddlecloudgroupconsistsofAltostratusandAltocmulusclouds. Thebaseofamiddlecloudabovethesurfacecanbeanywherefrom2000-8000minthetropicsto2000-4000minthepolarregion.3.

LowClouds ThelowcloudgroupconsistsofStratus,Stratocumulus,andNimbostratusclouds.Lowcloudsconsistofwaterdroplets.Thebaseofalowcloudisfromthegroundsurfaceto2000m.CloudChartⅥ.BuysBallot’SLaw IntheNorthernHemisphere,standwithyourbacktothewind;thelowpressureareawillonyourleft.ThisisbecausewindtravelscounterclockwisearoundlowpressurezonesintheNorthernHemisphere.ItisreverseintheSouthernHemisphere.ApplicationofBuysBallot’sLawinNorthernHemisphereLesson2WeatherReportsI.TermsRelatedtoWeatherReportsVeering&BackingFront;Coldfront;WarmfrontDepressions;OccludedfrontorOcclusionIsobars;Pressuregradient.Cyclone;tropicalcyclone;cyclonicdepression.anticyclonehurricane;typhoon;tropicalcyclonesorseverecyclonicstorms.SquallBarometer;AneroidbarometerII.WeatherReports Acompleteweatherreportsnormallyincludesthefollowingthreeparts:

PartOne:Warnings 1)GaleWarnings; 2)StormWarnings; 3)HurricaneWarnings;

PartTwo:Synopses "GeneralSituation"."SynopticSituation","Synopsis","Summary"orsuchothersimilarexpressions.PartThree:Forecasts Thesemessagesgiveastatementofexpectedconditioninacertainareaoveraperiod12or24hours.Theyincludedirectionandspeedofwind,theweather,temperature,visibilityandstateoftheskyandsea.Ⅲ.Samplesof

WeatherReports1.Shai/Xsg240240UTCSEPSHAIOBSYSYNOPTICSITUATION231800Z…24HOURWEATHERFORECASTFROM240200Z…2.FMGUAMRADIO/NPNREADASFOLLOWSSTORMWARNING…GALEWARNING…FORECAST…3.FMPORTISHEAD/GKAATLANTICWEATHERBULLETIN–17THDECEMBERPART1–STORMWARNING…PART2–SYNOPSIS…PART3–FORECAST…Lesson3RadioFacsimileChartI.CategoryofWeatherFacsimileChart

Theweatherfaxchartincludes：timelysurfaceanalysischart；surfaceforecastchartofdifferenttimeframe；

isobaricanalysisandforecastchartofdifferentaltitude；

oceanwaveanalysisandforecastchart；

stormwarningchart；

seaiceconditionchart；

averagewatertemperaturechart；

oceancurrentchart；

meteorologicalsatellitecloudchart,cloudanalysischart,etc.1.

SurfaceAnalysis Thesurfaceanalysesaregeneratedfourtimesperday(00Z,06Z,12Z,and18Z)foreachocean.SurfaceAnalysisChartofNorthPacificOcean(westandeastpartsoverlapped)2.

48-HourSurfaceForecasts Thesesurfaceforecastproductsgeneratedtwiceeachdayforeachoceanbasedonthe00Zand12ZGlobalForecastSystem(GFS)forecastmodelrunoutputswithadditionalguidancefromothergovernmentagenciessuchastheNAVYsNavyOperationalGlobalAtmosphericPredictionSystem(NOGAPS).48-HourSurfaceForecastChartofNorthPacificOcean3.

SeaStateProducts

SeaStateAnalysisChartisonceadayperoceanat00ZfortheNorthPacificand12ZfortheNorthAtlanticwithanalysisofshipsynopticreportsandautomatedweatherstationssuchasCMANsforseastatein"meters".SeaStateAnalysisChartofPacificOceanII.TerminologyandWeatherSymbols

Weathermapshavebeenusedsinceancienttimestorepresentvariousphases,types,andtheever-changingcharacteristicsofclimateindifferentpartsoftheworld.Thesignsthatareusedforsuchrepresentationsinthesemapsarecalledweathersymbols.Inthefieldofmeteorology,readingsandvaluesofvariousatmosphericparametersaretakenatspecificintervalsaroundtheglobeatweatherstations.Thesevaluesarethenprocessedandinterpretedbymeteorologistsusinglatestsoftwareprograms,andconclusionsaredrawnusingthisdatatoprepareweathermaps.Thetypeandnumberofsymbolsaredecideddependingonthekindofweatheroftheregionwherethereadingsaretaken.Thefollowingsymbolsandtextabbreviationsarecommonlyusedinthefacsimilechartforprovidingtheweatherinformationfortheshipsatsea.

1.

GraphicalProductsLegendGraphic