TheUnitedStatesistheworld'sveryimportantbigcountry,itslandareaislocatedinthefourthintheworld,behindRussia,CanadaandChina.TheUnitedStatesislocatedinNorthAmerica,neighboringcountriessuchasCanadaandMexicohave,theUnitedStatesalsoincludesthevergeoftheArcticterritoryofAlaskaandHawaiiPacific.TheUnitedStateseconomicandtechnologicalpowerintheworldnoonecanchallenge,arewell-deservedsuperpower.

　　TheUnitedStateswiththediversenatureoftheclimate.InwhichtheUnitedStatesinthenorthlatitudeofapproximately25°to49°between,withtheexceptionofthesoutherntipofFloridapeninsulaasatropicalclimate,areforthetemperateandsubtropicalclimate.Unevenprecipitation,generallyspeaking,theeastandhumid,aridwesternregion.North-easterncoastalandGreatLakesregions,thenorthbythecoldLabradorandtheimpactofthecold,coldwinter,theaverageJanuarytemperatureofabout-6℃insummerthanmild,wet,theaverageJulytemperatureof16℃orso;annualaverageabout1000mmofprecipitation.ThecentralGreatPlainsarea,northandsouthbecauseoftheterrainopen,thecoldwinteraircanbesouth,thesummercanbehotsoutherlyblowingconstantly,andthewintercoldandsummerheat.Theareaaroundthenorthern,luptothemonthofminimumtemperatureof-40℃,7monthuptoamaximumtemperatureof45℃.Theannualaverageprecipitationisnormally500to1000mm.South-eastandtheGulfofMexicocoasttosubtropicalclimate.AffectedbytheGulfStream,warmandhumid,theaverageJanuarytemperatureof9℃aroundtheaverageJulytemperatureof24~27℃.OfteninlatesummerearlyautumnhurricanehittheGulfCoast,resultingindisaster.Theannualaverageprecipitation1500mm.Westerninlandplateau,theclimateisaridwithcoldwinter,hotsummer,theannualaverageprecipitationat500mmbelowthesoutherndesertplateaulessthan250mmofprecipitation.ThePacificcoastofthenorthernpartoftheclimate,rainfall,ltheaveragetemperatureinthemonthofmorethan4℃,theaveragetemperatureinAugustdonotexceed14℃,theaverageannualprecipitation1500mm.PacificRimisthesouthernMediterranean-typeclimate,warmandrainywinter,dryhotsummer,theaverageJanuarytemperatureof12℃,8monthmorethan22℃,theaverageannualprecipitationis300~500mm.Alaska,about1/3islocatedintheArcticCircle,isacold,dryandcoldclimate.SoutheasternAlaskaalongthePacificcoastduetotheimpactofwarm,humidclimatemoremoderate.HawaiianIslandsislocatedintropical,hotclimate.Ingeneralthewind-richprecipitationinthenorth-eastslope,leewarddrierdrysouthwestslope,theslopeofindividualwindofupto12,000millimetersofannualprecipitation.

　　Americanflagforarectangularshape,lengthandwidthratioof19:10fortheStarsandStripes(theStar-SpangledBanner),theupper-leftcornerflagforthebluestarssurfaceareaofthestarsafewprovisionsintherespectivedepartments,theUnitedStatesisthestateflagonthenumberofafewofthestars.Star13isoutsidetheredandwhitestripes,13stripesonbehalfoftheoriginal13coloniesinNorthAmerica.AccordingtoWashington,said:symboloftheUnitedKingdomwithredstripes,whitestripesandasymboloffreedomfromit.Moregeneralargumentthattheredsymbolofstrengthandcourage,asymbolofpurityandinnocenceofwhite,blueisasymbolofvigilance,perseveranceandjustice.In1818theU.S