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1、Hurricane（飓风）Katrina Ahurricaneisafiercelypowerful,rotating（旋转的）formoftropicalstormthatcanbe124to1,240milesindiameter.ThetermhurricaneisderivedfromHurican,thenameofanativeAmericanstormgod.Hurricanesaretypicalofacalmcentralregionoflowpressurebetween12to60
2、milesindiameter,knownastheeye.Theyoccurintropicalregions.Overitslifetime,oneofthesecan releaseasmuchenergyas10,000nuclearbombs. Theseedforhurricaneformationisacluster（聚集）ofthunderstomsoverwarmtropicalwaters.Hurricanescanonlyformandbefedwhenthesea-surface
3、temperatureexceeds27℃andthesurroundingatmosphereiscalm.TheserequirementsaremetbetweenJuneandNovemberinthenorthernpartoftheworld. Undertheseconditions,largequantitiesofwaterevaporate（蒸发）andcondense（冷凝）intocloudsandrain-releasingheatintheprocess.Itisthishe
4、atenergy,combinedwiththerotationoftheEarth,thatdrivesahurricane. Whenthewarmcolumnofairfromtheseasurfacefirstbeginstorise,itcausesanareaoflowpressure.Thisinturncreateswindasairisdrawnintothearea.Thisspinningwinddragsupmoremoistairfromtheseasurfaceinaproc
5、essthatstrengthensthestorm.Coldairfallsbacktotheoceansurfacethroughtheeyeandontheoutsideofthestorm. Initially,whenwindspeedsreach23milesperhour,thesemild,wetandgreyweathersystemsareknownasdepressions,orlowairpressure.HurricaneKatrinaformedinthiswayoverth
6、esouth-easternBahamason23August2005.KatrinahashadadevastatingimpactontheGulfCoastoftheUS,leavingadisasterzoneof90,000squaremilesinitswake（尾迹）-almostthesizeoftheUK.Thousandshavebeenkilledorinjuredandmorethanhalfamillionpeoplehavebecomehomelessinahumanitari
7、an（人道主义的）crisisofascalenotseenintheUSsincetheGreatDepression.Thecostofthedamagemaytop$100billion. 36.Theeyeofahurricanereferstoits A.lowerpart. B.rotatingpart. C.calmcentralpart. D.mostviolentpart. 37.WhichofthefollowingisNOTa"requirement"fortheform
8、ationofahurricane? A.Calmsurroundingatmosphere. B.Highairpressure. C.Warmsea-surfacetemperature. D.Agroupofthunderstormsoverwarmtropicalwaters. 38.Whenthewarmairfromtheseasurfacebeginstorise,it A.createsanarea
