首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
The recent, apparently successful prediction by mathematical models of an appearance of El Nino—the warm ocean current that peri
The recent, apparently successful prediction by mathematical models of an appearance of El Nino—the warm ocean current that peri
admin
2009-04-27
57
问题
The recent, apparently successful prediction by mathematical models of an appearance of El Nino—the warm ocean current that periodically develops along the Pacific coast of South America—has excited researchers. Jacob Blerkness pointed out over 20 years ago how winds might create either abnormally warm or abnormally cold water in the eastern equatorial Pacific. Nonetheless, until the development of the models no one could explain why conditions should regularly shift from one to the other, as happens in the periodic oscillations between appearance of the warm El Nino and the cold so-called anti-El Nino. The answer, al least if the current model that links the behavior of the ocean to that of the atmosphere is correct, is to be found in the ocean.
It has long been known that during an El Nino, two conditions exist: (1) unusually warm water extends along the eastern Pacific, principally along the coasts of Ecuador and Peru, and (2) winds blow from the west into the warmer air rising over the warm water in the east. These winds tend to create a feedback mechanism by driving the warmer surface water into a "pile" that blocks the normal upwelling of deeper, cold water in the east and further warms the eastern water, thus strengthening the wind still more. The contribution of the model is to show that the winds of an El Nino, which raise sea level in the east, simultaneously send a signal to the west lowering sea level. According to the model, that signal is generated as a negative Rossby wave, a wave of depressed, or negative, sea level that moves westward parallel to the equator at 25 to 85 kilometers per day. Taking months to traverse the Pacific, Rossby waves march to the western boundary of the Pacific basin, which is modeled as a smooth wall but in reality consists of quite irregular island chains, such as the Philippines and Indonesia.
When the waves meet the western boundary, they are reflected, and the model predicts that Rossby waves will be broken into numerous coastal Kelvin waves carrying the same negative sea-level signal. These eventually shoot toward the equator, and then head eastward along the equator propelled by the rotation of the Earth at a speed of about 250 kilometers per day. When enough Kelvin waves of sufficient amplitude arrive from the western Pacific, their negative sea-level signal overcomes the feedback mechanism tending to raise the sea level, and they begin to drive the system into the opposite cold mode. This produces a gradual shift in winds, one that will eventually send positive sea-level Rossby waves westward, waves that will eventually return as cold cycle-ending positive Kelvin waves beginning another warming cycle.
选项
A、cold coastal water near Peru.
B、winds blowing from the west.
C、random occurrence.
D、worldwide effects.
答案
B
解析
事实细节题。本文第二段首句指出"人们早已知道,在厄尔尼诺出现期间,有两个条件存在:(1)异常的暖流沿东太平洋延伸,主要是沿着厄瓜多尔和秘鲁沿岸;(2)风从西部吹入东部温暖的海水上方所升起的较暖空气"。因此风从西部吹过来是厄尔尼诺的一个特征,这正是答案选项内容。
转载请注明原文地址:https://kaotiyun.com/show/jPa4777K
0
考研英语一
相关试题推荐
Icametofeminismthewaysomepeoplecometosocialmovementsintheirearlyyears:outofself-interest.Igotontheequalit
Itwasjustafootnotecomparedwiththemoreinfectiousdisasterthatkilledmillionsmorepeoplein1918,butthe1957influen
Governmentsarerestrainingbusinesstravelersandtouristswithcumbersomevisarequirementsthatdolittletomaketheircount
Runningmaybethesinglemosteffectiveexercisetoincreaselifeexpectancy,accordingtoanewreviewandanalysisofpastre
AnonymityisnotsomethingwhichwasinventedwiththeInternet.Anonymityandpseudonymityhasoccurredthroughouthistory.For
NowthatmembersofGenerationZaregraduatingcollegethisspring—themostcommonly-accepteddefinitionsaysthisgeneration
Groupgrillinghaslongbeenpopularamongacademics,governmentagenciesandnon-profitorganizations—sectorsthatpreferdecis
Writeanessayofabout150wordsbasedonthefollowingdrawing.Inyouressay,youshould1)describethedrawingbriefly,
LastSeptember,theU.S.governmentannouncedthatitsbirthratefellto"anotherrecordlow".Morallyspeaking,there’snothin
Fordecadesthemarketforexpensiveheadphoneswasmainlylimitedtohi-fifans.But【C1】________theboxystereosysteminthec
随机试题
Whetherfaggedbythethreedays’runningchase,andtheresistancetohisswimmingintheknottedhamperhebore;orwhetherit
无菌区域:
下列关于土工合成材料加筋垫层作用机理的论述中,哪个选项是不正确的?()
吹填工程施工中,布设吹填区内管线应考虑的因素有()。
为了防止灌注混凝土过程钢筋骨架上浮,当混凝土拌合物上升到骨架底口( )m以上时,提升导管,使其底口高于骨架底部2m以上,然后恢复正常灌注速度。
下列各项中,不属于被投诉者的义务是()。
定量研究参照自然科学研究的模式,其基本程序包括()。
含有两个销售中介机构的渠道叫作()。
利息率的高低有一定的界限,在一般情况下
在一个关系中要找出某些字段组成新关系,应使用的操作是
最新回复
(
0
)