按写作方式分类 
形形色色的GRE文章，绝大多数可分为两种基本写作类型。 

1．Presentation，即立论型的文章。在此类文章中，作者阐明一个自己提出的观点、理论、解释，没有对立面；或者文章后半段稍有不同意见，但都被作者反驳掉，不足为据。 

　　例文：
The　recent,　apparently　successful,　prediction　by　mathematical　models　of　an　appearance　of　E1　Nino—the　warm　ocean　current　that　periodically　develops　along　the　Pacific　coast　of　South　America—has　excited　researchers.　Jacob　Bjerknes　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　appearances　of　the　warm　E1　Nino　and　the　cold　so-called　anti-E1　Nino.　The　answer,　at　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　E1　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　up-welling　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　E1　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　Rossby　waves　westward,　waves　that　will　eventually　return　as　cold　cycle　ending　positive　Kelvin　waves,　beginning　another　warming　cycle. 

　　此文中，作者始终在说当前预测厄尔尼诺的一个模型是如何地好，优于以前的同类理论，见不到一点其他人的评价。 

转贴于：GRE-考试_考试大

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