2、另一个具体的记不清了，有4段，
第一段大概讲的是，大西洋的hurricane在多久以前平均每年登陆美国的数量可能只有1-2个，后来变多了（大概7、8个？）。。。（中间失忆）。。。然后有人就推测原因：sher wind（反正就是什么wind）和海水温度升高导致的。
第二段好像这两个东西因素还导致了另外两个ecological phenomena
第三段。。。
第四段提到了El Nino现象还是La Nina现象，
https://www.livescience.com/1581-corals-show-hurricane-spike-norm.html
https://www.sciencenewsforstudents.org/article/stormy-history
是原文吗？
The recent spike in hurricane activityin the North Atlantic—a trend that some scientists blame on climate changeactuallyreflects a return to normal frequency after a lull in the 1970s and 1980s, anew analysis confirms. Between 1995 and 2005, meteorologistsrecorded an annual average of 4.1 category-3-or-stronger hurricanes in theNorth Atlantic and the Caribbean. Such hurricanes exhibit steady wind speedsexceeding 178 kilometers per hour. From 1971 through 1994, however, an averageof only 1.5 such hurricanes swept through the same region each year, says K.Halimeda Kilbourne, a paleoclimatologist with the National Oceanic andAtmospheric Administration in Boulder, Colo. Two factors thought to stronglyinfluence hurricane formation are wind shear—an atmospheric phenomenon in whichadjacent layers of air move at different speeds or in different directions—andsea-surface temperature. Strong wind shear tends to rip apart tropical stormsbefore they strengthen into hurricanes, says Kilbourne. On the other hand, asea-surface-temperature rise can provide more energy to a hurricane as itforms. ==================↑P1=================================== Kilbourne and her colleagues studied avariety of marine records to estimate year-to-year variations in wind shearback to 1730. For instance, the luminescence of growth rings in coral underultraviolet light reveals how much organic matter has been washed from land bythunderstorms, which don't form as readily or as often if wind shear is high.Also, the number of marine microorganisms in seafloor sediment—in particular,that of a species called Globigerina bulloides—indicates the upwelling ofnutrient-rich waters, another measure of wind shear at the ocean's surface. ===================↑P2，但是内容不够=============================== When the researchers looked forcorrelations between wind shear, other scientists' estimates of sea-surfacetemperature, and hurricane frequency, they found that wind shear has a muchstronger influence in the North Atlantic than surface temperature does. Theyalso found that large variations in hurricane frequency have been the norm,they report in the June 7 Nature. Overall, between 1730 and 2005, theNorth Atlantic has experienced an average of 3.25 category-3-or-strongerhurricanes each year, says Kilbourne. However, at least six lengthy intervalssince 1730 had hurricane activity comparable to today's. In general, suchboosts in hurricane frequency occurred when wind shear was weak. Most periodsof low hurricane activity since 1730 were marked by strong wind shear, shenotes. Some of these intervals even occurred when sea-surface temperatures werehigher than normal. =================↑好像有，但是我忘记了原文位置==============OTZ========= Other analyses of long-term naturalrecords bolster the connection between strong wind shear and reduced hurricanefrequency, says Jeffrey P. Donnelly, a coastal geologist at Woods Hole (Mass.)Oceanographic Institution. By studying sediments from a lake inEcuador and a lagoon in eastern Puerto Rico, he and his colleagues compared thetiming of hurricanes during the past 5,000 years with that of El Niños—weatherphenomena that increase wind shear over the North Atlantic. =============↑最后一P，但是少内容==================================== The researchers reported in the May 24Nature that periods with strong, frequent El Niños experienced alower-than-average number of hurricanes.
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发表于 2018-8-22 22:51:49
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