天造还是人为？
<p>○沙尘暴发生的三要素是大风、不稳定的大气层结状态和地面的沙尘源，所以常常发生在春季</p><p><span word="The">The</span> <span word="three">three</span> <span word="factors">factors</span> <span word="of">of</span> <span word="sandstorm">sandstorm</span> <span word="are">are</span> <span word="strong">strong</span> <span word="wind">wind</span>, <span word="unstable">unstable</span> <span word="atmospheric">atmospheric</span> <span word="stratification">stratification</span> <span word="and">and</span> <span word="dust">dust</span> <span word="source">source</span> <span word="on">on</span> <span word="the">the</span> <span word="ground">ground</span>, <span word="so">so</span> <span word="it">it</span> <span word="often">often</span> <span word="occurs">occurs</span> <span word="in">in</span> <span word="spring">spring</span></p><p>○沙尘暴产生的年代已很久远，但近期有加剧的趋势</p><p><span word="The">The</span> <span word="sandstorm">sandstorm</span> <span word="has">has</span> <span word="been">been</span> <span word="produced">produced</span> <span word="for">for</span> <span word="a">a</span> <span word="long">long</span> <span word="time">time</span>, <span word="but">but</span> <span word="there">there</span> <span word="is">is</span> <span word="a">a</span> <span word="trend">trend</span> <span word="of">of</span> <span word="aggravation">aggravation</span> <span word="in">in</span> <span word="the">the</span> <span word="near">near</span> <span word="future">future</span></p><p>○沙尘暴的发生与沙漠化有关，自然成因和人为因素都起作用</p><p><span word="The">The</span> <span word="occurrence">occurrence</span> <span word="of">of</span> <span word="sandstorm">sandstorm</span> <span word="is">is</span> <span word="related">related</span> <span word="to">to</span> <span word="desertification">desertification</span>, <span word="and">and</span> <span word="both">both</span> <span word="natural">natural</span> <span word="and">and</span> <span word="human">human</span> <span word="factors">factors</span> <span word="play">play</span> <span word="a">a</span> <span word="role">role</span></p><p>春天终于来了，北方人在感受花红柳绿、燕舞莺歌之前，总是躲不开几次沙尘的“洗礼”。你知道如何确定沙尘暴天气吗？当你站在户外混浊的空气中看不到离你一公里远的地方时，这便是沙尘暴天气了。沙尘暴一来遮天蔽日，户外的人们苦不堪言。狂暴的风沙阻断交通，摧毁通讯线路甚至建筑，毁伤人命。我们平常所说的沙尘暴，实际上是沙暴和尘暴两者的总称。一般说来，沙暴是就地起沙(扬沙)，它携带的沙物质搬运的距离不远，而尘暴(浮尘)却能在高空中飘移几千公里之外，甚至更远。去年夏天，法国波尔多大学地质学家弗朗西斯与他的同事竟然在欧洲阿尔卑斯山的积雪中发现了来自中国的这些“不速之客”。近年来媒体对沙尘暴的关注很多，体现了社会各界对此问题的焦虑及治理的重视。要想找到治理的正确途径必须先把它的形成机理搞清楚。那么沙尘暴是几个简单原因造成还是多个系统复合作用的结果？沙源是短期形成、发生的，还是长期形成、发生的，甚至是一个地质变化过程？沙尘暴是自然成因为主还是人为的结果？本文试着就这些问题作一探讨。</p>
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