沙尘暴的成因与防治
<p>沙尘暴天气的形成要具备三个基本条件：</p><p><span word="There">There</span> <span word="are">are</span> <span word="three">three</span> <span word="basic">basic</span> <span word="conditions">conditions</span> <span word="for">for</span> <span word="the">the</span> <span word="formation">formation</span> <span word="of">of</span> <span word="sandstorm">sandstorm</span>:</p><p>一是要有沙源，</p><p><span word="First">First</span>, <span word="there">there</span> <span word="should">should</span> <span word="be">be</span> <span word="a">a</span> <span word="source">source</span> <span word="of">of</span> <span word="sand">sand</span>,</p><p>二是要有强冷空气即大风，</p><p><span word="Second">Second</span>, <span word="there">there</span> <span word="should">should</span> <span word="be">be</span> <span word="strong">strong</span> <span word="cold">cold</span> <span word="air">air</span>, <span word="i">i</span>.<span word="e">e</span>. <span word="strong">strong</span> <span word="wind">wind</span>,</p><p>三是要有冷暖空气相互作用。沙源来自于沙漠，退化的林草地或没有植被覆盖的干松土地以及城乡建筑工地的泥沙。气旋和低压产生一种垂直的上升运动，把沙尘吹扬了起来，形成沙尘暴天气。扬沙、浮尘和沙尘暴天气的差别在气象上是以能见度加以区分的：水平能见度在1—10公里之间的为扬沙或浮尘天气。出现浮尘天气时，空中弥漫的是一些细小颗粒物，沙尘多由外地而来；扬沙天气卷起的尘土是一些较大的颗粒物，它们基本是本地产生的。而水平能见度小于1公里的就是沙尘暴天气，它属于灾害性天气现象，所带来的危害最为严重。气象专家介绍，由于沙尘暴起因包括了风力、高空大气强对流和地表状态三方面因素，而前两者属气候因素，人力不可抗拒，因此，根除沙尘暴目前尚无可能。</p><p><span word="Third">Third</span>, <span word="there">there</span> <span word="should">should</span> <span word="be">be</span> <span word="interaction">interaction</span> <span word="between">between</span> <span word="warm">warm</span> <span word="and">and</span> <span word="cold">cold</span> <span word="air">air</span>. <span word="The">The</span> <span word="source">source</span> <span word="of">of</span> <span word="sand">sand</span> <span word="comes">comes</span> <span word="from">from</span> <span word="deserts">deserts</span>, <span word="degraded">degraded</span> <span word="forest">forest</span> <span word="and">and</span> <span word="grassland">grassland</span>, <span word="or">or</span> <span word="dry">dry</span> <span word="pine">pine</span> <span word="land">land</span> <span word="without">without</span> <span word="vegetation">vegetation</span> <span word="cover">cover</span>, <span word="as">as</span> <span word="well">well</span> <span word="as">as</span> <span word="the">the</span> <span word="sediment">sediment</span> <span word="of">of</span> <span word="urban">urban</span> <span word="and">and</span> <span word="rural">rural</span> <span word="construction">construction</span> <span word="sites">sites</span>. <span word="The">The</span> <span word="cyclone">cyclone</span> <span word="and">and</span> <span word="the">the</span> <span word="low">low</span> <span word="pressure">pressure</span> <span word="produce">produce</span> <span word="a">a</span> <span word="vertical">vertical</span> <span word="upward">upward</span> <span word="movement">movement</span>, <span word="which">which</span> <span word="blows">blows</span> <span word="up">up</span> <span word="the">the</span> <span word="dust">dust</span> <span word="and">and</span> <span word="forms">forms</span> <span word="a">a</span> <span word="dust">dust</span> <span word="storm">storm</span>. <span word="The">The</span> <span word="weather">weather</span> <span word="difference">difference</span> <span word="of">of</span> <span word="sand">sand</span> <span word="blowing">blowing</span>, <span word="floating">floating</span> <span word="dust">dust</span> <span word="and">and</span> <span word="sandstorm">sandstorm</span> <span word="is">is</span> <span word="distinguished">distinguished</span> <span word="by">by</span> <span word="visibility">visibility</span> <span word="in">in</span> <span word="meteorology">meteorology</span>: <span word="the">the</span> <span word="weather">weather</span> <span word="with">with</span> <span word="horizontal">horizontal</span> <span word="visibility">visibility</span> <span word="between">between</span> 1-10<span word="km">km</span> <span word="is">is</span> <span word="sand">sand</span> <span word="blowing">blowing</span> <span word="or">or</span> <span word="floating">floating</span> <span word="dust">dust</span>. <span word="When">When</span> <span word="the">the</span> <span word="floating">floating</span> <span word="dust">dust</span> <span word="weather">weather</span> <span word="occurs">occurs</span>, <span word="the">the</span> <span word="air">air</span> <span word="is">is</span> <span word="filled">filled</span> <span word="with">with</span> <span word="some">some</span> <span word="small">small</span> <span word="particles">particles</span>, <span word="most">most</span> <span word="of">of</span> <span word="which">which</span> <span word="come">come</span> <span word="from">from</span> <span word="other">other</span> <span word="places">places</span>; <span word="the">the</span> <span word="dust">dust</span> <span word="rolled">rolled</span> <span word="up">up</span> <span word="by">by</span> <span word="the">the</span> <span word="floating">floating</span> <span word="dust">dust</span> <span word="weather">weather</span> <span word="is">is</span> <span word="some">some</span> <span word="larger">larger</span> <span word="particles">particles</span>, <span word="which">which</span> <span word="are">are</span> <span word="basically">basically</span> <span word="generated">generated</span> <span word="locally">locally</span>. <span word="The">The</span> <span word="sandstorm">sandstorm</span> <span word="with">with</span> <span word="horizontal">horizontal</span> <span word="visibility">visibility</span> <span word="less">less</span> <span word="than">than</span> 1<span word="km">km</span> <span word="is">is</span> <span word="a">a</span> <span word="kind">kind</span> <span word="of">of</span> <span word="disastrous">disastrous</span> <span word="weather">weather</span> <span word="phenomenon">phenomenon</span>, <span word="which">which</span> <span word="brings">brings</span> <span word="the">the</span> <span word="most">most</span> <span word="serious">serious</span> <span word="harm">harm</span>. <span word="According">According</span> <span word="to">to</span> <span word="meteorologists">meteorologists</span>, <span word="the">the</span> <span word="causes">causes</span> <span word="of">of</span> <span word="sandstorm">sandstorm</span> <span word="include">include</span> <span word="wind">wind</span> <span word="force">force</span>, <span word="high">high</span>-<span word="altitude">altitude</span> <span word="atmospheric">atmospheric</span> <span word="strong">strong</span> <span word="convection">convection</span> <span word="and">and</span> <span word="surface">surface</span> <span word="state">state</span>, <span word="while">while</span> <span word="the">the</span> <span word="former">former</span> <span word="two">two</span> <span word="are">are</span> <span word="climatic">climatic</span> <span word="factors">factors</span> <span word="and">and</span> <span word="irresistible">irresistible</span> <span word="by">by</span> <span word="manpower">manpower</span>, <span word="so">so</span> <span word="it">it</span> <span word="is">is</span> <span word="impossible">impossible</span> <span word="to">to</span> <span word="eradicate">eradicate</span> <span word="sandstorm">sandstorm</span> <span word="at">at</span> <span word="present">present</span>.</p>
页:
[1]