太空中计算河流流量
文章来源:未知 文章作者:enread 发布时间:2014-03-19 05:55 字体: [ ]  进入论坛
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The frustrated1 attempts of a UCLA graduate student to quantify the amount of water draining from Greenland's melting ice sheet led him to devise a new way to measure river flows from outer space, he and his professor report in a new study. The new approach relies exclusively on the measurements of a river's width over time, which can be obtained from freely available satellite imagery.
 
Currently, hydrologists(水文学者) calculate a river's discharge -- the volume of water running through it at any given time -- by taking a series of measurements on the ground, including not just the river's width but also its depth at multiple points and the velocity2(速率) of its flows. Politics, financial considerations and terrain3 often stand in the way of obtaining such measurements.
 
"Our new method doesn't require access to the country or getting in the river to safely take measurements in the field," said Colin Gleason, lead author of the study and a doctoral student in geography in UCLA's College of Letters and Science. "As long as we can get multiple pictures of a river and apply this method to them, we can tell you how much water was flowing in the river at the time the images were taken."
 
The discovery is highlighted March 17 in the online edition of Proceedings4 of the National Academy of Sciences (PNAS).
 
With the potential to be applied5 anywhere in the world, the new approach is expected to provide information that will benefit agriculture, sanitation6 and flood preparation, especially in countries without the resources to physically7 measure and monitor their rivers.
 
Additionally, it holds promise for improving the accuracy of climate models, which track recycling of water between the atmosphere and land, and ensuring that countries with trans-boundary rivers comply with international water-sharing agreements.
 
"This work represents a breakthrough in our ability to address one of the most pressing environmental challenges of the 21st century, which is ensuring access to sufficient water supply for human beings and ecosystems," said Laurence C. Smith, co-author of the study and chair of UCLA's geography department. "I'm very excited about this discovery."
 
A noted8 authority on climate change and its affect on the Arctic, Smith has been trying for the past 20 years to figure out a way to estimate river discharge on Earth from outer space. The closest he had been able to get to the goal was an approach that employed satellite imagery but still required on-site verification.
 
"You still needed measurements on the ground to calibrate9 the method, which defeated the purpose," he said. "But now we can estimate discharge with river width alone, and width we can see from space."
 
For the PNAS proof-of-concept study, Gleason and Smith used their new system and satellite imagery from the U.S. government's Landsat program to measure the discharge of three rivers -- the Mississippi, Canada's Athabasca and China's Yangtze. They then compared those results with discharge figures from respected government agencies that monitor those rivers and whose calculations are recognized as highly accurate. The estimates of the UCLA geographers10 came within 20 to 30 percent of those figures.
 
"That might sound like a big error, but right now, we have no idea about the flow rates of most rivers around the world," Smith said. "To get a number that is within even 30 percent of accurate is incredibly helpful."


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1 frustrated ksWz5t     
adj.挫败的,失意的,泄气的v.使不成功( frustrate的过去式和过去分词 );挫败;使受挫折;令人沮丧
参考例句:
  • It's very easy to get frustrated in this job. 这个工作很容易令人懊恼。
  • The bad weather frustrated all our hopes of going out. 恶劣的天气破坏了我们出行的愿望。 来自《简明英汉词典》
2 velocity rLYzx     
n.速度,速率
参考例句:
  • Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
  • The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。
3 terrain sgeyk     
n.地面,地形,地图
参考例句:
  • He had made a detailed study of the terrain.他对地形作了缜密的研究。
  • He knows the terrain of this locality like the back of his hand.他对这一带的地形了如指掌。
4 proceedings Wk2zvX     
n.进程,过程,议程;诉讼(程序);公报
参考例句:
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
5 applied Tz2zXA     
adj.应用的;v.应用,适用
参考例句:
  • She plans to take a course in applied linguistics.她打算学习应用语言学课程。
  • This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。
6 sanitation GYgxE     
n.公共卫生,环境卫生,卫生设备
参考例句:
  • The location is exceptionally poor,viewed from the sanitation point.从卫生角度来看,这个地段非常糟糕。
  • Many illnesses are the result,f inadequate sanitation.许多疾病都来源于不健全的卫生设施。
7 physically iNix5     
adj.物质上,体格上,身体上,按自然规律
参考例句:
  • He was out of sorts physically,as well as disordered mentally.他浑身不舒服,心绪也很乱。
  • Every time I think about it I feel physically sick.一想起那件事我就感到极恶心。
8 noted 5n4zXc     
adj.著名的,知名的
参考例句:
  • The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
  • Jim is noted for arriving late for work.吉姆上班迟到出了名。
9 calibrate vTvyu     
校准;使合标准;测量(枪的)口径
参考例句:
  • Pesticide levels in food are simply too difficult to calibrate.食品中杀虫剂的含量很难精确测定。
10 geographers 30061fc34de34d8b0b96ee99d3c9f2ea     
地理学家( geographer的名词复数 )
参考例句:
  • Geographers study the configuration of the mountains. 地理学家研究山脉的地形轮廓。
  • Many geographers now call this landmass Eurasia. 许多地理学家现在把这块陆地叫作欧亚大陆。
TAG标签: water space river
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