Posted on 2010-10-31 19:34 PHP博客 阅读(182) 评论(0)  编辑 收藏 引用 网摘


Their shade cools the planet and their water vapor traps heat from the sun.




·Clouds have both cooling and warming effects on Earth's surface. Figuring how they balance is tricky.


·Determining global cloud cover over time is a major aspect of understanding climate change.


(image illustration)Clouds play a crucial role in regulating Earth's climate.

Some clouds help cool the Earth, but other clouds help keep Earth warm – in part depending on how high up they are in our atmosphere. That’s according to Steven Platnick, a satellite researcher with NASA. He studies clouds and how they connect with Earth’s climate. He said that low, fluffy clouds keep us cooler.


有些云彩能为地球降温,也有些云彩能为地球保暖——某种程度上取决于云彩在大气层中的高度。这一观点是由美国国家航空航天局的卫星研究学者Steven Platnick(史蒂芬·普兰尼克)提出来的。他负责研究云彩以及它们与地球气候的关系。他曾经说过,低空的絮状云更能使我们感到凉爽。

SP: You can appreciate that if you go out on a hot and sunny day, and a cloud passes by overhead, it’s a great relief from the heat. And the reason of course is because the cloud is reflecting sunlight.


But it’s a different story for clouds that are high up in the atmosphere, said Platnick. Those high, wispy clouds actually keep Earth warm, like a blanket, by preventing heat from escaping into space. Platnick uses NASA’s Aqua satellite to determine the height of clouds, and other properties of clouds as well -- like what’s inside them, how much water they have, and whether a cloud is primarily liquid or ice. The satellite also tracks the amount of cloud cover all over the world.


Steven Platnick: The most important thing to trying to understand their effect on global climate is we need to know how they’re globally distributed and how they vary over the course of a year. And you need satellites to really obtain the statistics over those scales. It’s really impossible for most of those quantities to get the same statistics from ground-based or aircraft observations.


Platnick explained to EarthSky what scientists mean when they talk about climate.


SP: When scientists talk about climate, what we’re talking about is the statistics of weather. And normally we’re talking about that on multi-decadal time scales, and longer, even centuries and millennium. An example might be the average surface temperatures, something that most people can relate to. Or also, the minimum and maximum surface temperatures. And there’s other examples -– precipitation, the amount of rainfall during the month, or snowfall, or snow pack. But when we talk about recent climate change, and the causes of recent climate change, and that’s over the last several decades including the last several centuries since the start of the industrial revolution, then we start to study the effect of human activities, and how humans can directly modify climate.

SP:科 学家们在谈论气候时,实际都是在谈论关于天气的统计数据。一般来说,我们谈论的这些数据的时间跨度有的几十年,有的几百年,有的甚至长达几千年。比如平均 地表温度,很多人谈论时都会提到它,有的人还会谈到最高地表温度和最低地表温度。其他例子如降水量、月降雨量、降雪量、积雪量等等。但当我们谈到近年来的 气候变化和变化的原因时,由于最近这几十年涵盖了工业革命以来的几个世纪,我们就需要开始研究人类活动对气候的影响以及人类怎样直接改变了气候。

Platnick said that there are several ways that humans can directly impact climate. The best understood of these, he said, and what’s likely the most important in the long run, is the release of greenhouse gases into the atmosphere.


SP: And that includes not just carbon dioxide, but methane, ozone, there’s other gases as well. And these greenhouse gases perturb the radiation balance of climate. And what they do is move the climate system to a warmer state. And it does that because of the way that gases reduce the emissions of infrared radiation to space by the Earth and its atmosphere. And this so-called greenhouse gas forcing on the climate system is well-understood.

SP:温 室气体不仅包括二氧化碳,还包括甲烷、臭氧等其他气体。这些温室气体会扰乱气候的辐射平衡。它们会使气候系统进入一种增温状态。这一现象的产生是因为这些 气体使地球及其大气层散入到太空的红外线辐射减少了。这些所谓的温室气体,对气候系统施加强迫性,这一点已经得到了很好的理解。

He said that what’s less well-understood is how the climate responds to this forcing.


SP: And that is the focus of much climate modeling research today. It’s certainly the motivation behind many of NASA’s satellite observations and the modeling studies that we do, and that’s in fact what a large part of my own work involves.


Platnick told EarthSky what he thought was the most important thing people should know about Earth’s clouds and climate.


SP: Earth is a dynamic system of components. On the largest scales you have the atmosphere, the land, the ocean, snow and ice on the ground. And these systems connect with each other in different ways, through the exchange of water, and energy, and chemistry, such as the exchange of carbon. We need to be able to better understand the consequences of these connections. Clouds are the prime example of this interconnection, because they play a key role in these systems, especially in the water and energy connections.

SP:地 球是一个由不同成分组成的动态系统。从最大的范围来看,大气、土地、海洋、地面冰雪都包括在内。此外,通过交换水分、能量和化学元素(如碳元素),这些系 统还以不同的方式互相联系着。我们需要更好地把这些联系带来的影响弄懂。在这个互相联系的系统网络中,云彩是个典型的例子,因为云彩在这一联系网络中发挥 着关键作用,特别是水和能量之间的联系。

NASA satellites and instruments, along with our international partners are helping us to get better observations we need to understand these cloud physical processes and to enable cloud model improvements as well.



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