2007年VOA标准英语-NASA Exploring Polar Ice Clouds

By Paul Sisco
Washington
20 April 2007
 

NASA is preparing to launch a mission to the mesosphere, a region at the top of Earth's atmosphere where mysterious night shining clouds are formed.  Little is known about the mesosphere, but its unique ice clouds are being seen lower and brighter in the sky than ever before.  It is causing some scientists to think human induced climate changes are reaching the edge of space. VOA'S Paul Sisco reports.

Clouds in the mesosphere are of interest to scientists

The AIM spacecraft is scheduled for launch next Wednesday (April 25th) from Vandenberg Air Force Base in the western U.S. state of California. AIM stands for Aeronomy of Ice in the Mesosphere.

The craft will study mysterious ice clouds way above Earth's polar regions -- clouds that can be seen from Earth with the naked eye in the night sky -- and that fascinate AIM's principal investigator¹ James Russell.

"I became interested in these clouds when I was in Stockholm, Sweden at a conference, and I saw them for the first time. As I said before, they are very interesting, very beautiful -- iridescent² blues³ and whites and a lot of structure in them -- and they capture your imagination," says Russell.

Little is known about these night-shining clouds, or the distant mesosphere, 80 kilometers above Earth's surface where they form, except, that they are changing.

"These clouds are changing, and they are changing in ways that we don't understand,” admits Russell. “There are more of them than ever before.  They are seen at a lower latitudes⁴ than ever before and they are brighter."

Some scientists believe it may be the result of human induced climate changes.

"One possible explanation is -- that the buildup of carbon dioxide in the atmosphere at low altitudes is also occurring at high altitudes, and it's causing the atmosphere to cool.  And you need cold temperatures at these very low pressures in order for these clouds to form, so there is a possible connection with global change at the Earth's surface causing global change at high altitudes."

From orbit the spacecraft's instruments will watch the clouds form, measure their composition, and the atmospheric⁵ conditions giving rise to them.  Scientists want to know why icy clouds form at an altitude where it is 100-thousand times drier than the hottest deserts on Earth, and what is behind the mysterious changes in their behavior.

1 investigator   

n.研究者，调查者，审查者

参考例句：

• He was a special investigator for the FBI.他是联邦调查局的特别调查员。
• The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。

2 iridescent   

adj.彩虹色的，闪色的

参考例句：

• The iridescent bubbles were beautiful.这些闪着彩虹般颜色的大气泡很美。
• Male peacocks display their iridescent feathers for prospective female mates.雄性孔雀为了吸引雌性伴侣而展现了他们彩虹色的羽毛。

3 blues   

n.抑郁，沮丧；布鲁斯音乐

参考例句：

• She was in the back of a smoky bar singing the blues.她在烟雾弥漫的酒吧深处唱着布鲁斯歌曲。
• He was in the blues on account of his failure in business.他因事业失败而意志消沉。

4 latitudes   

纬度

参考例句：

• Latitudes are the lines that go from east to west. 纬线是从东到西的线。
• It was the brief Indian Summer of the high latitudes. 这是高纬度地方的那种短暂的晚秋。

5 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。