时间:2019-03-09 作者:英语课 分类:英语听力文摘 English Digest


英语课

  Airplane Contrails

Have you ever seen a perfectly 1 cloudless sky?  Cloudless–that is–except for two or three long white lines smeared 2 across the perfect blue sky by airplanes like smudges on a pane 3 of glass.  Why do airplanes sometimes leave contrails behind? Actually, contrails, short for condensation 4 trails, are essentially 5 clouds.  They are no different from the cirrus clouds(卷云) that naturally form in that region of the atmosphere.

High in the atmosphere, water can exist in one of two basic forms.  It can either be invisible water vapor 6–a gas–or it can condense around microscopic 7 dust particles into tiny droplets 8 or ice crystals(冰晶).  Every cloud you see is made of tiny droplets or crystals like this, and so is a contrail.


  To make an airplane contrail, you need water and some kind of microscopic particle for the water to condense around.  When jet fuel(喷气燃料) burns, it releases both water vapor and microscopic particles(微观粒子) of exhaust.  A contrail occurs when the jet’s water vapor condenses around its own exhaust particles.

If you see a plane that’s leaving no contrail–or a very short one–this means the upper atmosphere is relatively 9 dry.  Dry air reabsorbs the water as invisible vapor almost as soon as it condenses.  On the other hand, if you see a contrail that lasts a long time, this means the upper atmosphere is already (1)saturated with as much water vapor as it can hold.

Because of this, you sometimes can use contrails to predict the weather.  Quickly fading ones suggest a dry upper atmosphere and fair weather.  If you see a lot of long contrails in the sunset though, you might carry an umbrella the next day!

Notes:

(1)saturate 10 with v.使饱和

If a medium other than water is to be used, saturate it with oxygen in a similar manner.

若使用的介质不是水也用类似方法以氧饱和之。



adv.完美地,无可非议地,彻底地
  • The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
  • Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。
弄脏; 玷污; 涂抹; 擦上
  • The children had smeared mud on the walls. 那几个孩子往墙上抹了泥巴。
  • A few words were smeared. 有写字被涂模糊了。
n.窗格玻璃,长方块
  • He broke this pane of glass.他打破了这块窗玻璃。
  • Their breath bloomed the frosty pane.他们呼出的水气,在冰冷的窗玻璃上形成一层雾。
n.压缩,浓缩;凝结的水珠
  • A cloud is a condensation of water vapour in the atmosphere.云是由大气中的水蒸气凝结成的。
  • He used his sleeve to wipe the condensation off the glass.他用袖子擦掉玻璃上凝结的水珠。
adv.本质上,实质上,基本上
  • Really great men are essentially modest.真正的伟人大都很谦虚。
  • She is an essentially selfish person.她本质上是个自私自利的人。
n.蒸汽,雾气
  • The cold wind condenses vapor into rain.冷风使水蒸气凝结成雨。
  • This new machine sometimes transpires a lot of hot vapor.这部机器有时排出大量的热气。
adj.微小的,细微的,极小的,显微的
  • It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
  • A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。
n.小滴( droplet的名词复数 )
  • Droplets of sweat were welling up on his forehead. 他额头上冒出了滴滴汗珠。 来自辞典例句
  • In constrast, exhaled smoke contains relatively large water droplets and appears white. 相反,从人嘴里呼出的烟则包含相当大的水滴,所以呈白色。 来自辞典例句
adv.比较...地,相对地
  • The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
  • The operation was relatively painless.手术相对来说不痛。
vt.使湿透,浸透;使充满,使饱和
  • We'll saturate California with the rise in its crime rate.我们将使加利福尼亚州的犯罪案件增长率达到饱和点。
  • Saturate the meat in the mixture of oil and herbs.把肉浸泡在油和作料的卤汁里。
学英语单词
activized
adapter bearing
adaptive distributed minimal spanning tree algorithm
akoka
alimentary lipemia
amnioss
anilidic
anxiety-ridden
associationism
austrian airlines
back labors
Bad Schallerbach
beginner
biomethanation
blanket gas analysis
borrowest
bulgren
cat (children's apperception test)
clk.
cock-and-pie
comprime
crash out
cross-country flight
crystal clathrate
derivative rights
dirty poll
Do as you're bidden and you'll never bear blame.
down-draft manifold
dressed to the nines
El Salado, R.
elastic limit in shear
Elatostema subcuspidatum
elbe (labe)
electrical anemometer
equitative
feedthrough capacitor
fertilizer-distributor
field ampere-turn
fight to a finish
flauntily
flexibility matrix
floating thumb
fogden
fourth stage
Gornovodnoye
harping
hiked up
hitch roll
hypertypic
inamoratos
Indigofera rigioclada
industrial-instrument
intestine loop
iris scan
Kaliningradskaya Oblast'
left dorso-posterior position
loss due to anchorage temperature difference
ludent
marine centrifugal type refrigerating compressor unit
metallibure
milch goat
neisseria gonorrhoeaes
nonhierarchically
Nymphula
objective cap
office speaker
oozier
other multimode fiber optic cable
pajamas
panama, gulf of
personal allowances
podheads
Port Noarlunga
quod erat faciendum
radiator thermometer
rallentando
re-furbish
rhinoneurosis
river inversion
rotary expansion engine
sagaciate
sand pike
Saxifraga triaristulata
smooth-bore
Solana
soloman r.
spalike
spiking maul
stationary-welding machine
strongbark
swirl defect
teleprinter receiver
thiamins
Third Lateran Council
time interval analyser
ultrarunner
unrecorded income
unwashable
vapour transport
variable structure computer
waggonwright
yellow paper test