【英语时差8,16】飞机凝结尾流（下）

To make an airplane contrail, you need water and some kind of microscopic¹ particle for the water to condense around. When jet fuel burns, it releases both water vapor² and microscopic particles 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 relatively³ 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 saturated⁴ 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!

 

1 microscopic   

adj.微小的，细微的，极小的，显微的

参考例句：

• 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。

2 vapor   

n.蒸汽，雾气

参考例句：

• 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。

3 relatively   

adv.比较...地，相对地

参考例句：

• 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。

4 saturated   

a.饱和的，充满的

参考例句：

• The continuous rain had saturated the soil. 连绵不断的雨把土地淋了个透。
• a saturated solution of sodium chloride 氯化钠饱和溶液