Clouds are sometimes seeded with silver iodide to induce precipitation.是什么意思？

Clouds are sometimes seeded with silver iodide to induce precipitation.

人们有时在云里播撒碘化银,以诱使降雨.

clouds

n. 云( cloud的名词复数 )，团，群，造成不愉快或不明朗的事物；

例句
The presence or absence of clouds can have an important impact on heat transfer...
有无云层对热量的传递会产生重要的影响。

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

sometimes

adv. 有时，间或，时

例句
I want to work at home on a Tuesday but as it turns out sometimes it's a Wednesday or a Thursday.
我想周二在家工作，但实际上有时却是周三或是周四。

seeded

adj. 已播种的； 有籽的；

例句
All the seeded players got through the first round.
所有种子选手都闯过了第一轮比赛。

with

prep. 和，跟，随着，关于，和…一致；

例句
A waiter entered with a tray...
侍者端着托盘进来了。

silver

n. 银，银币，银制品，银色；adj. 银制的，像银的，银色的，银白色的；vt. （在某物上）镀银，使具有银色光泽，使变成银色；

例句
...antique silver jewellery...
古董银首饰

iodide

n. 碘化物；

例句
A supply of electricity will cause the dysprosium iodide to vapourize to glow.
它通电后放电,使碘化镝气化发光.

to

prep. 向，朝着，到，关于，属于；adv. 朝一个方向的，到某种状态，关闭；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

induce

vt. 引诱，引起，[电]感应，归纳；

例句
Taking a brisk walk can often induce a feeling of well-being...
快步行走常常会使人感到身心舒畅。

precipitation

n. 匆促，沉淀，（雨等）降落，某地区降雨等的量；

例句
Strontium aluminate long persistence phosphors were prepared through homogeneous precipitation method.
采用均匀沉淀法制备铝酸锶基质长余辉发光材料.