cloud base

例句：

1. 1. The scientists were studying the clouds in the base of the mountain.
   科学家们正在研究山顶云层的底部。
2. 2.The weather forecast predicted a cloud base at 10,000 feet.
   天气预报预测在10,000英尺处有云层底部。
3. 3.The pilot had to make an emergency landing because of the base of the cloud.
   飞行员不得不紧急着陆，因为云层底部。