As they're forced upwards 在被迫抬升的过程中

39. There is one simple and massive cause -
    这里有一个简单而又重要的原因
40. the Himalayas.
    喜马拉雅山脉
41. Clouds blowing from the south hit this gigantic barrier.
    从南方过来的暖湿气流 撞上了这面巨大的屏障
42. As they're forced upwards
    在被迫抬升的过程中
43. so they empty their moisture on the mountain slopes,
    水汽在山坡上逐渐凝结
44. leaving little for the land on the other side.
    只有一小部分到达另一边的土地
45. From the space deserts are very conspicuous.
    从太空中看 沙漠非常显眼

来自《行星地球 第一季 第五集 Planet Earth S01E05 沙漠》第 42 行