This is the 3560th most frequent Chinese word.
海拔
Altitude; elevation above sea level.
In this sentence, '海拔' (altitude) is used as a noun to describe the elevation above sea level of a specific place.
这里的海拔是3000米。
The altitude here is 3000 meters.
Here, '海拔' (altitude) is used in the adjective phrase '高海拔' to describe regions situated at a higher elevation above sea level.
高海拔地区的空气较稀薄。
The air is thinner in high-altitude regions.
In this case, '海拔' (altitude) appears as part of the object '海拔的变化' referring to changes in elevation during an activity like climbing.