gradient speed

例句：

1. 1. The road is steep and narrow, making it difficult to navigate.
   这条路陡峭且狭窄，难以通行。
2. 2.The sun's rays are emitted at different inclinations, affecting the Earth's temperature.
   太阳的光线以不同的角度发射出来，影响地球的温度。
3. 3. The car's speed increases with altitude, demonstrating the concept of gradient speed.
   汽车的速度随着海拔的升高而增加，展示了梯度速度的概念。