urban boundary layer

例句：

1. 1. The urban boundary layer is a critical factor in determining the air quality of a city.
   城市边界层是决定一个城市空气质量的关键因素。
2. 2.The urban boundary layer plays an important role in the transportation of pollutants in cities.
   城市边界层在城市污染物的运输中起着重要的作用。
3. 3.The urban boundary layer is a complex system that needs to be studied and understood for effective urban planning.
   城市边界层是一个复杂的系统，需要被研究和理解，以便进行有效的城市规划。