Maximum ground level concentrations occur a few hours after sunrise when inversion layers are broken up and brought to the ground.
hillayas
Rift-block mountain
The region in California that consists of long mountain ranges and valleys is called the Sierra Nevada mountain range.
valleys
* plain * hill * mountain * valleys
Yes, of course there are valleys in West Virginia. The state is nicknamed "The Mountain State," so wherever there are mountains, there will be valleys.
mountain passes, rivers, mountains, valleys .
mountain valleys
I think it's valleys.
Highland
in the valleys or on planteaus
Valleys and basins are two landforms that can help smog form by trapping air pollutants within their boundaries due to limited air circulation. As a result, pollutants can concentrate in these areas, leading to the formation of smog.