Definition of boundary layer

1) An area in the troposphere which is affected by the solar heating, radioactive cooling, and surface friction of the earth. The height of the boundary layer can range anywhere from 100m to 300 km and coincides with the height at which pollutants are mixed.

source: [Journal of Applied Meteorology; v28, pages 885-903; 1989] [Atmospheric Environment; v37n16; pages 2193-2205; 2003]