Task: Class Definition Understanding (ontology: Earth_Environment/SWEET)

Which of the following definitions best describes 'atmospheric boundary layer'?

A. Same as transition layer. The lowest atmospheric layer immediately adjacent to a surface covered with relatively large roughness elements such as stones, vegetation, trees, or buildings.
B. A layer within the atmosphere bounded below by the surface, and above by a more or less sharp discontinuity in some atmospheric property. Internal boundary layers are associated with the horizontal advection of air across a discontinuity in some property of the surface (e.g., aerodynamic roughness length or surface heat flux) and can be viewed as layers in which the atmosphere is adjusting to new surface properties. See thermal the concept, mechanical the concept.
C. The bottom layer of the troposphere that is in contact with the surface of the earth.
D. For flow over a hill, the top layer in the boundary layer that accelerates relative to its upstream value due to the Bernoulli effect.

Answer: The bottom layer of the troposphere that is in contact with the surface of the earth.