Boundary Layer Definition and Scale

Definition: 

• The earth's surface is the lower boundary on the atmospheric domain and hence, interacts with the lower part of the earth's atmosphere
• The Boundary Layer can be defined as: "that part of the troposphere that is directly influenced by the presence of the earth's surface and responds to surface forcings with a time scale of about an hour or less."

Scale:

• Boundary layer depth is variable, however, it is typically between 100-3000 m deep (see Fig. 1.1)
• Note that the tropospheric depth is on one order of magnitude greater that boundary layer depth
  • ratio of tropospheric depth to radius of earth: 10 km/6400 km = 0.001 or .1%
  • ratio of boundary layer depth to radius of earth: 1 km/6400 km = 0.0001 or 0.01% !!!!!!