Explain and interpret the following: (a) Air pollution is often trapped within the boundary layer. (b) Clear-air turbulence (CAT) experienced by airplane passengers is widespread, but usually not very strong in the boundary layer. It tends to be more sporadic and also more intense near the tropopause. (c) Air within the free troposphere exhibits only a small diurnal temperature range. (d) Boundary layers over deserts are often much deeper than over vegetated terrain. (e) The warmest and highest-