If you are going to college the actual answer is the Planetary Boundary Layer. The Troposphere might be excepted in Elementary or High school.

Faith Ann Heinsch has written:

'Transportation and the atmospheric boundary layer' -- subject(s): Mathematical models, Planetary boundary layer, Evapotranspiration

John P. Gleason has written:

'Single-station assessments of the synoptic-scale forcing on the marine atmospheric boundary layer' -- subject(s): Planetary boundary layer, Measurement

Chandrakant M. Bhumralkar has written:

'A survey of parameterization techniques for the planetary boundary layer in atmospheric circulation models' -- subject(s): Atmospheric circulation, Boundary layer (Meteorology), Mathematical models

'Parameterization of the planetary boundary layer in atmospheric general circulation models' -- subject(s): Atmospheric circulation, Boundary layer (Meteorology), Mathematical models

'Relation between air-sea exchange over the Arabian Sea and the fluctuations of the Western Indian summer monsoon' -- subject(s): Climate, Monsoons, Ocean-atmosphere interaction, Oceanography