Evolution of the boundary layer - 3PM

3 PM:

• surface heating is maximum

• therefore, thermal turbulence is strongest at this time of the day - generate fair-weather cu

• thermals mix down even stronger wind speeds to the surface - generates larger mechanical turbulence

• surface winds are strongest at this time - breezy

• boundary layer is about 1-1.5 km deep

• air in the boundary layer is well-mixed (i.e., has uniform properties) due to thermal and mechanical turbulence