Which factor causes the atmospheric boundary layer to change during the day?

Which factor causes the atmospheric boundary layer to change during the day?

• A. Tides
• B. Lunar phases
• C. Diurnal heating and cooling
• D. Seasonal shifts

Answer: (C)

The daily rise and fall of the atmospheric boundary layer is driven by the sun’s heating and the subsequent cooling of the surface. When daylight heats the ground, the air near the surface becomes warmer and lighter, promoting strong vertical mixing and convection. This deepens the boundary layer and increases turbulence, often reaching well into the lower atmosphere by afternoon. After sunset, the surface cools radiatively, making the near-surface air more stable and dense, which suppresses mixing and shallowens the boundary layer. Other factors like tides or lunar phases don’t drive this daytime cycle, and seasonal shifts affect the overall, longer-term depth and stability rather than the everyday diurnal change.

The daily rise and fall of the atmospheric boundary layer is driven by the sun’s heating and the subsequent cooling of the surface. When daylight heats the ground, the air near the surface becomes warmer and lighter, promoting strong vertical mixing and convection. This deepens the boundary layer and increases turbulence, often reaching well into the lower atmosphere by afternoon. After sunset, the surface cools radiatively, making the near-surface air more stable and dense, which suppresses mixing and shallowens the boundary layer.

Other factors like tides or lunar phases don’t drive this daytime cycle, and seasonal shifts affect the overall, longer-term depth and stability rather than the everyday diurnal change.