What causes the wind to shift direction when it is near the Earth’s surface?

The wind shifts direction near the Earth’s surface primarily due to frictional force. As the wind moves, it interacts with the surface of the Earth, including terrain features, vegetation, and buildings, which creates drag. This friction slows down the wind and causes it to change direction.

When wind flows at higher altitudes, it is less affected by these surface features, and thus it maintains a more direct directional flow, usually following the pressure gradients established in the atmosphere. However, as the wind approaches the ground, the frictional forces come into play, causing the wind to veer off in different directions rather than flowing straight down the pressure gradient.

The other options, while they are important factors in atmospheric dynamics, do not specifically account for the directional shift of winds near the surface. Gravity primarily affects the vertical motion of air but does not directly cause a change in wind direction. The Coriolis effect influences the direction of winds on a larger scale, primarily affecting wind patterns globally due to the rotation of the Earth, and does not have a significant impact on local surface winds. Thermal expansion plays a role in the formation of wind due to temperature differences but is not responsible for changes in wind direction at the surface.