What type of turbulence is primarily caused by moving water and air currents?

Wake turbulence is primarily caused by the disturbance in the air created by the movement of an aircraft through the atmosphere. When an aircraft flies, it displaces air and generates vortices, particularly at the wingtips, where the air pressure differences between the upper and lower surfaces of the wings create swirling patterns of air. These vortices can persist for a significant time and distance, particularly in calm conditions, and can affect following aircraft, especially during takeoff and landing phases.

The other types of turbulence are influenced by different factors. Thermal turbulence arises from the uneven heating of the Earth's surface, causing the air to rise and fall. Mechanical turbulence occurs when wind interacts with physical obstacles like buildings and mountains, which disrupts the flow of air. Clear air turbulence happens in clear conditions at high altitudes, often associated with jet streams, and is typically not related to the presence of water but to air pressure differences. In contrast, wake turbulence is specifically linked to moving air currents generated by aircraft, making it the correct choice in this context.