Which type of turbulence can occur due to changes in wind direction and speed?

Wind shear is the correct answer as it specifically refers to variations in wind speed and direction over a short distance. This phenomenon can occur vertically or horizontally and is crucial for pilots to understand, as it can significantly affect an aircraft's performance during takeoff and landing phases, as well as in-flight stability.

Wind shear can lead to unexpected altitude changes or control issues if not anticipated, making it vital for pilots to be aware of conditions that could create it, such as flying near thunderstorms or landing on runways where various weather conditions might impact wind patterns.

The other types of turbulence mentioned, while related to different aspects of atmospheric conditions, do not directly pertain to the changes in wind speed and direction in the same way. For instance, wake turbulence is generated by the passing of an aircraft, mechanical turbulence occurs due to obstacles like buildings or terrain, and convective turbulence is associated with thermal updrafts in the atmosphere—each with its distinct causes and effects.