How does the friction layer's surface roughness affect wind velocity?

The surface roughness of the friction layer significantly impacts wind velocity by slowing it down. As wind moves over various terrains and surface features, such as forests, buildings, or uneven ground, it encounters increased friction. This friction results from the irregularities and obstacles that disrupt the smooth flow of air.

When the surface is rough, the wind is impeded, causing it to lose energy and reduce its speed as it mixes and tumbles over the surface variations. This effect is most pronounced at lower altitudes, where the influence of surface roughness is greatest. In contrast, over smooth surfaces, such as water or flat terrain, wind can flow more freely and maintain higher speeds.

Understanding this relationship between surface roughness and wind velocity is crucial in meteorology, influencing everything from weather forecasting to the design of structures to withstand wind loads.