Why might winds at 5,000 ft AGL be different from surface winds?

Winds at 5,000 feet above ground level (AGL) can differ significantly from surface winds primarily due to the influence of friction between the wind and the Earth’s surface. At higher altitudes, such as 5,000 feet, the wind is less affected by surface roughness, topography, and obstructions like buildings or trees. These surface features create friction that slows down the wind close to the ground, leading to a significant difference in speed and direction when compared to the more streamlined winds found at higher altitudes.

As wind flows over varying terrain, the frictional drag can result in turbulence and a reduction of wind speed at lower levels. This friction decreases with altitude, allowing winds to flow more freely at higher elevations, which is why we often see stronger and more consistent wind patterns higher up in the atmosphere compared to those at the surface.

The other options, while they can influence wind behavior, are not the primary reason for the difference between winds at 5,000 feet and those at the surface. Effects of altitude might refer to changes in wind patterns, but it does not address the direct impact of surface friction. Thermal currents can affect local winds but are not solely responsible for the difference seen at these two altitudes