Which statement best describes winds aloft?

• A. They are in the upper atmosphere and are unaffected by friction
• B. They occur at ground level and are heavily affected by friction
• C. They only occur at night
• D. They are always gusty

Answer: (A)

Winds aloft refer to air flow high above the surface where friction from the ground and obstacles is negligible. In that part of the atmosphere, winds are driven mainly by large-scale pressure gradients and the Coriolis effect, so they tend to be faster and more uniform than wind at ground level. The friction that slows and twists surface wind near hills, trees, and buildings doesn’t have much influence up where winds aloft occur, which is why they’re described as being in the upper atmosphere and largely unaffected by friction. They aren’t limited to nighttime, and while they can contribute to gusty conditions in certain situations, the defining feature isn’t constant gustiness but the minimal influence of surface friction.