Effects of subtropical jet streams include...

• A. They lie below regions of low pressure and slow the wind.
• B. They are not associated with equator distance.
• C. They are belt of strong upper-level winds lying above regions of subtropical high pressure; the farther from the equator, the faster the easterly flow.
• D. They occur only over land.

Answer: (C)

Subtropical jet streams are narrow bands of very fast winds in the upper part of the atmosphere that circle the globe near about 30 degrees latitude. They form where warm tropical air and cooler mid-latitude air meet, creating a strong horizontal temperature (and pressure) gradient at upper levels. The rotation of the Earth (Coriolis effect) helps concentrate these winds into a fast, west-to-east flow that sits above the subtropical high-pressure belts. As you move away from the equator within the subtropics, the gradient strengthens and the jet speeds up. They aren’t limited to land and aren’t located below low-pressure systems. The important point is that the jet lies above subtropical high pressure and that its upper-level winds intensify with distance from the equator.