Pumping Up Surface Air

摘要

Towering cumulus clouds associated with thunderstorms enable the spread of pollution on intercontinental scales. Many nitrogen, hydrocarbon, and sulfur pollutants involved in acid rain and photochemical smog are usually removed within hours or days near Earth's surface, but have much longer lifetimes if they reach the cold and dry upper troposphere at altitudes from 8 to 12 km. Towering cumulus clouds associated with thunderstorms (see the figure) can rapidly transport these pollutants to the upper troposphere.