FIGURE 1. An atmosphere as an upside-down violin.

The strings are the troposphere, vibrating with many eastward- and westward-propagating waves. The bridge is the tropopause, transmitting the waves up into the soundbox, the stratosphere. The primary difference is that, unlike a typical string instrument, a stratosphere responds by dropping the input frequencies down by two or more orders of magnitude — from periods of minutes and days down to years.

B. MCDERMID/REUTERS