A balloon-borne instrument sailing in the Arctic stratosphere in June obtained some of the best observations to date on the high-speed, Sun-driven winds that howl through the thermosphere more than 100 kilometers (60 miles) above Earth.

Every so often, a dome of upper-level high pressure sits in place for a few days, sometimes as long as several weeks. A major block can produce seemingly endless stretches of blazing heat or bitter cold. By the time it dissipates, it may leave behind a whole stack of broken weather records and an array of disastrous consequences.