Dr Joanne Simpson was a trailblazer. In 1949 she became the first woman in the US to earn a PhD in meteorology, and she went on to make significant breakthroughs in understanding clouds.
With her colleague Herbert Riehl, Simpson showed how clouds played a big role in the world’s climate. They realised that tropical cumulonimbus clouds could tower to 15km tall, so high they reached the top of the lower atmosphere. They called these gigantic clouds “hot towers” because they behaved like chimneys, pumping heat and moisture from the ocean’s surface high into the atmosphere.
And in 1958 they came up with an even more revolutionary concept: that about 1,500 of these hot towers spread around the equatorial regions at any one time would get rid of so much heat they would pump hot air away from the tropics, and so play a key role in how the atmosphere circulates around the planet. It was a theory so far ahead of its time that it was verified 20 years later.
Simpson also showed how hot towers around the eye of a hurricane drove the storm. Hurricanes feed on warm, humid air over tropical seas, and the hot towers are the heat engines that turn moist ocean air into furious winds and rains.
