Hurricanes and water go hand in hand – they form over oceans, use warm moist air as an energy source, and are known to dump huge amounts of rain onto areas in their path. But researchers from Purdue University and MIT have now made a surprising discovery by tweaking a hurricane simulation – the storms can occur under much colder and drier conditions than previously thought, which may be common on other planets.
Current understanding of hurricanes says that they form over large bodies of warmer water, usually tropical oceans. They draw energy from the evaporation of that water and the eventual condensation that follows as the air cools again, which is why they weaken pretty quickly after making landfall – although of course, not before wreaking substantial havoc on coastal areas.
Given how integral water is to the process as we know it, it's hard to imagine how hurricanes could form without it. But the team on the new study says that it is possible.
"We have theories for how hurricanes work at temperatures that we're used to experiencing on Earth, and theoretically, they should still apply if we move to a colder and drier climate," says Dan Chavas, co-author of the study. "We wanted to know if hurricanes really need water. And we've shown that they don't – but in a very different world."
To investigate how hurricanes might form under unusual circumstances, the team used a computer model that simulates the storms. Normally, that takes the form of a basic atmosphere with an ocean below it, but for these tests the team tweaked it to be far colder and drier.
Surprisingly, that didn't stop hurricanes from forming. Temperatures in the simulations ranged from -33° to 27° C (-27° to 80° F), and it was found that at the coldest end of the scale storms formed far more often than they do under Earthly conditions. That said, they were also generally smaller and weaker.
But the strangest find of all was a dead zone in the middle of the temperature range. Between -23° and -3° C (-10° and 26° F), no hurricanes formed at all. The researchers admit that they're stumped as to why that is.
"Maybe that means there are ideal regimes for hurricanes to exist and the current world we live in is one," says Chavas. "Or you could be in another world where there's no water, but it's still capable of producing many hurricanes. When people are considering whether we could live on a dry, rocky planet like Mars, this could be something to consider."
The research was published in the Journal of the Atmospheric Sciences.
Source: Purdue University