Raindrops continue to fall on the outer planets
One day, humanity may set foot on another habitable planet. This planet may seem very different from Earth, but one thing is for sure – rain.
A recent study published in 2005 JGR PlanetsHarvard researchers have found that raindrops are very similar in different planetary environments, the planets being Earth and Thursdays. Understanding the behavior of raindrops on other planets is not the only way to find ancient climates on such planets Tuesday But identifying planets that can live outside our solar system.
“The life cycle of clouds is very important when it comes to the viability of the planet,” said Keithlin Loftus, a graduate student in the Department of Earth and Planetary Science and the primary author of this article. “But clouds and rain are really complex and more complex to fully form. We are looking for simple ways to understand how clouds form. The first step is whether the clouds evaporate into the atmosphere or end up on a surface like rain.”
“The humble raindrop is an essential part of the planetary rain cycle,” says Harvard John A. Said Robin Wordsworth, associate professor of environmental science and engineering at the Paulson School of Engineering and Applied Sciences (SEAS) and the primary author of this article. . “If we understand how individual raindrops work, we can better represent rainfall in complex climate models.”
An important aspect of raindrop behavior is, at least for climate designers, whether raindrops reach the planet’s surface because atmospheric water plays an important role in the planet’s climate. For this purpose, size is important. Regardless of whether the water, methane or liquid iron is too hot, it is too large and the droplet will break due to insufficient surface tension. Exoplanar This is called WASP-76b. Very small and the droplets evaporate before hitting the surface.
Wordsworth Loftus defined a zone of moderate raindrop size using only three properties: droplet shape, drop rate and evaporation rate.
“The intelligence we gain by thinking about raindrops and clouds in different contexts is important for understanding the foreign habitat.”
– Robin Wordsworth, Associate Professor of Environmental Science and Engineering
The fall patterns are the same in different rain products, and depend on how heavy the fall is. Many of us can imagine a traditional teardrop-shaped fall, the raindrops are actually spherical in shape, enlarging until they turn into the shape of the surface of a hamburger loaf. The rate of fall depends on this shape and the thickness of the gravity and ambient air.
Evaporation rates are highly complex and are affected by atmospheric composition, pressure, temperature, and relative humidity.
Taking all these properties into account, Loftus and Wordsworth calculated that only a fraction of the possible droplet size of a cloud could reach the surface, as it calculates the drop of a raindrop over a wide range of planetary conditions.
“We can use this to guide us by modeling cloud rotations on exoplanets,” Loftus said.
“The intelligence we gain by thinking about raindrops and clouds in different contexts is important for understanding the outer space habitat,” Worthworth said. “In the long run, they will also help gain a deeper understanding of the Earth’s own climate.”
Note: Cattell Loftus and Robin D. “The Physics of Raindrops Fall into Different Planetary Atmospheres”. Worthworth, March 15, 2021 JGR Planets.
DOI: 10.1029 / 2020JE006653
This study was supported by the National Science Foundation with a grant of AST-1847120.