|What causes wind? Any elementary science textbook will tell you it’s about pressure differences: Hot air rises and cool air rushes into the void, creating wind in the process. This is the driving force of our climate system as a whole. The existing paradigm relies on temperature alone to create these pressure differences, but new numbers suggest that a much less conspicuous driver of air movement—condensation—may actually be dictating the planet’s weather patterns.
Praying mantises are really preying mantises, capable predators that capture and eat smaller insects. In the case of the larger, stronger female mantises, “smaller insects” also famously includes males of the same species. To mate with a potential predator, the males have to sneak up on their ladies, and a new study suggests that they use the wind to help them out: males approached females more readily when a breeze shook the females’ perch and disguised the males’ motion.
For mantises to mate, the male must creep up to the female and leap onto her back. If he fails, he will become a meal before he has a chance to reproduce. (Even if he succeeds, the female may bite his head off during copulation—but the decapitated male body is still able to continue mating and pass on his genes. So, mission accomplished?) Reaching the female undetected is thus an important male ability, and researchers tested how wind would affect it. They placed a male Chinese mantid on a kudzu leaf, upwind from a female, and set up a fan to blow air at them. Once the male detected the female, the researchers timed how long it took him to make his move, and whether the female would detect and attack him. With the artificial wind shaking the leaf, the male tried to mate with the female more quickly than in windless conditions. Windy conditions also impaired the female’s ability to sense the male: she was less likely to attack him when the fan was on.
Strawberry tongue, a symptom of Kawasaki disease.
Scientists don’t know much about the cause of Kawasaki disease—a disease of blood vessel inflammation most commonly found in Japan—but they do know one thing: Japanese outbreaks are highly correlated with winds from central Asia. When those same winds blow thousands of miles across the Pacific to Hawaii and California, Kawasaki disease ends up there too.
The disease affects generally children under the age of five. Blood vessels through the body become inflamed, leading to rashes, a characteristic “strawberry tongue,” and death in some untreated cases. Japanese pediatrician Tomisaku Kawasaki described the first case in 1960, and incidence of the mysterious disease have been rising ever since.
In the latest issue of Nature, Jennifer Fraser profiles scientists who are looking to the wind for answers about Kawasaki disease. There are a couple examples of windspread fungal spores, just as Aspergillus sydowii that follows dust storms from Africa to the Caribbean, but conditions up high are so extreme that wind had not been seriously considered capable of spreading disease across the Pacific:
Thank god for air friction. Without it, falling rain would smack into our heads at hundreds of miles per hour. But friction works both ways—falling raindrops also slow down the movement of air molecules in the atmosphere. A new paper in Science calculated that raindrops dissipate as much kinetic energy from the atmosphere as air turbulence. Granted, at 1.8 watts per square meter and 0.75% of the atmosphere’s total kinetic energy, that’s not very much. What’s surprising is that rain drops are pulling more than their weight, as they make up only 0.01% of the atmosphere’s mass.
Researchers calculated the kinetic energy dissipated by a single raindrop and put it together with precipitation rates around the world. Since satellite precipitation data also show the height from which rain started falling, the researchers could plug how far raindrops fell into their energy calculations. It all adds up across the whole globe: the researchers estimate the total rate of energy dissipation from rainfall to be 1015 Watts. That’s a lot of energy, but still unlikely to affect major weather phenomena like hurricanes or tornados.
[via Nature News]
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