Storm chasers know that puffy cumulus clouds often cause sudden rainstorms, while storms associated with stratus clouds form more slowly. Now physicists at England’s Open University have finally found an explanation.
They propose that neighboring water droplets in a stable stratus cloud don’t crash into each other because they’re all moving at about the same speed. But fast-forming, turbulent cumulous clouds contain water droplets moving at many different speeds. They crash into each other and form larger drops. As the turbulence grows, the drops grow quickly and fall as rain within a few minutes.
Sun and rain
Ever noticed the bright, moving lines on the bottom of a stream, bathtub, or swimming pool? They’re called caustics, and they’re caused when ripples on the water’s surface focus sunlight. (Caustics form whenever light rays are bent by a curved surface or object and then projected onto another surface.
Caustics have a characteristic shape. Physicists can graph the phenomenon mathematically, and the graph also describes other phenomena, such as particle motion or the movement of raindrops within a cumulus cloud.
Atmosphere to outer space
The researchers say their finding won’t have any impact on weather forecasting. But particle collisions in turbulent gases must have been involved in planet formation. Perhaps the same theory can be applied?
If you're at the museum on Saturday afternoon (11/18), the MakeIt team can help you play with caustics. Does bending mylar in a different direction produce a new pattern? Does using a different color flashlight or a brighter or dimmer light affect the design?
You can also play with caustics at home.
NASA scientists spent a month flying a sensor-packed airplane into storms brewing off the western coast of Africa. Data collected from these missions might someday allow better storm prediction and forecasting, and will definitely contribute to our knowledge of how hurricanes form and sustain themselves.
There's been a rash of cool weather sites written up in the Twin Cities newspapers and other media lately.
Here are just a few:
Skeetobiteweather is one of the most popular hurricane sites run by amateurs. Jonathon Grant, of Lakeland, Florida, runs it. He says the site gets 1.8 million page views a week, and you can plug in your zip code and get a prediction of wind forces for your block, hour-by-hour, before a hurricane hits. (Not even the National Weather Service does that.) And pretty soon, you'll be able to enter your exact address.
Mark Sudduth, of Wilmington, North Carolina, runs HurricaneTrack and HurricaneLiveNet. He deploys several battery-powered, waterproof cameras at the exact points where hurricanes are expected to hit. He also collects weather data to accompany the live, streaming video.
Jesse Bass, of Hampton Roads, Virginia, is a weather chaser who posts photos and commentary on his website, VAStormPhoto.
HurricaneCity, despite its name, is one of the more comprehensive severe weather sites. Jim Williams, of Delray Beach, Florida, focuses on the city being hit, and you can see all live, streaming radio stations or TV from the site. He also has a towercam on his roof, which captured images from Hurricane Wilma last year, and he hosts "The Hurricane Warning Show" from his living room.
Mike Watkins, of Coconut Creek, Florida, covers Atlantic hurricane action on TropicalUpdate. And if there's no news on the hurricane front, he hosts an Internet radio show where he interviews the "celebrities" of the weather world--guys like Max Mayfield, of the National Hurricane Center, or William Gray, the Colorado State University professor who's known for his hurricane season forecasts.
A new study found a link between human use of fossil fuels and an increase in the severity of hurricanes. The burning of fossil fuels has increased the level of greenhouse gases in the atmosphere, which has led to the warming of oceans in regions where hurricanes develop. The warmer the ocean water, the more severe the hurricane.
UK doctors have warned mobile phone users of the risks associated with mobile phone usage during thunderstorms. Metal found in mobile phones is able to send lightening currents directly into your body-possibly creating lots of damage!
The National Museum of American History is in the planning stages of building an exhibition displaying numerous Hurricane Katrina artifacts. The exhibit will be on display after the museum reopens in 2008.
Living in Minneapolis, I often ride my bike for exercise around the city lakes. The other day, while trying to get a ride in between rain showers, I was presented with a stunning rainbow. Actually, only a small portion of the arc was visible when I first saw it at Lake Harriet, but by the time I reached the west side of Lake Calhoun it had grown into a full blown double arced rainbow.
I stopped to admire it and regretted not having my camera with me because it was truly one of the best rainbows I had witnessed in a long time. A kid next to me, snapping a picture of it with his cell phone, wondered out loud, “How far away do you think that rainbow is?”
It was a good question and made me want to learn more about the atmospheric phenomenon.
Basically, rainbows are the result of sunlight being once reflected and twice refracted by raindrops. Certain conditions are required. First and foremost, the viewer needs to be located between the sun and rain clouds. A ray of sunlight enters an individual drop of water and is refracted (bent) as it enters, then reflected from the back of the drop, and refracted again as it exits the drop. The refractions cause the white sunlight to divide into separate colors. Each color refracts in slightly different amounts, red the least, and violet the most. A particular raindrop will reflect red light because it is positioned at just the right angle from your eye (42°). This is known as the “rainbow ray”. Another droplet located at a slightly different position will reflect blue light to your eye. Now multiply this by the innumerable suspended water droplets that make up a rain cloud, and you have a rainbow.
The main colors in a primary rainbow will have red at the top followed by orange, yellow, green, blue, indigo, and violet. An easy way to remember the order is to note that the first letter of each color spells out the name ROY G. BIV.
The rainbow I witnessed had a second, fainter rainbow just above the first. This is the result of some light being reflected twice, and at a higher angle. The colors in a secondary arc are reversed with red on the bottom and violet on top.
The inside of a rainbow is always brighter than the sky outside the arc. This is because other rays of light are reflected from individual raindrops at angles smaller than the rainbow ray. Since this scattered light is made up of all the other incidental colors the light inside the bow is white.
So, how far away is a rainbow? I’ll let you figure that out for yourselves. The answer may surprise you.
After all the rain we've had recently, parents of toddlers in the Twin Cities area surely have two questions on their minds:
I can't help with the first question.
But the second, that's a topic for Science Buzz!
I always thought that the worms came out of the ground when it rained to avoid being drowned in their burrows. Turns out I was wrong, wrong, wrong.
A series of Straight Dope articles, by Cecil Adams, have enlightened me.
Turns out that the worms are in no danger of drowning. They can actually survive underwater for quite a long time. They are out on the sidewalk after it rains to engage in, um, "amorous activity." For the slimy details, read the Adams' column!
Of course, that's not ALL the worms are doing. They're also trying to move safely to new areas; vulnerable to drying out as they are, they can only do this aboveground at night or after a rain.
My toddler will be blown away by all this. Her explanation is that worms come out because of some altruistic notion that robins are hungry...
For more information about earthworms, check out this JourneyNorth Q&A page.
Tornado season is here for those of us living in the Midwest. Tornadoes fascinate me – they’re so incredibly powerful and stunning and scary all at once. I used to have all sorts of elaborate emergency escape plans to the basement when I was a kid, and even had a pecking order for what prized possessions I would save and how. I also remember as a kid being told that if there was the threat of a tornado to open up a window a crack before heading to the basement so that the pressure inside the house would normalize with the pressure outside generated by the tornado thus preventing the roof from being blown off. I did this all the way up until last summer – but no more.
It turns out that a majority of damage to homes is the result of wind blowing into open (or broken) windows pushing up on the roof at the same time as winds are blowing over and under them, generating a lifting force, which increases the chances of the roof being blown off. So, all this time I’ve been making my house less safe, rather than safer. Doh.
Although it is likely wishful thinking on my part to hope that a single pane of glass is going to remain intact during a tornado, especially with all the debris that will be flying around. It makes more sense to close them to keep the rain out than to save the house from tornado damage, but it feels good to do something during those times when you have no real control. Better still to just forget the windows and get to the basement. With my most prized possessions.