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Why Your Car Dashboard Says It's a Lot Hotter Than It Really Is

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When you first turn on your car in the middle of a sunny day, chances are your dashboard probably says it’s quite hot out. Like, a lot hotter than it feels. There’s a reason why car thermometers don’t always seem accurate, according to atmospheric scientist Greg Porter at The Washington Post.

Your dashboard temperature reading actually comes from something called a thermistor, which is similar to a thermometer but instead of mercury, it uses electrical current to measure changes in temperature. (Remember that temperature is an indication of how fast or slow gas molecules in the air are moving around. The higher the reading, the greater the molecules' kinetic energy.) In a car, that thermistor is located just behind the grill in the front of the car. Therein lies the problem: Your car's temperature readings come from an unusually hot location.

Asphalt roads get really, really hot in warm weather (enough so that cities become significantly hotter than their greener surroundings in the summer), so a temperature reading taken just above the surface of the road isn’t going to be super accurate. Heat radiates up from the road—as you can see on particularly hot days when the highway starts to look shimmery—and the thermistor in your car picks up that excess heat. It’s like measuring the temperature of a large room by sticking the thermometer an inch away from the fireplace.

That doesn’t mean your dashboard temperature readings are useless. When it’s not as hot out, there isn’t much interference from heat rising off the road. It’s also more effective when you’re moving—if you’re traveling down the highway, it will pick up less heat radiation from the road than if you were sitting in a parked car. However, Porter warns, the thermistor isn’t sensitive enough to distinguish between one-degree differences, which can be dangerous if you’re driving in the winter and need to know if temperatures have hit freezing or are floating just above.

In short, as nice as it is to know how temperatures are changing from one destination on your road trip to another, take that dashboard number with a grain of (road) salt.

[h/t The Washington Post]

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Weather Watch
3 Ways We Can (Kind of) Control the Weather, and 5 Ways We Can't

Humans have the incredible ability to control the world around us. We can move mountains and land robots on other planets. We can keep each other alive longer than ever before and even bring entire species back from the brink of extinction. But despite all of our leaps forward, we're still unable to control the weather, a tremendous force that affects every human being on this planet. Still, humans have come up with some pretty crafty ways of influencing the weather—in small doses.

1. WE CAN MAKE IT RAIN … SOMEWHAT.

The desire to control weather has been a mainstay of imagination since, well, the beginning of imagination. The fortunes of entire societies can hinge on flood or drought. We have strong motivation to want to create a rainstorm in one spot or moderate snowfall in another. But the greatest success we've ever had is a technique that can (maybe) encourage a tiny bit of rain to form over a tiny area.

Cloud seeding is a process through which fine particles like silver iodide are released into a cloud in order to encourage the formation of rain or snow. These particulates serve as a nucleus around which water vapor can condense and turn into a raindrop or a snowflake. This is most commonly done with small airplanes, but it can also be accomplished by launching tiny rockets or flares from the ground.

In theory, the practice of cloud seeding could have innumerable uses around the world, including crop maintenance, providing drinking water, and even possibly weakening severe thunderstorms or hurricanes. There's only one problem: It doesn't work all that well.

The effectiveness of cloud seeding is a hot topic of debate among scientists, but most studies have either found negligible impacts on precipitation, or the researchers were unable to determine the exact impact of cloud seeding. Cloud seeding is a great concept if you want to help one cloud produce a little extra rain or snow just to say you can do it, but it's not the way to go if you're desperate and want to trigger a deluge. This process requires the pre-existing presence of clouds, so even if the technology improves in the future, it's not a viable solution for drought-stricken areas that haven't seen meaningful clouds in weeks.

2. WE CAN DEFINITELY ATTRACT LIGHTNING USING ROCKETS.

Lightning safety is one of the things you learn from a very young age. "When thunder roars, go indoors," as the motto goes. We learn to stay away from open areas and water during thunderstorms. But what if you wanted to attract lightning? It's surprisingly easy to do if you have the right equipment and really, really want to encounter some of nature's fury.

Scientists who want to study lightning can bring it right to their doorstep by using specially designed rockets attached to conductive wires that lead to the ground below. When a thunderstorm blows over the observation station, operators can launch these rockets up into the clouds to trigger a lightning strike that follows the wire right down to the ground where the rocket was launched. Voila, instant lightning. Just add rocket fuel.

3. WE CAN CREATE CLOUDS AND HEAT—EVEN WHEN WE DON'T MEAN TO.

Most of the ways in which we control—or, more accurately, influence—the weather is through indirect human actions—often unintentional. "Whoops, the nuclear power plant just caused a snowstorm" isn't as crazy as it sounds. Steam stacks can and do produce clouds and updrafts with enough intensity to create rain or snow immediately downwind. The very presence of cities can generate microclimates with warmer temperatures and heavier rain. And there's also climate change, the process in which our accumulated actions over a long period of time are influencing the very climate itself.

BUT WE CAN'T DO THE FIVE FOLLOWING THINGS.

Despite our limited ability to influence a few aspects of weather over small areas, there are some rather colorful conspiracy theories about whether or not governments and organizations are telling the whole truth about how much we can accomplish with today's technology. There are folks who insist that the trails of condensed water vapor, or "contrails," left behind jet aircraft are really chemicals being sprayed for sinister purposes. (They're not.) There are theories that a high-frequency, high-power array of antennas deep in the Alaskan wilderness can control every weather disaster in the world. (It doesn't.) There are even folks who insist that Doppler weather radar carries enough energy to "zap" storms into existence on demand. (Dr. Evil wishes.)

There are also some bizarre and unworkable theories that are offered in good faith. A meteorologist a few years ago opined on whether building an excessively tall wall across middle America could disrupt weather patterns that could lead to tornado activity. And every year the National Hurricane Center is peppered with questions about whether or not detonating nuclear bombs in a hurricane would disrupt the storm's structure. Unfortunately, while pseudoscience offers up great theories to test in the movies, when it comes to weather, we're still not in control.

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Weather Watch
NASA Figures Out Why When It Rains, It (Sometimes) Drizzles
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What’s the difference between drizzle and rain? It has to do with updrafts, according to new research by NASA scientists into the previously unexplained phenomenon of why drizzle occurs where it does.

The answer, published in the Quarterly Journal of the Royal Meteorological Society, could help improve how weather and climate models treat rainfall, making predictions more accurate.

Previously, climate researchers thought that drizzle could be explained by the presence of aerosols in the atmosphere. The microscopic particles are present in greater quantities over land than over the ocean, and by that logic, there should be more drizzle over land than over the ocean. But that's not the case, as Hanii Takahashi and her colleagues at the Jet Propulsion Laboratory found. Instead, whether or not rain becomes full droplets or stays as a fine drizzle depends on updrafts—a warm current of air that rises from the ground.

Stronger updrafts keep drizzle droplets (which are four times smaller than a raindrop) floating inside a cloud longer, allowing them to grow into full-sized rain drops that fall to the ground in the splatters we all know and love. In weaker updrafts, though, the precipitation falls before the drops form, as that light drizzle. That explains why it drizzles more over the ocean than over land—because updrafts are weaker over the ocean. A low-lying cloud over the ocean is more likely to produce drizzle than a low-lying cloud over land, which will probably produce rain.

This could have an impact on climate modeling as well as short-term weather forecasts. Current models make it difficult to model future surface temperatures of the Earth while still maintaining accurate projections about the amount of precipitation. Right now, most models that project realistic surface temperatures predict an unrealistic amount of drizzle in the future, according to a NASA statement. This finding could bring those predictions back down to a more realistic level.

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