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6 Ways Humans Influence the Weather

Girls eat popsicles and cool off in a Tokyo park during a 2014 heat wave. Image credit: Yoshikazu Tsuno/AFP/Getty Images

If you’ve ever spent any length of time on Twitter or talking to friends from northern California, you’ve probably heard a thing or two about humans secretly having the ability to control the weather. While we don’t have the capability to control the weather outside of the movies, we humans and our everyday activities really are able to indirectly influence the weather in ways that go far beyond our addiction to greenhouse gases.

1. CITIES FORM HEAT ISLANDS. 

They’re not exactly wrong when they call the capital of Georgia “Hotlanta.” Most populated areas generate heat simply by existing. The dense web of asphalt roads, concrete sidewalks, brick facades, and tar roofs are able to absorb a significant amount of heat from the daytime sun, even in the dead of winter. This human-made insulation, called the urban heat island effect, keeps city centers a tad hotter on hot days and a little less cool on cold days.

The urban heat island effect is most noticeable during winter storms when air temperatures are hovering right around freezing, putting you right on the line between wet snow, an icy mix, or a cold rain. The artificial warmth from cities can influence the precipitation type in these storms, potentially lowering a city’s snow accumulations compared to its suburbs.

A 2011 study published in the Journal of Applied Meteorology and Climatology [PDF] also found that the urban heat island effect can have a pronounced impact on thunderstorms that form over cities. The researchers studied 91 summertime thunderstorms that formed over Indianapolis, Indiana, and found that their research models could not replicate those thunderstorms without the influence of the urban area beneath the storms.

2. CROPS JACK UP THE HUMIDITY. 

If cities can absorb the heat of the day and make it even hotter, you can imagine how the vast swaths of crops that blanket the countryside can also affect our daily weather. Instead of making it hotter, crops can make a humid day unbearable by sending moisture levels almost off the charts on a putrid summer’s day.

Corn crops are notorious for pushing dew points—the temperature at which the air reaches 100 percent humidity—up above 80°F in the middle of the summer, creating a dangerous heat index that soars far above 100°F. Compare that to a muggy day, which has a dew point around 70°F, or a comfortably dry day with a dew point in the low 50s.

The harvest can have the opposite effect, as seen in northern Oklahoma this summer when farmers harvested their winter wheat crops. The state’s Mesonet, a network of weather stations, found that the newly harvested areas were hotter and had a lower dew point than their cooler but muggier surroundings.

3. PAVING INCREASES THE INTENSITY OF FLOODS.

Vehicles left stranded on a flooded Interstate 45 in Houston, Texas on May 26, 2015. Image credit: Aaron M. Sprecher/AFP/Getty Images 

Our obsession with construction doesn’t stop at influencing temperatures. Paving over porous earth with relatively impervious materials like asphalt and concrete has also had a major impact on flooding during heavy rain events. Fewer places for rainwater to escape means that the sudden influx of water builds up in urban areas or runs off and inundates places that had never seen flooding before.

4. NUCLEAR POWER PLANTS CAN TRIGGER NUCLEAR-EFFECT SNOW.

Lake effect snow is a yearly phenomenon across North America’s Great Lakes, where bitterly cold air flows over the warm lake water, triggering convection that blows ashore as heavy bands of snow. The bands of snow are so intense that communities can see many feet of snow in one day, sometimes accompanied by thunder and lightning.

It’s not only bodies of water that can cause this phenomenon. Nuclear power plants release large amounts of steam during the course of their operations, and on cold mornings when there’s enough moisture in the air, locations immediately downwind of a power plant’s steam stacks can experience “nuclear-effect snow,” which forms through similar means as lake effect snow. The phenomenon isn’t limited to just nuclear power plants, but they produce enough steam that it’s noticeable over a large area. Thankfully for residents nearby, it doesn’t produce much snow—and it’s not radioactive.  

5. URBAN DENSITY CAN AMPLIFY WINDS.  

The robes of Pope Francis are blown over his head by a gust of wind in St. Peter's Square in Vatican City. Image credit: Franco Origlia/Getty Images

If you’ve ever walked down a city street on a windy day, you’ve probably noticed that it sometimes feels like you’re being buffeted by air shot out of an industrial fan instead of a regular windstorm. Dense building construction can amplify the winds and cause gusts to blow much faster than they would out in the open. This wind tunnel effect can cause serious damage, blowing out windows, knocking down trees, and sending dangerous debris hurtling toward the busy streets below.

The principle is the same as holding your thumb over the end of a garden hose to make the water spray out faster—the wind speeds up dramatically as it presses between the buildings. This is also why you should never take shelter underneath a bridge during a tornado. The tornadic winds squeezing underneath the bridge will speed up, increasing the odds that you’ll be pelted by debris or sucked out into the open.

6) JETS CREATE CIRRUS CLOUDS.

The simple act of flying can also create intricate patterns of clouds in the sky that wouldn’t have formed had we not perfected the art of air travel. The hot water vapor produced by the engine exhaust of a high-flying jet aircraft leave contrails, short for condensation trails, in their wake. Contrails can dissipate right away or linger for hours depending on upper-level humidity and winds. These man-made cirrus clouds are most common at high cruising altitudes, but places like Arctic and Antarctic get cold enough that contrails can form at or near ground level. 

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Live Smarter
Interactive Chart Tells You How Long It Takes to Get Frostbite
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For many people, winter means dry skin and high heating bills. But if you find yourself outdoors in the right conditions, it can also mean frostbite. Frostbite occurs when the skin and the tissue beneath it freezes, causing pain, loss of sensation, or worse. It's easier to contract than you may think, even if you don't live in the Siberian tundra. To see if frostbite poses a threat where you live, check out this chart spotted by Digg.

The chart, developed by Pooja Gandhi and Adam Crahen using National Weather Service data, looks at three factors: wind speed, air temperature, and time spent outdoors. You can hover your cursor over data-points on the table to see how long you'd need to be exposed to certain wind chills for your skin tissue to freeze. If the wind chill is -22°F, for example (10°F air temperature with 5 mph winds), it would take 31 minutes of being outside before frostbite sets in. You can also look at the time scale above the chart to calculate it a different way. If you bring your cursor to the 40-minute mark, a window will tell that frostbite becomes a risk after exposure to -17°F wind chill for that amount of time. You can play with the interactive table at Tableau Public.

Chart of cold weather conditions.
Adam Crahen, Pooja Gandhi

If you can't avoid being outside in extreme wind and cold, there are a few steps you can take to keep your skin protected. Wear lots of layers, including multiple socks, and wrap your face with a scarf or face mask before venturing into the cold. Also, remember to stay hydrated. According to the American Academy of Dermatology, drinking at least one glass of water before going outside decreases your risk of contracting frostbite.

[h/t Digg]

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Photo composite, Mental Floss. Car, ticket, Simon Laprise. Background, iStock.
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Design
This Snow Sculpture of a Car Was So Convincing Cops Tried to Write It a Ticket
Photo composite, Mental Floss. Car, ticket, Simon Laprise. Background, iStock.
Photo composite, Mental Floss. Car, ticket, Simon Laprise. Background, iStock.

Winter is a frustrating time to be on the road, but one artist in Montreal has found a way to make the best of it. As CBS affiliate WGCL-TV reports, his snow sculpture of a DeLorean DMC-12 was so convincing that even the police were fooled.

Simon Laprise of L.S.D Laprise Simon Designs assembled the prank car using snow outside his home in Montreal. He positioned it so it appeared to be parked along the side of the road, and with the weather Montreal has been having lately, a car buried under snow wasn’t an unusual sight.

A police officer spotted the car and was prepared to write it a ticket before noticing it wasn’t what it seemed. He called in backup to confirm that the car wasn’t a car at all.

Instead of getting mad, the officers shared a good laugh over it. “You made our night hahahahaha :)" they wrote on a fake ticket left on the snow sculpture.

The masterpiece was plowed over the next morning, but you can appreciate Laprise’s handiwork in the photos below.

Snow sculpture.

Snow sculpture of car.

Snow sculpture of car.

Note written in French.

[h/t WGCL-TV]

All images courtesy of Simon Laprise.

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