Posted by: newperspectives85 | August 27, 2013

8.7.13 10 myths about summer weather

Ten myths about summer weather

By Amanda Morgenthal, Published: August 7 at 12:30 pm

Some say a green sky indicates a tornado. But that is just one of many weather myths. At first glance the picture above looked to be of a tornado, but on further investigation turned out to be a more benign shelf cloud (Kevin Ambrose)

Some say a green sky indicates a tornado. But that is just one of many weather myths. At first glance the picture above looked to be a tornado, but on further investigation turned out to be a more benign shelf cloud. (Kevin Ambrose)

There are many misconceptions about summer weather and its effects on people and the environment. In order to stay both safe and informed, don’t fall prey to these myths….

#10: “Soda quenches your thirst”

After a hot day in the sun, you may feel as though nothing would refresh you more than a glass of Coke. And perhaps you would feel as though you were sufficiently rehydrated. But that sugary drink might actually cost your body more fluids.

Unlike the folklore, which states that caffeine is the reason that soda is dehydrating, the refined sugars in artificially sweetened drinks actually cause your body to pull more fluid and work extraordinarily hard to metabolize them.

Although this has been a controversial topic of study over the years, water is always the healthiest way to rehydrate after a long day in the sun. Some sports drinks are too high in sugar to end up being rehydrating, although isotonic (containing similar concentrations of salt and sugar as the human body) sports drinks may reduce exhaustion during an intense workout.

A good read on the “water versus sports drink” debate is Sam Murphy’s piece in The Guardian.

Just remember, if you’re out in the sun, you’re constantly sweating and using fluids. It’s important to replace them to stay hydrated and avoid heat-related illness!

#9: “Humid air is denser than cold air”

Listening to the way people talk about a humid day, the phrase “hot and heavy” is often thrown around. While the humidity may feel oppressive, the moist air around you is actually lighter.

The molecular weight of water is lighter than that of dry air, which contains mostly nitrogen and some oxygen. Hydrogen displaces some of the nitrogen in the moist air, making for a lighter parcel.

Related: Why dry air is heavier than humid air

Those who are aware of this often hear the associated myth that “a baseball flies farther in humid air than in dry air.” While this is true for simply moist air, it is another myth when it comes to actual humidity.

To debunk said myth, we can look to “Ask Tom” in the Chicago Tribune: “…when it’s humid out, a baseball absorbs moisture making it less bouncy, which translates to about a 3-foot decrease in travel for each 10 percent increase in humidity. The number of home runs hit in Denver has decreased since the Colorado Rockies began storing baseballs in a humidor in 2002.”

CWG’s Dan Stillman takes a look at the weather’s effect on baseballs and Stephen Strasburg’s pitching here.

#8: “Ceiling fans cool a room”

While feeling the cool breeze of a ceiling fan may feel delightful after coming inside, to keep an air-conditioned room cooler while you’re away, leave the fan off until you enter.

Fans don’t actually cool air at all – they simply provide moving air, which will evaporate the sweat on our bodies faster than still air. This leads to a cooling effect on our skin. However, in your house, the energy it takes to run the fan dissipates into heat energy due to inefficiency.

Not only that, but according to geojerry.com, “The surfaces of the ceiling, exterior walls, and windows are warmer than the rest of the room. When you turn on a ceiling fan, it circulates the air in the room. This mixes the air in the room faster, which makes the air cooler next to the walls and ceiling, which in turn makes heat move faster through the walls into the room from outside.”

So save some electricity and turn off the fan when you leave!

#7: “A sun tan is healthy”

Even the most educated of people somehow manage to fall victim to this myth. Just because someone has had more exposure to the sun does not make him or her any more invincible to skin damage.

“Any tan at all is a sign of skin damage,” says the Skin Cancer Foundation. “A tan is the skin’s attempt to repair sun damage and prevent further injury.” This does not make tanned skin a shield against UV rays.

The skin that has already been damaged is working even harder to repair itself, and can’t devote all of its energy to fighting future damage. This actually makes tanned skin more susceptible to both sunburn and, more dangerously, skin cancer. It’s important to remember sunscreen when going out in the summer heat!

#6: “Heat lightning is caused by the temperature”

The lightning that is often seen in the summer months around nighttime within distant clouds is usually referred to as “heat lightning,” but this name is a misnomer.

Heat lightning is not caused by the temperature outside, but is merely a distant thunderstorm, usually from 60-100 miles away. CWG’s Jason Samenow has an entire piece on the subject.

#5: “August is the hottest month”

As we enter the month of August, many of us dread the associated ideas of impending heat waves. While there may be elevated temperatures, the past indicates that we’ve made it through the worst of the summer weather.

July is actually the hottest month in most locations, with the most days of record-breaking temperatures across the U.S. Looking at last year’s summer weather as an indicator, the month of July was the hottest month of all time on record. “In 118 years of U.S. records, July 2012 stands as king, hotter than any month previously observed,” writes Jason Samenow.

Shlomi Dagan of The Weizmann Institute of Science writes a great myth-debunking piece on this very subject. “The most influential factor is the Earth’s heat capacity,” indicating that the point in time at which the Earth has retained the most heat from the sun is the warmest.

The sun provides the Northern Hemisphere with most sunlight on June 21, or the summer solstice. However, because the Earth needs time to absorb the sunlight from the sun, “the difference usually leads up to 4-6 weeks,” placing us in the month of July.

#4: “Summer is when the Earth is closest to the sun”

While it may seem logical to believe that summer is when the Earth is closest to its heat source, the sun, it is important to remember that it is not the distance from the sun, but the Earth’s axis tilt, that produces the seasons.

Related: Summer solstice 2013: Northern Hemisphere’s longest day, highest sun of the year

Keeping that in mind, it is actually interesting to note that the Earth is farthest from the sun in the first week of July (this year it was July 5), which is actually the hottest month (see myth #5).

Due to the Earth’s tilt, the Northern Hemisphere points towards the sun in the summer months, while the Southern Hemisphere (experiencing winter) is pointing away from it. This allows those in the north to receive the most direct sunlight during the summer months, which in turn, warms it up.

The longer days also heat up the Earth’s surface for a longer period of time, and that heat is retained and reflected to create warmer temperatures.

#3: “Green skies indicate tornadoes”

During the summer, it’s always important to be on high alert for tornadic weather. We know the tell-tale signs – funnel clouds, rotating severe thunderstorms… and a green sky?

Meredith Knight’s explanation in Scientific American may shed light on the origin of the green sky myth: “water droplets absorb red light, making the scattered light appear blue. If this blue scattered light is set against an environment heavy in red light—during sunset for instance—and a dark gray thunderstorm cloud, the net effect can make the sky appear faintly green.”

Someone likely made the connection that because most thunderstorms occur between the hours of 4 and 9 pm (NOAA), when the sky is most likely to turn green, there is an elevated chance of tornadoes.

While a green sky may be associated with evening thunderstorms, it doesn’t necessarily mean a tornado is imminent.

#2: “Lightning always goes from the ground up”

The first lightning myth most of us learn is that “lightning comes down from the clouds.” Of course, when this is debunked, we learn that the lightning we see is actually transmitted from the ground up toward the clouds.

What is not always explained, however, is that there are unseen cloud-to-ground lightning strokes that do occur prior to the bolt we see!  So, lightning comes from both the cloud and the ground.

Related: A few words about lightning myths | Lightning myths revealed | More lightning content

NOAA’s National Severe Storms Laboratory describes the process: “A typical cloud-to-ground flash lowers a path of negative electricity towards the ground in a series of spurts. Objects on the ground generally have a positive charge. Since opposites attract, an upward streamer is sent out from the object about to be struck. When these two paths meet, a return stroke zips back up to the sky. It is the return stroke that produces the visible flash.”

There are other types of lightning, as well, such as the mythical ball lightning, which may have nothing to do with cloud and ground interactions at all. The current theory is that it is the “accumulation of ions on the outside of non conducting surfaces” (Discovery News).

Watch a video of ball lightning here.

Related: Ball lightning: real or fantasy?

#1: “Counting the number seconds between lightning and thunder determines the distance away from the storm”

With this misconception, the idea is that every second that passes after a lightning flash indicates one mile of distance from the storm. While this is a myth, there is a hint of truth to it.

“It takes five seconds for the sound of super-heated air (thunder) to travel one mile,” writes Paul Fuhr, in the Cleveland Weather Examiner. “So, if you see a flash of lightning and count 10 seconds until you hear thunder, the storm is two miles away.”

(The author of this post, Amanda Morgenthal, is a Capital Weather Gang summer intern. She is an atmospheric science major at the University of Virginia. More info.)

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