Chapter 5

ATMOSFEAR

Is there anything to fear in the atmosphere? You know there is! But the blanket of air that separates us from the vacuum of space is a wonder and a protector to life on Earth. It's a thick blanket of intricately complex layers, each serving to protect and provide for our fragile bodies in different ways
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The chart at left displays the atmosphere's thermal layers, with altitude upward from the Earth's surface to 150 miles. The term "thermal layer" refers to the fact that gas molecules in the atmosphere do not always get colder with height above the Earth. Instead they either heat or cool with increasing altitude depending on the atmospheric layer in which they are located. The snaking line rising through the diagram shows temperature increase and decrease. To understand other kinds of layers (not shown in this diagram), like the Ozonosphere and the Ionophere, we must first understand the thermal layers.

The Troposphere, shown in the diagram at left as the lowest layer (in sky blue color) is only about 7 miles thick. That's not much compared to the 200 miles or so of atmospheric thickness that surrounds the Earth. Because of the gravitational pull of the Earth, however, most of the air molecules (measured as air pressure) within the 200 mile thick blanket are found in this lowest layer, the Troposphere. It gets colder as you rise in the Troposphere for 2 reasons. First, it gets colder mostly because, as you rise above the Earth's surface, you increase distance from the source of heat.

I can see your forehead wrinkle with confusion! If the source of the heat energy is the Sun... why doesn't it get warmer as you rise in the air? Because the Sun isn't the source of heat in the Troposphere! The Earth is! The Sun is the source of nearly all energy on Earth. What does that say? Let's be more specific. The Sun is the source of nearly all energy on the surface of the Earth! It is the Earth, not the Sun, however, which heats the air in the Troposphere (the lowest layer of the atmosphere).

This will require a few diversions to explain, so please bear with me and relish the tidbits of wonder which are about to unfold!

Solar energy is radiated outward through space in short-wavelengths. Short-wave energy is intense energy and it's source is Solar nuclear reactions. Atomic bombs, by the way, also generate nuclear energy and that energy also travels outward in tight (short) wavelengths and (this is a surprise) that energy is also very intense... it can curl your hair!

When I was a young guy in Geography class I learned that Solar energy heats the Earth's surface and the warmed surface then re-radiates energy outward into the atmosphere in long wavelengths. But I don't teach it that way because, in fact, the Earth's surface is warm! Sure, it's warmth comes from the Sun, but whatever the source, it's warm! And heat rises. The heat energy that rises is not re-radiation (this is not refried beans), it is long-wave Terrestrial radiation (a whole new food group)! Long-wave Terrestrial radiation is not intense and is not harmful to human beings! Short-wave Solar radiation, however (like radiation from an atomic bomb), is harmful. This is a very important distinction. We don't want the air we breathe to blind us when we open our eyes... or vaporize our flesh before we have a chance to exhale!

How very convenient that the atmosphere is thick enough to permit the existence of a Troposphere! Were the atmosphere thinner, skin cancer and any number of ailments would result from the short-wave radiation from the Sun. Our atmosphere is not only the ideal thickness to support air breathing creatures, but it's layered in a manner precisely fit to remove the most harmful Solar radiation while receiving beneficial rays... light in a variety of colors, and warmth!

Permit a brief explanation about radiation. As the spokes of a bicycle radiate outward from a hub, or center, energy waves radiate outward from an energy source.

It may seem odd, but thinkers in the 19th century believed that Solar energy traveled through a medium, which they called "ether," because they knew that energy doesn't travel without a medium. So they imagined that some clear gas filled the distance between Earth and Sun across which Solar energy could travel.

Ocean waves are long, typically having a wavelength of a few hundred yards (the distance from one wave crest to the next). Solar energy travels in waves, as noted, that are short... mostly in wavelengths between 0.1 and 4.0 micrometers ( m). A micrometer is a millionth of a meter, or about 4/100,000 of an inch. Gotta squint into a microscope to see that! But ocean waves travel very much like Solar energy waves do, the difference being wavelength and medium of travel rather than anything else. So, a bit more about ocean waves may be helpful.

Solar energy warms the Earth's surface differentially... more in some areas than others. The uneven distribution of heat on the Earth's surface then warms the lowest layer of air above it (the Troposphere). The air then moves around in a frenetic effort to distribute that heat evenly (being ever faithful to the second law of thermodynamics)! Wind blows in a determined effort to equalize heat energy in the Troposphere. Now, when the wind blows over an ocean much of it's energy is transmitted into the water. That energy then moves outward from the source of the energy (wind in this case) in waves! Waves carry energy but not matter. Thus ocean waves do not move the water! They travel through the water! Sound wrong? Keep reading. I (have no fear) shall explain this thing in the final chapter! Taking these words on faith (if you dare) let's look again at the movement of Solar energy through space in waves.

The term "electro-magnetic" is used of Solar energy waves because they're different than ocean waves which radiate outward from an energy source but use water as the medium of travel. Electro-magnetic waves use the magnetic field that invisibly connects all of the space magnets called planets and stars and moons!

Take a look at the diagram below to understand this radiation business a little better.

the lower diagram describes the wavelength spectrum for colors of visible light
source: http://www.geog.ouc.bc.ca/physgeog/contents/6f.html

Solar energy therefore travels to the Earth across the invisible magnetic field which connects all objects in space. The energy travels in short wavelengths, including wavelengths in the diagram above from gamma through infrared rays. Gamma- and X-rays are obviously harmful. We put on goop at the beach to keep our tender flesh from burning! Sunburn is blamed on those harmful ultraviolet-rays. Guess what? Those UV-rays hardly affect us at all compared to the amount of UV energy that is blasted at us from the Sun. This is because above the Troposphere there's a Stratosphere!

The Stratosphere is a hotel in Las Vegas. No. Scratch that. The Stratosphere is the layer of air above the Troposphere. It begins about 7 miles above the Earth's surface, although it's real altitude varies seasonally and with geographic location... it's always higher where it's warm and lower where it's cold. Thus around 12 miles thick in the tropics and 4 or 5 miles thick in the polar regions. It's also higher in summer, lower in winter. This information is not trivial... it's important!
The Stratosphere, which is shown in yellow in the diagram on page 29, is an atmospheric layer that warms with increasing height above the Earth. It gets warmer as you rise in the Stratosphere! Why? Excellent question! Because the Stratosphere is full of ozone! Ozone is a molecule that consists of 3 atoms of oxygen chemically bonded together. And ozone eats ultraviolet-rays for lunch!

Amazing! A single atom of oxygen is called oxygen. Two atoms of oxygen bonded together is called... oxygen. Three of them, however, is not breathable by Earth creatures and is not oxygen. It's ozone! Ozone is lighter than the combination gas called air (which consists of nitrogen, oxygen, argon, and other gases chemically bonded together at the molecular level) and thus it naturally rises to that layer where atmospheric density allows it to float luxuriously... in the Stratosphere!

It gets warmer with increased altitude in the Stratosphere simply because the ozone is so busy gobbling up the harmful UV-rays from the Sun. Eat 3 hot fudge sundaes (try it!) and notice how your body temperature increases. The massive intake of calories (which is a measurement of heat) will warm your bod. Likewise, ozone molecules warm up as they consume UV-rays! Their single intent is to protect us fragile creatures on the Earth's surface! Light rays, which we like, are unaffected by ozone and they are transmitted to us in just the right proportions. What a coincidence!

Another coincidence of physics. The Troposphere is deeper in warm climates because warm air expands. Air contracts in polar regions because cold air relaxes and shrinks as the air molecules "chill-out!" So... the UV eating ozone layer is located farthest above our hairlines where the UV is most intense!

The angle of incidence of Solar energy is more direct and thus more intense in the tropics than at the poles. Thus the UV-rays are more abundant per surface area in the tropics than at the poles. And the ozone layer is thicker, to better protect us, where more needed in the tropics! Furthermore, it's farther above the Earth's surface in the tropics, providing greater separation between those harmful UV-rays and the ‘Girl from Ipanema' (a song from the 1960's) as she strolls along the beach. And don't we all care greatly about her skin? (Ipanema is in Rio de Janeiro, Brazil... a tropical location.)

Is there more? Indeed so. Notice in the diagram on page 29 that air temperature (represented by the snaking vertical line in the center of the diagram) also rises with increasing altitude in the Thermosphere. That's because the Ionosphere is located there.

An ‘ion' is a broken atom. An atom has an equal number of electrons (particles with a negative electrical charge) and protons (positively charged particles). In the Ionosphere, atoms in air molecules are bombarded by short wavelength Solar energy and electrons are knocked off or added in the violence. The result is that electrically charged particles, called ions, are bouncing around up there in great abundance! Turns out to be useful for radio communications. It's even more useful, however, for filtering out harmful Solar energy before it reaches my balding crown! The energy absorption produces heat, thus Thermosphere temperatures rise with increasing altitude.

"I have a query for you. It seems that the media is no longer making a big deal about the hole in the Ozone layer. Why is this? Is the hole still there? Is it larger in size? Can it be repaired? If so, how?" Yaron.

Received that email from my Aussie buddy as I was writing. What are the odds?
Great question! I have a series of photos I show my classes. The famous ozone hole over Antarctica grew during the 1980's, then a 1994 photo shows it decreasing! Then, in 1999, it increased greatly in size. We do not know as much about this stuff as newspaper articles imply and although ozone levels have been recorded in Europe since the early 1900's, no records for Antarctica predate the 1970's (that I'm aware of, at any rate). The thickness of the ozone layer at the poles is somewhat inconsequential, anyway. It does, however, make for great politics.

The ozone layer is lower and thinner over the poles because the air is colder there. Colder air is by nature descending air because cold atoms are too calm to rise (warm air rises!). Furthermore, it's the very same Solar UV-rays that ozone absorbs which produce Stratospheric ozone! And, because of the low angle of incidence of Solar rays at the Poles, much less UV reaches into the atmosphere in the high latitudes, thus reducing the natural production of ozone in the polar atmospheric regions.

Ozone depletion is a big deal and may be caused by chlorine pollution from wasteful, selfish, underworked, capitalistic Americans (Australians?). I say "may be caused" because there are some problems with the idea. Nonetheless, records do indicate that ozone in the Stratosphere has been depleted by about 3% since the 1970's. Could be a result of cyclical variables unknown to science at this time. Could be because of your panzy habits and demand for air conditioning and hair spray (I use neither... unless I'm hot or want to look good)! Of great importance (and I'll bet you've never heard a politician or journalist tell you this), the depletion is greatest at high latitudes (where least needed) and least in the tropics (where most needed).

The ozone layer, it is popularly believed, will be repaired as resident chlorine (actually, chloro-fluoro-carbon) dissipates with environmental measures already enacted internationally.

In fact, however, studies are currently showing that the ozone depletion does not seem to be slowing as predicted. Explanations have been forwarded, but I alone have wondered whether the real cause of the depletion may simply be unrelated to capitalistic excesses. Which would explain the failure of predicted repair to the Ozonosphere, as well.

But the ozone layer must not be too thick, either! Too much ozone would be bad for us because those scary ultraviolet-rays have considerable benefit... It's important that the Ionosphere and the Ozonosphere not remove all of the UV-rays from the Sun. A major example of benefit is that UV stimulates production of vitamin D in our skin, which is necessary (can you guess?) for life!

The blue planet's atmosphere is immensely complex, many of it's most dramatic features (e.g. tornadoes and hurricanes and jet streams) are yet to be fully explained. Remarkably, however, we know enough to say that it's characteristics are brilliantly designed to benefit, rather than harm, life.
There is an amazing balance in the air up there... just right for protecting human beings as they ponder the origin of it all.

Earth's atmosphere is divided into layers, which have various characteristics.
Source: NOAA Aeronomy Laboratory, 1998