Could anyone tell me what the ozone layer is?

Answer 1

The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone (O3). This layer absorbs 97-99% of the sun's high frequency ultraviolet light which is potentially damaging to life on Earth.[1] Over 90% of ozone in earth's atmosphere is present here. [1]"Relatively high" means a few parts per million—much higher than the concentrations in the lower atmosphere but still small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from approximately 15 km to 35 km above Earth's surface, though the thickness varies seasonally and geographically.[2] The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958 Dobson established a worldwide network of ozone monitoring stations which continues to operate today. The "Dobson unit", a convenient measure of the total amount of ozone in a column overhead, is named in his honor.

[edit] Origin of ozone

Ozone-oxygen cycle in the ozone layer.
The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930. Ozone in the earth's stratosphere is created by ultraviolet light striking oxygen molecules containing two oxygen atoms (O2), splitting them into individual oxygen atoms (atomic oxygen); the atomic oxygen then combines with unbroken O2 to create ozone, O3. The ozone molecule is also unstable (although, in the stratosphere, long-lived) and when ultraviolet light hits ozone it splits into a molecule of O2 and an atom of atomic oxygen, a continuing process called the ozone-oxygen cycle, thus creating an ozone layer in the stratosphere, the region from about 10 to 50 km (32,000 to 164,000 feet) above Earth's surface. About 90% of the ozone in our atmosphere is contained in the stratosphere. Ozone concentrations are greatest between about 15 and 40 km, where they range from about 2 to 8 parts per million. If all of the ozone were compressed to the pressure of the air at sea level, it would be only a few millimeters thick.

Ten percent of the ozone in the atmosphere is contained in the troposphere, the lowest part of our atmosphere where all of our weather takes place. Tropospheric ozone has two sources: about 10 % is transported down from the stratosphere while the remainder is created in situ in smaller amounts through different mechanisms.


[edit] Ultraviolet light and ozone

Levels of ozone at various altitudes and blocking of ultraviolet radiation.Although the concentration of the ozone in the ozone layer is very small, it is vitally important to life because it absorbs biologically harmful ultraviolet (UV) radiation emitted from the Sun. UV radiation is divided into three categories, based on its wavelength; these are referred to as UV-A, UV-B, and UV-C. UV-C, which would be very harmful to humans, is entirely screened out by ozone at around 35 km altitude. However it is interesting to note that ozone gas is a pollutant at lower levels and cause severe problems like oedema, hemorrage etc. UV-B radiation can be harmful to the skin and is the main cause of sunburn; excessive exposure can also cause genetic damage, resulting in problems such as skin cancer. The ozone layer is very effective at screening out UV-B; for radiation with a wavelength of 290 nm, the intensity at Earth's surface is 350 billion times weaker than at the top of the atmosphere. Nevertheless, some UV-B reaches the surface. Most UV-A reaches the surface; this radiation is significantly less harmful, although it can potentially cause genetic damage.

Depletion of the ozone layer allows more of the UV radiation, and particularly the more harmful wavelengths, to reach the surface, causing increased genetic damage to living organisms.


[edit] DNA sensitivity to UV

UV energy levels at several altitudes. Blue line shows DNA sensitivity. Red line shows surface energy level with 10% decrease in ozone.To appreciate the importance of this ultraviolet radiation screening, we can consider a characteristic of radiation damage called an action spectrum. An action spectrum gives us a measure of the relative effectiveness of radiation in generating a certain biological response over a range of wavelengths. This response might be erythema (sunburn), changes in plant growth, or changes in molecular DNA. There is much greater probability of DNA damage by UV radiation at various wavelengths. Fortunately, where DNA is easily damaged, such as by wavelengths shorter than 290 nm, ozone strongly absorbs UV. At the longer wavelengths where ozone absorbs weakly, DNA damage is less likely. If there were a 10% decrease in ozone, the amount of DNA damaging UV insolation increases, in this case, by about 22%. Considering that DNA damage can lead to maladies like skin cancer, it is clear that this absorption of the sun's ultraviolet radiation by ozone is critical for our well being.[citation needed]


[edit] Distribution of ozone in the stratosphere

Global monthly average total ozone amountThe thickness of the ozone layer—that is, the total amount of ozone in a column overhead—varies by a large factor worldwide, being in general smaller near the equator and larger as one moves towards the poles. It also varies with season, being in general thicker during the spring and thinner during the autumn. The reasons for this latitude and seasonal dependence are complicated, involving atmospheric circulation patterns as well as solar intensity.

Since stratospheric ozone is produced by solar UV radiation, one might expect to find the highest ozone levels over the tropics and the lowest over polar regions. The same argument would lead one to expect the highest ozone levels in the summer and the lowest in the winter. The observed behavior is very different: most of the ozone is found in the mid-to-high latitudes of the northern and southern hemispheres, and the highest levels are found in the spring, not summer, and the lowest in the autumn, not winter. During winter, the ozone layer actually increases in depth. This puzzle is explained by the prevailing stratospheric wind patterns, known as the Brewer-Dobson circulation. While most of the ozone is indeed created over the tropics, the stratospheric circulation then transports it poleward and downward to the lower stratosphere of the high latitudes.


Brewer-Dobson circulation in the ozone layer.The ozone layer is higher in altitude in the tropics, and lower in altitude in the extratropics, especially in the polar regions. This altitude variation of ozone results from the slow circulation that lifts the ozone-poor air out of the troposphere into the stratosphere. As this air slowly rises in the tropics, ozone is produced by the overhead sun which photolyzes oxygen molecules. As this slow circulation bends towards the mid-latitudes, it carries the ozone-rich air from the tropical middle stratosphere to the mid-and-high latitudes lower stratosphere. The high ozone concentrations at high latitudes are due to the accumulation of ozone at lower altitudes.

The Brewer-Dobson circulation moves very slowly. The time needed to lift an air parcel from the tropical tropopause near 16 km (50,000 feet) to 20 km is about 4-5 months (about 30 feet per day). Even though ozone in the lower tropical stratosphere is produced at a very slow rate, the lifting circulation is so slow that ozone can build up to relatively high levels by the time it reaches 26 km.

Ozone amounts over the continental United States (25°N to 49°N) are highest in the northern spring (April and May). These ozone amounts fall over the course of the summer to their lowest amounts in October, and then rise again over the course of the winter. Again, wind transport of ozone is principally responsible for the seasonal evolution of these higher latitude ozone patterns.

The total column amount of ozone generally increases as we move from the tropics to higher latitudes in both hemispheres. However, the overall column amounts are greater in the northern hemisphere high latitudes than in the southern hemisphere high latitudes. In addition, while the highest amounts of column ozone over the Arctic occur in the northern spring (March-April), the opposite is true over the Antarctic, where the lowest amounts of column ozone occur in the southern spring (September-October). Indeed, the highest amounts of column ozone anywhere in the world are found over the Arctic region during the northern spring period of March and April. The amounts then decrease over the course of the northern summer. Meanwhile, the lowest amounts of column ozone anywhere in the world are found over the Antarctic in the southern spring period of September and October, owing to the ozone hole phenomenon.


[edit] Ozone depletion
Main article: Ozone depletion
The ozone layer can be depleted by free radical catalysts, including nitric oxide (NO), hydroxyl (OH), atomic chlorine (Cl), and atomic bromine (Br). While there are natural sources for all of these species, the concentrations of chlorine and bromine have increased markedly in recent years due to the release of large quantities of manmade organohalogen compounds, especially chlorofluorocarbons (CFCs) and bromofluorocarbons. These highly stable compounds are capable of surviving the rise to the stratosphere, where Cl and Br radicals are liberated by the action of ultraviolet light. Each radical is then free to initiate and catalyze a chain reaction capable of breaking down over 100,000 ozone molecules. Ozone levels, over the northern hemisphere, have been dropping by 4% per decade. Over approximately 5% of the Earth's surface, around the north and south poles, much larger (but seasonal) declines have been seen; these are the ozone holes.


[edit] Regulation
On January 23, 1978, Sweden became the first nation to ban CFC-containing aerosol sprays that are thought to damage the ozone layer. A few other countries, including the United States, Canada, and Norway, followed suit later that year, but the European Community rejected an analogous proposal. Even in the U.S., chlorofluorocarbons continued to be used in other applications, such as refrigeration and industrial cleaning, until after the discovery of the Antarctic ozone hole in 1985. After negotiation of an international treaty (the Montreal Protocol), CFC production was sharply limited beginning in 1987 and phased out completely by 1996.

On August 2, 2003, scientists announced that the depletion of the ozone layer may be slowing down due to the international ban on CFCs. [3] Three satellites and three ground stations confirmed that the upper atmosphere ozone depletion rate has slowed down significantly during the past decade. The study was organized by the American Geophysical Union. Some breakdown can be expected to continue due to CFCs used by nations which have not banned them, and due to gases which are already in the stratosphere. CFCs have very long atmospheric lifetimes, ranging from 50 to over 100 years, so the final recovery of the ozone layer is expected to require several lifetimes.

Compounds containing C–H bonds are being designed to replace the function of CFC's (such as HCFC), since these compounds are more reactive and less likely to survive long enough in the atmosphere to reach the stratosphere where they could affect the ozone layer.

Answer 2

Ozone layer, where appreciable concentration of ozone,O3,a blue gas, is found, lies in the lower stratosphere.It plays an important part in the radiation balance of the atmosphere.
Highly unstable,an ozone molecule readily splits up when hit by ultra-violet radiation.The energy of the life-damaging UV rays is thus converted into harmless heat by this ozone layer and the UV rays never reach the earth's surface.
The break up leaves a free oxygen atom(O) and an oxygen molecule(O2).The O and O2 , in an ongoing cycle,recombine to form new ozone molcules.
The ozone layer lies roughly betwen 10 and 50 Kms with maximum ozone concentration at about 20 to 25 Kms.
A severe depletion in the ozone layer will result in an increase in the cases of skin cancer,eye cataract and the suppression of the immune system in humans and other species.Food crops sensitive to UV rays will also be affected.

Answer 3

The ozone layer is a ZONE just above our heads where
zero thoughts occur. No one can really go there, because it is a void. Voids don't exist. So we really can't go there. But Buddhists try to go to the ozone. In Sanskrit it is called the Viraja river and is between the material world and the spiritual world. Due to the influence of Al Gore, we know more about it now. They say the ozone is being destroyed.
From darkness, maybe there will be some light. And we see at the end of the ozone this huge eyeball. My God! It's a person! The ozone is this big eyeball!!

Answer 4

The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone (O3). This layer absorbs 97-99% of the sun's high frequency ultraviolet light which is potentially damaging to life on Earth.[1] Over 90% of ozone in earth's atmosphere is present here. [1]"Relatively high" means a few parts per million—much higher than the concentrations in the lower atmosphere but still small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from approximately 15 km to 35 km above Earth's surface, though the thickness varies seasonally and geographically.[2] The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958 Dobson established a worldwide network of ozone monitoring stations which continues to operate today. The "Dobson unit", a convenient measure of the total amount of ozone in a column overhead, is named in his honor.

Answer 5

The ozone layer is a portion of the Earth’s atmosphere which contains relatively high levels of ozone. The Earth’s atmosphere consists of many different layers, and is made up primarily of nitrogen, with oxygen being the second-most common element. The ozone layer is important for a number of reasons, but primarily because it helps to protect life on earth from damaging ultraviolet radiation.

Ozone itself is a particular form of oxygen, where three atoms of the element have bonded together. It is poisonous for us to breathe directly, and is considered a pollutant if it’s found near the surface. The name for ozone comes from the word for the particular smell is it associated with, which occurs during lightning storms.

The ozone layer, like the Earth’s atmosphere itself, has no exact boundary. In general, it is viewed as being the layer of gasses 10 to 20 miles (15-35km) above the Earth’s surface. The concentration of ozone in the ozone layer is high in comparison to anywhere else, but is still relatively low. Even in the most densely-concentrated portions of the ozone layer, ozone makes up only a few parts per million.

Ozone is particularly important to us because it has the unique property of absorbing ultraviolet radiation. There are three main types of ultraviolet (UV) radiation, known as UV-A, UV-B, and UV-C. When functioning properly, the ozone layer completely removes UV-C radiation, which is the most harmful to humans. It also drastically reduces the amount of UV-B that reaches the Earth’s surface — UV-B is the radiation responsible for many types of skin cancer and sunburns.

In the 1970s, it became apparent that the ozone layer was slowly disappearing. It was discovered that this was a direct result of the use of certain catalysts being released in large amounts by humans. A number of countries took small steps to reduce the emission of these catalysts — particularly chlorofluorocarbons (CFCs) — but the steps were generally quite limited. In 1985, however, an enormous hole in the ozone layer was discovered above Antarctica.

This hole in the ozone layer provided the necessary impetus for a worldwide movement to help protect the ozone layer. Within two years of its discovery, the Montreal Protocol was ratified, severely limiting the production of ozone-depleting compounds. By the mid-1990s the use of ozone-depleting compounds had been drastically reduced, and the ozone layer was on its way to recovery.

Although the ozone layer is still well below its historic levels of ozone, its depletion does seem to have slowed dramatically, and the most immediate danger seems to have passed. The ozone layer serves as a poignant example for many people that the nations of the world are capable of taking relatively quick and concrete action in the face of an impending global catastrophe.

Answer 6

The protective layer in the atmosphere, about 1 5 miles above the ground, that absorbs some of the sun's ultraviolet rays, thereby reducing the amount of potentially harmful radiation that reaches the earth's surface.

Answer 7

minimum consequence on the ozone layer if that reactor melts down and joins the middle. Jerry J has provided the only considerate answer on your question. confirm you decide on that as superb answer!

Answer 8

it's this layer around the earth (kinda hard 2 explain) that traps some of the heat that comes from the sun inside. I hope i helped.

Answer 9

it keeps the UV rays out yes some still get in also its the layer of the atmosphere the news talked about us destroying with hair spry. that didn't catch on so now their on global warming

Answer 10

so simple question to be answered...well as i am familiar with it , it is the one that we may say the reason why we are not dead right now. It minimize the amount of light rays or heat from the sun to enter earths atmosphere..so thats why we are alive right now..hahaha