The Global Ozone Observing system provides information on total Ozone contents from the ground based monitoring stations round the “WORLD”.

Measurements of total Ozone made in Pakistan Meteorological Department at Geophysical Centre Quetta represent a fundamental Data-set the same is communicated to World Data Centre, Canada for assessment of changes of the Ozone Layer and for creation of strategy of its international Preservation. This paper contains information focusing the state of Ozone Layer, its depletion and preservation and also this paper is prepared in compliance with the World Meteorological Organization Programme for the commemoration of International Day for Ozone Layer preservation.
 
 

From a distance Space, Planet Earth looks like a beautiful blue sphere. The special colour and beauty “Nature” arises from the vast greeneries of forest, vegetation and life found on Earth. The apparent abundance of this life-giving source depends on the thickness of the life protecting “OZONE LAYER” surrounding the “Planet Earth” and safe guards life on this planet. The Ozone molecules which concentrated mainly between altitudes of 15 to 35 Kilometer above the Earth, where the umbrella of Ozone Layer absorbs the harmful ultraviolet radiation emitting from the Sun and facilitate life giving source of Solar energy to the planet Earth. But over the past half-century, humans have placed the Ozone Layer in jeopardy. Un-knowingly humans have released into atmosphere, chemicals that are destroying part of the Ozone Layer and thus upsetting the delicate balance established by the nature. Thickness of ozone layer is not a fixed quantity. It fluctuates in time and space. That’s why we need basic “data”. It is believed that Ozone layer depletion problem can be alleviated if public have awareness and good knowledge about their natural environment.
 
 

The chemical formula of Ozone is O3. The molecule of Ozone consists of the atoms and is form of high energy of the element Oxygen O2. It is an unstable pale bluish gas with a characteristic pungent penetrating Odour. It is liquefied at minus 112°C and solidified at minus 251°C. It is dense, soluble in water and is also a more active oxidizing agent, acting directly on mercury and Silver to form oxides, affecting many organic compounds.

Ozone is rare in our atmosphere. It is mainly found in two regions of the Earth’s atmosphere. About 90% of Ozone is found in layer surrounding the Earth’s atmosphere between approximately 10 and 50 kilometers i.e. about 6 to 30 miles above the Earth’s surface. This region of Earth’s atmosphere is known as stratosphere and the layer of Ozone found there is called “Stratospheric Ozone Layer”. The remaining Ozone is in the lower region of Earth’s atmosphere, the troposphere, which extends from the Earth’s surface up to 10 kilometers.
 
 

The “Ozone hole” is a region of atmosphere over Antarctica from which “total ozone” has extremely decreased. Every year, the hole appears in August (austral spring) and develops during September / early October; after that, it declines gradually, and finally vanishes during the end of November and December (austral summer).

A stream of air that swirls around the South Pole, the so-called polar night / vortex, develops in Antarctic winter stratosphere, which isolates the stratosphere above the Antarctic from the surrounding atmosphere. During the winter, the polar night zone receives almost no light from the sun inside polar vortex, air temperature become so low that nitric acid and water freezes to form ice crystal’s clouds called polar stratospheric clouds. Through chemical reaction on the surfaces of ice crystals of these polar stratospheric clouds, chlorine gas is produced in the Ozone layer from inactive chlorides such as chlorine nitrate and hydrogen chloride. The chlorine gas that accumulates during the winter releases chlorine atoms when spring comes and the sun shine on it, and this chlorine begins to reduce ozone. As such the Ozone hole is born, through absorption of solar radiation toward summer, the polar night vortex gradually warms up from its inside and therefore weakens, finally dissipating completely; exchange of air begins between inside of the vortex and outside, then the Ozone hole disappears. The Ozone poor air, on this occasion, diffuses away from Antarctica and reduces Ozone layer of the Southern Hemisphere surrounding the Antarctic.
 
 

The Scientists involved into the Scientific assessments of “Ozone Depletion”, over the past two decades, have provided an excellent and un-biased advice to the International Communities and Governments and showed them the effective path to save the Earth’s protective Ozone shield. The use of economic instruments has played an important role in the phase out achieved so for by the industrialized countries of the world. 

Among the recent major scientific findings and observations mentioned in the Executive Summary of the Ozone Assessment 1998 are:

• The combined total abundance of ozone-depleting compounds in the troposphere (the lowest part of the atmosphere) peaked in 1994 and is now slowly declining. However, total concentrations of bromine are still increasing;
• In the northern polar latitudes, in six out of the last nine boreal winter-spring seasons, ozone has declined during some months by 25% to 30% below the 1960’s average;
• In the Antarctic, the appearance of the ozone hole during the austral springs has continued unabated, with ozone column losses usually exceeding 50% during the months of September and October;
• Only over the middle latitudes in both the northern and southern hemispheres has the ozone decline slowed in comparison with the previous scientific assessment in 1994;
• If measures had not been taken in accordance with the Montreal Protocol and its Amendments and Adjustments, the ozone decline would have been much stronger and would have continued for many more decades;
• Ozone losses in the stratosphere may have caused part of the observed cooling of the lower stratosphere in the polar and upper middle latitudes (about 0.6°C per decade since 1979);
• The increase of ozone in the troposphere since pre-industrial times is estimated to have contributed 10% to 20% of the warming due to the increase in long-lived greenhouse gases during the same period;
• The abundance of ozone-depleting substances in the stratosphere is expected to peak by the year 2000. However, when changing atmospheric conditions are combined with natural ozone variability, detecting the start of the ozone layer recovery may not be possible for perhaps another 20 years.