Few Facts:

• Atmosphere’s balance is menaced by human activity, which causes greenhouse effect, global warming, air contamination, ozone belt destruction and acid rains.
• About 20 % of the Earth’s population breathes severely contaminated air, especially with carbon monoxide and sulfur dioxide resulting from industrial processes. This increases the number of respiratory conditions, especially amongst children and elders.
• The frequency of skin cancers is increased by the thinning of the ozone layer. This is due to chlorinated hydrocarbons and fluorocarbons from aerosols, fridges, detergents and polystyrenes. These gases rise into the atmosphere and decompose into chloride ions that destroy the ozone layer. In 1985, a hole into the ozone layer was observed in Antarctica. In 1995, a similar hole was spotted into the ozone layer over the Arctic. Now, chlorinated hydrocarbons and fluorocarbons are replaced with other chemicals in the industrial processes.
• Acid rains form when sulfur dioxide or nitrogen oxides combine in the atmosphere with water vapors, forming acids. The resulting acid rains destroy plants and animals, killing entire forests. If this acid reaches rivers or lakes, it destroys all the organisms living there.

Scientists all over the world recognized many decades ago the importance of observing the behavior of the whole atmosphere. They acknowledge that not only climate & weather, but also the quality of the air we are breathing cannot be forecasted unless the physics and the chemistry of the atmosphere is known in detail, from the ground to the upper layers. Since it is too expensive to probe all the time and at each altitude the air, researchers took advantage of new technologies such as remote sensing: multiwavelength imagery or radiometry, laser or radio sounding.