The term “air” refers generally to gas, but exactly which gas depends on the context in which the term is used. Let’s learn about the modern definition of air in scientific disciplines and the earlier definition of the term.


Air is the general name for the mixture of gases that makes up the Earth’s atmosphere. This gas is primarily nitrogen (78%), mixed with oxygen (21%), water vapor (variable), argon (0.9%), carbon dioxide (0.04%), and trace gases. Pure air has no discernible scent and no color. Air typically contains dust, pollen, and spores; other contaminants are referred to as “air pollution.” On another planet—Mars, for example—the so-called air would have a different composition since there is technically no air in space.


Air is also an early chemical term for a type of gas. In the older definition, many individual types of so-called air made up the air we breathe: Vital air was later determined to be oxygen; what was called phlogisticated air turned out to be nitrogen. An alchemist might refer to any gas released by a chemical reaction as its “air.”


Air masses are classified into groups depending on their basic temperature and humidity characteristics.

There are six main types of air masses that affect the British Isles. We classify these air masses primarily by the area in which they originate.

They are classified as continental or maritime – dependent on whether they originate over land or sea – and arctic or antarctic, equatorial, tropical, or polar, depending on the particular region in which they form.

There are a total of six air masses that affect the British Isles, they are classified as follows:

Tropical continental

This air mass originates over North Africa and the Sahara (a warm source region). It is most common during the summer months June, July and August, although it can occur at other times of the year.

Our highest temperatures usually occur under the influence of tropical continental air (over 30 °C by day and around 15 to 20 °C at night).

Visibility is usually moderate or poor due to the air picking up pollutants during its passage over Europe and from sand particles blown into the air from Saharan dust storms. Occasionally, the Saharan dust is washed out in showers producing coloured rain and leaving cars covered in a thin layer of orange dust.

Tropical maritime

The source region for this air mass is warm waters of the Atlantic Ocean between the Azores and Bermuda. The predominant wind direction across the British Isles, in a tropical maritime air mass, is south-westerly.

Tropical maritime air is warm and moist in its lowest layers and, although unstable over its source region, during its passage over cooler waters becomes stable and the air becomes saturated. Consequently when a tropical maritime air mass reaches the British Isles it brings with it low cloud and drizzle, perhaps also fog around windward coasts and across hills. To the lee of high ground though, the cloud my break up and here the weather, particularly in the summer months, can be fine and sunny.

This is a mild air stream and during the winter month in particular, can raise the air temperature several degrees above the average.

Polar continental

This air mass has its origins over the snow fields of Eastern Europe and Russia and is only considered a winter (November to April) phenomena.

The weather characteristics of this air mass depend on the length of the sea track during its passage from Europe to the British Isles: this air is inherently very cold and dry and if it reaches southern Britain with a short sea track over the English Channel, the weather is characterised by clear skies and severe frosts. With a longer sea track over the North Sea, the air becomes unstable and moisture is added giving rise to showers of rain or snow, especially near the east coast of Britain.

The lowest temperatures across the British Isles usually occur in this air mass, lower than -10 °C at night, and sometimes remaining below freezing all day.

Polar maritime

This air mass has its origins over northern Canada and Greenland and reaches the British Isles on a north-westerly air stream.

This air mass is characterised by frequent showers at any time of the year. In the winter months when instability (convection) is most vigorous over the sea, hail and thunder are common across much of the western and northern side of the British Isles. However, eastern Britain may see fewer showers as here the surface heating is reduced. During the summer, the reverse is true, land temperatures are higher than sea temperatures and the heaviest showers occur over eastern England.

Arctic maritime

An arctic maritime air mass has similar characteristics to a polar maritime air mass, but because of the shorter sea track the air is colder and less moist.

Arctic air is uncommon during the summer, but when it does occur it may bring heavy showers or thunderstorms and unseasonably low temperature.

An arctic maritime air mass has its origins over the North Pole and the Arctic Ocean.

Polar low-pressure systems forming in this air mass can sometimes lead to widespread and heavy snowfall, but otherwise inland areas remain free of cloud in the winter months. In northern Scotland, arctic maritime is usually the coldest air mass, but over the rest of Britain, this air mass is not as cold as polar continental.

Returning polar maritime

Returning polar maritime is another version of polar maritime, but this time with a longer sea track which takes the air first southwards over the North-Atlantic, the north-eastwards across the British isles.

During its passage south, the air becomes unstable and moist but on moving north-east it passes over cooler water making it stable in its lowest layers.

Although the weather across the British Isles in this air mass is largely dry, there can be extensive cloud cover.


Air is a natural resource and is available abundantly. It is an essential element of nature that support life on earth. Air is equally important for living organisms for their survival just like water. Air is very useful and has many applications. Uses of air are as follows:

* Sustain life and growth
* Combustion
* Maintaining Temperature
* Supplier of Energy
* Photosynthesis

Sustain Life and Growth

Oxygen present in the air is one of the main life-sustaining gas. All living things breathe in and breathe out the air in the form of oxygen and carbon dioxide. Nitrogen and Carbon dioxide are vital for plants and their growth.


Another use of air is that it supports burning or combustion. The oxygen present in air help in the burning of the fuels leads to carry out activities like cooking food, running industries, and vehicles as well as generating heat and electricity.

Temperature Control

Air helps in maintaining the temperature on the earth’s surface by circulating hot and cold air. Air acts as a conductor of heat. The phenomena of the water cycle are also dependent on air.

Supplier of Energy

Air which consists of energy is one of the main suppliers of energy. Living things are made up of cells and these cells extract oxygen within the blood to produce energy in the form of ATP. The generation of ATP which is biochemical in nature is essential to maintain life on the Earth.


Carbon dioxide which is also a component of air is used by plants during the process of photosynthesis and oxygen, water vapor is released by plants as a by-product.

Apart from these gases, other gases are also useful such as nitrogen is used in the production of ammonia.