Condensation occurs when the air is saturated with water molecules. The maximum quantity of water molecules that air can contain depends on the temperature of the air. If the temperature is higher, air is able to contain a larger the quantity of water molecules. Many people believe desert air is dry. This is certainly not always the case.

The quantity of water molecules in the air is defined by the term (atmospheric) humidity. Absolute humidity shows how much water vapour there is per cubic meter of air. In the rest of this paper we will use relative humidity. Relative humidity shows to what extent the air is already saturated.

It is important to understand that air with a relative humidity of 65% with an air temperature of +40° Celcius contains more humidity than air of +4° Celcius with 65% relative humidity. The air of +4° Celcius is crimped in comparison to the air of +40° Celcius. So although both have a relative humidity of 65%, the hot air contains more absolute humidity than the cold air. This means that if we have hot conditions with a relative humidity of 65% we have more water in the air than with cold conditions with a relative humidity of 65%. The reason is that when hot air crimps, there is less space between the molecules and the water molecules that are in between the air molecules, have to leave the air. We see this phenomenon happening in various forms.

There are actually 4 forms of production of water from air:

1) Rain: this is condensation of water that is caused by air, on higher heights, crimping through cold. The air crimps so strongly that water molecules are forced to being bigger and through cohesion they form drips that get too heavy to remain floating and they start to fall. The production of rain is a lot higher than we imagine. In many deserts annual precipitation (rainfall) is between 250 to 500 mm and in various deserts it goes up to 1,000 mm. That is 1,000 litres of water per m2. The problem is that many times it falls within a week and during the other 51 weeks of the year it is dry again. The AquaPro WaterBoxx uses this principle.

2) Fog: this is condensation of water caused by air, on lower heights, crimping through cold. The crimp is not so strong that the water molecules form drips that fall however leaves do get wet from this phenomenon and use this water.

3) Dew: this is condensation of water that is caused by air, around one to two meters above the soil, above canals or in the lower parts of valleys, crimping through cold. The crimp is not so strong that the water molecules form drips that fall however leaves get wet from this phenomenon and use this water.

4) Giving out: this is condensation of water that is caused by air that touches cold surfaces that got cold losing their energy through infrared radiation. The surface of the material gets wet from air that crimps because of touching the cold surface, in this way reaching its dew point. The surrounding air itself shows no fog or dew. The AquaPro WaterBoxx uses this principle.

Condensation through ‘giving out’ occurs in many areas of the world. Every morning many people find their car wet of condensation. Some of you will recognise the feeling when it’s getting clammy at the end of a nice summer evening out in the garden. People in colder areas will know the activity of scratching ice off the windshield of their cars after a clear winter night. In many places in the world plants ‘drink water’ through their infrared water producing technique.

Find the figures of the place where you live: http://www.worldclimate.com.

Other interesting links:
http://www.earthobservatory.nasa.gov/Laboratory/Biome/graphs.html#desert
http://www.encarta.msn.com/encnet/RefPages/RefMedia.aspx?refid=461530746
http://www.aquaproholland.com