CONDENSATION

CONDENSATION
The physical process of transformation from the vapour to the liquid state is condensation. It occurs only when large masses of air experience a steady drop in temperature below the dew point, or when there is enough water vapour within the air mass for it to reach saturation point.

The rising of air mass to high elevations is necessary for this to happen. Condensation occurs when temperature reaches the dew point and the water vapour in the form of tiny droplets becomes visible in the form of clouds at a height of about one kilometre or more above the sea level.

DEW POINT is the temperature at whlch the air is fully saturated and below which condensation normally occurs; water vapour starts to condense to form water droplets.
DEW is the deposition of water droplets on the ground and objects, such as plants, near the ground. It occurs when the temperature of the ground surface falls and the air in contact with it is cooled below its dew point. Water vapour from the air or diffused from the soil then condenses and is deposited as droplets. The favourable conditions are moist air, light winds and clear night skies to ensure
maximum cooling by radiation.

FROST is a weather condition that occurs when the air temperature is at or below ODe. Moisture on the ground surface and objects freezes to form an icy deposit. Con­
ditions favourable for its formation are similar to those in the case of dew formation.

FOG is made of the droplets of water suspended in the lower layers of the atmospher~, resulting from the condensation of water vapour around nuclei of floating dust or smoke particles. A visibility of less ~han 1 kilometre is the internationally-recognised definition of fog.

SMOG, also called smoke fog, is a form of fog that occurs in areas where the air contains a large amount of smoke. Smoke particles provide a high concentration of nuclei around which condensation occurs. Condensation can occur around these nuclei even when the air is not saturated and therefore it forms. earlier, becomes denser and lasts longer than fog that develops in unpolluted air. The smoke, because of its chemical contents, gives an acid taste to fog.

MIST is the term for a reduction of visibility between 1-2 km caused by condensation producing water droplets
within the lower layers of atmosphere. It is intermediate between fog and haze.

HAZE is normally formed by water particles that have condensed around nuclei in the atmosphere, but may also be a result of particles of smoke, dust or salt in the air. In meteorology, it is an obscurity of the lower atmosphere that limits visibility to under 2 km but over 1 km. This term is also used for other phenomena that limit visibility.

CLOUDS are masses of minute water droplets and! or ice crystals formed by the condensation of water vapour and held in suspension in the atmosphere. Condensation, which results from cooling, usually takes place around nuclei such as dust, smoke particles and salt. The cooling may be caused by convection, uplift over mountains or
ascent in depressions. Clouds may be present at heights ranging from ground level up to over 13,000 metres.