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21
ANNEX I. DEW POINT THEORY
Dew point
or
dew point temperature
is defined as the temperature at which the air
mass is notable to hold more water and, thus, the water begins to condense.
Therefore, dew point temperature only depends on the amount of water in the air
(absolute humidity) as well as the pressure in the mass of air. So that, only modifying
the air temperature, the dew point temperature does not vary.
The
relative humidity
is, approximately, the ratio of the amount of humidity in the air to
the total amount of humidity the air can hold (saturation). On the other hand, as air
temperature increases, the capacity to hold water increases as well. This means that,
keeping the absolute humidity constant, the relative humidity varies with the air
temperature, according to:
Temperature
↑, relative humidity ↓
Temperature
↓, relative humidity ↑
For this reason, it can be understood that relative humidity relates the current
temperature of the air to the absolute humidity of the air, and hence the dew point
temperature. In such a way, an approximation of the dew point temperature could be
known by lowering the air temperature until a relative humidity of 100% was obtained,
which is known as the saturation point.
An approximation of the ratio between the dew point temperature and the temperature
of the air can be represented according to the following formula:
𝑇
𝐷𝑃
= 𝑇
𝑎𝑖𝑟
+ 35 log (𝑅𝐻 100
⁄
)
