Humidity and its types discussion essay

Humidity is the amount of water vapor present in the air. Increased humidity in the air decreases the rate of exchange of heat between the skin and its surroundings. The different types of humidity are absolute humidity, relative humidity, and specific humidity:

· Absolute humidity: The water content present in the air is called absolute humidity. It is expressed in grams per kilogram or grams per cubic meter. It is defined as the ratio of the mass of water vapor to the volume of air and water mixture. Its mathematical expression is,

\Delta H=\frac{{{m}_{{{\text{H}}_{\text{2}}}\text{O}}}}{{{V}_{\text{net}}}}ΔH=
V
net
​

m
H
2
​
O
​

​

In this expression, {{m}_{{{\text{H}}_{\text{2}}}\text{O}}}m
H
2
​
O
​
is the mass of water vapor and {{V}_{\text{net}}}V
net
​
is the volume of mixture of air and water vapor. In the atmosphere, the absolute humidity ranges from 0 to 30 grams per cubic meter. The value of absolute humidity varies with change in the temperature of air and pressure. Volumetric humidity is defined as the mass of water vapor per unit volume.

· Relative humidity: The ratio of pressure exerted by water vapor in the mixture to the vapor pressure of water at equilibrium over a surface having pure water, at a particular temperature, is called relative humidity. It is expressed in percentage. If the percentage is high, then the humidity of the air-water mixture is high. Relative humidity helps in weather forecast by predicting the possibility of fog, dew, or precipitation. In hot summers, the increase in relative humidity hinders the evaporation of sweat from the human skin and hence, increases the temperature for humans.

· Specific humidity: The ratio of the mass of water vapor to the total mass of air is called specific humidity. It is also equal to the ratio of the mass of water vapor to the mass of dry air in a parcel of air. The amount of water vapor that is required to attain the saturation point decreases with a decrease in temperature.

Heat Index
The temperature felt by the human body when relative humidity is combined with the temperature of the air is called the heat index. The resultant temperature felt by humans is called felt air temperature. At high temperatures, the heat index is increased due to an increase in the relative humidity. The air temperature and relative humidity are combined to form the heat index, which determines the equivalent temperature that is experienced by human beings. This resultant temperature is also known as apparent temperature. If the value of the heat index is between 26°C to 32°C, then on prolonged exposure, it may lead to heat cramps. The value of the heat index between 32°C to 41°C may lead to heat exhaustion and heatstroke. Further, the value of the heat index from 41°C to 54°C is a dangerous situation as it leads to heatstroke. Above 54°C, the effects of heat index are extremely dangerous.