Humidity

The concentration of water vapour present in the air is known as humidity. The widely employed primary measurements of humidity are: absolute humidity, relative humidity and specific humidity. In this article, let us learn more about the three primary measurements of humidity.

Types of Humidity

Absolute Humidity

Absolute humidity describes the water content present in the air and is expressed in either grams per cubic meter or grams per kilogram. The absolute humidity in the atmosphere ranges from near zero to roughly 30 grams per cubic metre.

Mathematically absolute humidity is defined as mass of the water vapour divided by the volume of the air and water mixture, which is expressed as

\(\Delta H=\frac{m_{H_{2}O}}{V_{net}}\)

The absolute humidity varies with respect to air temperature and pressure changes, if the volume is not fixed. The mass of water vapour per unit volume in the equation is also defined as volumetric humidity.

Relative Humidity

The relative humidity of an air water mixture is defined as the ratio of the partial pressure of water vapour in the mixture to the equilibrium vapour pressure of water over a flat surface of pure water at a given temperature.It is normally expressed as a percentage. Higher percentage indicates that the air-water mixture is more humid.

Relative humidity is a crucial metric that is used in weather forecast as it an indicator of the likelihood of precipitation, dew or fog. In hot summer weather, a rise in relative humidity increases the temperature to humans by hindering the evaporation of perspiration from the skin.

Specific Humidity

The ratio of mass of the mass of water vapour to the total mass of the air parcel is known as specific humidity.

Effects of Humidity

Animals and Plant Life

Humidity is a determinant of which animals and plants can thrive in a given environment. The human body dissipates heat through perspiration and its evaporation. When the atmosphere is as warm as or warmer than the skin during times of high humidity, the blood brought to the surface cannot dissipate the heat to the air. With so much blood going to the body, less blood goes to the active muscles and brain. As a result, physical strength decreases and fatigue occurs sooner than it would otherwise.

Electronics

Electronic devices are designed to operate under specific humidity. During high humid conditions, the moisture may increase the conduction of permeable insulators leading to malfunction. Low humidity makes materials brittle. One substantial danger to electronic items regardless of the stated humidity range is the condensation. When an electronic item is moved from a cold place, say a garage to a humid such as the house, condensation coats circuit boards and other insulators, short circuiting the equipment. Low humidity favours the build up of static electricity which results in the shutdown of computers when the discharge occurs.

Industry

High humidity has a negative effect on the capacity of chemical plants that use furnaces as part of certain processes.

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