What Is Humidity And How Does It Affect Life On Earth?

 High humidity in Polipoli Spring State Recreation Area, Maui, Hawaii, USA.
High humidity in Polipoli Spring State Recreation Area, Maui, Hawaii, USA.

The amount of water vapor present in the air is called humidity, and it indicates the likelihood of precipitation in a place. Cities ranked as very humid in the world are located in proximity to coastal regions and the equator. Such cities include Singapore, Kuala Lumpur, and Jakarta.

Definition Of Humidity

Humidity is a significant element of the atmosphere, and is invisible as water vapor is water in the gaseous state. Humidity is sighted only when water vapor condenses to precipitation, fog, or dew. Higher humidity translates to reduced evaporation of moisture from the skin which reduces the effectiveness of sweating in cooling the body. The amount of water vapor necessary to reach saturation decreases with increasing temperatures because of the molecule movements at higher temperatures which hamper condensation.

Types Of Humidity

There are three types of humidity:

  • Absolute humidity a termed used to define the total mass of water vapor measured in a particular volume of air. It takes into account the temperature of the air and increases in relation to the increase in water vapor.
  • Relative humidity refers to the air-water mixture and is expressed as the ratio of the partial pressure of the water vapor in the mixture to the equilibrium vapor pressure of water at a specific temperature over a flat surface of pure water. It is usually expressed as a percentage.
  • Specific humidity is measured as the ratio of water vapor mass to the total mass of the air parcel. An air parcel holds different amounts of water vapor at different temperatures. As temperatures decreases, an air parcel needs less water vapor to achieve saturation.

Measurements Of Humidity

Several devices have been invented to measure as well as regulate humidity. A hygrometer or a psychrometer is used to measure humidity. A psychrometer employs the use of two thermometers to measure relative humidity accurately. The thermometers simultaneously measure the wet-bulb and dry-bulb temperatures. A common device used to measure relative humidity by meteorologists is the sling psychrometer which is swung around. A humidistat is a device which responds to moisture. It has a switch, and it is fitted with equipment such a microwave ovens and humidifiers. Remotely located satellites are used to measure humidity on a global scale. The satellites are sensitive to the concentration of water in the troposphere between altitudes of 2.5 to 7.5 miles. Sensors which respond to infrared radiation are fitted on the satellites to enable them to measure water vapor. The water vapor absorbs and re-radiates radiation. Weather forecasts particularly rely on imagery depicted by these satellites which are also used to monitor climatic conditions.

Effects Of Humidity

Humidity affects human beings, animals, and plants. In a given environment, humidity is one of the determining factors for which particular flora and fauna can thrive. The human body depends on perspiration to get rid of excessive heat. During high humidity, evaporation of sweat from the body is reduced. Blood relies on conduction of heat from the body to the atmosphere to cool. In high humidity conditions, blood does not get rid of excessive heat, and it may lead to hyperthermia. Since most of the blood is heading to the body’s surface, the internal organs such as the brain receive less blood leading to fatigue and reduced physical strength. Humidity also has impacts on electronic devices and refineries and chemical plants which employ the use of furnaces.


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