The wet-bulb temperature is the minimum temperature reached by adiabatic water evaporation in the air until the air becomes saturated.

Evaporation of water necessitates the use of heat. If the evaporation is adiabatic, the heat from the surroundings is removed, causing the air to cool and be more humid. When we get out of the bath or the pool, the same thing occurs. The water on our bodies evaporates, removing heat from our bodies and causing us to become chilly.

Why in News?

Part 2 of the Intergovernmental Panel on Climate Change (IPCC) 6th assessment report recently highlighted the trend in ‘Wet Bulb’ Temperature in South Asia.

The trend will offer an indicator of the combined effects of heat and humidity and their influence on health.

Read on to make UPSC notes on this topic.

What is The Wet Bulb Temperature?

Wet bulb temperature is the minimum temperature at which air may be cooled by evaporating water into the air under constant pressure.

WBT is a heat and humidity limit beyond which people cannot endure high temperatures.

The temperature of adiabatic saturation is the Wet Bulb temperature. The temperature reported by a wet thermometer bulb exposed to air flow is this.

An adiabatic process is one where the system does neither absorb or lose heat.

The temperature of a wet bulb may be monitored with a thermometer while the bulb is covered in damp muslin.

The adiabatic evaporation of water from the thermometer and the cooling effect is indicated by a “wet bulb temperature” lower than the “dry bulb temperature” in the air.

The rate of evaporation from the wet bandage on the bulb, and the temperature difference between the dry bulb and wet bulb, depending on the humidity of the air.

The evaporation is reduced when the air contains more water vapour.

A wet-bulb temperature of 31°C is exceedingly harmful to humans, while a temperature of 35°C is unsurvivable for more than 6 hours.

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What are Dew Point and Dry Bulb Temperatures?

Dry Bulb Temperature

The Dry Bulb temperature, sometimes known as “air temperature,” is the most widely utilized air characteristic. When people talk about the temperature of the air, they usually mean the temperature of a dry bulb.

The ambient air temperature is referred to as the Dry Bulb Temperature. It’s termed a “Dry Bulb” because the air temperature is measured by a thermometer that is unaffected by humidity.

A standard thermometer, fully exposed to the air but covered from radiation and moisture, can be used to measure the temperature of a dry bulb.

The temperature of the dry bulb is a good indicator of heat content.

Dew Point Temperature

The Dew Point is the temperature where water vapour starts to condense out of the air (the temperature at which air becomes completely saturated).

Above this temperature, the moisture stays in the air.

If the dew-point temperature is close to the dry air temperature – the relative humidity is high.

If the dew point is well below the dry air temperature – the relative humidity is low.

The Dew Point temperature is always lower than the Dry Bulb temperature and will be identical with 100% relative humidity (the air is at the saturation line).

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How Do You Determine The Temperature of a Wet Bulb?

A thermometer with a mercurial reservoir in a cotton cuff can be used to measure the temperature of the wet bulb. It is maintained moist by a cotton thread connection to a water tank. The thermometer is suspended in mid-air. Heat is taken from the environment, such as the mercurial reservoir, as the water evaporates, and the recorded temperature drops.

It would also forsake society’s most vulnerable individuals and provide no assistance to those who must travel outdoors.

The water continues to evaporate until the air becomes saturated, at which point the relative humidity reaches 100%. The temperature approaches a point of equilibrium, which is the temperature of the wet bulb. When the air is dry, more water may evaporate, lowering the temperature of the wet bulb. The bigger the temperature differential between the dry bulb (or normal) and the wet bulb temperature, the dryer the air is and the more water may evaporate.

How Will This Trend Impact India?

If emissions continue to grow, cities such as Lucknow and Patna are expected to hit wet-bulb temperatures of 35°C, whereas Chennai, Bhubaneswar, Mumbai, Indore, and Ahmedabad are ‘at danger’ of reaching wet-bulb temperatures of 32°C-34°C.

Parts of central India, especially Vidarbha, are at risk of reaching wet bulb temperatures of 32-34°C if emissions continue.

This will have ramifications such as an increase in heat-related mortality or decreased output.

Using artificial cooling to combat rising temperatures will drive up energy consumption, putting many people at risk of power outages.

It would also forsake society’s most vulnerable individuals and provide no assistance to those who must travel outdoors.


Hopefully, you’ve found this information to be really beneficial in your UPSC preparation. To accurately respond to questions in the exam, you must try your best to stay up with current facts and events.

You should seek out the most credible sources of knowledge during your UPSC preparation so that you can study and retain everything. You should make the most of your UPSC preparation session and learn about all of the programs and events in order to adequately serve your country.

For more current affair topics, visit UPSC Pathshala.

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Madhurjya Chowdhury

Madhurjya Chowdhury, a web content writer in Ufaber EduTech has a very strong passion for writing and alluring the readers. You can find him writing articles for the betterment of exam aspirants and children. With immense interest in research-based content writing and copywriting, he likes to reach out to more and more people with his creative writing style. On the other side, he is an Electronics and Communication Engineer from LPU, Jalandhar. In his leisure time, he likes to play badminton or read about space discoveries. Apart from this, he is a pro gamer on PC, PS and Mobile gaming platforms.

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