Context (NDTV): India is experiencing a severe heatwave coupled with high wet bulb temperatures.
The Dry bulb, Wet bulb and Dew point temperatures help understand the state of humid air.
What is the Wet bulb temperature?
It is also known as “isobaric wet-bulb temperature,” “thermodynamic wet-bulb temperature,” and “adiabatic saturation temperature.”
Wet bulb temperature is a meteorological term for the lowest temperature that can be reached by evaporating water into the air at constant pressure.
It is measured by covering a thermometer bulb with a wet cloth and letting the water evaporate.
As the water evaporates, it cools the thermometer, showing the wet bulb temperature.
This temperature helps measure humidity affecting things like comfort, farming and weather patterns.
Difference between Dry bulb and Wet bulb temperatures depends on the humidity of the air.
At 100% relative humidity, the wet-bulb temperature is equal to the dry-bulb temperature; at lower humidity, the wet-bulb temperature is lower than the dry-bulb temperature.
Sate wet bulb temperature
Internationally, the agreed-upon safe wet bulb temperature is below 30°C, and the highest limit is 35°C.
Between 30°C and 35°C, the human body undergoes hyperthermia, in which the body temperature increases, leading to discomfort and impacts on various organs, including the brain and the heart.
Currently, this is not captured in the IMD definition of a heatwave.
The dew point is the temperature the air needs to be cooled to (at constant pressure) to achieve a relative humidity (RH) of 100%. At this point, the air cannot hold more water in the gas form.
