HEAT INDEX
WHY IN NEWS ?
- Recently, Iran recorded a scorching heat index of 70 degrees Celsius (°C) in the coastal part of the country.
MORE ABOUT THE NEWS:
- Iran had declared public holidays on August 2 and 3 on account of “unprecedented heat”.
- This is not the first time this year that Iran is dealing with extreme heat.
- In July, U.S.based weather observer Colin McCarthy reported that the Persian Gulf Airport recorded a heat index of 66.7 °C.
WHAT IS HEAT INDEX ?
- Heat index, also known as apparent temperature, is a measure of how the temperature feels to humans.
- Relative humidity is an important factor that determines heat index, along with air temperature.
MEASURING HEAT INDEX :
- Dew point, which is the temperature at which gas is transformed into a liquid state, is an important factor in the calculation of heat index.
- In terms of atmospheric moisture, it’s the temperature at which air cannot hold any more water vapour, and droplets of water begin to form. Dr. Steadman used 14 °C as the dew point in his calculations.
IMPACT OF HIGH HUMIDITY AND EXTREME HEAT:
- High humidity can lead to heat stress, meaning the body is unable to get rid of excess heat.
- Humans usually maintain a core temperature in the range of 36.1 to 37.2 °C.
- When the body is unable to get rid of excess heat, the heart rate increases due to a rise in core temperature, leading to heat related exhaustion and rashes, among other symptoms.
- It can also be fatal if not addressed promptly.
- At high temperatures, the human body can lose excess heat through perspiration and cool itself.
- But when humidity is high as well, it is difficult to sweat and then for that sweat to evaporate because the air around is already saturated with moisture.
- This makes it difficult for the body to lose heat.
- On the other hand, if the humidity is low, evaporation of sweat is easier, thus making the apparent temperature feel close to the actual air temperature.
- This is why a measure of heat index is more useful than just the temperature to gauge the impact of heat on humans.
SYLLABUS: PRELIMS, ENVIRONMENT
