Context:
Earlier in August, Iran recorded a scorching heat index of 70 degrees Celsius (°C) in the coastal part of the country, a metric at which survival of life is unfathomable, if not impossible. The country had also declared public holidays on August 2 and 3 on account of “unprecedented heat,” Reuters reported.
Relevance:
GS I: Geography
Dimensions of the Article:
- What is heat index?
- Heat Index Calculation: Understanding the Science Behind It
- The Significance of Measuring Heat Index
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.
Color Codes for Experimental Heat Index:
The Experimental Heat Index uses color codes to represent different ranges of “feel like” temperatures:
- Green: Experimental Heat Index below 35°C
- Yellow: Experimental Heat Index between 36°C and 45°C
- Orange: Experimental Heat Index between
Heat Index Calculation: Understanding the Science Behind It
Origins of the Formula
- Dr. Robert Steadman, a professor at Colorado State University, unveiled a complex formula for calculating the heat index in 1979.
- His work included two pivotal papers: “The Assessment of Sultriness – Part I: A Temperature-Humidity Index Based on Human Physiology and Clothing Science” and “Part II: Effects of Wind, Extra Radiation, and Barometric Pressure on Apparent Temperature.” These papers detailed his intricate calculations for the heat index.
Standard Assumptions
- Dr. Steadman’s study employs a hypothetical “typical adult human of either sex,” characterized by a height of 1.7 meters and a weight of 67 kg.
Dew Point’s Significance
- The heat index calculation places significant importance on the dew point, which marks the temperature at which gas transitions into a liquid state.
- In terms of atmospheric moisture, it signifies the temperature at which air becomes saturated with water vapor, leading to the formation of water droplets.
- Dr. Steadman’s calculations use a dew point of 14°C.
National Variations
- Various countries have devised their unique heat index systems instead of relying on Dr. Steadman’s formula.
- Canada, for instance, uses the “Humidex,” its distinct measure of heat index, based on specific criteria.
- The U.S. National Weather Service (NWS) utilizes its chart to determine the heat index.
- India’s Forthcoming Heat Index
- India is poised to launch its heat index in 2024, tailored to gauge the impact of heat on its population.
- This initiative will also generate location-specific, impact-based heat wave alerts, enhancing public safety.
The Significance of Measuring Heat Index
Effect of Temperature and Humidity
- As temperature increases, the air’s capacity to hold moisture rises, impacting the apparent temperature or heat index.
- Heat waves often coincide with elevated humidity levels, resulting in a heat index higher than the actual temperature.
- Humid air can make heat feel more intense to humans.
Heat-Related Stress
- High humidity can lead to heat stress, where the body struggles to dissipate excess heat.
- The human body typically maintains a core temperature between 36.1 to 37.2°C.
- Inability to shed excess heat can elevate heart rate, causing heat-related issues like exhaustion and rashes.
- If not addressed promptly, heat stress can be fatal.
The Role of Humidity
- At high temperatures, the body can cool itself through perspiration.
- However, in high humidity, it’s challenging for sweat to evaporate as the air is already moisture-saturated.
- Low humidity, on the other hand, supports efficient sweat evaporation, making the apparent temperature closely align with the actual air temperature.
Heat Index’s Value
- The heat index serves as a more comprehensive metric than mere temperature in assessing heat’s impact on humans.
- For instance, the U.S. National Weather Service’s chart illustrates that at 31°C, a 40% relative humidity calls for caution with prolonged exposure and physical activity.
- However, at the same temperature, a 95% relative humidity implies a risk of heat cramps, exhaustion, and heat stroke during prolonged exposure or physical exertion.
Addressing Extreme Heat
- Heat index values exceeding 67°C pose severe danger to individuals and animals with direct, prolonged exposure.
- As climate change drives record-breaking heat indices worldwide, preparations and adaptations are crucial.
- Strategies include investing in early warnings, adjusting work schedules, and implementing sustainable cooling solutions to combat extreme conditions.
-Source: The Hindu
