68 dead in Ballia amid heatwave: How high temperatures combined with high humidity can be fatal
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68 dead in Ballia amid heatwave: How high temperatures combined with high humidity can be fatal
Subject: Geography
Section: Physical geography (Climatology)
Context:
- Amidst the scorching heatwave conditions, the temperatures soar up to 43.5 degrees Celsius in the eastern Uttar Pradesh region.
Details:
- The IMD in its forecast mentioned that Ballia’s maximum temperature on Monday (June 19) is likely to touch 45 degrees Celsius but would come down by 2 degree Celsius the next day.
- The mercury in the city is expected to go below 40 degrees Celsius only after June 22.
What are heat waves?
- A Heat Wave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India. Heat Waves typically occur between March and June, and in some rare cases even extend till July. The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, sometimes resulting in death.
- The Indian Meteorological Department (IMD) has given the following criteria for Heat Waves :
- Heat Wave need not be considered till maximum temperature of a station reaches atleast 40°C for Plains and atleast 30°C for Hilly regions
- When normal maximum temperature of a station is less than or equal to 40°C Heat Wave Departure from normal is 5°C to 6°C Severe Heat Wave Departure from normal is 7°C or more
- When normal maximum temperature of a station is more than 40°C Heat Wave Departure from normal is 4°C to 5°C Severe Heat Wave Departure from normal is 6°C or more
- When actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, heat waves should be declared. Higher daily peak temperatures and longer, more intense heat waves are becomingly increasingly frequent globally due to climate change. India too is feeling the impact of climate change in terms of increased instances of heat waves which are more intense in nature with each passing year, and have a devastating impact on human health thereby increasing the number of heat wave casualties.
About Heat Index:
| Topic | Information |
| What is the heat index? | The heat index is the combination of air temperature and relative humidity, it is the measure of how hot it really feels when relative humidity is factored in with the actual air temperature. |
| Aim of the new index | To quantify the impact of heat on its population and generate impact-based heatwave alerts for specific locations. |
| Parameters to be used | Temperature, humidity, wind, and duration of exposure |
| Significance | The analysis will help generate heat hazard scores, which will be used as thresholds to issue impact-based heatwave alerts for specific locations. |
| Heat Waves in India | According to IMD data, there was a 24% increase in the number of heat waves during 2010-2019 compared to 2000-2009. Between 2000 and 2019, the mortality rate for tropical cyclones decreased by 94% whereas it increased by 62% for heat waves. Heat waves is not notified as a natural disaster at the national level in the country. |
| Impact of heat waves | Heat waves cause cramps, exhaustion, stress, heat stroke and very severe heat waves even lead to death. The elderly, children, and people with heart and respiratory problems, kidney diseases and psychiatric disorders are particularly affected. Extreme periods of high temperatures can lead to a significant reduction in crop yields and cause reproductive failure in many crops. |
Why do heat waves cause deaths?
- High temperatures alone aren’t fatal in nature. It’s when high temperatures are combined with high humidity, known as the wet bulb temperature, heatwaves become lethal.
- Humans lose heat generated within their bodies by producing sweat that evaporates on the skin. The cooling effect of this evaporation is essential in maintaining a stable body temperature.
- As humidity rises, sweat does not evaporate —just like clothes take a long time to dry in humid locations – and makes it difficult to regulate body temperature. And this could cause a heat stroke, which takes place only when the body temperature goes above 40 degrees Celsius.
- What happens is that excessive heat increases metabolic activity in the body, leading to a drop in blood pressure and oxygen levels with increased sweating — this is a condition called hypoxia.
- Metabolism goes haywire (in such conditions), creating a toxin overload which affects multiple organs. At that stage, things are extremely difficult to manage outside ICU care.
- Prolonged exposure to even moderate heat, with poor nutrition and hydration levels in these circumstances, can lead to hypoxia. Those with pre-existing metabolic disorders like diabetes, the obese or the elderly, are more vulnerable.
