What is Heat Wave?

What’s in today’s article?

• Why in News?
• What is Heat wave?
• What is Criterion for Declaring Heat wave?
• How India Meteorological Department (IMD) Monitors the Heat wave?
• How Does Heatwave Affect Human Body?
• How to Avoid Heat Stroke?

Why in News?

• Amid heatwave deaths being reported in parts of the country, Union Health minister Mansukh Mandaviya held a meeting with senior officials of the India Meteorological Department, National Disaster Management Authority, and the Health ministry.

What is Heat wave?

• Qualitatively, heat wave is a condition of air temperature which becomes fatal to human body when exposed.
• Quantitatively, it is defined based on the temperature thresholds over a region in terms of actual temperature or its departure from normal.
• In certain countries it is defined in term of the heat index based on temperature and humidity or based on extreme percentile of the temperatures.

‹ ›

What is Criterion for Declaring Heat wave?

• Heat wave is considered if maximum temperature of a station reaches at least 40⁰C or more for Plains and at least 30⁰C or more for Hilly regions.
• For coastal regions –
  • When maximum temperature departure is 4.5⁰C or more from normal, Heat Wave may be described provided actual maximum temperature is 37⁰C or more.
• Period of Heat wave over India –
  • It is occurring mainly during March to June and in some rare cases even in July. The peak month of the heat wave over India is May.
• Heat wave prone areas of India –
  • Heat wave generally occurs over plains of northwest India, Central, East & north Peninsular India during March to June.

How India Meteorological Department (IMD) Monitors the Heat wave?

• IMD has a big network of surface observatories covering entire country to measure various metrological parameters like Temperature, Relative humidity, pressure, wind speed & direction etc.
• Based on daily maximum temperature station data, climatology of maximum temperature is prepared for the period 1981-2010 to find out normal maximum temperature of the day for particular station.
• Thereafter, IMD declared heat wave over the region as per its definition.

How Does Heatwave Affect Human Body?

• We all feel drained and tired after stepping out on an extremely hot day.
• This is referred to as heat exhaustion, which happens when the body sweats excessively to keep the core temperature low.
• A heat stroke happens when the ambient temperature is so high that the body is unable to sweat to regulate the core temperature, which shoots up to 40⁰C.
• In these cases, there is a severe imbalance of salts such as sodium and potassium in the body.
• The high core temperature coupled with salt imbalances disrupts organs, leading to a host of symptoms.
• It can affect the brain, making a person foggy, drowsy, and in severe cases may also lead to a person going into a coma.
• It can lead to kidney and liver damage as well. A cascade of such symptoms leads to death due to heat stroke.

How to Avoid Heat Stroke?

• The primary aim should be to bring down the core temperature of the body fast.
• This can be done by pouring cold water over the person, making them drink cold drinks, and giving them electrolytes to balance salt levels.
• To prevent heat stroke, it is better to avoid stepping out in direct sunlight, especially between noon and 3 pm. You should avoid strenuous activity during this time.

Q1) What is a heat dome?

A heat dome is caused when atmosphere traps hot ocean air, as if bounded by a lid or cap. Heat domes happen when strong high pressure atmospheric conditions combine with the influence of a La Niña.

Q2) What do you mean by temperature inversion?

A temperature inversion is a layer in the atmosphere in which air temperature increases with height.

Source: Heatwave deaths: Why a heat stroke kills, and how to stay safe | IMD