What is a heatwave ? Why is it caused ? What are its impacts?

 Why is it in the news ?

1.Intense heat is sweeping large parts of India in April with maximum temperature going to 4-6 degree C above normal in many areas. Parts of Odisha, Rayalaseema (Andhra Pradesh), Gangetic West Bengal, Jharkhand, Vidharbha, Chhattisgarh, Madhya Pradesh, Telangana, Tamil Nadu and Gujarat are experiencing heat waves. The number of days of heatwaves are also increasing with the passage of every year. 

2.This phenomenon is not restricted to India but it has impacted south and south east Asia. Authorities in Bangladesh were forced to close schools twice over the last two weeks amid the heat waves when the temperature soared to 110 degree F. Similarly, several parts of Myanmar have recorded high temperatures of more than 115 degree F. In the Philippines authorities had to close schools due to soaring temperatures. In Thailand, Vietnam the heat waves are causing disruption in the normal life of the people. 

What is a heatwave ?

1.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 part of India. Heat waves typically occur between March and June, and in some cases it may extend to July. The threshold of a heat wave is met when the maximum temperature of a station reaches at least 40 degree C in plains, 37 Degree C in the coastal areas and 30 degrees C in the hilly region and the departure from the normal is at least 4.5 degree C. A severe heat wave is declared if the departure from the normal temperature exceeds 6.4 degree C. 

2. Heat wave is a condition of air temperature which becomes fatal to the human body when exposed. 

3.When the actual temperature of a station goes 45 degree C, it is called a heat wave  and when there is an increase of 2 degree C or more it is called a severe heat wave.

4.If there is an increase of 4 to 5 Degree C in the normal temperature for two consecutive days it is called a heat wave.  

What is the difference between loo wind and heat wave?

1.A loo is a strong dusty, gusty hot and dry summer local wind from the west which originates from the Thar desert and blows over the Indo Gangetic region of northern India and Pakistan in the month of May and June. It lacks humidity.  It is a local dry wind of India and Pakistan like the dry winds of foehn of Europe and Chinook of North America. In loo, the temperature may go to 45 degree C to 50 degree C and even more. 

2.A heat wave is a period of excessively hot weather which may be accompanied by high humidity especially in oceanic climate countries and coastal areas. There is a lack of wind blowing and it remains stagnant. In heat waves the temperature is measured in comparison to the previous year and the sudden rise of 4.5 degree C from the normal temperature of a station. 

What are the causes of heat waves ? 

1.High pressure systems - Heat waves are formed when high pressure at the altitude of 3000 to 7600 metres remains over a region for several days to several weeks. High pressure systems force air downward. This force prevents air near the ground from rising. The sinking air acts like a cap. It traps warm ground air in place. This high concentration of pressure makes it difficult for other weather systems to move into the area. The high pressure inhibits winds. It also prevents clouds from entering the region. The end result is a continuous buildup of heat at the surface that people experience as a heat wave. 

When high pressure systems settle over an area, they suppress cloud formation and trap heat at the surface leading to rising temperatures. 

2.Large scale weather patterns - global weather patterns can influence regional climates. For example- a persistent shift in wind patterns can bring hot air masses to a particular area.

3.Rising global temperature - due to climate change contributes to more intense and frequent heat waves. 

4.Scholars are of the view that the rise in the temperature of the central Pacific ocean is causing heat waves in south and southeast Asia. 

Impact of heat waves -

1.It causes 

• Heat cramps 

• Edema (swelling)

• Syncope (fainting)

• High Fever 

• Fatigue

• Weakness

• Dizziness 

• Headache

• Nausea 

• Vomiting

• Muscle cramps

• Sweating

• Heat stroke when the body temperature increases to 40 degree C or 104 Degree F or more along with delirium, seizures or coma.

• Dehydration

Heat waves in India cause thousands of deaths every year. 

• Heat waves would impact the poor the most. It is likely to cause crop damage, leading to the miserable life of the farmers.

Remedy -

1.Stay hydrated : drink plenty of water and cooling beverages throughout the day. 

2.Avoid exercising or working outdoors during the hottest part of the day.

3.Wear loose lightweight clothing, cotton fabric to allow sweat to evaporate, take cool showers or baths regularly. 

4.Avoid alcohol tea,coffee and carbonated soft drinks which dehydrates the body. 

5.Distribution of oral rehydration solution.

6.Provision of cool drinking water at public places.

7.Closure of schools and colleges during peak hours.

8.Providing access to parks and other shaded places to people.

9.Regulation of construction activities.

10.Avoidance of non essential activities during the peak hours of heat waves. The timings of school, colleges and office should be tweaked. 

11.All organised outdoor activities like sports should be regulated. 

12. To cut the greenhouse gas (carbon dioxide, methane, ozone, nitrous oxide, chlorofluorocarbons and water vapour) emission and encourage renewable sources of energy. 

13. Planting of trees