Heatwaves are a common meteorological phenomenon in India, particularly during the summer months. These events are characterized by prolonged periods of excessively high temperatures, often accompanied by hot and dry winds. India, due to its geographical location and diverse climate, experiences heatwaves that can have significant impacts on the population, agriculture, and various sectors of the economy

HEATWAVES AND IMD

• Defined based on the temperature thresholds over a region in terms of actual temperature or its departure from normal
• Heat wave is considered if maximum temperature of a station reaches at least 40 C or more for Plains and at least 30 C or more for Hilly regions.
• For coastal stations – When maximum temperature departure is 4.50C or more from normal, Heat Wave may be described provided actual maximum temperature is 370C or more
• In India, heat waves mainly occur during March to June and in some rare cases even in July  and peak in the month of  May
• Heat wave generally occurs over plains of northwest India, Central, East & north Peninsular India during March to June. It covers Punjab, Haryana, Delhi, Uttar Pradesh, Bihar, Jharkhand, West Bengal, Odisha, Madhya Pradesh, Rajasthan, Gujarat, parts of Maharashtra & Karnataka, Andhra Pradesh and Telengana. Sometimes it occurs over Tamilnadu & Kerala also
• 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.

Causes:

1. Geographical Factors:
   • India’s geographical location, with its vast plains and proximity to the equator, contributes to intense solar radiation and high temperatures.
   • The Thar Desert in the northwest further amplifies heat conditions.
2. Seasonal Winds:
   • Pre-monsoon months, especially May and June, witness the onset of heatwaves as the land heats up before the arrival of the monsoon.
   • Hot and dry winds, such as the Loo, exacerbate the heat during these periods.
3. Climate Change:
   • Climate change has led to alterations in weather patterns, contributing to more frequent and intense heatwaves.
   • Rising global temperatures have a direct impact on extreme weather events.

Characteristics:

1. Temperature Extremes:
   • During a heatwave, temperatures can soar well above the seasonal average, often exceeding 40°C (104°F).
   • Nighttime temperatures may remain elevated, providing little relief.
2. Duration:
   • Heatwaves can persist for several days to weeks, causing prolonged exposure to extreme heat.
3. Humidity Levels:
   • Heatwaves in India are often associated with low humidity levels, leading to dry and arid conditions.

Impact:

1. Health Impact:
   • Heatwaves pose severe health risks, leading to heat-related illnesses such as heatstroke, dehydration, and heat exhaustion.
   • Vulnerable populations, including the elderly, children, and individuals with pre-existing health conditions, are at higher risk.
2. Agriculture:
   • Prolonged exposure to high temperatures can adversely affect crops, leading to heat stress and reduced yields.
   • Water scarcity during heatwaves exacerbates the impact on agriculture.
3. Water Resources:
   • Heatwaves contribute to the evaporation of water bodies, reducing water availability.
   • Drying up of rivers and reservoirs can impact water supply for agriculture and urban areas.
4. Energy Consumption:
   • Increased demand for cooling, especially in urban areas, raises energy consumption during heatwaves.
   • Overreliance on air conditioning contributes to increased greenhouse gas emissions.
5. Livestock Impact:
   • Livestock faces heat stress, impacting milk production and overall animal health.
   • Adequate water supply becomes crucial for the well-being of animals.

Preparedness and Mitigation:

1. Early Warning Systems:
   • Meteorological agencies issue heatwave alerts to provide advance notice to the public and authorities.
   • Awareness campaigns help people prepare for extreme heat conditions.
2. Urban Planning:
   • Urban planning measures, such as green spaces, tree planting, and cool roofs, aim to mitigate the urban heat island effect.
   • Building designs that promote natural ventilation and energy-efficient cooling are encouraged.
3. Healthcare Infrastructure:
   • Adequate healthcare facilities, with a focus on heat-related illnesses, are crucial during heatwaves.
   • Public health campaigns educate people on staying hydrated and cool.
4. Water Management:
   • Efficient water management practices, including water conservation and storage, are essential to mitigate the impact on agriculture and water resources.
5. Community Engagement:
   • Community involvement in disaster preparedness and response is crucial.
   • Outreach programs educate communities on coping strategies and the importance of staying hydrated.
6. Climate Adaptation:
   • Long-term climate adaptation strategies involve addressing the root causes of climate change, reducing greenhouse gas emissions, and building resilience in vulnerable communities.

Recent Trends:

1. Increasing Frequency:
   • There is a noticeable trend of increasing frequency and intensity of heatwaves in India in recent years.
   • Climate models predict a continued rise in the occurrence of extreme heat events.
2. Urban Heat Islands:
   • Rapid urbanization contributes to the creation of urban heat islands, where cities experience higher temperatures than surrounding rural areas.
   • Urban planning strategies aim to counteract this effect.

Heatwaves are a recurring climate challenge in India, requiring a multi-faceted approach involving meteorological monitoring, public awareness, and adaptive measures across various sectors. As climate change continues, understanding and addressing the impacts of heatwaves become increasingly important for sustainable development and the well-being of the population.