Geographical and Climatic Factors Influencing Heatwaves | 17 May 2025

Source:TH 

Why in News?  

Andhra Pradesh and Telangana experience intense heat waves during summer due to a combination of unique geographical features and climatic conditions. 

How do Geographical and Climatic Factors Influence Heat Waves? 

• Geographical Factors: 
  • Latitude and Solar Intensity: Areas near the Tropic of Cancer, such as Andhra Pradesh and Telangana, receive intense solar radiation during summer when the sun is nearly overhead.  
    • This vertical solar incidence increases ground heating and raises temperatures significantly. 
  • Terrain and Surface Characteristics: Rocky and barren landscapes, such as the Deccan plateau in Telangana, absorb more heat compared to vegetated or moist surfaces.  
    • Black soils prevalent in these regions also retain heat longer, contributing to elevated daytime temperatures. 
    • Conversely, regions with dense vegetation or irrigated agricultural land experience cooling due to evapotranspiration (sum of all processes by which water moves from the land surface to the atmosphere via evaporation and transpiration) . 
  • Landlocked Regions: Landlocked regions, such as most of Telangana, experience higher heatwave risks due to the absence of nearby water bodies, leading to greater temperature variations, a pattern also observed in north-central and northwest India. 
    • The coastal regions experience moderated temperatures due to cooling effects from large water bodies, which have higher heat capacity and promote evaporative cooling. 
    • Urban Heat Islands, characterized by high population density, extensive concrete and asphalt surfaces, and limited vegetation, absorb and retain more heat, creating localized zones of elevated temperatures, which lead to more intense heat waves. 
• Climatic Factors: 
  • Rainfall and Humidity: Low pre-monsoon rainfall leads to dry soils and reduced moisture, limiting evaporative cooling (process of removing heat from a surface due to the evaporation of water).  
    • Minimal cloud cover increases solar radiation, raising surface temperatures leading to intense heat waves.  
    • High humidity worsens heat stress by reducing sweat evaporation, raising the heat index. 
  • Wind and Atmospheric Conditions: Weak winds during heat waves prevent heat from dispersing, causing it to build up near the ground and intensify surface temperatures. 
    • Stable atmospheric conditions can trap heat close to the ground (temperature inversion), prolonging and intensifying heatwaves. 
    • High atmospheric conditions, such as anti-cyclonic flows (high-pressure systems), promote clear skies, dry air, and sinking air masses that enhance surface heating and heatwave development. 
    • El Niño effect, and phenomena like the "Loo" wind contribute to the frequency and intensity of heat waves. 
      • El Niño weakens the monsoon-driving trade winds. This leads to reduced cloud cover and lower rainfall, causing dry soils and higher surface temperatures creating ideal conditions for heatwave formation and intensification. 
      • "Loo," is a hot, dry, and dusty wind that blows during the summer months 

What are Heat Waves? 

• About: Heat waves are periods of unusually high temperatures relative to the normal climate of a region.  
  • The threshold for declaring a heat wave varies by location, depending on the region’s historical temperature patterns. 
  • In India, Heat Waves occur mainly from March to June and in some rare cases even in July. The peak month of the heat wave over India is May. 
  • Heat Waves are not officially classified as natural disasters under the Disaster Management (DM) Act of 2005 despite their severe impacts. 
• India Meteorological Department (IMD) Criteria for Declaring Heat Wave: 

What is the Impact of the Heat Waves? 

• Impact on Human Health: Heatwaves lead to a surge in illnesses such as heat cramps, edema (swelling), syncope (fainting), heat exhaustion, and life-threatening heat stroke. 
  • The elderly, outdoor laborers, low-income groups, and people with pre-existing health conditions are especially at risk. 
  • According to the "Heat Watch 2024" report, 733 heatstroke deaths were reported across 17 Indian states between March and June. 
• Economy: Workers in industries like construction, mining, power plants, and refineries experience prolonged heat exposure, increasing health risks and reducing efficiency. 
  • High heat exposure results in the loss of up to 162 working hours annually for laborers engaged in heavy physical work, significantly impacting economic productivity. 
  • Heatwaves reduce air density, requiring aircraft to use longer take-off distances, simulating high-altitude conditions and increasing operational expenses and energy consumption. 
• Environmental Damage: Increased forest fires due to heat waves harm ecosystems and human settlements. 
  • Forest Survey of India has estimated that 21.4% area under forest is vulnerable to forest fires 
  • Heatwaves accelerate evaporation, reducing water availability and affecting agriculture, livestock, and livelihoods. 
• Agricultural Impact: Extreme heat stresses plants, stunts their growth, and can cause plant mortality, leading to lower yields and poor-quality produce, especially impacting Kharif crops like rice and threatening food security in affected states. 
  • 1 % increase in heatwaves led to a 15% reduction in crop yield in 2022, and  
    Every 1°C rise in temperature beyond 30°C during the grain filling period reduces wheat yield by 3–4%. In 2022, a 1% increase in heatwave events led to a 15% reduction in crop yield. 

What are India’s Initiatives to tackle Heat Waves Issue? 

• Heat Action Plans (HAPs): The Indian government has updated HAPS  across 23 states, aiming to strategically combat and manage heatwaves. 
  • HAPs typically include a region’s heat profile, past heatwave data, temperature trends, and vulnerability assessments to identify high-risk areas. 
  • They provide response plans with recommendations for mitigating heat wave impacts before, during, and after events, specifying roles for departments like disaster management, labor, and police. 
• IMD Heat Wave Warnings: India Meteorological Department issues following colour code impact-based heat warning jointly with National Disaster Management Authority. 

• Jal Shakti Abhiyan: Focuses on water conservation and restoring water bodies, crucial during heatwaves for hydration and urban cooling. 
• Smart Cities Mission: Promote green cover, water-sensitive urban design, and climate-resilient infrastructure.  Encourages creation of urban green spaces and cool zones. 
• Cool Roof and Urban Cooling Initiatives: Cool Roof programs (e.g., in Hyderabad) promote the use of reflective paints or materials to reduce indoor temperatures. 
  • States like Telangana, Gujarat, and Maharashtra have included cool roofs in building codes and public housing schemes.