URBAN HEAT ISLAND AND URBAN COOL ISLAND

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Context: A recent study conducted by researchers from the School of Earth Ocean and Climate Sciences at IIT Bhubaneswar.

Details

• Recent study conducted by researchers from IIT Bhubaneswar highlights the effect of urbanization on land surface temperature.
• Findings published in the journal Environment, Development and Sustainability.

Increased Land Surface Temperature:

• Urbanization has led to increased land surface temperature in Bhubaneswar and Cuttack over the past 20 years.
• Urban areas of Bhubaneswar and Cuttack are approximately 0.75°C and 1.22°C warmer than surrounding rural areas, respectively.
• Core city areas are warmer than recently developed suburban regions.
• Suburban areas in both cities have experienced rapid temperature changes, with suburbs witnessing almost twice the warming compared to the entire city.

Daytime Temperature Changes:

• Increase in relatively cooler regions during daytime in Bhubaneswar and Cuttack.
• Percentage of cooler fractional land cover during daytime has increased from 27% and 40% (2001-2010) to 73% and 63% (2011-2020) in Bhubaneswar and Cuttack, respectively.
• Factors contributing to the decline in daytime land surface temperature require further analysis.

Nighttime Temperature Changes:

• Urban areas exhibit the urban heat island effect during nighttime.
• Bhubaneswar experiences a surface urban heat island intensity (SUHI) of 0.75°C, while Cuttack experiences a SUHI increase of 1.22°C.
• Nighttime land surface temperature has shown a growth rate of 0.18°C and 0.13°C per decade for Bhubaneswar and Cuttack, respectively.
• Urban sprawl in the city's periphery contributes to the largest changes in trend.

Reasons for Temperature Changes:

• Daytime urban cool island observed in Cuttack during winter and pre-monsoon seasons, likely due to unique geographic features.
• Bhubaneswar exhibits weak daytime heat island effect during dry seasons with decreased green cover in surrounding areas.
• Nights are warmer in cities compared to surrounding regions, while daytime warming occurs in both cities and their surroundings.

Expansion of Hotspot Area:

• Increased area with nighttime land surface temperature higher than the 20-year climatological value.
• Bhubaneswar shows a higher expansion in the hotspot area compared to Cuttack due to unconstrained growth.

Implications and Conclusion:

• Urban heat island effect is not restricted to larger cities and affects smaller developing cities as well.
• Proper urban planning can help reduce urban heat island effect and vulnerability to heat in the future.

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