33WAF/29NWP Dynamic Assessment of Delhi's Urban Heat Island Considering the Urban Sprawl Over the Past Three Decades

Urban expansion is a major global phenomenon, particularly in emerging countries where population growth coincides with rapid city growth, driving the extension of built-up regions. Urbanization frequently results in an increase in impervious surface area, which increases thermal energy and reduces thermal comfort. The Urban Heat Island (UHI) effect, which causes localized heating in urban areas when compared to rural areas, is a critical consequence of this urban expansion. This effect is mostly caused by the removal of natural vegetation and the installation of impermeable surfaces, including buildings and roads, which retain and absorb heat. The UHI impact is often more noticeable at night due to the persistence of human activity and the intensity of artificial illumination. This study examines the link between urban development and the intensification of the UHI effect during the past three decades, with a focus on the Delhi National Capital Region (NCR), one of India's fastest-growing metropolitan cities. The geographical and temporal dynamics of urban expansion and UHI intensity in the region were examined using the MODIS global land cover product (MCD12Q1.061) with a resolution of 500 meters and the aqua MODIS daily land surface temperature (LST) data (MYD11A1.061) with a resolution of 1000 meters. It was observed that Delhi NCR's built-up area increased significantly between 2001 and 2021, rising from 1375 km² to 1548 km² in 2011 and finally to 1650 km² in 2021. The percentage increase was found to be 12.6% from 2001 to 2011 and 20% by 2021 from 2001. The night-time LST data is used to quantify the UHI intensity, which has increased in tandem with this rapid urban expansion. The intensity of urban heat islands (UHIs) increased from 1.22°C in 2001 to 1.87°C in 2021, suggesting that urban areas are experiencing more thermal stress. To achieve an accurate representation of geographical patterns of UHI intensity, the Dynamic Equal Area (DEA) technique is used to establish buffer zones surrounding the NCR region. This approach avoids bias by generating a homogeneous buffer that accurately depicts the spatial patterns. The outcomes of this study highlight the critical need to address the growing UHI effect in rapidly urbanizing areas such as Delhi NCR.

Keywords: Urban expansion, Urban Heat Island (UHI), Dynamic Equal Area (DEA)