Spatiotemporal Variation and Trend Analysis of Surface Temperatures over Chennai City in India

The urban heat island (UHI) effect, a phenomenon where urban areas experience higher temperatures than their rural surroundings, was examined in Chennai using statistical methods to understand its impact on local climates. Significant trends in land surface temperature (LST) were identified for both urban and rural regions. In urban areas, a notable increase in LST was observed, with Kendall’s τ value of 0.714, indicating a strong positive trend. The annual average night LST in urban regions varied around 25°C, reaching a maximum of 25.9°C, whereas rural areas exhibited a lower average LST of approximately 23.5°C, with a maximum of 24.5°C. The urban heat island intensity (UHII) was also analyzed, showing an annual variation between 0.71°C and 1.43°C, with an overall mean of 1.15°C. The Mann–Kendall trend test demonstrated that the UHII was more pronounced during the winter season compared to summer. Kendall’s τ for UHII was 0.481 for winter and 0.333 for summer, reflecting a stronger trend in colder months. The maximum average UHII, recorded at 2.2°C, occurred during the winter of 2019. These results highlighted the seasonal variability and intensity of the UHI effect, with winter months showing the highest heat island intensity. The study provided valuable insights into the thermal differences between urban and rural areas, suggesting the need for sustainable mitigation strategies to reduce the impact of urbanization on local climates.