Assessing thermal environmental changes of a semi-arid city using multi-temporal LCZ approach: a case study of Pune, India.

The unprecedented growth of urbanization demands making cities and human settlements inclusive, safe, resilient, and sustainable. The present study is the first multi-temporal local climate zones (LCZ) mapped in India. It is used to assess the spatio-temporal growth of the city over the past two decades and its impact on its thermal environment. Pune is a Class-I semi-arid city that witnessed rapid urban sprawl between 2005 and 2020 and still continues to grow. It was found that the built-up area increased from 31% to 68.3% while the natural land cover area decreased from 69 to 31.7%. As a result, LST decreased (increased) significantly at a rate of 0.2 ℃/year (0.1 ℃/year) during the day (night), respectively. Near the city center, where built-up density increases in an existing built-up area, both LST increase around 0.1 ℃/year (0.03-0.06 ℃/year) in the day. However, when natural barren land turned into built-up, LST decreased (increased) at more than 0.2 ℃/year (0.1 ℃/year), respectively. Barren lands converted to industrial areas are showing a significant increase in LST at a rate of 0.4-0.8 ℃/year (0.12-0.16 ℃/year), respectively. The dried-up parts of the river show significantly increasing LST at a rate of 0.3 ℃/year (0.03 ℃/year), respectively. We also note that plantation programs do indicate a cooling effect. Overall, the changes in LST are dependent on the type of LCZ and its transformation into different categories. The results from this case indicate that peripheral zones of the city are experiencing rapid and significant changes and have implications for policy and city planning.