Spatiotemporal change in urban landscape and its effect on behavior of diurnal temperature range: a case study of Pune District, India

Urbanization plays a crucial role in the urban landscape dynamics, contributing to numerous ecosystems and urban climate changes. Diurnal variation of land surface temperature (LST) is a significant index for estimating local climate change as a response to urbanization. This research analyzes the impact of urbanization on the LST-based diurnal temperature range (DTR) for Pune, India, in three steps: (a) detection of spatiotemporal variation in DTR, (b) assessment of DTR behavior in different land use and land cover (LULC) classes, and (C) examining the interrelationship between urban density and DTR. The study utilizes a time series LST estimates from the MODIS satellite for 12 years (2003-2014). The preliminary spatiotemporal assessment shows a decrease in annual averaged DTR across Pune, from 25.79 degrees C in 2003 to 21.82 degrees C in 2014. Further investigation in LULC classes revealed a similar downward non-monotonic DTR trend in all classes except for the Built-up class, exhibiting a significant monotonous downtrend with a decrease of 5.67 degrees C, and the DTR anomalies are also consistent with this trend. The Mann-Kendall test confirms a significant trend with a p-value of 0.029, and Sen's slope analysis with - 0.167 establishes a decreasing DTR trend with a negative slope. The evaluation of urban density in Pune Metropolitan Region (PMR) for DTR variation shows a rise in area under DTR (below 17 degrees C) in the Dense Built-up class from 0.1 to 7.52% across 2003-2014. Whereas DTR (above 25 degrees C) in Less Dense Built-up saw a sharp decrease in the area from 16.37 to 0.05% during the same period. Thus the DTR trend in varying urban densities signifies the role of intense urbanization on DTR behavior. These findings are alarming and provide insight into the local climate issues that should help policymakers and urban planners to make informed decisions toward sustainable development in the Pune Metropolitan Region.