Spatiotemporal trends of land surface temperature and surface urban heat island intensification across India.
Dense population, rapid urbanization, and industrialization make India a highly vulnerable country to the consequences of global warming. This study examines spatiotemporal trends of diurnal land surface temperature (LST) over the past 25 years (2000-2024) and analyzes the surface urban heat island (SUHI) intensities across the country and for 50 major cities, respectively, including the influence of zonal biogeography. The significance of the LST trends is statistically confirmed by using the Mann-Kendall test and zonal heterogeneity is analyzed by using ANOVA test. The study covers total span of 25 years (2000-2024) which is classified in two periods, pre-COVID-19 years (2000-2019) and including the post-COVID-19 years (2000-2024). In the period from 2000 to 2019, the mean LST variability range (minimum to maximum) has substantially widened by 7.8 °C and 2.3 °C for daytime and nighttime, respectively. The LST change during the COVID-19 period was significantly hindered; the change in daytime and nighttime LST for May month was 0.18 °C and 0.04 °C, respectively, whereas during 2020-2024, it has become -1.24 °C and -0.2 °C, respectively. In general, the zones follow the country-level LST trends for 2000-2019 as well as for 2020-2024 periods, with variable LST change rates. The highest annual daytime LST growth (+ 0.15 year-1) is observed for the Desert (DES) zone, whereas the highest nighttime LST rise (+ 0.07 year-1) is observed for the Western Ghats (WG). Notably, the Himalaya and Trans-Himalaya (HTH) zones exhibit negative LST growth rate (-0.08 and -0.09 for daytime and nighttime, respectively). Further, SUHI analysis indicates that the cities within theIndo-Gangetic Plain (IGP), Semi-Arid Region (SAR), Deccan Plateau (DP), and Western Coastal Region (WCR) zones are found to be largely impacted by SUHI intensification, ranging between 1 and 5 °C for daytime as well as nighttime. Interestingly, even trivial SUHI values of DES cities (1-3 °C for daytime) could be consequential, as the zonal LST is extremely high. The study points out the requirement of urgent policy intervention and mitigation measures.