Spatio-temporal analysis of Karachi metropolitan as an urban heat island

Karachi occupies over 79 % of the geographically rugged and arid region. Urbanization has been increasing rapidly which is unplanned and uncontrolled. It is therefore a concrete jungle of buildings and infrastructures formed in Karachi. The built environment traps heat from the environment in its surroundings and thus heat accumulates. In existing research contagious metropolitan region of Karachi has been monitored. Landsat 8 and 9 images for May have been used. Remote sensing indices i.e., NDBI, NDVI, LST, and UHI were used to analyze for 2013, 2018, and 2023. Land cover change has also been measured through ArcGIS Pro. Observation-Based Environmental Surveying and Mapping (OBESM) were done in 2023 followed by weather data collected for 2013 and 2018. Interpolation (IDW method) has been performed in ArcGIS 10.8. The built-up index increased from 0.2, 0.3, and 0.39 in 2013, 2018, and 2023 respectively. NDVI ranges approx. 0.52 to −0.2 in years 2023 and 2013 respectively while for the year 2018 NDVI ranges from 0.42 to −0.1 approx. 0.52 is a good value for NDVI. The highest surface temperature range is recorded in 2018 i.e. 43.8–48.3 °C. The average temporal change between 2013, 2018, and 2023 for LST is 3.6 °C. A 3.9 °C rise in temperature has been recorded within the Karachi metropolis. The exact situation fits the UHI effect as through the analysis it has been assessed that the temperatures of Karachi metropolis reach up to 43.4 °C. Comparing the 2023 results to 2013 more hot spots of high temperatures emerged thus depicting LULCC affected the variations in weather activity. LULC classification estimated built-up land increased by 6.24 % from 2013 to 2023. TOA (2023) ranges from 8.51 to 11.5, BT (2023) ranges from 18 − 39.84 and, PVI (2023) ranges from 0.1 to 0.9. The existing study is novel and deals with NDBI, NDVI, LST, UHI, and LULCC through SC, TOA, BT, and PVI. This research will be signified in identifying the hotspots of urban heat islands and implementing the mitigation techniques. © 2024 COSPAR