Impact of urbanisation on urban heat island intensity during summer and winter over Indian metropolitan cities

Industrial and economic development along with the rapid growth in urban population over the global cities is generating a warmer inner core in comparison to the surrounding natural landscape, the common feature of the phenomena of urban heat island (UHI). In the earlier part of the study, the spatial relationship of the changes in the land cover types and land surface temperature (LST) is analysed for metropolitan cities of India during winter season using remote sensing techniques. In the present study, an attempt has been made to estimate the UHI intensities over the metropolitan cities of India during summer season. The LST estimated using the Landsat 7 ETM+ images reveals the presence of a unique form of surface UHIs in the dense built-up areas of different cities. The intensities of UHIs over these cities during summer season are noticed to be in the range of 10.5-14 degrees C. Delhi possesses the highest UHI intensity in the range of 13.4-14.0 degrees C, and Kolkata possessed the lowest UHI intensity in the range of 10.5-11.7 degrees C. Higher-temperature zones (hotspots) are noticed to be increasing within the builtup areas and barren lands. The temperature of hotspots for the northern cities Delhi and Jaipur is observed to be in the range of 45-50 degrees C and is highest among the cities under consideration. On comparison with the winter results, the LST ranges, UHI intensities and the hotspot ranges for summer season are found be noticeably higher. The LST distribution and the UHI pattern of these cities are found to different during summer season in comparison to the winter season.