Seasonality of Surface Urban Heat Island in Delhi City Region Measured by Local Climate Zones and Conventional Indicators

Urbanization can change the local climate of an area, one manifestation of which is a rise in the local temperature of built-up areas, a phenomenon known as an urban heat island. The thermal response of built-up areas in comparison to natural areas is quantified in terms of surface urban heat island (SUHI) intensity. The work presented here evaluates the seasonal SUHI intensities in Delhi using local climate zones (LCZs) and conventional SUHI indicators in parallel. Statistical analyses are carried out to determine the relationship between them and to delineate heat stressed zones in the Delhi city region. The present study is the first one that utilizes LCZs for seasonal SUHI analysis in Delhi. The land surface temperature (LST) is assessed using a hundred and five night-time images from MODIS. Unambiguous night-time SUHI effect is seen for all seasons. The maximum night-time SUHI intensity is 3.5° C, between “compact low-rise” (LCZ 3) and “low plants” (LCZ D) in summer and winter. The conventional indicator “Inside urban-Inside rural” gives the highest night-time SUHI intensity of 3.3° C, in autumn. Statistical analyses show that “compact low-rise” (LCZ3) and “large low-rise” (LCZ8) are the most heat-stressed LCZs. The largest number of distinct thermal zones is created in the monsoon, followed by summer and winter. The results suggest that in order to minimize the UHI effect, further urban expansion in the Delhi region should be restricted to LCZ 5 (open mid-rise) and LCZ 6 (open low-rise).