6. Role of Local Level Relative Humidity on the Development of Urban Heat Island Across the Delhi Metropolitan Region

In the present study we have analyzed the spatial patterns of local level atmospheric humidity levels across the Delhi Metropolitan Region (DMR). Hourly measurements of temperature and humidity conditions were collected over a 1 year period from May 2007 to June 2008 across 13 stations in the DMR. The results of our study revealed substantial variations in the spatial distribution of humidity levels, with pockets of higher humidity clustered around the River Yamuna and central sections of the DMR. Relatively lower levels of humidity were observed in the west and eastern sections of the DMR. The spatial patterns of humidity across the study area were determined by the local level land-use as well as the seasonal level atmospheric conditions. For instance, the minimum spatial variations in humidity levels were observed during the monsoon season due to predominantly cloudy conditions, compared to the summer months when maximum spatial variations were observed due to predominantly clear sky conditions. Lower levels of humidity also overlapped with dense built-up multi-family residential areas in the east and western sections of the DMR.