Study of intra-city urban heat island intensity and its influence on atmospheric chemistry and energy consumption in Delhi

Urban heat island intensity (UHII) has been determined as difference in air temperatures between two locations of Delhi namely Safdarjung (SAFD) and National Physical Laboratory (NPL) regions which represent urban and sub-urban areas respectively. High UHI has been obtained in morning time as compared to day and night times, with the highest magnitude ranging from 2.8 to 3° C in spring (MAM), autumn (SON) and winter (DJF) seasons in morning hours (0700-0900 h). Monsoon season (JJA) shows less UHII values compared to other seasons. Wind speed reduced the UHII. Larger impervious area (i.e. 67.2% in SAFD as compared to 33.4% in NPL), lesser vegetated area (i.e. 32.8% in SAFD as compared to 66.6% in NPL) and low Normalized Difference Vegetation Index (NDVI) value (0.15 in SAFD as compared to 0.24 in NPL) in SAFD area supports the existence of UHI there. Ambient O3 concentrations show maximum values during April and May for both regions and remain insignificantly influenced by UHI. Intra city temperature difference of 0.2-3 °C is capable of raising electricity demand by 37.87-1856 GWh over the base electricity requirement of the city with corresponding increase in CO2 emissions by 0.031-1.52 million ton.