Bangalore: Urban heating or urban cooling?

Abstract Bangalore, one of the Indian metropolitan cities, has witnessed rapid urbanization during the last decade with an overwhelming spatial growth of 696 sq. km to 2185 sq.km within a span of ten years (2006 to 2016). With this exponential rate of urban growth, the city is experiencing a shift in its micro- climatic condition. This paper aims to identify the surface urban heat island (SUHI) effect by comparing normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI) and the fraction of impervious surface area (ISA) as indicators of SUHI. Landsat 8 datasets were used to estimate the land surface temperature (LST) for two different seasons representing winter (January) and summer (April) using radiative transfer algorithm. A spatial map of ISA was generated using normalized spectral mixture analysis (NSMA) showing a standard error of 9.25%. Correlations between NDVI, NDBI and fraction of ISA with LST indicate a strong linear negative relationship between LST and ISA with a coefficient of correlation 0.85 and 0.94 s for January and April respectively and is contrary to the conventionally accepted positive SUHI phenomenon. The relationship between LST and NDVI was in particular negative at areas bearing high NDVI values. Results indicate that ISA is quantitatively a better metric indicating that the city experiences cool island effect indicative of high vegetative cover presence in the Bangalore Urban (BU) area. Also, NDVI is greatly affected by seasonal variation and NDBI shows mixing of soil characters and hence failed in providing conclusive results.