Impact of rapid urban growth on heat and moisture islands in Pune City, India

The detailed horizontal structure of the heat and moisture islands of the Pune city is investigated. Changing shapes and intensities of warm and cool pockets and development of cliffs and plateaus at minimum temperature epoch are elucidated and also compared with similar aspects for Pune city documented in earlier studies. Dry and wet bulb temperature data obtained by whirling psychrometers in a mobile survey conducted in April 1997 formed the base of analysis. In total 9,9 routes were devised for moving observations to give data for 170 locations within the city region. Results indicate that at night, the core of the city appears as both heat and moisture islands whereas at the time of sunrise as heat and dry islands. Morphological variations in hill slope include barren, vegetated and residential area induced cool katabatic airflow of varying intensity as there has been formation of a cool pool in the first case, linearity in the main heat island in downwind direction in the second case and development of secondary warm pockets in the last one. Situated in a basin-like topography, the city experiences stronger influence of katabatic winds rather than the thermal circulation systems arising from spatial inhomogeneity in thermal and moisture patterns.