Nights getting warmer in Hyderabad, thanks to urban heat island effect

HYDERABAD: Nights become unbearable in the summer, especially during powercuts and one reason behind it is the Urban Heat Island (UHI) effect, which becomes pronounced at nights. This results in the city becoming warmer than its surrounding areas making the city a ‘heat island’.  N Sridhar, pursuing his postdoctoral research at Geography and Geoinformatics department in OU said, “The heat absorbed across the day by land and man-made structures in city like buildings, is emitted during the night.

With urban areas getting more concretised, the heat absorbed in the course of a day is higher than the peri-urban areas. As a result, the heat emitted at night by a city is also higher than the surrounding areas. Even in a city, the heat absorbed in a day and emitted at night varies from one place to another depending on the land use pattern in different areas. The variation can be in the range of 5-6 degree Celsius.” Keeping the rapid concretisation of the city, it should not come as a surprise that as part of a study conducted by Sridhar, , the variations in temperature from core areas of Greater Hyderabad to its suburbs was 7-8 degree Celsius.

The study titled, ‘Seasonal Analysis of Urban Heat Island of Greater Hyderabad Using Thermal Remote Sensing’ published recently in Journal of Remote Sensing & GIS, reports that while the average Land Surface Temperature at night in densely built up areas of the city was 29.11 degree Celsius, it was recorded at 21.69 degree Celsius in a rural area outside the city, which is a difference of 7.420C.

The study notes, “The boundary of urban heat island night time to a greater extent coincides with city limits.” It also notes, “The urban heat island formation is more conspicuous during night time because rural areas cool off faster at night time than cities.”  and therefore maximum urban heat island effect.”

What is UHI?

UHI is based on the concept that as urban areas develop, open spaces like agricultural lands, forests or lakes in a city are replaced by man-made structures.