HYDERABAD: The next time someone tells you that Hyderabad is a furnace, tell them that they’re not far off the mark. Urban Heat Island (UHI) effect on the city has been talked about for long but now researchers from Indian Institute of Technology (IIT)-Kharagpur have quantified the UHI impact on Hyderabad and the results have surprised quite a few.
Satellite-based thermal remote sensing images of area under Greater Hyderabad Municipal Corporation (GHMC) limits were used. Continuous storage of heat in surfaces of urban conglomerates leads to a rise in mercury. As a result, areas outside its boundary are relatively cooler, turning the city into an urban heat island, explained Srikanta Sannigrahi, lead researcher of the study and PhD scholar at Department of Architecture and Regional Planning, IIT Kharagpur.
Hyderabad burning up
The IIT researchers found UHI Intensity data for area under GHMC limits and divided it into five intensity classes - green island (GI), weak heat island (WHI), medium heat island (MHI), strong heat island (SHI) and extremely strong heat island (ESHI).
The study reported that area under ESHI intensity increased from being just under 1 per cent in 2002 to almost 6 per cent in 2015. Area under SHI increased from 4 per cent to almost 24 per cent. City under MHI increased from 19 per cent to 48 per cent. Land use and land cover changes (LULC) were also noted in the research.
Under vegetation area in GHMC limits decreased from 21.3 per cent in 2002 to just 10.18 per cent in 2015. The area with infrastructure rose from 41.35 per cent in 2002 to 62.87 per cent in 2015. In the same period the area under Urban green space decreased from 11.45 per cent to 6.15 per cent. Area under water bodies decreased from 1.86 per cent to 1.33 per cent. Moreover, farmland temperatures decreased from 20.26 per cent to 5.17 per cent. While fallow land heat rose from 5.66 per cent to 14.3 per cent.
While maximum temperatures did not show an increasing trend, the mean LST in built up areas, increased from 25.5 degree Celsius in 2002 to 26.2 degree Ceslius. A reason behind it is the increase in minimum LST. In built up areas, minimum LST increased from 16.1 degree Celsius to 18.7 degree Celsius. In areas covering aquatic vegetation, it rose from 16.3 to 19.1 degree Celsius.
Farmland heat saw an increase from 17.1 to 19.7 degree Celsius. Under fallow land, mercury rose from 16.5 to 19.4 degree Celsius. Green spaces became hotter from 16.6 to 19.0 degree Celsius.
Land Surface Temperature up
The IIT study also found that Land Surface Temperature (LST) increased by a whopping 1-1.5 degree Celsius, in just 13 years between 2002 and 2015 in various areas of Hyderabad
What is UHI?
Urban Heat Island (UHI) is a man-made phenomenon. It occurs when land under concrete increases while land area under vegetation, farms and water bodies decreases. As a result there is a decrease in evaporative cooling in the process of heat exchange between earth and atmosphere. This results in excessive storage of heat in surfaces which increases Land Surface Temperature(LST).