March 5, 2009 11:29:11 pm
If the summer feels harsher than usual this year,its not without a reason: while the mercury hovers around 37°C,Mumbai has also been recording a rather high heat index exceeding 40°C in several areas,over the past two days.
The weather station at IIT Powai,which is part of the Brihanmumbai Municipal Corporations rainfall monitoring system,showed that the heat index soared close to 43°C at 1 pm on Monday. On the Powai campus,the heat index has been rather high 41.9°C on Monday noon; and on Tuesday at 39.1°C at 11.51 am and 42°C at 1.18 pm.
Heat index,also called apparent temperature,is the temperature being felt by the human body,and is measured by adding the relative humidity to the actual air temperature.
According to Kapil Gupta,associate professor,civil engineering,temperature in built-up urban areas is increasing because of increased concretisation and the subsequent reflected heat from these surfaces. Use of air-conditioners and automobiles also contribute to increased temperature.
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Gupta attributes these high temperatures to the urban heat island phenomenon. Quoting from a review that his team has compiled from the available literature,he said,climatic changes in the urban areas are vastly dependent on factors like concretisation,blockage in air flow owing to concentration of high-rises,increased use of vehicles etc. Besides making the atmosphere warmer,these factors also affect cloud movement and result in increased rainfall.
He said studies have indicated that developed urban areas tend to be warmer by 1-10°C than the surrounding sea-facing areas or rural regions.
That would also explain why temperature recorded by the India Meteorological Department at Colaba is always lower than that recorded in Santacruz. K Sathi Devi,director of IMD,Mumbai,said,our weather observatory in Colaba is close to the sea and as a result air circulation is better here. On the other hand,the Santacruz observatory is in a congested region close to the airport. In areas close to the sea and having open spaces,the air has space to move and cooling is more.
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