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Urbanization, their problems and their remedies - Urban heat island
                                                                                                    January 14, 2018


Every winter, the whole of north India is covered by dense fog. But a phenomenon called urban heat island is burning holes in this grey shroud over New Delhi and other cities on the Indo-Gangetic Plain, says a new study.

Impacts:

The urban heat island effect is so strong in Delhi, the largest city in the region, that it saw 50% less fog than surrounding areas. In Delhi, the heat island effect also appears to be suppressing the very formation of fog. Scientists found that while areas outside Delhi have seen a 20 per cent increase in fog in the period 2012-2016 compared with 2000-2004, Delhi itself did not see an increase.

Reasons behind this:

The analysis found a correlation between the size of the urban population and that of the fog hole. Population size has been shown to be related to the intensity of urban heat islands since they are an indicator of urban growth.

Way ahead:

The findings from the study are important since dense and polluted winter fog envelopes north India, Pakistan, Nepal and Bangladesh every year from December to January severely affecting air quality and disrupting air, rail and road traffic. The study will be very useful in understanding the process of why fog occurs and ultimately to predict its occurrence.

What is urban heat island effect?

The urban heat island is a phenomenon when the heat gets trapped near the earth’s surface as a result of a decline in green cover, rapid urbanisation, energy-intensive activities, and concrete structures.

Concerns:

Urban heat islands can have worse air and water quality than their rural neighbours. UHIs often have lower air quality because there are more pollutants (waste products from vehicles, industry, and people) being pumped into the air. These pollutants are blocked from scattering and becoming less toxic by the urban landscape: buildings, roads, sidewalks, and parking lots. Water quality also suffers. When warm water from the UHI ends up flowing into local streams, it stresses the native species that have adapted to life in a cooler aquatic environment.