IIT team tracks urban heat island effect in 89 cities:

IIT team tracks urban heat island effect in 89 cities:

Context:

• Between February and May, most of the Indian cities that are to be developed as Smart Cities have been found to be 1-5 degree C cooler during the day relative to the surrounding non-urban areas.

Introduction:

1. More than 60% of the total 89 urban areas are 1-5 degrees C cooler during April.
2. This observation is in contrast with the globally witnessed phenomenon of urban areas getting significantly warmer during the day compared with the surrounding areas as a result of urban heat island effect.
3. In contrast, during the post-monsoon period(October to January), about 80% of the  urban areas show typical urban heat island effect and are 1-6 degree C warmer than the surrounding non-urban areas.
4. During the night, all the cities are warmer(1-5 degree C) than the surrounding non-urban areas due to urban heat island effect regardless of the season and location.
5. Compared with other cities, urban areas in semi-arid and arid regions of western India show higher warming in the night.
6. The night time warming is driven mainly by heat stored in building and impervious concrete areas.

What is Urban Heat Island effect?

• An urban heat island is an urban area that is significantly warmer than its surrounding rural areas due to human activities.
• The temperature difference usually is larger at night than during the day, and is most apparent when winds are weak.
•   It is most noticeable during the summer and winter.

Causes of urban heat island effect:

•    Modification of land surfaces: The main cause of the urban heat island effect is from the modification of land surfaces.
•   Waste heat generated by energy usage is a secondary contributor.
• Due to rise in population pressure, it tends to expand its areas and increase its average temperature.
• Dark surfaces absorb significantly more solar radiation, which causes urban concentrations of roads and building to heat more than suburban and rural areas during the day.
• Evapotranspiration: Another major reason is the lack of evapotranspirtion , for example through lack of vegetation in urban areas. With a decreased amount of vegetation, cities also lose the shade and cooling effect of trees, and the removal of carbon dioxide.
•   Geometric effects. This is another causes of urban heat effect. The tall buildings within many urban areas provide multiple surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated. This is called the “urban canyon effect”
•   Waste heat from automobiles, air conditioning, industry, and other sources also contribute to the urban heating effect.

Consequences of urban heat island effect:

1- Impact on whether and climate:

•  Monthly rainfall is greater downwind of cities, partially due to urban health island
•  Increases in heat within urban centers increases the length of growing seasons, and decreases the occurrence of weak tornadoes.
• The urban health island decrease air quality by increasing the production of pollutants such as ozone.
•  It decreases the water quality as warmer waters flow into area streams and put stress on their ecosystem.
•   Contribution to global warming.
•  On energy usage: Another consequence of urban heat islands is the increased energy required for air conditioning and refrigeration   in cities that are in comparatively hot climates.

2- On water quality: It also impairs water quality. Hot pavement and rooftop surfaces transfer their excess heat to stormwater, which then drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes.

3- Health effect: Urban health islands have the potential to directly influence the health and welfare of urban residents. Research has found that the mortality rate during a heat wave increases exponentially with the maximum temperature an effect that is exacerbated by the UHI. The nighttime effect of UHIs can be particularly harmful during a heat wave, as it deprives urban residents of the cool relief found in rural areas during the night. Increased temperatures have been reported to cause heat stroke, heat exhaustion, heat syncope, and heat cramps.

Smart Cities Program:

• • Smart Cities Mission is an urban renewal and retrofitting program by the Government of India with a mission to develop 100 cities all over the country making them citizen friendly and sustainable.
  • The Union Ministry of Urban Development is responsible for implementing the mission in collaboration with the state governments of the respective cities.
  • Smart Cities Mission envisions developing an area within 100 cities in the country as model areas based on an area development plan, which is expected have a rub-off effect on other parts of the city and nearby cities and towns.Cities will be selected based on the Smart Cities challenge, in which cities will compete in a countrywide competition to get the benefits from this mission.

As of June 2017, 90 cities have been selected to be upgraded as part of the Smart Cities Mission after they defeated other cities in the challenge.

• It is a five-year program, where all of the Indian states and Union territories are participating except West Bengal by nominating at least one city for the Smart City challenge.
• Each city will create a corporate company headed by a full-time CEO to implement the Smart Cities Mission. The execution of projects may be done through joint ventures, subsidiaries, public-private partnership (PPP), turnkey contracts, etc suitably dovetailed with revenue streams

Aerosols:

• An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. It can be natural or anthropogenic.  Examples of natural aerosols are fog, forest, exudates and geyser stream.  Examples of artificial aerosols are haze, dust, particulates air pollutants and smoke.

What needs to be done?

• The government is planning to develop smart cities, it would be much better if it uses more sustainable building materials that absorb less heat during the day.
• There is also need to include passive cooling measures such as increased tree cover, increased ventilation in building and orientation of building in modern building designs to reduce the night-time urban heat island effect.
• There should be an optimal combination of impervious cover , vegetation cover, and water bodies within the cities.
• Mitigation of urban heat island effect can be accomplished through the use of green roofs.
• ·  The use of lighter-colored surfaces in urban areas, which reflect more sunlight and absorb less heat.