Urban heat island effect in Hong Kong

An urban heat island (UHI) is a city or metropolitan area that is apparently warmer than its surrounding rural areas due to the activities of people. The phenomenon was first discovered by Luke Howardin the 1810. The temperature difference usually is larger at night than the day, and it is more easy to happen when winds are weak. It is most noticeable in the summer and winter.

The urban heat island effect happens due to the modification of land surfaces. Unnecessary heat generated by energy usage is one of the factors. When urbanization grows, it appears to expand and increase its average temperature.

A bird eye view of  central, Hong Kong 

"Urban Heat Island” (UHI) occurs in a densely populated area, Hong Kong is a one of the most crowded cities in the world, it has a  higher temperature than surrounding rural areas. In the urban development of Hong Kong , the changes of land use and the landscape, the densely located urban infrastructure and anthropogenic heat has caused the poor cooling effect in built-up areas, resulting in forming the Urban Heat Islands.

I lived in Hong Kong for a long time, during the summer time, the constantly high temperature has caused sickness and deaths associated with excessive heat exposure. As UHI exacerbates heat waves, which increases the risks of heat stroke and exhaustion, especially on those with chronic diseases and people who are working outdoors.

However, vegetation cover and using proper building materials can help reducing the UHI effect. But it is always hard to convince developer to have more green space and spend more money on building materials when it doesn't bring any economical benefits to the company. 

It is happy to hear that there is a Remote Sensing technologies and Geographic Information Systems (GIS) according to Dr Charles Wong Man-sing at the Department of Land Surveying and Geo-Informatics, it can help to improve town planning based on data gathered. By using this we can design ventilation pathways by mapping out the Frontal Area Index (a ratio of total area of the building facets exposed to the wind) of each building gathered from GIS data and reducing the paths of the lowest air flow resistance. This helps town planners to have better decisions in environmental design without blocking the main ventilation corridors. If we can maintain the ventilation then UHI effect can be mitigated.

Reference:

"Urban Heat Islands." Wikipedia. Accessed March 18, 2016. https://en.wikipedia.org/wiki/Urban_heat_island. 

 "Mitigating Urban Heat Islands for Better Living Environment." Mitigating Urban Heat Islands for Better Living Environment. Accessed March 18, 2016. http://www.polyu.edu.hk/cpa/excel/en/201504/viewpoint/v1/index.html.