Understanding Urban Microclimates Key to Good Urban Planning 2

Thursday, June 16th, 2016
liked this article
Autodesk – 300 X 250 (expire December 31)
urban heat
FavoriteLoadingsave article

Global temperatures have officially reached the highest on record and Australia has felt the brunt of this with record breaking temperatures for the end of summer and early autumn.

Sydney and its suburbs were particularly affected with reports that February had a record 31 straight days above 26 degrees Celsius, shattering its previous record of 19 days in 2014. What is noticeably lacking on Australian weather news are the differences in urban temperatures according to suburb, due to distance from the coast, buildings, green space and ultimately urban planning – basically the urban microclimate.

As new urban developments are on many city council planners’ and developers’ desks or currently being built – the Sydney skyline is dotted with cranes – research into fully understanding our urban microclimates where buildings, street layouts and greenery affect temperature could not be more important. Our urban environments need to be adapted and new urban design must cater for this rising heat, lest we fry.

Going ahead with developments that do not take urban microclimates into account so the best urban design and building materials are used to cope with increasing temperatures could cause future problems for residents and councils. This is because costly adaptive changes to the urban layout and green space may be required later on down the track.

In addition, the CSIRO recently reported that for the first time we have reached a major milestone of 400 parts per million of CO2 recorded in the Southern Hemisphere. With increasing carbon levels climate change will continue to take a grip, so it looks like rising temperature trend will continue, for a while at least.

Of course with the commitment of 195 countries to the recent COP21 agreement, we all hope global temperatures will be brought under control and ultimately reduced, though this will not happen overnight. Doing the research to provide architects, developers and city planners with the tools and information on how to adjust design for urban microclimates, select the best materials and utilise green infrastructure is imperative.

Research led by the CRC for Low Carbon Living (CRCLCL) is taking place around Australia – particularly in Sydney, Adelaide and Melbourne – with a focus on the links between urban microclimates, outdoor thermal discomfort and public life. This is so we can also understand the Urban Heat Island effect, where a city is hotter than its surrounding rural areas due to buildings, cars, urban design high population and subsequent human activity.

Recent research from the University of South Australia used three different case studies to report on  the correlations between heat sensitive outdoor activities and urban greenery and revealed that necessary and optional activities start to decline once temperatures reached 28 to 32 degrees Celsius, while activities in public spaces with more urban greenery showed higher resilience to heat stress.

Such results indicate that heat resilience is a quality indicator for public space and supports the use of greenery in making urban settings more resilient to heat stress.  You may think this is quite obvious, but the uptake of the use of greenery in urban design has been reportedly resisted by some town planners and urban designers. This resistance can be due cost, politics and other influences, but it definitely needs to change. As our climate gets hotter, we need to use our natural vegetation to help provide relief to the population and keep temperatures down.

Understanding urban microclimates means to also understand the effects of buildings, their materials, design and location on temperature as well.  In a recent article in the Conversation, UNSW Senior Lecturer Dr Paul Osmond and PhD student Jonathan Fox highlighted the fact that in urban areas, temperature can vary from precinct to precinct or street to street.

These temperature variances are due in the main to the direct effects of the sun on the urban environments – the buildings, the types of surface materials and street orientation, all of which ultimately affect the comfort of those on the ground and the overall ‘outdoor microclimate.’


Image: Jonathan Fox

Osmond and Fox express a concern that the vertical aspects of buildings and their facades, particularly on high rise buildings. Whem in direct contact with the sun all day, they can get extremely hot, which turn can affect the air temperature itself.  This heat absorbed by the building can continue to be emitted even after sundown, so the variance continues into the night. In fact it is the lack of “normal” nocturnal cooling in urban microclimates that is the real problem during heat waves, as daytime heat stress is compounded by lack of relief at night. Climate change drives more intense and frequent heat waves and the urban heat island drives the continuation of high temperatures into the night.

We are being warned to prepare for more heat waves, and if our current urban design is creating heat traps, this design needs to change and adapt, as does our future urban planning.

The issue of urban microclimates is recognised internationally with the Fourth International Conference on Countermeasure to Urban Heat Islands held at the end of May, where Osmond presented the CRCLCL research to the international community. Scientists, engineers, builders, architects, and government officials concerned with improving the urban environment attended, though it is not the converted that we need to address. Town planners, developers and politicians also need to sit up and listen in regard to the future of our cities and how they will cope with rising temperatures.

Later in the year, the CRCLCL is bringing together a national benchmark on what evidence exists and where the gaps are to host a National Forum on Urban Microclimate.

FavoriteLoadingsave article


 characters available
*Please refer to our comment policy before submitting
  1. Dr Hans-Dieter Hensel

    Interesting statistic on the number of days in February. In Australia, as far as I am aware, we only have 28 days in February unless it is a leap year, when we have 29. It never has 31

  2. Joe O'Keefe

    Great article…these lessons have not been internalised by Town Planners.