Installation of a temperature sensor in a street tree (Queensland brush box)
Installation of a temperature sensor in a street tree (Queensland brush box)

Ten days into summer, this year, the Bureau of Meteorology’s only weather station in Penrith, in Sydney’s outer west, recorded a temperature of 41.2 degrees Celsius. The Penrith Lakes station is more than three kilometres from the city’s central business district, where temperatures would have been even higher.

Residents know temperatures can vary dramatically across their local government area, sometimes by as much as 10 degrees. But until now, Penrith Council hasn’t had the evidence to support this.

That’s about to change thanks a partnership between the council and Western Sydney University (WSU) to collect detailed temperature data from 120 heat sensors that have been installed across Sydney’s hottest local government areas (LGAs).

The data will be combined with temperatures collected in three nearby LGAs to create a giant temperature map for Western Sydney, which is set to absorb half of Sydney’s future population growth.

Research already done last summer in Parramatta, Cumberland and Campbelltown, which tracked the microclimates of specific suburbs, has revealed that those LGAs are exposed to far more extreme heat than the BoM has recorded, according to Dr Sebastian Pfautsch, a Senior Research Fellow at WSU, who is leading the research.

“The process of developing Western Sydney contributes massively to heat,” Dr Pfautsch says.

Heat map nighttime
Nighttime heat map: Variation of average nighttime temperature (i.e. the mean temperature between 22:00 and 5:00) across the Parramatta LGA (white outline). The map shows warmer temperatures in the southern suburbs cooler nighttime temperatures for the suburbs in the north as result of difference in urban green space, population and road density and elevation of the landscape. Also, a clear Urban Heat Island effect for Parramatta CBD is captured.

“By converting open, green surfaces to impermeable ones made from bitumen or concrete, we reduce the capacity of water seeping into the soil and evaporating from it, whereby it cools the air.”

By the time the Penrith project is finished, the WSU team will have recorded more than 1.7 million individual measurements of air temperature across Western Sydney. Councils will be able to drill down into the data, which will provide a scientific basis for new council policies to tackle rising urban heat.

The study at Parramatta was a world’s first systematic study of microclimatic variation across an entire LGA. The study across Penrith is covering the largest area – more than 400 square kilometres – ever studied for variation in local air temperatures.

The scale of the project was possible thanks to Dr Pfautsch’s simple but ingenious heat sensor design: a small electronic temperature measuring device is suspended within an aluminium can, with holes at the top of the can that allow air to circulate. The cans are hung about four metres high in trees, where they will record air temperatures every 10 minutes for the whole of summer.

Commercially-manufactured sensors are expensive, so this solution significantly reduced the cost of the project, says Dr Pfautsch.

“It is a ‘dumb’ sensor but it takes smart people to deploy them correctly,” he quips.

In Penrith, 100 sensors have been scattered across the LGA, another 10 have been placed at strategic points, such as the Mulgoa Rd carpark and the Hawkesbury River, and another 10 are in St Mary’s CBD, where WSU is studying the link between urban heat and active use of public space.

“This kind of information helps councils forward plan,” says Dr Pfautsch.

Penrith Council will get detailed data that could, for example, show that some areas that are hot during the day, cool quickly at night, making them suitable for something like a night market.

Every location monitored will have a georeference to enable the monitoring to be replicated at a later date to see how temperatures have changed, or to see if action taken to cool an area has worked.

The sensors will capture information about temperatures during the day and night, about the frequency of heat waves, about when cool changes arrive, and the places that cool down the fastest.

“There are so many questions you could answer with this data set,” says Dr Pfautsch.

“It is really very detailed information across many, many square kilometres of urban space.”

Prior to the installation of 100 WSU heat sensors last year, the nearest weather stations to the Cumberland LGA were in North Parramatta and Olympic Park.

Cumberland Mayor Greg Cummings said at the time his council felt it wasn’t good enough to rely on heat mapping from a satellite or weather stations outside of the LGA.

“To know how hot it feels to residents, we need to record the air temperatures across the whole LGA. This is what the heat sensors are doing now.”

In December, 2018, Campbelltown also partnered with WSU to do a heat sensor project to measure the air temperature in 110 locations across the council area over that summer. The research is being used to help draft new policies aimed at reducing urban heat and cooling the suburbs.

A similar WSU study in Parramatta over the summer of 2018/2019 that measured air temperatures at more than 140 locations revealed that residents were exposed to more extreme heat (>40°C) than previously known. The data also showed there were large differences in cooling capacity between urban tree species.

Sebastian Pfautsch

Temperature data from each LGA will be shared with the respective local council, and the reports generated from each study will be made publicly available for free by WSU. The researchers also plan to talk about the significance of the data to local land owners, industry, the Greater Sydney Commission, the Western Sydney Regional Organisation of Councils and Resilient Sydney.

Groups such as these need to help the public change the course of Sydney’s unsustainable development patterns, says Dr Pfautsch.

“But you have to have hard data to prove your case, and you should use the evidence to inform and educate people … to really make sure no one can say they didn’t know about [rising urban heat].”

Penrith Mayor, Ross Fowler OAM, says his council needs accurate new heat data from across the LGA to make the business case for change to industry, and especially to developers.

“If we continue to build the same way tomorrow as we do today, without considering urban heat, we are locking ourselves in to high heat for the coming decades,” he says.

Dr Pfautsch doesn’t think the data will stop the development that will accompany a projected 50 per cent increase in Western Sydney’s population by 2036. But he says it could make a difference to how that development proceeds.

“What we are doing [in development] at the moment is just unsustainable. It is absolutely staggering what is planned for Western Sydney,” he says.

“Everything is geared towards this growth… it will happen. But hopefully, our work will change how we do the development.”

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  1. Good grief – Dr Pfautsch doesn’t think that life threatening temperatures are enough to stop a 50% increase in population and correspondingly more hot island effect.