Benchmarking Heat Across Cumberland Council, New South Wales

Air temperature in complex urban terrain can vary. While roads and buildings can lead to higher temperatures in urban landscapes, trees and other green urban infrastructure can provide cooling. Here, we report on microclimatic variation across the LGA of Cumberland Council, New South Wales. During the summer of 2018/19, more than 1.4 million individual measurements of air temperature were recorded at 97 locations in and around the LGA. These data were used to: (1) generate the first microclimate maps for Cumberland Council, (2) assess the spatio-temporal dynamics of heatwaves in the area and (3) develop a ranking matrix for the microclimate under street trees. An additional 104,000 measurements of air temperature were recorded at nine locations in the LGA of Bayside to contrast summer heat between coastal and landlocked suburbs in the Greater Sydney Basin. Our data analyses revealed that across the LGA hot and extreme air temperatures occurred more frequently (i.e. 41 days >35°C, 19 days >40°C) compared to a nearby official weather station (i.e. 10 days >35°C, 1 day >40°C). Thus, communities living in Cumberland Council are experiencing extreme heat more frequently than previously known. Summer daytime temperatures, and particularly those measured during heatwaves, were significantly lower across the coastal LGA of the City of Bayside compared to Cumberland. Due to pronounced cooling during the evening, however, mean nighttime temperatures were lower at Cumberland Council LGA. This new understanding of heat across the LGA of Cumberland Council is based on empirical evidence, making results pertinent and applicable. Analyses provided here offer real-world information to better plan, prepare and respond to increasing urban heat in the future

Guide to Climate-Smart Playgrounds: Research Findings and Application

Outdoor play is vital for positive socialisation and development of children including cognitive, psychological, and physiological benefits. Playing outdoors increases attention, creative thought processes and problem-solving skills as well as combating obesity, mental health problems and improving social skills of children. Encouraging and supporting outdoor play is particularly important today, where the daily time interval children are engaging in physical activity is contracting. However, the lack of shade and hot playground equipment make it unsafe for children to enjoy playgrounds in summer. This situation is particularly problematic in times where summer heat is increasing as result of climate change, which already limits the time for safe outdoor play. Now more than ever is it necessary to start building climate-smart playgrounds. This report has two parts. Part 1 establishes the facts around heat in playgrounds. We document surface, air and feels like temperatures in public playgrounds across the Cumberland Local Government Area. All playgrounds were visited repeatedly during warm and hot conditions in the summer of 2019/20 and 2020/21. Part 1 also provides systematic analyses of surface temperatures of SBR, EPDM, TPO, synthetic turf and real grass. In Part 2 we describe the process, outputs and outcomes of a playground transformation at Memorial Park in Merrylands. The playground is in the Local Government Area of Cumberland City Council in the geographic centre of Sydney. With support from the NSW Government, Cumberland City Council, industry partners and inputs from a range of stakeholders, we created Australia’s first dedicated UV-smart Cool Playground. Since October 2020, the playground is enjoyed by the local community. Research data showing the avoided heat, improved thermal comfort and reduced exposure to UV-A and UV-B are provided and demonstrate the functionality of the playground

Cool Roads Trial 2021

Intensifying summer heat and associated Urban Heat Island Effects are a risk to public and environmental health. They contribute to higher energy consumption and associated greenhouse gas emissions in cities. Across Greater Western Sydney, home of the fastest growing urban population in Australia, increasing heat is recognised as the largest risk to local populations and economies. A range of interventions across the region aim at mitigating the negative impacts of heat. The Cool Roads Trial is one of these interventions. It addresses the contribution of unshaded road and carpark surfaces to local heat island effects. In March 2020, 14,700 m2 of road and carpark surfaces were coated with a highly reflective asphalt emulsion in the local government areas of Blacktown, Campbelltown and Parramatta to reduce surface temperatures of pavements. The trial was accompanied by an environmental monitoring program. The program used measurements of surface, air and black globe temperatures to document the effectiveness of the surface coat on cooling. Data were collected between February 2020 and March 2021 using a full-factorial design with paired impact and control sites. Results showed that surface temperatures of unshaded coated pavements were on average 6°C and at maximum 11°C cooler compared to uncoated pavements. Tree shade reduced temperatures of uncoated surfaces by 20°C and that of coated surfaces by 14°C leading to identical surface temperatures in the shade on coated and uncoated surfaces. Surface coating did not systematically reduce air temperature during the day or night. Back globe temperatures during sunny days increased by 2.7°C on coated compared to uncoated sites as a result of increased reflectivity of the surface. The higher exposure to reflected solar incident radiation resulted in lower thermal comfort in the sun on coated surfaces. The Cool Roads Trial established important information for the management of heat in Western Sydney and beyond. Increasing albedo of roads and carparks will help reduce surface Urban Heat Island Effects due to lower surface temperatures. Ambient air temperatures were not lowered as a result of coating roads and carparks, which can potentially be a matter of scale. The Cool Roads Trial worked at the microscale where air cooling benefits could be masked by continuous mixing of local with surrounding air masses. The range of thermal effects documented in this report make it clear that mitigating the impacts of urban heat will require a broad suite of solutions. A clear definition of desired thermal outcomes will be necessary on a case-by-case basis. Only once thermal outcomes are defined can resilience of urban populations, infrastructure and ecosystems against intensifying summer heat be improved effectively

The best urban trees for daytime cooling leave nights slightly warmer

Summer air temperatures will continue to rise in metropolitan regions due to climate change and urbanization, intensifying daytime and nighttime air temperatures and result in greater thermal discomfort for city dwellers. Urban heat may be reduced by trees which provide shade, decreasing air and surface temperatures underneath their canopies. We asked whether tree height and canopy density can help to identify species that provide greater microclimate benefits during day and night. We also asked if increased canopy cover of street trees provides similar microclimate benefits. We used continuous measurements of near-surface air temperatures under 36 park trees and from two urban streets to assess these questions. In the park, trees were grouped according to their height (20 m) and canopy density (low, high), while the effect of canopy cover was tested using streets with high (31%) and low (11%) cover. Daytime near-surface air temperature declined with increasing height and canopy density providing significant cooling benefits. However, this trend was reversed at night when tall trees with dense canopies restricted longwave radiative cooling and trapped warm air beneath their crowns. High canopy cover of street trees reduced daytime air temperatures more, resulting in a lower number of days with hot (>35 °C) and extreme (>40 °C) air temperatures compared to the street that had low canopy cover. These findings suggest that tree species and streetscapes with dense canopy cover improve local thermal conditions during the day but do not seem ideal to allow for nighttime cooling, creating potential discomfort for residents during hot summer nights. Our results indicate that classifying trees using a simple metric can assist in selecting tree species that can alleviate the local negative effect of urban heat during the day, but at the same time, their effect in preventing optimal longwave radiative cooling during the night must be factored into planting strategies

The relationship between tree size and tree water-use : is competition for water size-symmetric or size-asymmetric?

Relationships between tree size and water use indicate how soil water is partitioned between differently sized individuals, and hence competition for water. These relationships are rarely examined, let alone whether there is consistency in shape across populations. Competition for water among plants is often assumed to be size-symmetric, i.e., exponents (b1) of power functions (water use ∝ biomassb1) equal to 1, with all sizes using the same amount of water proportionally to their size. We tested the hypothesis that b1 actually varies greatly, and based on allometric theory, that b1 is only centered around 1 when size is quantified as basal area or sapwood area (not diameter). We also examined whether b1 varies spatially and temporally in relation to stand structure (height and density) and climate. Tree water use ∝ sizeb1 power functions were fitted for 80 species and 103 sites using the global SAPFLUXNET database. The b1 were centered around 1 when tree size was given as basal area or sapwood area, but not as diameter. The 95% confidence intervals of b1 included the theoretical predictions for the scaling of plant vascular networks. b1 changed through time within a given stand for the species with the longest time series, such that larger trees gained an advantage during warmer and wetter conditions. Spatial comparisons across the entire dataset showed that b1 correlated only weakly (R2 < 12%) with stand structure or climate, suggesting that inter-specific variability in b1 and hence the symmetry of competition for water may be largely related to inter-specific differences in tree architecture or physiology rather than to climate or stand structure. In conclusion, size-symmetric competition for water (b1 ≈ 1) may only be assumed when size is quantified as basal area or sapwood area, and when describing a general pattern across forest types and species. There is substantial deviation in b1 between individual stands and species

Suburban Microclimate and How to Improve It

This report informs heat-responsive urban design in a subtropical climate, specifically the western Sydney region. Empirical measurements of air and surface temperatures in a masterplan-developed community are used asses how a wide range of materials and shade influences suburban microclimate. While all the principles outlined in this report apply to newly built suburbs, some also apply when aiming to improve the thermal performance of existing buildings or urban landscapes. The analyses make it clear that providing shade is the most effective way to cool urban space and positively improve thermal comfort. Yet, there are limitations to providing shade. For this reason, we also provide information related to the thermal performance materials used for the constructions of roads, driveways, buildings and for landscaping to offer practical guidance about which materials are preferable over others when attempting to build cooler suburbs. Based on these analyses, we make 30 recommendations to inform heat-responsive urban design, making this report a blueprint for positive change. It provides valuable information for developers, architects and homeowners, because effective urban cooling requires strategic actions at all involved scales - from landscape, to lot, house and garden

Benchmarking Tree Canopy in Sydney's Hot Schools

This project identified the 100 most vulnerable schools to heat in Greater Western Sydney using a newly developed Heat Score. The Heat Score combines socio-economic information that captures exposure, sensitivity and adaptivity of local communities to heat with environmental data related to surface and air temperatures of urban space. Following the identification of the 100 schools, high-resolution aerial imagery was used to remotely measure a range of attributes at each school. These attributes included the area covered by buildings and open space, as well as the area of tree canopy cover and manmade shade structures. We determined the size of close to 5,000 individual objects to establish a benchmark of shade in Sydney’s hot schools. Key findings: » Mean area covered by the 100 schools is 23,000 m². » On average 18% of that area is shaded » Tree canopy cover makes up the majority (15%) of the shaded area. » Tree canopy cover increases with the area covered by a school. » Public schools tend to cover larger areas and thus have more tree canopy cover compared to Catholic and independent schools. » Urban Heat Island effects were reduced when the area of shade was increased. Additional tree plantings will provide microclimatic benefits. However, the present study reveals that a dual approach is necessary to increase canopy cover among the target schools that differentiates between needs and opportunities. Catholic and independent schools have the highest need for additional tree canopy cover as their current cover is low. These schools tend to have less open space available for plantings. Successful strategies will require establishing low numbers of carefully selected trees at strategic planting locations to deliver the greatest local shading and cooling benefits. Public schools offer the greatest opportunities for mass planting of additional trees as they have large areas of open space available. Planting sizeable clusters of trees will provide the greatest cooling benefits not only for the school but generate microclimate and environmental benefits for the surrounding communities. Analyses provided in this report will assist the development of the most effective tree planting strategies for each of Sydney’s 100 hot schools

Outdoor playgrounds and climate change : importance of surface materials and shade to extend play time and prevent burn injuries

Surfaces in outdoor playgrounds get hot in the sun and can cause serious skin burns in children. In-situ measurements from 10 playgrounds in Sydney showed that the maximum and average surface temperatures of sunexposed playground equipment and flooring surfaces were frequently above skin contact burn thresholds. Black and dark-coloured wet pour rubber and synthetic turf were the hottest floor materials, all having maximum surface temperatures (Ts_max) > 80 ◦C. A blue rubber dolphin was the hottest piece of play equipment, with a Ts_max of 91.8 ◦C. A systematic assessment of common synthetic flooring materials exposed to full sun showed notable differences in Ts_max between material types and colour-tones. Synthetic turf with 40 mm long grass blades (STlng-GR) was the hottest material (Ts_max = 84.5 ◦C), followed by dark blue styrene butadiene rubber (SBRD-BL, Ts_max = 81.1 ◦C), dark green ethylene propylene diene polymer (EPDMD-GR-2, Ts_max = 77.8 ◦C), dark brown thermoplastic vulcanizate (TPVD-BR, Ts_max = 71.8 ◦C), and intermediate blue thermoplastic polyolefin (TPOI-BL, Ts_max = 65.0 ◦C). All these materials were hot enough to cause contact burns on typical, warm summer days when children are likely to visit outdoor playgrounds. Surface temperatures were significantly reduced in the shade and never reached burn threshold temperatures. Selection of appropriate material type and colourtone, together with the provision of shade can remove the hazard risk for contact skin burns from outdoor playgrounds. Results of this work will assist playground designers and managers to provide safer places for our children to play longer in increasingly warmer summers

Cool Schools

The Western Sydney University Cool Schools Initiative (CSI) was launched in 2018 to develop interdisciplinary research programs for heat-resilient primary and secondary school environments and design of heat-resilient curriculum. This report summarises current research in health and environmental sciences, planning policy, legislation and standards, sustainability education, and innovative design trends. Its purpose is to inform future research into student thermal comfort and cooling solutions for schools in Western Sydney and NSW

Temperature response measurements from eucalypts give insight into the impact of Australian isoprene emissions on air quality in 2050

Predicting future air quality in Australian cities dominated by eucalypt emissions requires an understanding of their emission potentials in a warmer climate. Here we measure the temperature response in isoprene emissions from saplings of four different Eucalyptus species grown under current and future average summertime temperature conditions. The future conditions represent a 2050 climate under Representative Concentration Pathway 8.5, with average daytime temperatures of 294.5 K. Ramping the temperature from 293 to 328 K resulted in these eucalypts emitting isoprene at temperatures 4–9 K higher than the default maximum emission temperature in the Model of Emissions of Gases and Aerosols from Nature (MEGAN). New basal emission rate measurements were obtained at the standard conditions of 303 K leaf temperature and 1000 µmol m−2 s−1 photosynthetically active radiation and converted into landscape emission factors. We applied the eucalypt temperature responses and emission factors to Australian trees within MEGAN and ran the CSIRO Chemical Transport Model for three summertime campaigns in Australia. Compared to the default model, the new temperature responses resulted in less isoprene emission in the morning and more during hot afternoons, improving the statistical fit of modelled to observed ambient isoprene. Compared to current conditions, an additional 2 ppb of isoprene is predicted in 2050, causing hourly increases up to 21 ppb of ozone and 24-hourly increases of 0.4 µg m−3 of aerosol in Sydney. A 550 ppm CO2 atmosphere in 2050 mitigates these peak Sydney ozone mixing ratios by 4 ppb. Nevertheless, these forecasted increases in ozone are up to one-fifth of the hourly Australian air quality limit, suggesting that anthropogenic NOx should be further reduced to maintain healthy air quality in future