Microclimate of isolated trees in the urban environment

Transcription

1 Microclimate of isolated trees in the urban environment Andy Coutts CRC Water Sensitive Cities School of Earth, Atmosphere and Environment Monash University january cn0t.html?selectedimage=5

2 How effective is WSUD and green infrastructure at improving urban microclimates? WSUD capable of lowering temperatures and improving human thermal comfort Harness the cooling and human thermal comfort benefits of trees Benefits depend on a multitude of factors WSUD can supply trees with water Street trees Tree size Canopy coverage Planting density Species LAI Root water avail. Tree health Location Urban geometry Met. Conditions Time of day

3 Trees provide a benefit, but by how much? Scale: City Neighbourhood Street Tree Key research questions: What impact do trees have on the urban environment? What impact does the urban environment have on trees? How can we best implement tree to deliver the greatest microclimate benefit (temperature reduction and improved human thermal comfort (HTC)? Key Outcomes Quantify benefits to support policy, decision making & cost/benefit Explore key mechanisms for cooling Provide data for model development and validation

4 The climate of the isolated urban tree is deserving of study (Oke et al., 1989) (pg 164) Smith St. tree pits Cemetery tree Passive irrigation trees Street trees

5 Key findings: Smith St. tree pits Very complex environment Light availability a key driver of plant water use Variations between side of street Variation between species Rapid wetting and drying of soil Good for stormwater, not so for some trees? Gerbert, L. Coutts, A.M., Tapper, N. J. (in prep) Tree response to the urban canyon microclimate

6 Key findings: Cemetery tree Up to 1.2 C cooler below than upwind of tree Differences greater under warm northerlies Cooling driven by shading Water use for isolated trees can be large when water is available Nocturnal water transport occurring Coutts, A. M., Moore, C., Tapper, N.J., White, E. C., (In Prep.) The microclimate and water use of an isolated tree in the dead centre of the city. International Journal of Biometeorology

7 Key findings: Passive Irrigation Passive irrigation from stormwater can deliver large amounts of water ~5000L over 6 months Evidence of stomatal control of water loss No clear benefit of passive irrigation at this site: sufficient soil moisture available Still need to process soil moisture data to understand variability between trees 31 January February February C 32.2 C 40.3 C Coutts, Thom, Livelsley, Szota (2015)

8 Key findings: Street trees Street trees can deliver dramatic improvements to HTC. Shading can reduce heat stress by one level (based on UTCI) Streets with trees can reduce mean street air temperature by up to ~1 C in hot conditions Benefits of tree more effective in wide, shallow streets Benefits are highly localized and variable, depending on tree cover, geometry, and prevailing meteorological conditions Coutts, A. M., White, E. C., Tapper, N. J., Beringer, J. & Livesley, S. J Temperature and human thermal comfort effects of street trees across three contrasting street canyon environments. Theoretical and Applied Climatology, 1-14.

9 Key interventions Existing street trees should be protected & maintained Passive and active irrigation in built up areas Maintain healthy canopies for shading More trees should be planted Prioritise canopy cover in areas of high solar exposure Highly localised benefit so trees must be distributed Tree species should be diverse Water should be supplied Right tree, right place Consider light, water availability, climate, etc Norton, B. A., Coutts, A. M., Livesley, S. J., Harris, R. J., Hunter, A. M. & Williams, N. S. G Planning for cooler cities: A framework to prioritise green infrastructure to mitigate high temperatures in urban landscapes. Landscape and Urban Planning, 134,

10 Future work Single Plant Ecosystem (SPE) modelling Use MAESPA to model isolated street trees Extensive work on model parameters Explore impacts of changing urban conditions Explore impacts of changing water availability

11 Key gaps in knowledge Very little research on interactions between the urban environment and vegetation and tree physiological responses Limits capacity to inform Right tree, right place How to represent and simplify microscale process in urban land surface schemes How urban trees will respond to climate change (drought, changing rainfall patterns, extreme heat) Little understanding of current and future water needs of urban trees Development of models/tools to inform urban design and planning (i.e. VTUF-3D) Application of urban climate models to various urban design scenarios Thom, J. K., Coutts, A. M., Broadbent, A. M., Tapper, N.J. (In prep.) The influence of increasing tree cover on mean radiant temperature across a mixed development suburb in Adelaide, Australia. Urban Forestry and Urban Greening

12 Key publications Coutts, A.M., Harris, R. J., Phan, T., Livelsey, S. J., Williams, N. S. W., Tapper, N. J., 2016 Thermal infrared remote sensing of urban heat: hotspots, vegetation, and an assessment of techniques for use in urban planning. Remote Sensing of Environment, Submitted Coutts, A. M., White, E. C., Tapper, N. J., Beringer, J. & Livesley, S. J Temperature and human thermal comfort effects of street trees across three contrasting street canyon environments. Theoretical and Applied Climatology, Coutts, A. M., Tapper, N. J., Beringer, J., Loughnan, M. & Demuzere, M Watering our Cities: The capacity for Water Sensitive Urban Design to support urban cooling and improve human thermal comfort in the Australian context. Progress in Physical Geography, 37, Coutts, A. M., Daly, E., Beringer, J. & Tapper, N. J Assessing practical measures to reduce urban heat: Green and cool roofs. Building and Environment, 70, Salmond, J. A., Tadaki, M., Vardoulakis, S., Arbuthnott, K., Coutts, A., Demuzere, M., Dirks, K. N., Heaviside, C., Lim, S., Macintyre, H., Mcinnes, R. N. & Wheeler, B. W Health and climate related ecosystem services provided by street trees in the urban environment. Environmental Health, 15, Norton, B. A., Coutts, A. M., Livesley, S. J., Harris, R. J., Hunter, A. M. & Williams, N. S. G Planning for cooler cities: A framework to prioritise green infrastructure to mitigate high temperatures in urban landscapes. Landscape and Urban Planning, 134, Demuzere, M., Coutts, A. M., Göhler, M., Broadbent, A. M., Wouters, H., Van Lipzig, N. P. M. & Gebert, L The implementation of biofiltration systems, rainwater tanks and urban irrigation in a single-layer urban canopy model. Urban Climate, 10, Part 1, Demuzere, M., Oleson, K., Coutts, A. M., Pigeon, G. & Van Lipzig, N. P. M Simulating the surface energy balance over two contrasting urban environments using the Community Land Model Urban. International Journal of Climatology, 33, Grimmond, C. S. B., Blackett, M., Best, M. J., Baik, J. J., Belcher, S. E., Beringer, J., Bohnenstengel, S. I., Calmet, I., Chen, F., Coutts, A., Dandou, A., Fortuniak, K., Gouvea, M. L., Hamdi, R., Hendry, M., Kanda, M., Kawai, T., Kawamoto, Y., Kondo, H., Krayenhoff, E. S., Lee, S. H., Loridan, T., Martilli, A., Masson, V., Miao, S., Oleson, K., Ooka, R., Pigeon, G., Porson, A., Ryu, Y. H., Salamanca, F., Steeneveld, G. J., Tombrou, M., Voogt, J. A., Young, D. T. & Zhang, N Initial results from Phase 2 of the international urban energy balance model comparison. International Journal of Climatology, 31,

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