gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 Modelling the city-wide impact of street trees: an application to Basel, Switzerland Gianluca Mussetti 1,2,3 S. Henne 1 , D. Brunner 1 , J. Allegrini 2,3 , S. Krayenhoff 4 , S. Schubert 5 , C. Feigenwinter 6 , R. Vogt 6 and J. Carmeliet 3 1 Laboratory for Air Pollution / Environmental Technology, Empa, Switzerland 2 Laboratory for Multiscale Studies in Building Physics, Empa, Switzerland 3 Chair of Building Physics, ETH Zurich, Switzerland 4 School of Environmental Science, University of Guelph, Canada 5 Geography Department, Humbolt-Universität zu Berlin, Germany 6 Research Group Meteorology, Climatology, and Remote Sensing, University of Basel, Switzerland
Street trees Local impact of street trees Daytime cooling of 0.2-1.1 K [1,2] Night-time warming [3] Improved thermal comfort [2] No studies on the city-wide impact of street trees [1] Shashua-Bar et al ., 2009; [2] Coutts et al ., 2016; [3] Souch and Souch, 1993 gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 2
Outline Aim: Quantify the city-wide impact of street trees Approach: Urban climate model with integrated street trees Evaluation over Basel, Switzerland City-wide impact of street trees in Basel Air Temperature Components of thermal comfort (surface T, humidity and wind speed) gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 3
Urban canopy model with trees COSMO-CLM (CCLM) BEP-Tree [4] [4] Krayenhoff et al. (2014, 2015) Mussetti et al . ( in preparation ) gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 4
Application: Basel, Switzerland [5] Simulation set-up: Simulation period: 1. REF Heat Wave 2015 (10 days) 2. NO TREES [5] https://www.stadtplan.bs.ch/ gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 5
Derivation of leaf area density (LAD) Street tree : tree over artificial surface LAI (street trees) Assumptions: LAD = 1 m 2 m -3 [6] Canopy base height = 3 m Mean = 0.59 Comparable other studies [6,7] [6] Klingberg et al., 2017; [7] Alonzo et al., 2015 gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 6
Derivation of leaf area density (LAD) Street tree : tree over artificial surface LAI (street trees) Assumptions: LAD = 1 m 2 m -3 [6] Canopy base height = 3 m Mean = 0.59 Comparable other studies [6,7] [6] Klingberg et al., 2017; [7] Alonzo et al., 2015 7
Evaluation: BKLI tower (40 m) 10-days averaged results gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 8
Evaluation: surface stations (2 m) Solid = 10-days average ; Shade = 10-days variability gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 9
Impact of street trees: air temperature 10 day averaged Time = 6 am - 9 pm Time = 9 pm - 6 am Mean = - 0.14 Mean = + 0.08 Max night Air Temperature Difference [K] gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 10
Impact of street trees: day 6 am - 9 pm Air T (2m) Urban Surface T [K] [K] Mean = - 0.14 Mean = - 0.83 Humidity Wind Speed [g kg -1 ] [m s -1 ] Mean = + 0.17 Mean = - 0.21 gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 11
Impact of street trees: night 9 pm - 6 am Air T (2m) Urban Surface T [K] [K] Mean = + 0.08 Mean = + 0.33 Humidity Wind Speed [g kg -1 ] [m s -1 ] Mean = + 0.06 Mean = - 0.07 gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 12
Impact of street trees: temporal Air T (2m) Urban Surface T warming warming [K] [K] cooling cooling Humidity Wind Speed increase [g kg -1 ] [m s -1 ] decrease Local Time Local Time Solid = 10-days average ; Shade = 10-days variability gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 13
Conclusions City-wide estimation of street trees cooling potential - 0.14 K (max - 1 K) during daytime Street trees do not mitigate the UHI (night) + 0.08 K (max + 0.3 K) during night-time Potentially positive impact on daytime average thermal comfort - 0.83 K (max – 5 K) in Surface T On-going Thermal comfort index at local scale Greening scenario gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 14
gianluca.mussetti@empa.ch | ICUC10 - 6 August 2018 Thank you
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