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Whenever possible, re-alignment of rows of parking stalls from north—south to east—west to allow trees to be planted in an east—west orientation, maximizing shading of the parking lot and addition of planting boulevards in parking lots both CTs and along wide streets Scarborough were also proposed.

The amount of long-wave terrestrial radiation emitted by most materials is directly related to their temperature [ 20 ]. Any strategy that reduces absorption of short-wave solar radiation by a material, and consequently its T sf , will also contribute to a reduction in long-wave terrestrial radiation emitted by the material into the surrounding landscape.

Additionally, the use of lighter-coloured i.

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These materials reflect more of the incoming short-wave solar radiation and thus decrease the amount of solar radiation absorbed and re-emitted by the ground surface as terrestrial radiation [ 2 , 36 ]. Although buildings are not accounted for in the calculation of pEB in the present study, the proposed use of roofing and building materials that better intercept e.

Maximizing exposure to predominant winds will work toward maximizing convective and evaporative heat losses by a human [ 20 ]. However, this strategy was not prioritized in the proposed designs per se for several reasons:. The compounding effects of high vapor pressure and high temperatures during EHEs in Toronto result in minimal changes to overall energy budgets with higher winds, as the vapor gradient between the above the skin and the air is weak [ 18 ].

That said, pruning of low branches will allow ground-level wind to pass under a tree and to reach a human enjoying the cool shade to the north and east of the tree as well as cooling provided through evapotranspiration. An additional layer of complexity occurs in highly dense urban areas e. In summary, in the context of the proposed designs, maximizing wind was a balance between tree maintenance and placement and not a design consideration. Comparison of pre- i. This involved generation of a raster image of the existing and proposed master plans of each selected CT.

These images were analysed for proportional areas of each of the land classes of interest and pEB was calculated. This method was validated by further comparing the pEB calculated for the pre-design i. There was no significant difference between the pEB values using these two methods of assessing pEB of the present-day, existing conditions. Proposed conditions within-CT, by paired t -test.

By comparison, these CTs were re-ranked in descending order using the pEB from the proposed master plans. Downtown changed from a ranking of 1st to th out of CTs th to 62nd percentile and Scarborough changed from a ranking of 6th to rd 88th to 52nd percentile. Findings presented in Graham et al. The proposed design modifications resulted in meaningful reductions in the daytime pEB during EHEs in the study CTs, nearly achieving a landscape of neutral thermal comfort, and suggest the possibility of post-design reductions in heat-related morbidity in these CTs.

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The bEBs, collated across four separate EHEs from 3 different years and across the range of the hot season, are very similar to those reported by Vanos et al. This is true both for absolute values by period i. There are other reports relating EB modelling at this spatial scale to various characteristics of the urban landscape [ 17 , 18 , 22 ].

Harlan et al. The magnitude of this finding by Vanos et al. These changes are greater than those predicted in the present study due to the more extreme methods applied by Brown et al. Further, although the modelled changes in surface albedo aided in reducing the energy budgets, related observational studies only controlling for surface albedo show slight increases in the absorbed radiation or mean radiant temperature due to a great amount of solar radiation imposed on a human as compared to lower albedo [ 37 , 38 , 39 ].

The combination of both shade and high-albedo surfaces, however, may cause varying results, yet further observational research in this area is needed. The methodology and findings presented in this study help to further quantify the impact of interacting UHI mitigation strategies, such as those proposed by Harlan and Ruddell [ 34 ] and Stone, Hess and Fumkin [ 40 ] within specific CTs. These changes would result in a much lower risk of heat stress and improved thermal comfort towards the neutral zone of comfort.

Published recommendations for microclimatically-appropriate design were applied to two CTs in Toronto that had high levels of heat-related ambulance calls during heat waves. Post-design pEB was lowered to a level nearing a range of thermal neutrality. This study demonstrated that pEB modelling can aid in the quantification of the thermal comfort benefits of proposed designs and help relate design proposals to beneficial health outcomes. Focusing future efforts on modifying the pEB model to accept the presence of buildings within an acceptable level of error would be a meaningful advancement.

Mean daily city-wide baseline energy budget bEB from 11h00 to 18h00 by period consolidated across all years. The authors would like to thank Toronto Emergency Medical Services for sharing the ambulance call data used herein. Drew A. Graham, Jennifer K. Vanos, Natasha A. Kenny, and Robert D. Brown conceived and designed the experiments; Drew A. Graham performed the experiments; Drew A. Graham and Robert D. Brown analyzed the data; Jennifer K.

Brown contributed modeling tools; Drew A. Brown wrote the paper. National Center for Biotechnology Information , U. Published online Jul Graham , 1 Jennifer K. Vanos , 2 Natasha A. Kenny , 3 and Robert D. Jennifer K. Natasha A. Robert D. William C. Author information Article notes Copyright and License information Disclaimer. Received May 30; Accepted Jul Abstract Urban residents are at risk of health-related illness during extreme heat events but the dangers are not equal in all parts of a city.

Keywords: landscape architecture, urban design, energy budget modeling.

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Introduction The global climate is changing and many areas are experiencing hotter summer weather. Results Two CTs met the selection criteria: Open in a separate window. Figure 1. Table 1 Characteristics of CTs selected for re-design. W, Front St. W, Yonge St. Scarborough N, McCowan Rd. Table 3 11h00—18h00 mean weather data from the stations used for modelling consolidated across all years.

Table 5 Typical summertime air temperatures at Lester B. Figure 3. Figure 4. Discussion The proposed design modifications resulted in meaningful reductions in the daytime pEB during EHEs in the study CTs, nearly achieving a landscape of neutral thermal comfort, and suggest the possibility of post-design reductions in heat-related morbidity in these CTs. Conclusions Published recommendations for microclimatically-appropriate design were applied to two CTs in Toronto that had high levels of heat-related ambulance calls during heat waves. Figure 2. Acknowledgments The authors would like to thank Toronto Emergency Medical Services for sharing the ambulance call data used herein.

Appendix A Figure A1. Figure A2. Appendix B Figure A3. Figure A4. Author Contributions Drew A. Conflicts of Interest The authors declare no conflict of interest. References 1. Oke T. The energetic basis of the urban heat island. Boundary Layer Climates. Chow W. Vulnerability to extreme heat in metropolitan Phoenix: Spatial, temporal, and demographic dimensions. Oleson K. Interactions between urbanization, heat stress, and climate change.

Tan J. The urban heat island and its impact on heat waves and human health in Shanghai. Reid C. Mapping community determinants of heat vulnerability. Health Perspect. Meehl G. Luber G. Climate Change and Extreme Heat Events. Smoyer K. Heat-stress-related mortality in five cities in Southern Ontario: — Semenza J. Robine J. Death toll exceeded 70, in Europe during the summer of Bassil K. Effectiveness of Public health interventions in reducing morbidity and mortality during heat episodes: A structured review.

Harlan S. Neighborhood microclimates and vulnerability to heat stress. Brown R. Designing urban parks that ameliorate the effects of climate change. Urban Plan. Ameliorating the effects of climate change: Modifying microclimates through design. Vanos J. Human energy budget modeling in urban parks in Toronto and applications to emergency heat stress preparedness.

Graham D. The relationship between neighbourhood tree canopy cover and heat-related ambulance calls during extreme heat events in Toronto, Canada. Importantly, human thermal comfort models can also be applied to predict how landscape modifications can reduce vulnerability to heat stress [ 18 ]. The design of the urban landscape can influence outdoor thermal comfort by modifying the microclimate [ 17 , 18 , 19 , 20 , 21 ].

A study in Phoenix [ 17 ] reported that human energy budgets modelled during an EHE correlated negatively with both the amount of open space and vegetation abundance in specific neighbourhoods. In another study, city-wide human energy budgets were strongly correlated to the frequency of heat-related EMR calls during a 3-day EHE in July , in Toronto [ 22 ].

This study builds on previous research [ 23 ] that reported higher heat-related Emergency Medical Response EMR calls related to two physical characteristics of neighborhoods: amount of tree canopy cover and amount of impervious surface. Areas with fewer trees and higher percentages of impervious surfaces received up to five times as many heat-related EMR calls during EHEs.

The goal of this study was to further explore the relationship between physical characteristics of neighborhoods and human heat-health through the application of a validated human thermal comfort model at the Census Tract CT level during EHEs in Toronto Canada. Landscape architectural design solutions that have been suggested as ways to cool overheated landscapes were tested through modeling and reported in terms of the reduction in expected heat-related EMR calls. The dates used for analyses were: 27—30 June ; 29 July—2 August ; 24—27 May ; and 29 August—2 September The seven days preceding Pre and following Post each EHE were also examined as a baseline for comparison.

Hourly weather data recorded at Toronto International Pearson Airport and Toronto Buttonville Airport were assessed for all dates studied [ 23 ]. EMR calls for all study dates were analyzed to identify heat-related illnesses by CT. The rationale for using this subset of reported conditions has been reported previously [ 23 ]. The Toronto land cover raster dataset was used to identify potential microclimate-modifying characteristics of CTs. Land cover data were extracted for each CT and the resulting attribute table exported as a text file. To test the accuracy and precision of the extraction method to cover an entire CT, by-CT pixel counts for each land class were converted to areas in ha.

By-CT sums of land class areas were compared to the CT areas generated by the geodatabase based on the geo-located CT boundary polygons. Differences ranged from 0. This analysis confirmed reasonable precision narrow range, low SD and accuracy mean close to 0 and thus a reliable and valid method of land cover-by-CT data extraction.

It calculates this through a summation of heat production from metabolic processes and absorbed short- and long-wave radiation and loss through sensible heat loss, emitted long-wave radiation, and evaporative heat loss. There are a variety of human physiological variables, meteorological variables, and physical properties used as inputs for COMFA [ 24 ]. The resulting EB provides an estimate of the thermal comfort level experienced by a person in a particular situation.

Hourly EB values were calculated for the period of 11h00—18h00 daylight savings time DST on each study date. This timeframe captures the hottest 8 hours of the day and the time of day when most people are outside e. It is also the time of day that urban design can have the largest effect on the EB of residents. The baseline energy budget bEB was calculated and used as the standard for comparison.

It was represented by the EB estimated under the prevailing conditions and in the measurement environment of the weather stations i.

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During the EHEs studied, it was estimated that the typical person would try to restrict intensity of physical activity and to wear clothing conducive to staying cool. Two Toronto CTs were selected for study based on the following criteria: 1 experienced a high number of EMR calls during EHEs; 2 be in different parts of the city; and 3 be CTs where it is possible that area residents can spend time outdoors i. CTs selected for re-design were examined in detail using aerial ArcMap and ground-level imagery Google Earth v.

A scaled base plan of existing conditions was generated for each CT. Climate normals for T a , solar radiation, and wind directions for Toronto during the May—September study period [ 30 , 31 ] were examined. Published design guidelines [ 8 , 19 , 20 ] for cooling of hot weather microclimatic conditions were applied to the design of the selected CTs.

The specific cooling interventions prioritized in the proposed master plan designs of the two CTs were:. Addition of deciduous trees, prioritizing areas to the south and west of high foot traffic routes e. Re-alignment of rows of parking stalls from north—south to east—west to maximize shading of the parking lot. Replacement of existing dark coloured low albedo asphalt pavements in roadways and parking lots with light coloured high albedo concrete pavements. Replacement of traditional dark coloured roofing materials with either a green roof or light coloured high albedo roofing material.

Since the goal of the re-design was to offer cooling solutions during EHEs, priority was placed on reducing radiation exposure short-wave solar and long-wave terrestrial radiation [ 20 ]. During heat waves in Toronto, the humidity is typically very high so very little evaporative cooling could be expected to occur. Air temperature and air humidity were not addressed as they are spatially conservative at the site scale and cannot be modified substantially through urban design [ 20 ].

Absolute pixel count of each shade of grey i.

Proportional areas for each CT before i. Pearson product-moment correlation procedures were used to examine the strength and direction of associations between pairs of weather variables. Spearman rank order correlations a non-parametric test were thus run for all correlation analyses involving CT-level call data.

Additionally, log transformation resolved normality in these CT-level call data. In some cases, Spearman correlations of non-transformed call data vs. Assumptions of linearity, lack of outliers, and homoscedasticity were assessed graphically scatter plots and were reasonably met in all cases.

Two CTs met the selection criteria: Characteristics and locations of selected CTs are presented in Table 1 and Figure 1 , respectively. Four EHEs occurred in Toronto during the period to [ 23 ]. Absence of superscript letters indicates that the main period effect was not statistically significant. Pre and Post periods were not significantly different from each other. Daily data from all days i. Event-to-event fluctuations exist in both the relationship strength between correlated variables and the presence of statistical significance for the correlations.

Typical weather i.

Typical summertime air temperatures at Lester B. Pearson International Airport weather station for the years — Wind patterns in sunny conditions are of particular interest for designing cooling microclimates. However, designing for a cool microclimate should consider all warm months. Leaving this range of directions unobstructed would maximize wind flow during summertime sunny conditions.

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Typical summertime wind directions during sunny conditions at Lester B. Data are in percentage of time during summer months. The resulting designs are shown in Figure A2 and Figure A4 and the explanation for the modifications is provided in the following sections. Additional benefits are offered by trees e. This strategy increased the relative canopy cover in Downtown by 5.

Specific species were not proposed in the designs, although those with low urban tolerance and with a high ozone-formation potential e. Deciduous species were chosen since most of these species defoliate in autumn and would therefore allow solar radiation to be maximized during the winter which would be desirable. Placement strategy of proposed trees was to the south and west of areas where humans were most likely to be e.

Additionally, proposed trees were placed to the south and west of infrastructure e. Some areas of Downtown that would otherwise have benefitted from shade trees are immediately north of a skyscraper. Since these buildings cast significant shadows to the north, trees were not proposed for these areas. Whenever possible, re-alignment of rows of parking stalls from north—south to east—west to allow trees to be planted in an east—west orientation, maximizing shading of the parking lot and addition of planting boulevards in parking lots both CTs and along wide streets Scarborough were also proposed.

The amount of long-wave terrestrial radiation emitted by most materials is directly related to their temperature [ 20 ]. Any strategy that reduces absorption of short-wave solar radiation by a material, and consequently its T sf , will also contribute to a reduction in long-wave terrestrial radiation emitted by the material into the surrounding landscape. Additionally, the use of lighter-coloured i. These materials reflect more of the incoming short-wave solar radiation and thus decrease the amount of solar radiation absorbed and re-emitted by the ground surface as terrestrial radiation [ 2 , 36 ].

Although buildings are not accounted for in the calculation of pEB in the present study, the proposed use of roofing and building materials that better intercept e. Maximizing exposure to predominant winds will work toward maximizing convective and evaporative heat losses by a human [ 20 ].

1. Introduction

However, this strategy was not prioritized in the proposed designs per se for several reasons:. The compounding effects of high vapor pressure and high temperatures during EHEs in Toronto result in minimal changes to overall energy budgets with higher winds, as the vapor gradient between the above the skin and the air is weak [ 18 ]. That said, pruning of low branches will allow ground-level wind to pass under a tree and to reach a human enjoying the cool shade to the north and east of the tree as well as cooling provided through evapotranspiration. An additional layer of complexity occurs in highly dense urban areas e.

In summary, in the context of the proposed designs, maximizing wind was a balance between tree maintenance and placement and not a design consideration. Comparison of pre- i. This involved generation of a raster image of the existing and proposed master plans of each selected CT. These images were analysed for proportional areas of each of the land classes of interest and pEB was calculated. This method was validated by further comparing the pEB calculated for the pre-design i. There was no significant difference between the pEB values using these two methods of assessing pEB of the present-day, existing conditions.

Proposed conditions within-CT, by paired t -test. By comparison, these CTs were re-ranked in descending order using the pEB from the proposed master plans. Downtown changed from a ranking of 1st to th out of CTs th to 62nd percentile and Scarborough changed from a ranking of 6th to rd 88th to 52nd percentile. Findings presented in Graham et al. The proposed design modifications resulted in meaningful reductions in the daytime pEB during EHEs in the study CTs, nearly achieving a landscape of neutral thermal comfort, and suggest the possibility of post-design reductions in heat-related morbidity in these CTs.

The bEBs, collated across four separate EHEs from 3 different years and across the range of the hot season, are very similar to those reported by Vanos et al. This is true both for absolute values by period i. There are other reports relating EB modelling at this spatial scale to various characteristics of the urban landscape [ 17 , 18 , 22 ]. Harlan et al. The magnitude of this finding by Vanos et al.

These changes are greater than those predicted in the present study due to the more extreme methods applied by Brown et al. Further, although the modelled changes in surface albedo aided in reducing the energy budgets, related observational studies only controlling for surface albedo show slight increases in the absorbed radiation or mean radiant temperature due to a great amount of solar radiation imposed on a human as compared to lower albedo [ 37 , 38 , 39 ].

The combination of both shade and high-albedo surfaces, however, may cause varying results, yet further observational research in this area is needed. The methodology and findings presented in this study help to further quantify the impact of interacting UHI mitigation strategies, such as those proposed by Harlan and Ruddell [ 34 ] and Stone, Hess and Fumkin [ 40 ] within specific CTs. These changes would result in a much lower risk of heat stress and improved thermal comfort towards the neutral zone of comfort. Published recommendations for microclimatically-appropriate design were applied to two CTs in Toronto that had high levels of heat-related ambulance calls during heat waves.

Post-design pEB was lowered to a level nearing a range of thermal neutrality. This study demonstrated that pEB modelling can aid in the quantification of the thermal comfort benefits of proposed designs and help relate design proposals to beneficial health outcomes. Focusing future efforts on modifying the pEB model to accept the presence of buildings within an acceptable level of error would be a meaningful advancement. Mean daily city-wide baseline energy budget bEB from 11h00 to 18h00 by period consolidated across all years.

The authors would like to thank Toronto Emergency Medical Services for sharing the ambulance call data used herein. Drew A. Graham, Jennifer K. Vanos, Natasha A. Kenny, and Robert D. Brown conceived and designed the experiments; Drew A. Graham performed the experiments; Drew A. Graham and Robert D.