The impact of the cooling effect of urban parks on thermal comfort from the physiological and the psychological perspective

6 Background: In densely populated urban centers, increased air temperature due to urban heat 7 island (UHI) effect can undermine the thermal comfort and health of citizens. Research has shown 8 that large urban parks can mitigate the effect of UHIs and improve thermal comfort, especially in 9 the warmer months of the year when temperature changes are more noticeable. This study 10 investigated the cooling effect intensity (CEI) of the Retiro Park in the center of Madrid at three 11 different distances from its southern edge and the impact of this cooling effect on thermal comfort 12 from physiological and psychological perspectives. This investigation was performed by 13 measuring microclimate data and conducting a survey simultaneously during the summer days. 14 Results : The results showed that the CEI of the park varies with distance from its edge. Because 15 of this effect, air temperature within the 130m and 280m distance of the park was respectively 16 1.6°C and 0.9°C lower than the temperature at the 520m distance (the nearest heat island). After 17 examining the effect of the park in terms of Physiological Equivalent Temperature (PET), it was 18 found that the PET at the 130m and 280m distance of the park was 9.3% and 5.4% less than the 19 PET in the heat island domain. More than 81% of the respondents (in all three areas) had a mental 20 image of the park as the place where they would experience the highest level of outdoor thermal 21 comfort, and this rate was higher in the areas closer to the park. The analysis of citizens’ responses 22 about perceived thermal comfort (PTC) showed that citizens in areas with higher CEI had 23 perceived a higher degree of thermal comfort from the psychological perspective. Conclusion: This study demonstrates the significant role of large urban parks located in the core 25 of the populated cities in providing thermal comfort for citizens from both physiological and 26 psychological perspectives.

about perceived thermal comfort (PTC) showed that citizens in areas with higher CEI had 23 perceived a higher degree of thermal comfort from the psychological perspective. 24 Conclusion: This study demonstrates the significant role of large urban parks located in the core 25 of the populated cities in providing thermal comfort for citizens from both physiological and 26 psychological perspectives. 27 28 Keywords: Urban Park; Urban Heat Island; Thermal comfort; Perceived Thermal Comfort; 29 Physiological Equivalent Temperature; Cooling Effect Intensity 30 31 Background 32 Climate change has had visible effects on many human communities all over the world, but these 33 effects are more deeply felt in large, densely populated cities (IPCC, 2019; Bulkeley, 2013). 34 Research has shown that urban areas are typically warmer than their rural counterparts; a difference 35 that can be attributed to the phenomenon known as urban heat island effect (UHI) (Ward et al.,36 2016; Oke, 1982;Taha, 2017). This effect is strong enough to cause major physical and mental 37 health problems for citizens ( to the temperature conditions that satisfy at least 80% of individuals (CIBSE, 2015). Human 54 thermal comfort depends on several factors including climate, air temperature, humidity, sunlight, 55 and air movements (Rupp et al., 2015). Ultimately, people's perception of environmental 56 conditions also depends on non-climatic factors such as clothing type, coping ability, age, gender, 57 physical appearance, subcutaneous fat, fitness, diet, and skin color (Djongyang et al., 2010;van 58 Hoof & Hensen, 2007). 59 Serious research on the subject of thermal comfort began in 1956 with the study of conditions of 60 human thermal comfort in indoor spaces and later expanded to outdoors (Orosa, 2009 PET is and is one of the four most widely used indexes in outdoor thermal comfort research (PET,  82 PMV, UTCI, SET*). PET has also been used in a wider range of climatic regions than other 83 indexes (Potchter et al., 2018). 84 ASHRAE defines thermal comfort not solely as an environmental and physiological phenomenon 85 but also as a condition of mind that expresses satisfaction with the thermal environment 86 (ASHRAE, 2010(ASHRAE, , 2015. In this definition, the term "condition of mind" refers to the fusion of 87 mental and physiological conditions in the concept of thermal comfort (ASHRAE, 2017 perception of their environment can be studied by the use of environmental psychology methods 106 and instruments. One of the most common of these instruments is cognitive maps (Kitchin, 1994;107 Heft, 2013; Wang & Schwering, 2015). These maps can represent people's knowledge of places 108 and their importance in people's minds, and can, therefore, be used in outdoor comfort studies to 109 gain an insight into how important people believe a place is in terms of contribution to thermal 110 comfort . In other words, these maps can help us examine the citizens' 111 perception of places based on their role in creating thermal comfort (Klemm et al., 2015b). 112 113 Given the role of urban green spaces in mitigating urban heat and creating thermal comfort in built-114 up spaces, they have a fundamental impact on the quality of life of citizens and sustainable 115 development of urban environments. In this study, we examined the cooling effect of a large 116 central park at different distances and the consequent impact on thermal comfort from 117 physiological and psychological perspectives. It should also be mentioned that a study similar to 118 the purpose and case study of this study was carried out in Madrid , but the 119 north part of the park was investigated in that study in the morning. 120 121

Methods 122
The measuring sites 123 This study was performed in Madrid, Spain (40°25′08″N; 3°41′31″W), which according to 124 Köppen-Geiger classification, has a "Hot-summer Mediterranean" climate (Kottek et al., 2006). 125 The case chosen for examining the effect of large urban green spaces on thermal comfort was the 126 Retiro Park, which, with an area of about 125 ha, is one of the largest parks in the center of Madrid. 127 The Narciso Serra district located 520m away from the southern edge of the park (marked red in Figure  132 1) (Román et al., 2017). For a more precise examination of the cooling effect of the park, two areas 133 at the intersection of Gutenberg-Valderribas-Fuenterrabía and Torrejón-Agustín Querol, which are 134 located in the orange and yellow zones at the 280m and 130m distance from the park, were also 135 included in the study. All selected intersections are physically and structurally identical. For easier 136 reference, hereafter, the Torrejón-Agustín Querol intersection (150m) is called intersection A, the 137 Gutenberg-Valderribas-Fuenterrabía intersection (280m) as called intersection B, and the 138 Granada-Narciso Serra intersection (520m) is called intersection C. 139

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The southern side of the Retiro Park has a regular and grid-like texture mostly consisting of 7-141 story buildings. The façade of most buildings in this area is made of red brick. The roads of the 142 area are asphalt and the sidewalks are mostly made of bright colored mosaic tiles ( Figure 2). 143 The data collected in this study were of two types: (I) Microclimate data including air temperature, 144 humidity, and wind speed, which were measured inside the Retiro Park and at all three 145 citizens' perceived thermal comfort and also cognitive maps whereby citizens were asked to 148 specify the places where they feel the most thermal comfort. 149 All data (both microclimatic and survey) were collected on clear sunny days. At each intersection, 150 data collection was performed over a 10 minute period, during which one group collected 151 temperature data and the other group conducted the survey. Since the peak temperature inside the 152 park in the summer of 2017 had been observed, on average, between 13:28 and 15:08 CEST 153 (AEMET, 2018), all stages of data collection were scheduled to start after 13:30. 154

155
Air temperature (Ta) and relative humidity (RH) were measured by a mobile microclimate station 156 (HOBO MX2301A Temperature/RH Data Logger, produced by Onset Computer Corporation Co., 157 MA, USA) with an accuracy of ±2.5% for RH and ±0.2°C for Ta. Wind speed (WS) was measured 158 by a Proster digital anemometer model MS6252a. All measurement devices were equipped with a 159 visor and installed 1.5 meters above the ground. A fisheye lens (Sigma 8 mm circular) was used 160 to assess the sky view and take fisheye photographs. Ta and RH data were automatically logged at 161 1-min intervals and averaged over every 10 minutes. Wind speed data were also recorded manually 162 at 1-min intervals and averaged over every 10 minutes. Climatic data including Ta and RH were 163 also collected from the AEMET station (Agencia Estatal de Meteorología) located inside the Retiro 164 Park (AEMET, 2018). 165   Table 1 The proportional percentages questionnaire data in the three investigated intersection (Nnode A= 46, Nnode B=43, Nnode C=44) on all the measured days. scores ranging from 1 (Very Low) to 5 (Very High) (   The investigation of psychologically perceived thermal comfort, which was done with the help of 240 questions and cognitive maps, showed that the cooling effect of the park has had a positive impact 241 on the minds of citizens, as people living or working closer to the park were feeling more thermally 242 comfortable than others who were farther away from the park and closer to one of the heat islands. 243 After processing the respondent's answers to direct questions about their perception of thermal 244 comfort (at the moment of the survey), which were scored from 1 to 5 (Very low = 1, Low = 2, 245 Medium = 3, High = 4, Very high = 5), the results showed that the mean score decreased from 246 3.16 for intersection A, which was 130m away from the park, to 3.07 for intersection B, which 247 was 280m away from the park, and finally to the sub-average score of 2.88 for intersection C, 248 which was 580m away from the park (Table 3). 249 250 10 *. The mean radiant temperature (Tmrt) has been calculated by RayMan 1.2.

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The analysis of the obtained cognitive maps with the AMMA software showed that out of 133 253 respondents, 108 people or about 81% marked the park. This means that the majority of citizens 254 know Retiro Park as the place where they would feel the highest degree of thermal comfort. As 255 expected, it was found that the people at the Andrés Torrejón-Agustín Querol intersection had the 256 highest rate of reference to the park (91.3%). In comparison, 81.4% of people at the Gutenberg-257 Valderribas-Fuenterrabía intersection and 70.5% of people at the Granada-Narciso Serra 258 intersection mentioned the park. The last figure is still quite high considering the relatively long 259 distance of the Granada-Narciso Serra intersection from the park. The results of the AMMA 260 analysis of the obtained maps were also plotted in the form of color spectra showing the places 261 most frequently marked by citizens. These plots also show that on every data collection day, the 262 Retiro Park was more frequently mentioned than any other public space in the study area ( Figure  263 4). 264 265 266   Since the results of ANOVA showed a significant difference between the average PETs of nodes 279 A, B, and C (P-value <0.05), Tukey's test was used to determine which of the response levels had 280 a significant difference (Tables 5 and 6). 281 282 Table 5. Multiple Comparisons Tukey PET analyses in the three investigated intersections.

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As mentioned earlier, the data collected by the questions included in the questionnaire were used 291 to determine PTC. As with PET, ANOVA Analysis was used to compare PTC in the three nodes 292 in the southern neighborhoods of the Retiro Park (Table 7). 293 294 Since the results of ANOVA showed a significant difference between PTC in different nodes (P-296 value<0.05), again, Tukey's test was used to identify the source difference between the response 297 levels. The results of this test are provided in the tables below (Table 8 and 9). 298 299

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The above results suggest that there is a significant difference between average thermal comfort 304 in the Andrés Torrejón-Agustín Querol intersection (Intersection A), which is 130m away from 305 the park and the Granada-Narciso Serra intersection (Intersection C), which is farther away from 306 the park and closer to the heat island. This test proves that the cooling effect of the park is well 307 perceived by the people living or working close to the park, causing them to have a significantly 308 different level of PTC than those living or working further away from the park. 309 310 Discussion 311 Research has shown that because of factors such as low albedo , extensive shading 312 , and moisture generation and evaporation from leaf surfaces (Vidrih & Medved,313 2013), the space within a park often has a lower ambient air temperature than the surrounding 314 environments (Park et al., 2017). The results of the present study showed that during the data 315 and Israel (Cohen et al., 2012), researchers have used PET index to measure the thermal comfort 332 generated by large urban parks, but there seems to be a gap in the research literature regarding of 333 the impact of this effect on the perceived thermal comfort from a psychological perspective. 334 Another gap in the existing literature is that previous studies have been mostly focused on the 335 space inside the park itself and neglected the consequent impacts on the spaces around the park. 336 Considering these gaps and the importance of this subject, the present study examined the cooling 337 effect of the Retiro Park on the neighborhoods to its south during hot summer days and the 338 consequent impact on the thermal comfort of citizens from both physiological and psychological 339 perspectives. The PET index was used to quantify the physiological aspect of this impact. The 340 psychological aspect of the subject was explored with the help of a researcher-made questionnaire 341 and through the analysis of cognitive maps. Since the questions included the questionnaire directly 342 asked the citizens about their perceived thermal comfort, the total score of the questionnaire was 343 defined as the measure of perceived thermal comfort (PTC Madrid plays an important role in reducing the impact of heat islands in this city. In the present 376 study, it was found that the cooling effect of the Retiro Park on the neighborhoods to its south 377 varies with the distance from the park and diminishes at the distance of 520m, which falls in the 378 domain of a heat island. The cooling effect intensity (CEI) of the park is higher in the areas closer 379 to the park, causing a 1.6°C reduction in air temperature within the 130m distance and a 0.9°C 380 reduction in air temperature within the 280m distance of the park compared to Granada-Narciso 381 Serra intersection (520m away from the park). 382 The results showed that any increase or decrease in the CEI of the Retiro Park will change the 383 level of thermal comfort of citizens who live or work near the park from both physiological and 384 psychological perspectives. The amount of PET within the 130m distance of the park was 4% less 385 than the PET at the 280m distance and 9.3% less than the PET at the 520m distance, which means 386 citizens within this distance of the park enjoy higher physiological thermal comfort. Also, the PET 387 at the 280m distance from the park was 5.4% less than the PET at the 520m distance. 388 The analysis of cognitive maps obtained from citizens to study the impact of the park's cooling 389 effect on their perception of thermal comfort showed that more than 81% of respondents had a 390 mental image of the park as the place that would provide them with the highest degree of thermal 391 comfort. This rate was above 81% and 91% in the two districts that were nearest to the park and 392 did not fall below 70.5% in the district that was farther from the park. The total score of the 393 questionnaire, which was used as a direct measure of PTC, showed that citizens in the area with 394 the highest CEI had the highest perception of thermal comfort from the psychological perspective 395 and citizens in the area with the lowest CEI had the lowest PTC. 396 The results of this study demonstrate the critical role of large urban parks in generating thermal 397 comfort for citizens from both physiological and psychological perspective.