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Perception of thermal comfort in outdoor public spaces in the medium-sized city of Chillán, Chile, during a warm summer
Urban Climate 30 (2019) 100525
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Perception of thermal comfort in outdoor public spaces in the medium-sized city of Chillán, Chile, during a warm summer
T
Pamela Smitha, , Cristián Henríquezb ⁎
a
Department of Geography and Center for Climate and Resilience Research (CR)2, Universidad de Chile, Chile Institute of Geography, Centre for Sustainable Urban Development (CEDEUS) and Centro de Cambio Global UC, Pontificia Universidad Católica de Chile, Chile
b
ARTICLE INFO
ABSTRACT
Keywords: Environmental comfort Perceived thermal comfort Public space Socioeconomic status
The study of thermal comfort in Latin American cities has been gaining great relevance for urban environmental planning. Some studies have evaluated the relationship between environmental and perceived comfort; however, the causes and social determinants of the different perceptions of the population have not been explored. The perception of thermal comfort in public spaces in the city of Chillán (Chile), which has an inland Mediterranean climate, is discussed in this context. First, we measured the environmental thermal comfort, adapting the Actual Sensation Vote index. A survey of 362 users of the five selected public spaces was carried out between 29 January and 01 February 2016 to obtain perceived comfort and relate it to the individual climatic history, use of public space and place of residence in the city. The results show that perceived thermal discomfort dominates over comfort on summer days; however, those users who visit public spaces for recreational purposes feel more comfortable, as well as those living in low socioeconomic status (SES) neighborhoods. On the other hand, users living in areas with higher socioeconomic status, have higher expectations regarding thermal environmental conditions.
1. Introduction Cities are nowadays the main habitat of human beings. In recent decades, there is an accelerated urbanization process, which has resulted in a 10% increase in urban population since 1995 (UN-HABITAT, 2016). Chile ranks above the Latin American average (75%), with 89.5% urban population in 2015, according to data published in the World Cities Report (UN-HABITAT, 2016). Although 50% of chilean urban population lives in the metropolitan areas of Santiago, Valparaíso, and Concepción, medium-sized Chilean cities have experienced the greatest growth (over 40% of their area) in the last two decades, according to calculations made for developed urban spots by MINVU (Chile's Ministry of Housing and Urbanism Planning) for the years 1993, 2003, and 2011. Changes already experienced by great metropolitan areas in Latin America, such as modification of the hydrological cycle, fragmentation of habitats, air pollution, and the creation of an urban climate are now being replicated in these cities. Traditionally, urban climatic studies the local scale, describing the patterns and attempting to understand climatic parameter, especially the temperature throughout the city, increasing knowledge of heat islands, as described by Oke (1987), land surface temperature (Tu et al., 2016 in China or Brazel et al., 2007 in the United States) and atmospheric air temperature (Cuadrat et al., 2005 in Spain; Papparelli et al., 2011 in Argentina; Mendonça and Lombardo, 2009 in Brazil). Studies seeking to recognize the factors that best explain both atmospheric and surface temperature patterns at local scale have been conducted in Chile. Those studies are
⁎
Corresponding author. E-mail address: [email protected] (P. Smith).
https://doi.org/10.1016/j.uclim.2019.100525 Received 5 June 2018; Received in revised form 17 January 2019; Accepted 11 August 2019 2212-0955/ © 2019 Elsevier B.V. All rights reserved.
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P. Smith and C. Henríquez
agreeing that the percentage of vegetation cover is one of the most significant factors (De la Barrera and Henríquez, 2017; Smith and Romero, 2016; Sarricolea and Martin-Vide, 2014; Smith and Andrade, 2013; Peña, 2009). In recent years, there has been an increase in the number of publications dedicated to the study of the urban microclimate. An initial approach to this scale has been the study of public spaces, such as urban canyons, among which is the study of the relationship between microclimate and site design (for example Smith and Henríquez, 2018 in Chile; De Schiller et al., 2001 in Argentina or Gomez & Ferrer, 2010 in Venezuela). Progress may be observed as well in the environmental thermal comfort of these spaces (Lamarca et al., 2016; Guzmán and Ochoa de la Torre, 2014), and to a lesser extent, in the analysys of users' perceptions regarding their satisfaction level with climatic conditions (Lenzholzer, 2010 in Germany; Zeng and Dong, 2015 in China; Nikolopoulou et al., 2004 in Greece). On this scale chilean studies have focused on the factors that explain the microclimatic conditions in Antofagasta (Guerra, 2008) and the main squares of eight Chilean cities (Del Castillo and Castillo, 2014). The work of Lamarca et al. (2016) is recognized as the first in Chile that in addition to describing microclimate, studies environmental and perceived thermal comfort. In this study, the environmental comfort was calculated from meteorological data collected in situ and perceived thermal comfort obtained from a survey. Studies on urban climate point out the impact of human behavior on human health, including outdoor thermal comfort, climatic efficiency, and building maintenance, use of public spaces, quality of life, and so on. Hence, it is important to consider the climate in urban planning in order to create more sustainable cities and generate greater thermal comfort conditions for their inhabitants (Nikolopoulou and Lykoudis, 2006). Body temperature may be affected by the surrounding environmental conditions, and even if this does not pose a health risk, it can have an impact on the satisfaction levels of people and, consequently, their experiences, modifying the use and permanence in a place exposed to unfavorable conditions (Perico-Agudelo, 2009; Nikolopoulou and Lykoudis, 2006; Guzmán and Ochoa de la Torre, 2014; Zeng and Dong, 2015). When studying urban climate at a human scale, people's perceptions are crucial: how do people experience the climate they live in and how does weather affect human comfort (Menotti, 2013). Thermal comfort is defined as a state of mind that expresses satisfaction with the environment that surrounds the person, without needing the increase or decrease of the current temperature (Vanos et al., 2010; Parsons, 2014). Thermal comfort depends on a series of objective and subjective parameters (Thabaz, 2011). The low correlations between the microclimate variables and the comfort perceived outdoors suggest that thermal physiology alone cannot fully describe these relationships (Nikolopoulou, 2011). An important part of human comfort and satisfaction about climate can be explained by subjective parameters, such as thermal history, expectations, and companionship, among others (Nikolopoulou, 2011; Lenzholzer et al., 2015). Thus, for example, a person in a colder climate zone is more sensitive to heat (Nikolopoulou et al., 2004). The purpose of this study is to compare the thermal comfort calculated for five public spaces in the city of Chillan with the perception of their users and determine its relationship with subjective factors, such as short, medium and long-term residence in Chillán and the neighborhood in which respondents live. Instrumental comfort, and subjective expectations regarding climatic conditions were also explored. The high summer temperatures in he city of Chillan impair the use of public spaces, which in addition to being very few, have been increasingly replaced by enclosed spaces, such as shopping centers, which maintain comfortable indoor climatic conditions at all time. Hence, Chillán represents the average rapid-growing Chilean and Latin American city: 37.7% in the past two decades, according to calculations made on the basis of developed urban spots by MINVU for the years 1993, 2003, and 2011 and a photo interpretation of its urban limits on a 2016 QuickBird image. Il also replicates large cities' environmental problems, such as scarcity of public spaces, with uneven distribution and quality due to the omission of climate in planning and urban design. In sharp contrast with the metropolitan spaces of the city, the suburbs include a series of privatized urban typologies, such as closed condominiums and “suburban plots” (Henríquez, 2014), and some socio-environmental amenities, such as vegetated spaces, swimming pools, and better ventilation. These conditions are for the exclusive use of the middle and upper classes and have important socio-spatial differences with the poorest groups residential environment. In this context, the working assumption is that there are subjective factors that affect the perceived thermal comfort in Chillan's public spaces. Thus, one might expect that users with lower socioeconomic status, D and E, feel more comfortable in public spaces and tend to be more tolerant to high temperatures than those with higher SES. 2. Materials and methods 2.1. Study area The city of Chillán is located in the Biobío region, Chile, and comprises the urban area of Chillán and Chillán Viejo cities. It is located at 36° 36′ south latitude, with an average altitude of 124 m above sea level; it has warm climate with winter rains, Csb, according to the Köppen classification for Chile (Sarricolea et al., 2016). It has a population of 204,180 inhabitants according to the data of the National Statistics Institute (INE, 2017), which classifies it as a medium-sized city, according to OECD criteria and medium-large, according to the types defined by the Ministry of Housing and Urban Development. Despite its location in the south-central zone of Chile, Chillán is one of the Chilean cities with the highest maximum average temperatures in the summer, with a pattern and intensity close to the cities of Arica and Iquique, which are located at inter-tropical latitudes (DMC, 2016). Chillán is one of the cities with the smallest area of public green areas per inhabitant in the country, with only 1.7 m2/per person. Chillán displays positive trend values in all indicators related with the increase in temperatures and the occurrence of heat waves during 1975 and 2015 (Smith and Henríquez, 2018). The Dirección Meteorológica de Chile (Chilean Meteorological Office - DMC) 2
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Fig. 1. Study Area and meteorological checkpoints in the city and inside of selected public spaces. Note. Each public space (picture right) has been divided into sections, assigned codes are bold.
defines heat waves as the occurrence of three or more consecutive days with temperatures above the summer threshold (considering the months of December, January and February). This threshold is determined from the 90th percentile of the maximum daily temperatures, using a 15-day moving average in the climatological period 1981–2010. Four heat waves events occurred in Chillan during the 2015–2016 summer, totaling 17 days, which means that almost 20% of the days in this season registered temperatures over the threshold average (32.4 °C). The highest temperatures registered in Chile for the summer period 2015–2016 correspond to the third heat wave event occurred in Chillán in the same period. This event concurred with the field campaign implemented by the current research; in the rural environment where the DMC station is located, the temperature reached 36 °C, while inside the urban area it rose over 39 °C, according to measurements made during the field campaign conducted in January and Febraury 2016. Public spaces in the city of Chillán occupy about 33% of its urban area; that is to say, 1008.6 ha; 83% of these correspond to paved surfaces (streets and sidewalks). The rest fall in the following categories: 115 median avenue strips (14.2 ha), 39 soccer fields (12.5 ha), one segmented waterfront drive (0.9 ha), one pedestrian walkway (0.7 ha), and 160 public squares and parks (41.8 ha). Squares and parks represent the largest percentage of those public spaces. Based on the regulatory plans of Chillán (2016) and Chillán Viejo (2012), the Intercommunal Plan Chillán-Chillán Viejo (2005), and consultation with municipal officials, five representative public spaces were selected (Fig. 1): -
Chillán Main Square (1.6 ha) Arauco Pedestrian Walkway (0.7 ha) Estero Las Toscas Park (1 ha) Sarita Gajardo Park (3 ha) Bernardo O'Higgins Monument Park (3.4 ha)
Analysis was based on climate information obtained from different fixed and mobile meteorological instruments and the field survey. 3
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Table 1 Level of environmental thermal comfort ambiental and perceived. ASV range
−5 −4 Discomfort by cold
−3
−2
−1 Comfort
0
1
2 3 Discomfort by hot
4
5
2.2. Environmental thermal comfort calculation The Actual Sensation Vote (ASV) index evaluated the environmental thermal comfort on a scale of −5 and + 5 score. According to the authors (Nikolopoulou et al., 2004), the value of thermal comfort is between the values of −1 and + 1. The authors propose ten different equations developed from the data of 10 different European cities (Eq. (1), built for Athenas, Greece). This paper proposes an equation to calculate the ASV of Chillán, built from multiple regression models presented by Nikolopoulou et al. (2004).
ASV = 0.034 Tair + 0.001Sol
0.086V
0.001HR
R2: 0.39
0.412
(1)
where: Tair = air temperature (in degrees Celsius); Sol = solar radiation (in Wm-2); V = wind speed (in m/s); RH = relative air humidity (in percentage) The model-dependent variable corresponds to the level of thermal comfort, perceived by users of public spaces (between - 5 and + 5, Table 1); the independent variables are the meteorological parameters included by the authors: temperature (in degrees Celsius), relative humidity (in percentages), global solar radiation (in W/m2) and wind speed (in meters per second). The climatic data (air temperature, air relative humidity, and wind speed) to construct the equation for Chillán comes from different sources: the air temperature recorders: 10 Logtag HAXO-8 (accuracy: 0.1 °C and 0.1% for humidity), 8 Datalogger HOBO Pendant UA-002-xx (accuracy: 0.53 °C), and 32 Ibutton Thermochron (accuracy: 0.5 °C) models installed inside and around the selected public spaces (Fig. 1). All instruments record hourly data, and the Logtag also measured relative humidity, continuously, during the summer 2015–2016. During the fieldwork carried out between January 29 and February 1, 2016. The meteorological parameters were measured every two hours (12, 14, 16, 18, and 20 h local time), at different points within the public spaces using VETO brand mobile instruments. Each public space selected had at least 10 measurement points, including fixed recorders and mobile measurements. The variations observed inside public spaces do not exceed 2.5 °C or 3 percentage points of relative humidity between the different measurement points. Global radiation was modeled in Autodesk Ecotect Analysis software, starting with the constructions 3D model and the weather data file of the city. The global solar radiation per hour was calculated in Wm-2, between 10 and 20 h on a grid of 15 m' cells for each public space (Fig. 2). In order to obtain the required data and calculate the ASV equation for the city of Chillán, each public space was sectored. The climatic data was obtained by measuring meteorological parameters (Fig. 1 and 3a). The average global solar radiation of its cells was
Fig. 2. Global solar radiation in Bernardo O'Higgins Park between 12:00 and 13:00 h calculated in Ecotect Analysis software. 4
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Fig. 3. Example of data identification, (a) sectors of the public space. (b) data series: variables for calculating ASV.
determined for each sector. With the data obtained, a series was constructed that contained the independent variables for each sector per hour, as shown in the table of Fig. 3b. The dependent variable, thermal comfort, was obtained by calculating the average thermal comfort perceived by the users in each sector at a given time. 2.3. Perceived comfort calculation 362 selected public space users were interviewed (Fig. 3) during the field work. The users survey was carried out on a continuous basis, from 11 to 20 h local time, between January 29 and February 1, 2016. The survey included four sections: (1) Respondent General Description; (2) User's perception; (3) Spatial Analysis; and (4) Public Space Use (Table 2). The respondents, men and women 5
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Table 2 Survey of perceived thermal comfort.
Date: Place in the public space:
Public space:
Hour:
Section 1. Respondent General Description Age: Gender Male Female Time on the street Contexture: Thin Normal strong Clothing: Little Normal lot Clothing color: Clear Mixed dark Section 2. User´s perception Thermal comfort: -5 -4 -3 -2 -1 0 1 Cold, very uncomfortable Good, Comfort Section 3. Spatial analysis Place of birth Current place of residence Time in the current residence Section 4. Use of public space Purpose of Doing sports Displacement Pet walking visit Work/study Waiting for / Meeting people
2
3 4 5 Hot, very uncomfortable
Recreation
Relaxation
over the age of 18 were visiting the studied public spaces. The perception was measured on a scale of 11 points, with values between −5 and + 5, where comfort ranges from −1 to +1, according to the adaptation of the Cheng method (2008). The result of environmental thermal comfort was compared with the thermal comfort value perceived by each user surveyed. We considered the sector, day and time in which each user was surveyed to obtain the corresponding climatic and solar radiation parameters. The location of the surveyed users, obtained from their place of residence, was spatialized by block to estimate their socioeconomic status, using the classification proposed by Adimark (2004) for the year 2013. Adimark identifies the following five socioeconomic status (SES) considering the level of education of the head of the household and the possession of a set of goods: ABC1 and C2, which correspond to the two higher-income groups; C3, which represents the medium-income quintile; and finally, the poorer groups, D and E (Table 3). In order to assess the conditions of perceived thermal comfort, different dimensions of psychological adjustment, regarding experiences, reasons for use, and expectations of users surveyed were considered. Previous experience was considered on two temporary scales: short- and medium-long term. The short-term experience was studied by relating the perceived comfort to the temperature registered on the days prior to the interview of each user, and the medium-long term experience included place of origin and length of residency in the city of Chillán. The reasons for their visit to a given public space were considered in the analysis of user's perceptions; as well as the environmental conditions of their permanent residence, determined through air temperature and socioeconomic status. Air temperature in the residence area of public space users was obtained by interpolating the data recorded by Hobo, Logtag, and Ibutton while they were surveyed, in order to determine the difference in temperature between the latter and the visitor's neighborhood. The field survey was reviewed and approved by the Comité de Ética de Ciencias Sociales, Artes y Humanidades (Ethics Committee of Social Sciences, Arts, and Humanities) of the Pontificia Universidad Católica de Chile (record n° 151,230,003). The assistants were committed by a signed document, to maintain the confidentiality of the research, and respondents were informed and approved for their participation by signing the informed consent form.
Table 3 Characteristics of socioeconomic status. Socioeconomic status
Level of education (average years)
Average possession of a set of goods
Income range (dollars)
% at country level
ABC1 C2
16.2 years (comlete university studies) 14 years (comlete technical studies or incomlete university studies) 11.6 years (complete high school) 7.7 years (incomplete high school) 3.7 years (incomplete primary school)
9.2 7.2
U$ 2858 or more U$867 - U$1735
7.2 15.4
5.7 4.4 2.3
U$578 - U$723 U$289 - U$433 Equal or less than U $231
22.4 34.8 20.3
C3 D E
Note: the average value of the dollar for the year was $691.3 Chilean pesos, according to the values published by the Internal Tax Service (SII in Spanish). 6
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Fig. 4. Place of residence of surveyed users of public spaces (circles). The socioeconomic levels of its neighborhoods (block color). The number shows the public space analyzed.
3. Results Thermal comfort was approached from two perspectives: through environmental indicators, and the user's perceptions. After analyzing the results of both approaches, their coincidences was analyzed. 3.1. Surveyed users description The largest number of surveyed respondents corresponded to the Chillán Main Square (121); the Arauco pedestrian walkway and Bernardo O'Higgins Monument Park occupied the second place, with 72 and 79 respondents, respectively. In the remaining public spaces around 45 users were surveyed, a number close to all their users. Most of the respondents were between 21 and 30 years (37% of the total); 45.5% (143) were women, and 54.5% (171) were men. The greatest percentage of users surveyed were employees or students. Of the total number of respondents, 326 lived in the city of Chillán, which represents 90%. Of the remaining 10% (34 people), 22 lived in another town of the Biobío region. Of the 326 living in the study area, only 208 were born there. Of the remainder, the majority was born in the Biobío region and, in second place, in the Metropolitan region—specifically in the city of Santiago. Most of the respondents belong to the socioeconomic status D and C3. The lowest proportion correspond to status E and ABC1, which coincides with the distribution of the socioeconomic status throughout the city. The diverse socioeconomic groups are not equally represented in all Chillán public spaces. ABC1 users were only found in the Arauco Pedestrian Walkway and the Chillán main square; on the other hand, Sarita Gajardo Park received very few C2 visitors but concentrated the largest number of D and E users (Fig. 4). 3.2. Environmental thermal comfort Six equations were used to calculate environmental thermal comfort (ASV), one for each public space studied (equation n°3 for the main square of Chillán, equation n°4 for Arauco, Pedestrian walk, equation n°5 for Estero Las Toscas park, equation n°6 for Sarita Gajardo park and equation n°7 for Bernardo O'Higgins park), the sixth, for the city of Chillán, was built from the data obtained in all public spaces in an aggregate manner. 7
Urban Climate 30 (2019) 100525
P. Smith and C. Henríquez 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
98
52
18
12
26
31
69
18
13
10
Main square of Pedestrian walk Estero Las Toscas Sarita Gajardo Chillán Arauco park park Good, comfortable
Bernardo O´Higgins park
Heat, very uncomfortable
Fig. 5. Perceived thermal comfort by public space.
The instrumental comfort, determined by the equations of ASV, yielded values ranging between 1.5 and 4.4, meaning that all users perceived thermal discomfort, due to heat.
ASV ASV
ASV ASV
Chillan city = 0.158Tair + 0.001Sol
0.408V
0.004RH + 1.39
R2: 0.23
(2)
0.296V
R2: 0.46
(3)
0.060RH + 2.49
R2:
0.32
(4)
0.035RH + 103
R2:
0.33
(5)
R2:
0.26
(6)
R2: 0.48
(7)
Chillan main square = 0.180Tair + 0.003Sol
Pedestrian walk Arauco = 0.095Tair + 0.008Sol Estero Las Toscas Park = 0.045Tair + 0.001Sol
0.009RH + 2.63
0.182V 0.312V
ASV
Sarita Gajardo Park = 0.073Tair + 0.003Sol
0.350V
ASV
Bernardo O ´Higgins Park = 0.118Tair + 0.002Sol
0.008RH + 5.43
0.092V
0.032RH + 6.35
3.3. Perceived thermal comfort When considering the total users of the five public spaces studied, the very uncomfortable category, associated with heat, represents 76% of the total number of answers. Heat discomfort prevails in Chillán main square, Arauco pedestrian walkway, and the Bernardo O'Higgins Monument park of Chillán Viejo, exceeding 80% of its users. Only in Estero Las Toscas park and Sarita Gajardo park (Fig. 5), show a higher percentage of users (up to 30%) declare to be in thermal comfort. According to the survey results, an inverse relationship between general comfort perception and wind speed and humidity (with a Spearman's correlation coefficient of −0.25) was observed. On the other hand, there is a direct and more intense relationship between perceived thermal comfort and exposure to sun, with a coefficient of 0.48. In all cases, the relationship was statistically significant at the 0.01 level. 3.4. The relationship between environmental thermal comfort and perceived thermal comfort the comfort feeling present a greater coincidence between perceived and calculated comfort; however, this is because, according to the ASV, 352 of the 362 surveyed users are in this condition. On the contrary, the discomfort categories present low coincidence between both methods for quantify the thermal comfort. Fig. 6 shows the relationship between the values obtained by the ASV for perceived thermal comfort (with a Spearman's correlation coefficient of 0.32). The chart shows a low dispersion, concentrated between values 1 and 5 (thermal discomfort), although 86 users reported feeling comfortable with weather conditions in general.
Fig. 6. Diferences between perceived thermal comfort and environmental thermal comfort (ASV). 8
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Table 4 Users surveyed in thermal comfort (C) and (D) thermal discomfort conditions in public spaces.
Total users surveyed Questions Categories Place of birth Chillán city Biobío region Other regions Other countries DR Current place of Chillán city residence Biobío region Other regions DR Time of residence less than a year One year 2 to 5 years 6 to 10 years > 10 years Whole life Not live in the city DR Purpose of visit Doing sports Displacement Waiting for/ Meeting People Pet walking Recreation Relaxation Work/Study Tourism DR
The main square of Chillán
Pedestrian walk Arauco
Estero Las Toscas park
Sarita Gajardo park
Bernardo O'Higgins park
Total number of users
121 C 7.4 2.5 5.8
72 C 4.2 6.9 4.2 1.4 10.8 12.5 1.4 2.8 12.5 1.4 4.2 1.4 0 4.2 1.4 4.2 13.9
46 C 10.9 8.7 8.7
44 C 25 6.8 6.8 0 2.3 38.6 2.3
79 C 10.1 0 2.5
59.1 0
0 6.8
4.5
362 C 36 13 21 1 16 62 5 5 16 4 3 3 6 8 46 10 25 2 7 16
D 42.1 23.1 15.7
D 47.2 8.3 15.3 1.4
3.3 11.6 1.7 2.5 3.3 0 0 2.5 2.5 1.7 3.3 4.1 9.1 0 3.3 5
1.7 9.9 22.3
0 2.8
15.3 11.1
4.3 2.2
13 19.6
0.1 4.1 2.5 0.8
7.4 18.2 14 7.4
1.4 4.2 8.3
9.7 16.7 19.4
8.7 4.3 8.7 2.2 4.4
17.4 6.5 8.7 0
3.3
72.7 7.4 0.8 5 2.5 19 15.7 7.4 19 8.3
66.7 4.2 0 2.8 2.8 22.2 6.9 13.9 13.9 6.9
11.1
6.5 26.1 2.2 0 6.5 0 0 0 0 10.8 10.8 2.2 15.2
D 34.8 17.4 13 54.3 4.3 6.5 0 2.2 13 4.3 21.7 8.7 10.1
D 45.5 9.1 2.3 2.3
2.3 0 4.5 25 2.3 0 2.3
4.5
11.4
9.1
0 11.4 11.4 4.5
2.3 15.9 22.7 4.5
0
4.5 4.5 0 45.6 0
0 12.7 0 0 0 0
D 51.9 20.2 15.1 81 3.8 2.5 3.8
0 1.3 1.3 10.1 0 0 1.3 1.3 1.3
11.4 5.1 7.6 53.1 6.3 8.9 7.6 7.6
0 8.6
1.3 53.2
0 1.3 1.3
6.3 0
0 21 13 13 2 17
D 162 67 44 2 251 17 6 10 3 32 18 17 152 25 11 36 57 11 81 41 34 0
Note. The values of comfort and discomfort are in percentages and have been calculated from the total number of each public space, except the bold values. DR is does not respond.
3.5. Analysis of the expectations on perceived thermal comfort Considering the complex nature of the thermal comfort concept, its analysis can be enhanced by including subjective variables, such as the level of expectations regarding the temperature. The expectations are dynamic and set new limits on the endurance of the individuals. These can be influenced by experiences associated with place of origin, place of residence, the season of the year, the weather on the previous days or hours, or the reason to use a public space, among others. 3.5.1. Selection of users: a reason to use public spaces The selection of users is mainly associated with the reasons which explain their presence in each of the public spaces. For the analysis, these were grouped into seven categories: (1) Play, sports, (2) place of transit (to walk from one place to another), (3) Walk a pet, (4) Recreation, (5) Relaxation, (6) Work or study, and (7) Use public space as a waiting/meeting place (Table 4). In most cases, > 80% of the responses express disconfort. The percentage is higher among those who use the public space as a meeting point, place of transit, for working, making transactions, or studying (close to 80%). In the latter case, most respondents correspond to Arauco pedestrian walkway, as well as walking around since the walk is a two-block urban canyon, with the presence of trees on both sides, without vehicular traffic and where users are in movement, passing by, without staying long periods of time in the public space. 3.5.2. Previous experience 3.5.2.1. Previous short-term comfort experience. Fig. 7 shows the proportion of users in comfort and discomfort by day. The result is examined considering the subjective dimension of comfort, related to the previous short-term experience. In this case, only the responses of users who live in the city have been included. It is important to bear in mind weather patterns associated with a frontal synoptic condition in the prior days to the fieldwork. On January 27, the temperatures did not exceed 26 °C, and precipitations reached only 5 mm. The next day, January 28, rain was not reported, but the temperature remained low for the season, with an averages of 20 °C. The above may explain the high proportion of perceived thermal comfort on January 29 (44%), when maximum temperatures were close to 30 °C. If we look at the graph, on January 30 (Saturday) thermal confort reaches 20%, descending to 14% on the next day, despite both correspond to o an intense heat wave episode that lasted until February 1, with a maximum temperature close to 36 °C, according to data from the Chilean National 9
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January 29
January 30
January 31
February 1 0%
20%
40%
Thermal comfort
60%
80%
100%
Thermal discomfort
Fig. 7. Relationship between perceived thermal comfort and measurements days.
Weather Service. 3.5.2.2. Medium- and long-term perceived comfort. An adaptation process to the meteorological conditions can be observed by comparing the proportion of users “in comfort” according to the length of residence in the city of Chillán. As described above, of the total number of users, 55% were born in the city (option “whole life” in Table 4), and at the same time, show the highest proportion of thermal comfort. This could also relate to a higher level of adaptation and c onsequent tolerance to weather conditions. Those residents who were not born in Chillan have been divided into four ranges: Less than a year, from 2 to 5 years, 6 to 10 years, and more than ten years living in the city of Chillán. As shown in the table, the lower the number of years of residence, the lower the comfort proportion. Those users who did not live in the city were divided into two groups: residents in any town of the Biobío region, and tourists from another region (category other regions and other countries in Table 4). The latter registered a higher level of comfort (46% of users) than those who live in the region (22%). This could be explained by the urban hierarchy of the place of origin, because those who come from the Biobío region live mainly in small towns, such as San Carlos, Pinto or rural areas like San Nicolás; on the other hand, the visitors are from other regions, for example, from Santiago and Temuco. 3.5.3. Comfort and neighborhood socio-environmental conditions The following two relationships try to demonstrate that the expectations regarding weather conditions change according to the environmental conditions of the place of residence, that is to say the climate the user currently experiences, which we can obtain, as well as his socio economic status, from his housing location (Smith and Henríquez, 2018). First, the temperature difference (DT) of the neighborhood where the user lives and the public space where the user was surveyed was defined as:
DT = Tneighborhood–Tsurveyed The results obtained with DT are presented in four categories (Fig. 8): -
DT > 2, when the temperature in the users neighborhood is 2 °C more than the public space where was surveyed. 0.5 < DT < 2, when the temperature in the users neighborhood is until 2 °C more than the public space where was surveyed. −0.5 < DT < 0.5, when the temperature is the same in both places. DT < −0.5, when the temperature in the users neighborhood is less than the public space where was surveyed.
Fig. 8. Relationship of temperature difference between the place of residence outdoors public space and the public space and the perceived thermal comfort. 10
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ABC1 C2 C3 D E 0%
10%
20%
30%
40%
50%
Thermal comfort
60%
70%
80%
90%
100%
Thermal discomfort
Fig. 9. Socioeconomic levels of all respondents versus perceived thermal comfort.
It is noted (Fig. 8) that there is a higher proportion of users who feel comfortable the two groups where DT > 0.5: for example, those users whose neighborhood show worse climatic conditions than the public space where they were interviewed, even when this difference only amounts to half a degree of temperature. Fig. 9 shows an inverse relationship between the socioeconomic level of users and the comfort they perceived in the public space. Those users who belong to the socioeconomic group ABC1 have higher expectations regarding climatic conditions, due to better environmental conditions in their residential environment. Therefore, they declare greater thermal discomfort in public spaces. In contrast, a greater proportion of users ranked C2 and D, which usually live in areas with a high density of construction and low percentages of plant cover, feel satisfied with the climatic conditions in public spaces. There are no differences in quantity and color of clothing associated with the socio-economic level of users. The ABC1 visitors, like the rest of the respondents, dressed a normal amount of clothing, generally light colored and never used formal wear. Only the Arauco Pedestrian walk Arauco and the Chillán main square registered visitors belonging to the ABC1 socioeconomic level. If the perception of thermal comfort among the population of the different socioeconomic levels is compared only in these two public spaces (Fig. 10) the results are similar to those presented in the previous paragraph. (Fig. 9), discarding the presence of a particularly disconfortable condition that could excplainthe different perceptions observed. The presence of the ABC1 group in the public space is mainly due to business transactions (80% of users in this group). In the remaining socioeconomic groups, partdicularly in C2 and D, the dominant responses are “to meet with people”, which is associated with using public space as a meeting place, and the options “walking around,” and “playing with the children,” which together account for almost 30% of the users in each socioeconomic group.
Fig. 10. Socioeconomic levels of respondents versus perceived thermal comfort in the main square of Chillán and Pedestrian walk Arauco.
4. Discussion In the first place, the difference between perceived thermal comfort and environmental thermal comfort, calculated by the ASV index, reaffirms the importance of considering that the perceived thermal comfort is affected by subjective factors, in addition, to the objective parameters mainly related to the meteorological parameters that are commonly included in the equations to measure comfort instrumentally (air temperature, relative humidity, wind, and solar radiation). The results obtained by connecting the perceived thermal comfort with some fewer common aspects in the literature, such as length of residence or the reason for use, highlight the importance of subjective and local factors associated with climate expectations and climate adaptation in urban environments (Nikolopoulou, 2011; Lenzholzer et al., 2015). Thus, for example, the results obtained when relating time of residence in the city versus thermal comfort are comparable to those obtained by Yu et al. (2013), which show that when individuals are used to high temperatures inside their homes tend to feel public spaces cooler than those used to lower indoor temperatures. According to our hypothesis, the results obtained allow us to discuss various aspects. In the first place, public spaces give access to good environmental conditions for those who live in poor quality neghbourhoods, and explains the higher level of comfort shown by users of public spaces belonging to socioeconomic groups D and E. People in the latter categories usually have no house gardens and, at the same time, the surrounding public spaces have a higher proportion of waterproof surfaces and a lower vegetation cover. 11
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Therefore, the city's planning and design should consider increasing the amount and quality of public spaces in those sectors. Secondly, the relationship between thermal confort and socioeconomic shows a lower tolerance to high temperatures in higherincome population, mainly ABC1 group. The lower tolerance to high temperatures is associated with the best environmental and climatic conditions in the private spaces where they reside, coupled with improved environmental housing conditions, which are associated with private condominiums and country plots, as well as abundant vegetation in a metropolitan setting, swimming pools, and low-density occupation, among other factors (Henríquez, 2014). Therefore, ABC1 users were only found at the Arauco walkway and the Chillán Main Square, where the main services trade areas are located. Finally, the results confirm the Perico-Agudelo (2009) proposals, in order to suggest that there is a direct relationship between perceived thermal comfort and place of residence of the citizen, which would explain the way in which the latter uses and appropriates public space. However, this author approaches this matter in theoretical terms, without developing it empirically. 5. Conclusions According to the results obtained, we can establish that there is an effect of previous short, medium, and long-term experiences on comfort perception: comfort level is higher in those born in Chillan, and consistently grows in its residents as the time of residence increases., which may account for a level of adaptation or accommodation to the weather conditions of the place. During the summer, thermal comfort in the selected public spaces is better perceived by low-income population, who mostly use these spaces, especially for recreational purposes. From the above, we may conclude that there is a significant climatic injustice, the poorest population has less access to quality public spaces because these are scarce in the neighborhoods and have neither the design not the necessary infrastructure to provide comfort conditions. In contrast, middle and high-classes have enough resources to solve their discomfort problems through wellequipped spaces with large vegetated surfaces, pools, and constructions with better ventilation, air conditioning, and other measures. This mid-sized city has very high-density neighborhoods, with few private vegetated spaces. Therefore, these public spaces, especially the parks, are the only alternative for its population to deal with episodes of extreme heat, such as those we have experienced these past few summers. Chillán has an environment with many advantages as agricultural land, areas with natural vegetation, ancient river beds, inlets, and canals, among other urban elements that have been inserted in the city as residual spaces, disconnected, and in some cases abandoned or urbanized. Regulatory plans have not taken advantage of this potential to articulate natural and semi-natural spaces with urban green spaces, such as median strips, bike lanes, squares, and parks that could set up a network of public spaces, promote the provision of urban ecosystem services, and improve the urban environmental quality. Acknowledgments Surveys and fieldwork measurement of meteorological parameters were conducted with the assistance of eight students from the History and Geography Teaching Program at the University of Biobío, Chillán. Cristóbal Lamarca, Architect, assisted the calculation of solar radiation. All hourly data related to air temperature, relative air humidity, wind direction, and wind speed were provided by the DMC's Bernardo O'Higgins station, located at the Chillán airport and the meteorological station at the University of Biobío, Campus La Castilla. This research was supported by FONDECYT Project N° 11180990 “La construcción social del clima urbano: hacia la calidad y justicia climática en las ciudades chilenas” and CEDEUS Center CONICYT/FONDAP15110020. References Cuadrat, J., Serrano, S., Saz, M., 2005. Los efectos de la urbanización en el clima de Zaragoza: La isla de calor y sus factores condicionantes. Boletín de la A.G.E 40, 311–327. Nikolopoulou, M., 2011. Outdoor thermal comfort. Front. Biosci. S3, 1552–1568. ADIMARK, 2004. Mapa socioeconómico de Chile. Nivel socioeconómico de los hogares del país basados en datos del censo. Brazel, A., Gober, P., Lee, S., 2007. Determinants of changes in the regional urban heat island in metropolitan Phoenix (Arizona, USA) between 1990 and 2004. Clim. Res. 33 (2), 171–182. Ilustre Municipalidad de Chillán, 2016. Ordenanzan Local Plan Regulador Comunal de Chillán. (49 pp). De la Barrera, F., Henríquez, C., 2017. Vegetation cover change in growing urban agglomerations in Chile. Ecol. Indic. 81, 265–273. Del Castillo, M., Castillo, C., 2014. Aproximación bioclimática para el diseño de espacios públicos, análisis inicial en distintas plazas chilenas. Arquitectura y Urbanismo XXXV (3), 69–82. Dirección Meteorológica de Chile – DMC, 2016. Umbrales de eventos extremos y ola de calor en Chile. Publicación interna, Santiago, Chile. Guerra, J., 2008. Diseño sustentable y calidad bioclimática del espacio público en zonas áridas. Revista Arquitectura del Sur 34, 30–43. Guzmán, F., Ochoa de la Torre, J., 2014. Confort térmico en los espacios públicos urbanos. Clima cálido y frío semi-seco. Revista Hábitat Sustentable 4 (2), 52–63. Henríquez, H., 2014. Modelando el Crecimiento de Ciudades Medias. Hacia un desarrollo urbano sustentable. Ediciones UC, Santiago de Chile (314 pp). Ilustre Municipalidad de Chillán & Ilustre Municipalidad de Chillán Viejo, 2005. Ordenanzan Plan Regulador Intercomunal Chillán – Chillán Viejo. (39 pp.). Instituto Nacional de Estadísticas, 2017. XIX Censo Nacional de Población y VIII de Vivienda o Censo de Población y Vivienda. Datos disponibles en. www. censo2017.cl. Lamarca, C., Quense, J., Henríquez, H., 2016. Thermal comfort and urban canyons morphology in coastal temperate climate, Concepción, Chile. Urban Climate 23, 159–172. Lenzholzer, S., 2010. Engrained experience – a comparison of microclimate perception schemata and microclimate measurements in Dutch urban squares. Int. J. Biometeorol. 54 (2), 141–150. Lenzholzer, S., Klemm, W., Vasilikou, C., 2015. New qualitative methods to explore thermal perception in urban spaces. In: Conference Proceedings ICUC9 – 9th International Conference on Urban Climate Jointly with the 12th Symposium on the Urban Environment. Mendonça, M., Lombardo, M., 2009. El clima urbano de ciudades subtropicales costeras atlánticas: el caso de la conurbación de Florianópolis. Revista de geografía Norte Grande 44, 129–141.
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Menotti, S., Monteiro, SantÁnna y, 2013. O conforto térmico nas escolas estaduais de president prudente/SP. Climatologia urbana e regional, cuestiones teóricas y estudios de caso. In: De, Costa (Ed.), Geografía en movimiento. Sao Paulo, Brasil, pp. 221–246. Nikolopoulou, M., Lykoudis, S., 2006. Thermal comfort in outdoor urban spaces: analysis across different European countries. Build. Environ. 41, 1455–1470. Nikolopoulou, M., Lykoudis, S., Kikira, M., 2004. Thermal Confort in Outdoor Spaces: Fiel Studies in Greece. Centre for Renewable Energy Source (C.R.E.S). Oke, T., 1987. Boundary-Layer Climate. Routledge, Second edition. . Papparelli, A., Kurbán, A., Cúnsulo, M., 2011. Isla de calor y ocupación especial urbana en San Juan, Argentina: análisis evolutivo. Cuadernos de vivienda y urbanismo 4 (7), 110–120. Parsons, K., 2014. Human Thermal Environments: The Effects of Hot Moderate and Cold Environments on Human Health. Comfort and Performance. Crc Press, USA. Peña, M., 2009. Examination of the land surface temperature response for Santiago, Chile. Photogramm. Eng. Remote. Sens. 75 (10), 1191–1200. Perico-Agudelo, D., 2009. Una aproximación desde el estudio de sus características microclimáticas. Cuadernos de Vivienda y Urbanismo 2 (4), 278–301 El espacio público de la ciudad. Sarricolea, P., Martin-Vide, J., 2014. El estudio de la Isla de Calor Urbana de Superficie del Área Metropolitana de Santiago de Chile con imágenes Terra-MODIS y Análisis de Componentes Principales. Revista de Geografía Norte Grande (57), 123–141. Sarricolea, P., Herrera-Osandón, M., Meseguer-Ruiz, O., 2016. Updating of the climatic regionalisation of continental Chile using Köppen classification. J. Maps 13, 66–73. De Schiller, S., Evans, J.M., Katzschner, L., 2001. Isla de Calor, Microclima Urbano y Variables de Diseño Estudios en Buenos Aires y Río Gallegos. Rev. AVERMA5 1–45. Smith, P., Andrade, X., 2013. Distribución termal intraurbana en las ciudades de Santiago y Valparaíso. Análisis comparativo de sus factores explicativos. Investigaciones Geográficas (46), 25–46. Smith, P., Henríquez, C., 2018. Microclimate metrics linked to the use and perception of public spaces: the case of Chillán City, Chile. Atmosphere 9 (186), 1–16. Smith, P., Romero, H., 2016. Factores Explicativos de la distribución termal urbana en Santiago de Chile. Revista de Geografía Norte Grande 63, 45–62. Thabaz, M., 2011. Psychrometric Chart as basis for Outdoor Thermal Analysis. Int. J. Archit. Eng Urban Plan. 21 (2), 95–109. Tu, L., Qin, Z., Li, W., 2016. Surface urban heat island effect and its relationship with urban expansion in Nanjing, China. J. Appl. Remote. Sens. 10 (2) (17 pp). UN-Habitat, 2016. Urbanization and Development: Emerging Futures. World Cities Report. (260 pp). Vanos, J.K., Warland, J.S., Gillespie, T.J., Kenny, N.A., 2010. Review of the physiology of human thermal comfort while exercising in urban landscapes & implications for bioclimatic design. Int. J. Biometeorol. 54, 319–334. Ilustre Municipalidad de Chillán Viejo, 2012. Plan Regulador Comunal de Chillán. (49 pp). Yu, J., Cao, G., Cui, W., Ouyang, Q., Zhu, Y., 2013. People who live in a cold climate: thermal adaptation differences based on availability of heating. Indoor Air 23, 303–310. Zeng, Y., Dong, L., 2015. Thermal human biometeorological conditions and subjective thermal sensation in pedestrian streets in Chengdu, China. Int. J. Biometeorol. 59, 99–108.
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Perception of thermal comfort in outdoor public spaces in the medium-sized city of Chillán, Chile, during a warm summer
T
Pamela Smitha, , Cristián Henríquezb ⁎
a
Department of Geography and Center for Climate and Resilience Research (CR)2, Universidad de Chile, Chile Institute of Geography, Centre for Sustainable Urban Development (CEDEUS) and Centro de Cambio Global UC, Pontificia Universidad Católica de Chile, Chile
b
ARTICLE INFO
ABSTRACT
Keywords: Environmental comfort Perceived thermal comfort Public space Socioeconomic status
The study of thermal comfort in Latin American cities has been gaining great relevance for urban environmental planning. Some studies have evaluated the relationship between environmental and perceived comfort; however, the causes and social determinants of the different perceptions of the population have not been explored. The perception of thermal comfort in public spaces in the city of Chillán (Chile), which has an inland Mediterranean climate, is discussed in this context. First, we measured the environmental thermal comfort, adapting the Actual Sensation Vote index. A survey of 362 users of the five selected public spaces was carried out between 29 January and 01 February 2016 to obtain perceived comfort and relate it to the individual climatic history, use of public space and place of residence in the city. The results show that perceived thermal discomfort dominates over comfort on summer days; however, those users who visit public spaces for recreational purposes feel more comfortable, as well as those living in low socioeconomic status (SES) neighborhoods. On the other hand, users living in areas with higher socioeconomic status, have higher expectations regarding thermal environmental conditions.
1. Introduction Cities are nowadays the main habitat of human beings. In recent decades, there is an accelerated urbanization process, which has resulted in a 10% increase in urban population since 1995 (UN-HABITAT, 2016). Chile ranks above the Latin American average (75%), with 89.5% urban population in 2015, according to data published in the World Cities Report (UN-HABITAT, 2016). Although 50% of chilean urban population lives in the metropolitan areas of Santiago, Valparaíso, and Concepción, medium-sized Chilean cities have experienced the greatest growth (over 40% of their area) in the last two decades, according to calculations made for developed urban spots by MINVU (Chile's Ministry of Housing and Urbanism Planning) for the years 1993, 2003, and 2011. Changes already experienced by great metropolitan areas in Latin America, such as modification of the hydrological cycle, fragmentation of habitats, air pollution, and the creation of an urban climate are now being replicated in these cities. Traditionally, urban climatic studies the local scale, describing the patterns and attempting to understand climatic parameter, especially the temperature throughout the city, increasing knowledge of heat islands, as described by Oke (1987), land surface temperature (Tu et al., 2016 in China or Brazel et al., 2007 in the United States) and atmospheric air temperature (Cuadrat et al., 2005 in Spain; Papparelli et al., 2011 in Argentina; Mendonça and Lombardo, 2009 in Brazil). Studies seeking to recognize the factors that best explain both atmospheric and surface temperature patterns at local scale have been conducted in Chile. Those studies are
⁎
Corresponding author. E-mail address: [email protected] (P. Smith).
https://doi.org/10.1016/j.uclim.2019.100525 Received 5 June 2018; Received in revised form 17 January 2019; Accepted 11 August 2019 2212-0955/ © 2019 Elsevier B.V. All rights reserved.
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agreeing that the percentage of vegetation cover is one of the most significant factors (De la Barrera and Henríquez, 2017; Smith and Romero, 2016; Sarricolea and Martin-Vide, 2014; Smith and Andrade, 2013; Peña, 2009). In recent years, there has been an increase in the number of publications dedicated to the study of the urban microclimate. An initial approach to this scale has been the study of public spaces, such as urban canyons, among which is the study of the relationship between microclimate and site design (for example Smith and Henríquez, 2018 in Chile; De Schiller et al., 2001 in Argentina or Gomez & Ferrer, 2010 in Venezuela). Progress may be observed as well in the environmental thermal comfort of these spaces (Lamarca et al., 2016; Guzmán and Ochoa de la Torre, 2014), and to a lesser extent, in the analysys of users' perceptions regarding their satisfaction level with climatic conditions (Lenzholzer, 2010 in Germany; Zeng and Dong, 2015 in China; Nikolopoulou et al., 2004 in Greece). On this scale chilean studies have focused on the factors that explain the microclimatic conditions in Antofagasta (Guerra, 2008) and the main squares of eight Chilean cities (Del Castillo and Castillo, 2014). The work of Lamarca et al. (2016) is recognized as the first in Chile that in addition to describing microclimate, studies environmental and perceived thermal comfort. In this study, the environmental comfort was calculated from meteorological data collected in situ and perceived thermal comfort obtained from a survey. Studies on urban climate point out the impact of human behavior on human health, including outdoor thermal comfort, climatic efficiency, and building maintenance, use of public spaces, quality of life, and so on. Hence, it is important to consider the climate in urban planning in order to create more sustainable cities and generate greater thermal comfort conditions for their inhabitants (Nikolopoulou and Lykoudis, 2006). Body temperature may be affected by the surrounding environmental conditions, and even if this does not pose a health risk, it can have an impact on the satisfaction levels of people and, consequently, their experiences, modifying the use and permanence in a place exposed to unfavorable conditions (Perico-Agudelo, 2009; Nikolopoulou and Lykoudis, 2006; Guzmán and Ochoa de la Torre, 2014; Zeng and Dong, 2015). When studying urban climate at a human scale, people's perceptions are crucial: how do people experience the climate they live in and how does weather affect human comfort (Menotti, 2013). Thermal comfort is defined as a state of mind that expresses satisfaction with the environment that surrounds the person, without needing the increase or decrease of the current temperature (Vanos et al., 2010; Parsons, 2014). Thermal comfort depends on a series of objective and subjective parameters (Thabaz, 2011). The low correlations between the microclimate variables and the comfort perceived outdoors suggest that thermal physiology alone cannot fully describe these relationships (Nikolopoulou, 2011). An important part of human comfort and satisfaction about climate can be explained by subjective parameters, such as thermal history, expectations, and companionship, among others (Nikolopoulou, 2011; Lenzholzer et al., 2015). Thus, for example, a person in a colder climate zone is more sensitive to heat (Nikolopoulou et al., 2004). The purpose of this study is to compare the thermal comfort calculated for five public spaces in the city of Chillan with the perception of their users and determine its relationship with subjective factors, such as short, medium and long-term residence in Chillán and the neighborhood in which respondents live. Instrumental comfort, and subjective expectations regarding climatic conditions were also explored. The high summer temperatures in he city of Chillan impair the use of public spaces, which in addition to being very few, have been increasingly replaced by enclosed spaces, such as shopping centers, which maintain comfortable indoor climatic conditions at all time. Hence, Chillán represents the average rapid-growing Chilean and Latin American city: 37.7% in the past two decades, according to calculations made on the basis of developed urban spots by MINVU for the years 1993, 2003, and 2011 and a photo interpretation of its urban limits on a 2016 QuickBird image. Il also replicates large cities' environmental problems, such as scarcity of public spaces, with uneven distribution and quality due to the omission of climate in planning and urban design. In sharp contrast with the metropolitan spaces of the city, the suburbs include a series of privatized urban typologies, such as closed condominiums and “suburban plots” (Henríquez, 2014), and some socio-environmental amenities, such as vegetated spaces, swimming pools, and better ventilation. These conditions are for the exclusive use of the middle and upper classes and have important socio-spatial differences with the poorest groups residential environment. In this context, the working assumption is that there are subjective factors that affect the perceived thermal comfort in Chillan's public spaces. Thus, one might expect that users with lower socioeconomic status, D and E, feel more comfortable in public spaces and tend to be more tolerant to high temperatures than those with higher SES. 2. Materials and methods 2.1. Study area The city of Chillán is located in the Biobío region, Chile, and comprises the urban area of Chillán and Chillán Viejo cities. It is located at 36° 36′ south latitude, with an average altitude of 124 m above sea level; it has warm climate with winter rains, Csb, according to the Köppen classification for Chile (Sarricolea et al., 2016). It has a population of 204,180 inhabitants according to the data of the National Statistics Institute (INE, 2017), which classifies it as a medium-sized city, according to OECD criteria and medium-large, according to the types defined by the Ministry of Housing and Urban Development. Despite its location in the south-central zone of Chile, Chillán is one of the Chilean cities with the highest maximum average temperatures in the summer, with a pattern and intensity close to the cities of Arica and Iquique, which are located at inter-tropical latitudes (DMC, 2016). Chillán is one of the cities with the smallest area of public green areas per inhabitant in the country, with only 1.7 m2/per person. Chillán displays positive trend values in all indicators related with the increase in temperatures and the occurrence of heat waves during 1975 and 2015 (Smith and Henríquez, 2018). The Dirección Meteorológica de Chile (Chilean Meteorological Office - DMC) 2
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Fig. 1. Study Area and meteorological checkpoints in the city and inside of selected public spaces. Note. Each public space (picture right) has been divided into sections, assigned codes are bold.
defines heat waves as the occurrence of three or more consecutive days with temperatures above the summer threshold (considering the months of December, January and February). This threshold is determined from the 90th percentile of the maximum daily temperatures, using a 15-day moving average in the climatological period 1981–2010. Four heat waves events occurred in Chillan during the 2015–2016 summer, totaling 17 days, which means that almost 20% of the days in this season registered temperatures over the threshold average (32.4 °C). The highest temperatures registered in Chile for the summer period 2015–2016 correspond to the third heat wave event occurred in Chillán in the same period. This event concurred with the field campaign implemented by the current research; in the rural environment where the DMC station is located, the temperature reached 36 °C, while inside the urban area it rose over 39 °C, according to measurements made during the field campaign conducted in January and Febraury 2016. Public spaces in the city of Chillán occupy about 33% of its urban area; that is to say, 1008.6 ha; 83% of these correspond to paved surfaces (streets and sidewalks). The rest fall in the following categories: 115 median avenue strips (14.2 ha), 39 soccer fields (12.5 ha), one segmented waterfront drive (0.9 ha), one pedestrian walkway (0.7 ha), and 160 public squares and parks (41.8 ha). Squares and parks represent the largest percentage of those public spaces. Based on the regulatory plans of Chillán (2016) and Chillán Viejo (2012), the Intercommunal Plan Chillán-Chillán Viejo (2005), and consultation with municipal officials, five representative public spaces were selected (Fig. 1): -
Chillán Main Square (1.6 ha) Arauco Pedestrian Walkway (0.7 ha) Estero Las Toscas Park (1 ha) Sarita Gajardo Park (3 ha) Bernardo O'Higgins Monument Park (3.4 ha)
Analysis was based on climate information obtained from different fixed and mobile meteorological instruments and the field survey. 3
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Table 1 Level of environmental thermal comfort ambiental and perceived. ASV range
−5 −4 Discomfort by cold
−3
−2
−1 Comfort
0
1
2 3 Discomfort by hot
4
5
2.2. Environmental thermal comfort calculation The Actual Sensation Vote (ASV) index evaluated the environmental thermal comfort on a scale of −5 and + 5 score. According to the authors (Nikolopoulou et al., 2004), the value of thermal comfort is between the values of −1 and + 1. The authors propose ten different equations developed from the data of 10 different European cities (Eq. (1), built for Athenas, Greece). This paper proposes an equation to calculate the ASV of Chillán, built from multiple regression models presented by Nikolopoulou et al. (2004).
ASV = 0.034 Tair + 0.001Sol
0.086V
0.001HR
R2: 0.39
0.412
(1)
where: Tair = air temperature (in degrees Celsius); Sol = solar radiation (in Wm-2); V = wind speed (in m/s); RH = relative air humidity (in percentage) The model-dependent variable corresponds to the level of thermal comfort, perceived by users of public spaces (between - 5 and + 5, Table 1); the independent variables are the meteorological parameters included by the authors: temperature (in degrees Celsius), relative humidity (in percentages), global solar radiation (in W/m2) and wind speed (in meters per second). The climatic data (air temperature, air relative humidity, and wind speed) to construct the equation for Chillán comes from different sources: the air temperature recorders: 10 Logtag HAXO-8 (accuracy: 0.1 °C and 0.1% for humidity), 8 Datalogger HOBO Pendant UA-002-xx (accuracy: 0.53 °C), and 32 Ibutton Thermochron (accuracy: 0.5 °C) models installed inside and around the selected public spaces (Fig. 1). All instruments record hourly data, and the Logtag also measured relative humidity, continuously, during the summer 2015–2016. During the fieldwork carried out between January 29 and February 1, 2016. The meteorological parameters were measured every two hours (12, 14, 16, 18, and 20 h local time), at different points within the public spaces using VETO brand mobile instruments. Each public space selected had at least 10 measurement points, including fixed recorders and mobile measurements. The variations observed inside public spaces do not exceed 2.5 °C or 3 percentage points of relative humidity between the different measurement points. Global radiation was modeled in Autodesk Ecotect Analysis software, starting with the constructions 3D model and the weather data file of the city. The global solar radiation per hour was calculated in Wm-2, between 10 and 20 h on a grid of 15 m' cells for each public space (Fig. 2). In order to obtain the required data and calculate the ASV equation for the city of Chillán, each public space was sectored. The climatic data was obtained by measuring meteorological parameters (Fig. 1 and 3a). The average global solar radiation of its cells was
Fig. 2. Global solar radiation in Bernardo O'Higgins Park between 12:00 and 13:00 h calculated in Ecotect Analysis software. 4
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Fig. 3. Example of data identification, (a) sectors of the public space. (b) data series: variables for calculating ASV.
determined for each sector. With the data obtained, a series was constructed that contained the independent variables for each sector per hour, as shown in the table of Fig. 3b. The dependent variable, thermal comfort, was obtained by calculating the average thermal comfort perceived by the users in each sector at a given time. 2.3. Perceived comfort calculation 362 selected public space users were interviewed (Fig. 3) during the field work. The users survey was carried out on a continuous basis, from 11 to 20 h local time, between January 29 and February 1, 2016. The survey included four sections: (1) Respondent General Description; (2) User's perception; (3) Spatial Analysis; and (4) Public Space Use (Table 2). The respondents, men and women 5
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Table 2 Survey of perceived thermal comfort.
Date: Place in the public space:
Public space:
Hour:
Section 1. Respondent General Description Age: Gender Male Female Time on the street Contexture: Thin Normal strong Clothing: Little Normal lot Clothing color: Clear Mixed dark Section 2. User´s perception Thermal comfort: -5 -4 -3 -2 -1 0 1 Cold, very uncomfortable Good, Comfort Section 3. Spatial analysis Place of birth Current place of residence Time in the current residence Section 4. Use of public space Purpose of Doing sports Displacement Pet walking visit Work/study Waiting for / Meeting people
2
3 4 5 Hot, very uncomfortable
Recreation
Relaxation
over the age of 18 were visiting the studied public spaces. The perception was measured on a scale of 11 points, with values between −5 and + 5, where comfort ranges from −1 to +1, according to the adaptation of the Cheng method (2008). The result of environmental thermal comfort was compared with the thermal comfort value perceived by each user surveyed. We considered the sector, day and time in which each user was surveyed to obtain the corresponding climatic and solar radiation parameters. The location of the surveyed users, obtained from their place of residence, was spatialized by block to estimate their socioeconomic status, using the classification proposed by Adimark (2004) for the year 2013. Adimark identifies the following five socioeconomic status (SES) considering the level of education of the head of the household and the possession of a set of goods: ABC1 and C2, which correspond to the two higher-income groups; C3, which represents the medium-income quintile; and finally, the poorer groups, D and E (Table 3). In order to assess the conditions of perceived thermal comfort, different dimensions of psychological adjustment, regarding experiences, reasons for use, and expectations of users surveyed were considered. Previous experience was considered on two temporary scales: short- and medium-long term. The short-term experience was studied by relating the perceived comfort to the temperature registered on the days prior to the interview of each user, and the medium-long term experience included place of origin and length of residency in the city of Chillán. The reasons for their visit to a given public space were considered in the analysis of user's perceptions; as well as the environmental conditions of their permanent residence, determined through air temperature and socioeconomic status. Air temperature in the residence area of public space users was obtained by interpolating the data recorded by Hobo, Logtag, and Ibutton while they were surveyed, in order to determine the difference in temperature between the latter and the visitor's neighborhood. The field survey was reviewed and approved by the Comité de Ética de Ciencias Sociales, Artes y Humanidades (Ethics Committee of Social Sciences, Arts, and Humanities) of the Pontificia Universidad Católica de Chile (record n° 151,230,003). The assistants were committed by a signed document, to maintain the confidentiality of the research, and respondents were informed and approved for their participation by signing the informed consent form.
Table 3 Characteristics of socioeconomic status. Socioeconomic status
Level of education (average years)
Average possession of a set of goods
Income range (dollars)
% at country level
ABC1 C2
16.2 years (comlete university studies) 14 years (comlete technical studies or incomlete university studies) 11.6 years (complete high school) 7.7 years (incomplete high school) 3.7 years (incomplete primary school)
9.2 7.2
U$ 2858 or more U$867 - U$1735
7.2 15.4
5.7 4.4 2.3
U$578 - U$723 U$289 - U$433 Equal or less than U $231
22.4 34.8 20.3
C3 D E
Note: the average value of the dollar for the year was $691.3 Chilean pesos, according to the values published by the Internal Tax Service (SII in Spanish). 6
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Fig. 4. Place of residence of surveyed users of public spaces (circles). The socioeconomic levels of its neighborhoods (block color). The number shows the public space analyzed.
3. Results Thermal comfort was approached from two perspectives: through environmental indicators, and the user's perceptions. After analyzing the results of both approaches, their coincidences was analyzed. 3.1. Surveyed users description The largest number of surveyed respondents corresponded to the Chillán Main Square (121); the Arauco pedestrian walkway and Bernardo O'Higgins Monument Park occupied the second place, with 72 and 79 respondents, respectively. In the remaining public spaces around 45 users were surveyed, a number close to all their users. Most of the respondents were between 21 and 30 years (37% of the total); 45.5% (143) were women, and 54.5% (171) were men. The greatest percentage of users surveyed were employees or students. Of the total number of respondents, 326 lived in the city of Chillán, which represents 90%. Of the remaining 10% (34 people), 22 lived in another town of the Biobío region. Of the 326 living in the study area, only 208 were born there. Of the remainder, the majority was born in the Biobío region and, in second place, in the Metropolitan region—specifically in the city of Santiago. Most of the respondents belong to the socioeconomic status D and C3. The lowest proportion correspond to status E and ABC1, which coincides with the distribution of the socioeconomic status throughout the city. The diverse socioeconomic groups are not equally represented in all Chillán public spaces. ABC1 users were only found in the Arauco Pedestrian Walkway and the Chillán main square; on the other hand, Sarita Gajardo Park received very few C2 visitors but concentrated the largest number of D and E users (Fig. 4). 3.2. Environmental thermal comfort Six equations were used to calculate environmental thermal comfort (ASV), one for each public space studied (equation n°3 for the main square of Chillán, equation n°4 for Arauco, Pedestrian walk, equation n°5 for Estero Las Toscas park, equation n°6 for Sarita Gajardo park and equation n°7 for Bernardo O'Higgins park), the sixth, for the city of Chillán, was built from the data obtained in all public spaces in an aggregate manner. 7
Urban Climate 30 (2019) 100525
P. Smith and C. Henríquez 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
98
52
18
12
26
31
69
18
13
10
Main square of Pedestrian walk Estero Las Toscas Sarita Gajardo Chillán Arauco park park Good, comfortable
Bernardo O´Higgins park
Heat, very uncomfortable
Fig. 5. Perceived thermal comfort by public space.
The instrumental comfort, determined by the equations of ASV, yielded values ranging between 1.5 and 4.4, meaning that all users perceived thermal discomfort, due to heat.
ASV ASV
ASV ASV
Chillan city = 0.158Tair + 0.001Sol
0.408V
0.004RH + 1.39
R2: 0.23
(2)
0.296V
R2: 0.46
(3)
0.060RH + 2.49
R2:
0.32
(4)
0.035RH + 103
R2:
0.33
(5)
R2:
0.26
(6)
R2: 0.48
(7)
Chillan main square = 0.180Tair + 0.003Sol
Pedestrian walk Arauco = 0.095Tair + 0.008Sol Estero Las Toscas Park = 0.045Tair + 0.001Sol
0.009RH + 2.63
0.182V 0.312V
ASV
Sarita Gajardo Park = 0.073Tair + 0.003Sol
0.350V
ASV
Bernardo O ´Higgins Park = 0.118Tair + 0.002Sol
0.008RH + 5.43
0.092V
0.032RH + 6.35
3.3. Perceived thermal comfort When considering the total users of the five public spaces studied, the very uncomfortable category, associated with heat, represents 76% of the total number of answers. Heat discomfort prevails in Chillán main square, Arauco pedestrian walkway, and the Bernardo O'Higgins Monument park of Chillán Viejo, exceeding 80% of its users. Only in Estero Las Toscas park and Sarita Gajardo park (Fig. 5), show a higher percentage of users (up to 30%) declare to be in thermal comfort. According to the survey results, an inverse relationship between general comfort perception and wind speed and humidity (with a Spearman's correlation coefficient of −0.25) was observed. On the other hand, there is a direct and more intense relationship between perceived thermal comfort and exposure to sun, with a coefficient of 0.48. In all cases, the relationship was statistically significant at the 0.01 level. 3.4. The relationship between environmental thermal comfort and perceived thermal comfort the comfort feeling present a greater coincidence between perceived and calculated comfort; however, this is because, according to the ASV, 352 of the 362 surveyed users are in this condition. On the contrary, the discomfort categories present low coincidence between both methods for quantify the thermal comfort. Fig. 6 shows the relationship between the values obtained by the ASV for perceived thermal comfort (with a Spearman's correlation coefficient of 0.32). The chart shows a low dispersion, concentrated between values 1 and 5 (thermal discomfort), although 86 users reported feeling comfortable with weather conditions in general.
Fig. 6. Diferences between perceived thermal comfort and environmental thermal comfort (ASV). 8
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Table 4 Users surveyed in thermal comfort (C) and (D) thermal discomfort conditions in public spaces.
Total users surveyed Questions Categories Place of birth Chillán city Biobío region Other regions Other countries DR Current place of Chillán city residence Biobío region Other regions DR Time of residence less than a year One year 2 to 5 years 6 to 10 years > 10 years Whole life Not live in the city DR Purpose of visit Doing sports Displacement Waiting for/ Meeting People Pet walking Recreation Relaxation Work/Study Tourism DR
The main square of Chillán
Pedestrian walk Arauco
Estero Las Toscas park
Sarita Gajardo park
Bernardo O'Higgins park
Total number of users
121 C 7.4 2.5 5.8
72 C 4.2 6.9 4.2 1.4 10.8 12.5 1.4 2.8 12.5 1.4 4.2 1.4 0 4.2 1.4 4.2 13.9
46 C 10.9 8.7 8.7
44 C 25 6.8 6.8 0 2.3 38.6 2.3
79 C 10.1 0 2.5
59.1 0
0 6.8
4.5
362 C 36 13 21 1 16 62 5 5 16 4 3 3 6 8 46 10 25 2 7 16
D 42.1 23.1 15.7
D 47.2 8.3 15.3 1.4
3.3 11.6 1.7 2.5 3.3 0 0 2.5 2.5 1.7 3.3 4.1 9.1 0 3.3 5
1.7 9.9 22.3
0 2.8
15.3 11.1
4.3 2.2
13 19.6
0.1 4.1 2.5 0.8
7.4 18.2 14 7.4
1.4 4.2 8.3
9.7 16.7 19.4
8.7 4.3 8.7 2.2 4.4
17.4 6.5 8.7 0
3.3
72.7 7.4 0.8 5 2.5 19 15.7 7.4 19 8.3
66.7 4.2 0 2.8 2.8 22.2 6.9 13.9 13.9 6.9
11.1
6.5 26.1 2.2 0 6.5 0 0 0 0 10.8 10.8 2.2 15.2
D 34.8 17.4 13 54.3 4.3 6.5 0 2.2 13 4.3 21.7 8.7 10.1
D 45.5 9.1 2.3 2.3
2.3 0 4.5 25 2.3 0 2.3
4.5
11.4
9.1
0 11.4 11.4 4.5
2.3 15.9 22.7 4.5
0
4.5 4.5 0 45.6 0
0 12.7 0 0 0 0
D 51.9 20.2 15.1 81 3.8 2.5 3.8
0 1.3 1.3 10.1 0 0 1.3 1.3 1.3
11.4 5.1 7.6 53.1 6.3 8.9 7.6 7.6
0 8.6
1.3 53.2
0 1.3 1.3
6.3 0
0 21 13 13 2 17
D 162 67 44 2 251 17 6 10 3 32 18 17 152 25 11 36 57 11 81 41 34 0
Note. The values of comfort and discomfort are in percentages and have been calculated from the total number of each public space, except the bold values. DR is does not respond.
3.5. Analysis of the expectations on perceived thermal comfort Considering the complex nature of the thermal comfort concept, its analysis can be enhanced by including subjective variables, such as the level of expectations regarding the temperature. The expectations are dynamic and set new limits on the endurance of the individuals. These can be influenced by experiences associated with place of origin, place of residence, the season of the year, the weather on the previous days or hours, or the reason to use a public space, among others. 3.5.1. Selection of users: a reason to use public spaces The selection of users is mainly associated with the reasons which explain their presence in each of the public spaces. For the analysis, these were grouped into seven categories: (1) Play, sports, (2) place of transit (to walk from one place to another), (3) Walk a pet, (4) Recreation, (5) Relaxation, (6) Work or study, and (7) Use public space as a waiting/meeting place (Table 4). In most cases, > 80% of the responses express disconfort. The percentage is higher among those who use the public space as a meeting point, place of transit, for working, making transactions, or studying (close to 80%). In the latter case, most respondents correspond to Arauco pedestrian walkway, as well as walking around since the walk is a two-block urban canyon, with the presence of trees on both sides, without vehicular traffic and where users are in movement, passing by, without staying long periods of time in the public space. 3.5.2. Previous experience 3.5.2.1. Previous short-term comfort experience. Fig. 7 shows the proportion of users in comfort and discomfort by day. The result is examined considering the subjective dimension of comfort, related to the previous short-term experience. In this case, only the responses of users who live in the city have been included. It is important to bear in mind weather patterns associated with a frontal synoptic condition in the prior days to the fieldwork. On January 27, the temperatures did not exceed 26 °C, and precipitations reached only 5 mm. The next day, January 28, rain was not reported, but the temperature remained low for the season, with an averages of 20 °C. The above may explain the high proportion of perceived thermal comfort on January 29 (44%), when maximum temperatures were close to 30 °C. If we look at the graph, on January 30 (Saturday) thermal confort reaches 20%, descending to 14% on the next day, despite both correspond to o an intense heat wave episode that lasted until February 1, with a maximum temperature close to 36 °C, according to data from the Chilean National 9
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January 29
January 30
January 31
February 1 0%
20%
40%
Thermal comfort
60%
80%
100%
Thermal discomfort
Fig. 7. Relationship between perceived thermal comfort and measurements days.
Weather Service. 3.5.2.2. Medium- and long-term perceived comfort. An adaptation process to the meteorological conditions can be observed by comparing the proportion of users “in comfort” according to the length of residence in the city of Chillán. As described above, of the total number of users, 55% were born in the city (option “whole life” in Table 4), and at the same time, show the highest proportion of thermal comfort. This could also relate to a higher level of adaptation and c onsequent tolerance to weather conditions. Those residents who were not born in Chillan have been divided into four ranges: Less than a year, from 2 to 5 years, 6 to 10 years, and more than ten years living in the city of Chillán. As shown in the table, the lower the number of years of residence, the lower the comfort proportion. Those users who did not live in the city were divided into two groups: residents in any town of the Biobío region, and tourists from another region (category other regions and other countries in Table 4). The latter registered a higher level of comfort (46% of users) than those who live in the region (22%). This could be explained by the urban hierarchy of the place of origin, because those who come from the Biobío region live mainly in small towns, such as San Carlos, Pinto or rural areas like San Nicolás; on the other hand, the visitors are from other regions, for example, from Santiago and Temuco. 3.5.3. Comfort and neighborhood socio-environmental conditions The following two relationships try to demonstrate that the expectations regarding weather conditions change according to the environmental conditions of the place of residence, that is to say the climate the user currently experiences, which we can obtain, as well as his socio economic status, from his housing location (Smith and Henríquez, 2018). First, the temperature difference (DT) of the neighborhood where the user lives and the public space where the user was surveyed was defined as:
DT = Tneighborhood–Tsurveyed The results obtained with DT are presented in four categories (Fig. 8): -
DT > 2, when the temperature in the users neighborhood is 2 °C more than the public space where was surveyed. 0.5 < DT < 2, when the temperature in the users neighborhood is until 2 °C more than the public space where was surveyed. −0.5 < DT < 0.5, when the temperature is the same in both places. DT < −0.5, when the temperature in the users neighborhood is less than the public space where was surveyed.
Fig. 8. Relationship of temperature difference between the place of residence outdoors public space and the public space and the perceived thermal comfort. 10
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ABC1 C2 C3 D E 0%
10%
20%
30%
40%
50%
Thermal comfort
60%
70%
80%
90%
100%
Thermal discomfort
Fig. 9. Socioeconomic levels of all respondents versus perceived thermal comfort.
It is noted (Fig. 8) that there is a higher proportion of users who feel comfortable the two groups where DT > 0.5: for example, those users whose neighborhood show worse climatic conditions than the public space where they were interviewed, even when this difference only amounts to half a degree of temperature. Fig. 9 shows an inverse relationship between the socioeconomic level of users and the comfort they perceived in the public space. Those users who belong to the socioeconomic group ABC1 have higher expectations regarding climatic conditions, due to better environmental conditions in their residential environment. Therefore, they declare greater thermal discomfort in public spaces. In contrast, a greater proportion of users ranked C2 and D, which usually live in areas with a high density of construction and low percentages of plant cover, feel satisfied with the climatic conditions in public spaces. There are no differences in quantity and color of clothing associated with the socio-economic level of users. The ABC1 visitors, like the rest of the respondents, dressed a normal amount of clothing, generally light colored and never used formal wear. Only the Arauco Pedestrian walk Arauco and the Chillán main square registered visitors belonging to the ABC1 socioeconomic level. If the perception of thermal comfort among the population of the different socioeconomic levels is compared only in these two public spaces (Fig. 10) the results are similar to those presented in the previous paragraph. (Fig. 9), discarding the presence of a particularly disconfortable condition that could excplainthe different perceptions observed. The presence of the ABC1 group in the public space is mainly due to business transactions (80% of users in this group). In the remaining socioeconomic groups, partdicularly in C2 and D, the dominant responses are “to meet with people”, which is associated with using public space as a meeting place, and the options “walking around,” and “playing with the children,” which together account for almost 30% of the users in each socioeconomic group.
Fig. 10. Socioeconomic levels of respondents versus perceived thermal comfort in the main square of Chillán and Pedestrian walk Arauco.
4. Discussion In the first place, the difference between perceived thermal comfort and environmental thermal comfort, calculated by the ASV index, reaffirms the importance of considering that the perceived thermal comfort is affected by subjective factors, in addition, to the objective parameters mainly related to the meteorological parameters that are commonly included in the equations to measure comfort instrumentally (air temperature, relative humidity, wind, and solar radiation). The results obtained by connecting the perceived thermal comfort with some fewer common aspects in the literature, such as length of residence or the reason for use, highlight the importance of subjective and local factors associated with climate expectations and climate adaptation in urban environments (Nikolopoulou, 2011; Lenzholzer et al., 2015). Thus, for example, the results obtained when relating time of residence in the city versus thermal comfort are comparable to those obtained by Yu et al. (2013), which show that when individuals are used to high temperatures inside their homes tend to feel public spaces cooler than those used to lower indoor temperatures. According to our hypothesis, the results obtained allow us to discuss various aspects. In the first place, public spaces give access to good environmental conditions for those who live in poor quality neghbourhoods, and explains the higher level of comfort shown by users of public spaces belonging to socioeconomic groups D and E. People in the latter categories usually have no house gardens and, at the same time, the surrounding public spaces have a higher proportion of waterproof surfaces and a lower vegetation cover. 11
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Therefore, the city's planning and design should consider increasing the amount and quality of public spaces in those sectors. Secondly, the relationship between thermal confort and socioeconomic shows a lower tolerance to high temperatures in higherincome population, mainly ABC1 group. The lower tolerance to high temperatures is associated with the best environmental and climatic conditions in the private spaces where they reside, coupled with improved environmental housing conditions, which are associated with private condominiums and country plots, as well as abundant vegetation in a metropolitan setting, swimming pools, and low-density occupation, among other factors (Henríquez, 2014). Therefore, ABC1 users were only found at the Arauco walkway and the Chillán Main Square, where the main services trade areas are located. Finally, the results confirm the Perico-Agudelo (2009) proposals, in order to suggest that there is a direct relationship between perceived thermal comfort and place of residence of the citizen, which would explain the way in which the latter uses and appropriates public space. However, this author approaches this matter in theoretical terms, without developing it empirically. 5. Conclusions According to the results obtained, we can establish that there is an effect of previous short, medium, and long-term experiences on comfort perception: comfort level is higher in those born in Chillan, and consistently grows in its residents as the time of residence increases., which may account for a level of adaptation or accommodation to the weather conditions of the place. During the summer, thermal comfort in the selected public spaces is better perceived by low-income population, who mostly use these spaces, especially for recreational purposes. From the above, we may conclude that there is a significant climatic injustice, the poorest population has less access to quality public spaces because these are scarce in the neighborhoods and have neither the design not the necessary infrastructure to provide comfort conditions. In contrast, middle and high-classes have enough resources to solve their discomfort problems through wellequipped spaces with large vegetated surfaces, pools, and constructions with better ventilation, air conditioning, and other measures. This mid-sized city has very high-density neighborhoods, with few private vegetated spaces. Therefore, these public spaces, especially the parks, are the only alternative for its population to deal with episodes of extreme heat, such as those we have experienced these past few summers. Chillán has an environment with many advantages as agricultural land, areas with natural vegetation, ancient river beds, inlets, and canals, among other urban elements that have been inserted in the city as residual spaces, disconnected, and in some cases abandoned or urbanized. Regulatory plans have not taken advantage of this potential to articulate natural and semi-natural spaces with urban green spaces, such as median strips, bike lanes, squares, and parks that could set up a network of public spaces, promote the provision of urban ecosystem services, and improve the urban environmental quality. Acknowledgments Surveys and fieldwork measurement of meteorological parameters were conducted with the assistance of eight students from the History and Geography Teaching Program at the University of Biobío, Chillán. Cristóbal Lamarca, Architect, assisted the calculation of solar radiation. All hourly data related to air temperature, relative air humidity, wind direction, and wind speed were provided by the DMC's Bernardo O'Higgins station, located at the Chillán airport and the meteorological station at the University of Biobío, Campus La Castilla. This research was supported by FONDECYT Project N° 11180990 “La construcción social del clima urbano: hacia la calidad y justicia climática en las ciudades chilenas” and CEDEUS Center CONICYT/FONDAP15110020. References Cuadrat, J., Serrano, S., Saz, M., 2005. Los efectos de la urbanización en el clima de Zaragoza: La isla de calor y sus factores condicionantes. Boletín de la A.G.E 40, 311–327. Nikolopoulou, M., 2011. Outdoor thermal comfort. Front. Biosci. S3, 1552–1568. ADIMARK, 2004. Mapa socioeconómico de Chile. Nivel socioeconómico de los hogares del país basados en datos del censo. Brazel, A., Gober, P., Lee, S., 2007. Determinants of changes in the regional urban heat island in metropolitan Phoenix (Arizona, USA) between 1990 and 2004. Clim. Res. 33 (2), 171–182. Ilustre Municipalidad de Chillán, 2016. Ordenanzan Local Plan Regulador Comunal de Chillán. (49 pp). De la Barrera, F., Henríquez, C., 2017. Vegetation cover change in growing urban agglomerations in Chile. Ecol. Indic. 81, 265–273. Del Castillo, M., Castillo, C., 2014. Aproximación bioclimática para el diseño de espacios públicos, análisis inicial en distintas plazas chilenas. Arquitectura y Urbanismo XXXV (3), 69–82. Dirección Meteorológica de Chile – DMC, 2016. Umbrales de eventos extremos y ola de calor en Chile. Publicación interna, Santiago, Chile. Guerra, J., 2008. Diseño sustentable y calidad bioclimática del espacio público en zonas áridas. Revista Arquitectura del Sur 34, 30–43. Guzmán, F., Ochoa de la Torre, J., 2014. Confort térmico en los espacios públicos urbanos. Clima cálido y frío semi-seco. Revista Hábitat Sustentable 4 (2), 52–63. Henríquez, H., 2014. Modelando el Crecimiento de Ciudades Medias. Hacia un desarrollo urbano sustentable. Ediciones UC, Santiago de Chile (314 pp). Ilustre Municipalidad de Chillán & Ilustre Municipalidad de Chillán Viejo, 2005. Ordenanzan Plan Regulador Intercomunal Chillán – Chillán Viejo. (39 pp.). Instituto Nacional de Estadísticas, 2017. XIX Censo Nacional de Población y VIII de Vivienda o Censo de Población y Vivienda. Datos disponibles en. www. censo2017.cl. Lamarca, C., Quense, J., Henríquez, H., 2016. Thermal comfort and urban canyons morphology in coastal temperate climate, Concepción, Chile. Urban Climate 23, 159–172. Lenzholzer, S., 2010. Engrained experience – a comparison of microclimate perception schemata and microclimate measurements in Dutch urban squares. Int. J. Biometeorol. 54 (2), 141–150. Lenzholzer, S., Klemm, W., Vasilikou, C., 2015. New qualitative methods to explore thermal perception in urban spaces. In: Conference Proceedings ICUC9 – 9th International Conference on Urban Climate Jointly with the 12th Symposium on the Urban Environment. Mendonça, M., Lombardo, M., 2009. El clima urbano de ciudades subtropicales costeras atlánticas: el caso de la conurbación de Florianópolis. Revista de geografía Norte Grande 44, 129–141.
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P. Smith and C. Henríquez
Menotti, S., Monteiro, SantÁnna y, 2013. O conforto térmico nas escolas estaduais de president prudente/SP. Climatologia urbana e regional, cuestiones teóricas y estudios de caso. In: De, Costa (Ed.), Geografía en movimiento. Sao Paulo, Brasil, pp. 221–246. Nikolopoulou, M., Lykoudis, S., 2006. Thermal comfort in outdoor urban spaces: analysis across different European countries. Build. Environ. 41, 1455–1470. Nikolopoulou, M., Lykoudis, S., Kikira, M., 2004. Thermal Confort in Outdoor Spaces: Fiel Studies in Greece. Centre for Renewable Energy Source (C.R.E.S). Oke, T., 1987. Boundary-Layer Climate. Routledge, Second edition. . Papparelli, A., Kurbán, A., Cúnsulo, M., 2011. Isla de calor y ocupación especial urbana en San Juan, Argentina: análisis evolutivo. Cuadernos de vivienda y urbanismo 4 (7), 110–120. Parsons, K., 2014. Human Thermal Environments: The Effects of Hot Moderate and Cold Environments on Human Health. Comfort and Performance. Crc Press, USA. Peña, M., 2009. Examination of the land surface temperature response for Santiago, Chile. Photogramm. Eng. Remote. Sens. 75 (10), 1191–1200. Perico-Agudelo, D., 2009. Una aproximación desde el estudio de sus características microclimáticas. Cuadernos de Vivienda y Urbanismo 2 (4), 278–301 El espacio público de la ciudad. Sarricolea, P., Martin-Vide, J., 2014. El estudio de la Isla de Calor Urbana de Superficie del Área Metropolitana de Santiago de Chile con imágenes Terra-MODIS y Análisis de Componentes Principales. Revista de Geografía Norte Grande (57), 123–141. Sarricolea, P., Herrera-Osandón, M., Meseguer-Ruiz, O., 2016. Updating of the climatic regionalisation of continental Chile using Köppen classification. J. Maps 13, 66–73. De Schiller, S., Evans, J.M., Katzschner, L., 2001. Isla de Calor, Microclima Urbano y Variables de Diseño Estudios en Buenos Aires y Río Gallegos. Rev. AVERMA5 1–45. Smith, P., Andrade, X., 2013. Distribución termal intraurbana en las ciudades de Santiago y Valparaíso. Análisis comparativo de sus factores explicativos. Investigaciones Geográficas (46), 25–46. Smith, P., Henríquez, C., 2018. Microclimate metrics linked to the use and perception of public spaces: the case of Chillán City, Chile. Atmosphere 9 (186), 1–16. Smith, P., Romero, H., 2016. Factores Explicativos de la distribución termal urbana en Santiago de Chile. Revista de Geografía Norte Grande 63, 45–62. Thabaz, M., 2011. Psychrometric Chart as basis for Outdoor Thermal Analysis. Int. J. Archit. Eng Urban Plan. 21 (2), 95–109. Tu, L., Qin, Z., Li, W., 2016. Surface urban heat island effect and its relationship with urban expansion in Nanjing, China. J. Appl. Remote. Sens. 10 (2) (17 pp). UN-Habitat, 2016. Urbanization and Development: Emerging Futures. World Cities Report. (260 pp). Vanos, J.K., Warland, J.S., Gillespie, T.J., Kenny, N.A., 2010. Review of the physiology of human thermal comfort while exercising in urban landscapes & implications for bioclimatic design. Int. J. Biometeorol. 54, 319–334. Ilustre Municipalidad de Chillán Viejo, 2012. Plan Regulador Comunal de Chillán. (49 pp). Yu, J., Cao, G., Cui, W., Ouyang, Q., Zhu, Y., 2013. People who live in a cold climate: thermal adaptation differences based on availability of heating. Indoor Air 23, 303–310. Zeng, Y., Dong, L., 2015. Thermal human biometeorological conditions and subjective thermal sensation in pedestrian streets in Chengdu, China. Int. J. Biometeorol. 59, 99–108.
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