New Research Article Thermal Comfort for Urban Parks in...

Hindawi Publishing CorporationAdvances in MeteorologyVolume 2013 Article ID 640473 8 pageshttpdxdoiorg1011552013640473

Research ArticleThermal Comfort for Urban Parks in Subtropics UnderstandingVisitorrsquos Perceptions Behavior and Attendance

Chuang-Hung Lin1 Tzu-Ping Lin2 and Ruey-Lung Hwang1

1 Department of Architecture National United University 1 Lienda Miaoli 360 Taiwan2Department of Architecture National Cheng Kung University 1 University Road Tainan 701 Taiwan

Correspondence should be addressed to Ruey-Lung Hwang rueylungnuuedutw

Received 23 February 2013 Revised 27 July 2013 Accepted 6 August 2013

Academic Editor Marialena Nikolopoulou

Copyright copy 2013 Chuang-Hung Lin et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The paper is an effort toward thermal comfort assessment for urban parks under the climatic conditions of Taiwan to help architectsachieve better climatic design Field interviews observations andmicrometeorologicalmeasurementswere conducted in this studyTheWBGTwas used as the thermophysiological index to investigate the effects of thermal conditions on visitorrsquos thermal perceptionand adaptive behavior in outdoor urban spaces In this study behavioral adaptations used by visitors as ameans of achieving comfortwere evaluated Observational results showed that the overall attendance was influenced by sun and thermal conditionsThere was arobust relationship between thermal sensation votes as well as thermal acceptability and thermal environment in terms ofWBGTThe upper and lower limits of 80 acceptability are 26∘CWBGT and 20∘CWBGT respectively

1 Introduction

Ensuring acceptable thermal comfort conditions in outdoorspaces is always one of the considerations of landscapedesign since thermal environmental conditions greatly affectindividual moods and activities in the outdoors as well asthe usage of the outdoor spaces In densely populated citieswith the continuously growing emphasis on the importanceof quality of life the public attaches greater value to thequality of thermal comfort in outdoor urban spaces At thesame time with the expansion of cities the urban heatisland effect is increasingly significant and the trend ofurban microclimate change is not optimistic Hence thearchitects or landscape designers must seriously considerthe actions required for outdoor space design to supportcomfortable conditions In recent years the thermal comfortof outdoor spaces has become an important issue attractinga considerable number of articles to analyze and discussoutdoor thermal comfort through field surveys for exampleSpagnolo and de Dear in Australia [1] Ahmed in Bangladesh[2] Nakano and Tanabe in Japan [3] Nikolopoulou andLykoudis in European countries [4]Oliveira andAndrade [5]and Andrade et al [6] in Portugal Cheng et al in Hong Kong

[7] Kariminia et al in Iran [8] and Lin [9] Hwang et al [10]and Lin et al [11] in Taiwan

Many of the research studies have generally used a ther-mophysiological index in outdoor thermal condition analy-sis Some of the indices for example physiological equiva-lent temperature (PET) standard new effective temperature(SETlowast) universal thermal climate index (UTCI) and so forthare based on comprehensive energy-balance models for thehuman body to describe outdoor thermal conditions Theoutdoor thermal comfort investigations conducted in Taiwan[9ndash12] found that the thermal comfort characteristics of apopulation adapted to hot and humid climate were differentfrom residents living in temperate climates Meanwhile itwas also found that thermo-physiological indices basedon energy-balance model cannot fully explain subjectiveperceptions or preferences of people due to the impacts oftheir personal psychological and behavioral adjustments [12]In addition thermo-physiological indices based on energy-balance model are general complex in calculation and resultin difficulties in application for those architects or landscapedesigners who are unfamiliar with energy-balance modelingIn this sense our research question is can simpler anddirectly measurable indices which correlate well with human

2 Advances in Meteorology

Figure 1 Photograph of investigated Wen-Xin Park in TaichungTaiwan

responses and thus enable reliable predictions to be madebe used to replace such complex indictors to help architectsachieve better climatic design Thus the objectives of thisstudy were to select a thermo-physiological index that can bedetermined from simple readings to analyze outdoor thermalcomfort and to discuss the relationship between the publicrsquosoutdoor adaptive behaviors and the selected index

2 Materials and Methods

21 Description of Study Park This study was based on ques-tionnaire surveys and weather measurements performedsimultaneously in Taichung City the third largest city ofTaiwan (longitude 120∘401015840E latitude 24∘091015840N) which islocated in central Taiwan and has approximately 1200000inhabitants The city has a hot and humid climate with mildwinters and hot and humid summers

The field investigations were conducted in the openarea of Wen-Xin Park (see Figure 1) which is one of thethree metropolitan parks in downtown Taichung City Thispark is used for leisure and sport activities such as lyingsitting promenading jogging and kite flying particularlyduring weekends and holidays The surveyed area has pavedsidewalks and green areas with about 80 of the total areacovered by grass There are a few benches facing the greenareas along the sidewalks however most people use the grassareasThe trees that provide shade are around the sidewalk inthe middle of the surveyed area and cover about 20 of thearea

22 Instrumentations and Microclimatic Measurements Acombination of portable equipment which complies with therequirements of instruments for measuring physical quan-tities in ISO 7726 [13] was assembled to allow monitoringof the microclimate during questionnaire interviews DataLogger Center 314 was used to collect measurements of dry-bulb temperature globe temperature and relative humidityThe globe thermometer is a standard black-painted matteglobeThedry-bulb temperature and relative humidity sensor

were shielded from radiation by a highly reflective alu-minized top film but were subject to free-flowing ventilationAir speed was monitored with a separate data logger theomnidirectional anemometers Delta HD 2103Metabolic rateand the insulation of clothing [14] were estimated based onthe answers to the questionnaire The thermo-physiologicalindex WBGT was calculated in order to evaluate the com-bined effects of atmospheric variables on thermal sensationvotes (TSV) The wet-bulb temperature was obtained bysubstituting the measured dry-bulb temperature and relativehumidity into the equations in the Chapter of PsychometricsASHRAE Handbook of Fundamentals [15] Besides the mea-surements of condition nearby the respondents two sets ofinstruments were installed in sunlit and tree-shaded area forcontinuous measurements on fieldwork days Meteorologicaldata were also obtained from a nearby local official weatherstation which is located in another downtown metropolitanpark about 4 km away from the study park

23 Questionnaire Interviews and Observation A team ofthree research assistants performed the questionnaire inter-views and observations every fieldwork day two of themwereresponsible for questionnaire interviews and the remainingassistant for observations The interviews were performed inChinese and required 15 minutes to complete The question-naires used in this study were created by modifying thosedeployed in earlier studies [9ndash11] divided into two partsnamely BACKGROUND and PERCEPTION

BACKGROUND covered questions regarding demo-graphics current clothing garments metabolic activitiesliving or working in the neighborhood of park the reasonfor being in the park and the frequency and duration of timespent in the park

PERCEPTION had questions concerning the subjectrsquosassessment of their immediate thermal environment at thatpoint in time The subjects were asked to report theirsensations of thermal environment through a 7-point scaleand of air movement through a 5-point scale The thermalsensation scale was the ASHRAE 7-point scale ranging fromcold (minus3) to hot (+3) with neutral (0) in the middle Thesubjects assessed the wind sensation on a 5-point scale still(minus2) weak (minus1) moderate (0) strong (+1) and very strong(+2) The final question in the PERCEPTION part askedsubjects whether or not they considered the weather ofthe fieldwork day suitable for leisure outdoor activities Theprotocol for each interview was as follows (1) two researchassistants approach subject ask if time is convenient andpresent the questionnaire (2) one of them gives the subjecta brief explanation about the aim and the context of ques-tionnaire while the other settles the instrumentations nearbyto measure thermal environmental variables (3) subjectcompletes questionnaire survey (4) during the survey a 15-minute sample of the thermal environment is made and (5)subject leaves and the assistants seek the next subject 60ndash120subjects were surveyed daily on fieldwork days

The number of visitors and their activities within thestudy area were investigated by observations on fieldworkdays Observations on each day were performed every 30

Advances in Meteorology 3

Table 1 Climatic characterization of fieldwork days

Fieldwork dateDaily average values Maximum DB temperature Δ119879max

dagger

DB RH Wind speed Solar radiation∘C ms MWm2 ∘C ∘C

Sep 19 274 745 13 156 312 minus28Sep 26 281 760 10 165 324 minus16Oct 03 281 755 15 122 307 minus19Oct 10 282 714 08 138 321 minus05Oct 17 279 691 10 144 323 minus03Oct 24 271 733 11 158 308 minus18Oct 31 212 614 26 183 262 minus64Nov 07 244 773 20 130 280 minus01Nov 28 215 680 08 142 264 minus17Dec 05 231 673 10 134 284 00Dec 12 197 724 09 136 270 minus14Dec 19 182 655 06 139 243 minus41Jan 09 166 736 29 134 200 minus29Jan 16 103 685 28 055 115 minus114daggerDifference between daily maximum temperature on fieldwork day and monthly maximum temperature

minutes from 1000 am to 500 pm for a daily total of 15observations The numbers of people in different subspaceswere observed according to the observation protocol Fieldinvestigations were conducted on Saturday or Sunday fromSeptember 2010 to January 2011 All fieldwork days weresunny and no festival celebrations held in the park

3 Results of Key Survey Questions

31 Descriptions of the Weather on Fieldwork Days Table 1summarizes the weather conditions on the fieldwork daysThe data in Table 1 are from the local weather station Thedifferences between maximum air temperatures of fieldworkdays and monthly maximum temperature are also shown forcomparison The mean dry-bulb temperature varies between103∘C and 282∘C Mean relative humidity and mean windspeeds are in the ranges of 614ndash773 and 06ndash29msrespectively

32 Characterization of Subjects The fieldwork team invited759 visitors to take part in the questionnaires Of the ques-tionnaire responses 43 were from male visitors of the parkand 57 were from female visitors Of the respondents 51live or work in neighborhood of the park and 49 are fromother regions The profile of subjectsrsquo age is 20 teenagers75 in the range of 20ndash50 years and 5 older than 50 years

The result of the question regarding how often thesubjects visit this park shows 9 visit more than 10 times17 visit 5ndash10 times and 35 visit 1ndash5 times per monthrespectively There are 27 of subjects seldom visiting thispark and 13 visiting this park for the first time Regardingthe question ldquoHow long are you going to spend in this parkrdquo37 answeredmore than two hours 33 answered 1-2 hours23 answered 05ndash1 hour and the remaining 7 answeredless than 05 hour Regarding the question ldquoFor what purpose

01020304050607080

0 1 2 3

Freq

uenc

y (

)

Thermalsensation votes

Windsensation votes

minus3 minus2 minus1 0 1 2minus2 minus1 0 1 2minus2 minus1

Votes on fieldworkdayrsquos weather

Figure 2

do you visit this parkrdquo and 69 said for the special reasonof sport relaxing or meeting other(s) 31 said for otherreasons such as being on the way to other places Basedon the results of observations the frequency distribution ofvisitorsrsquo activities shows that 32of the visitors observedwereengaged in light activities such as seating relaxed readingsun bathing and picnicking 39 were taking a walk 16were jogging and 14 were playing ball flying a Frisbeeflying a kite and so forth In addition it was observed thatvisitors prefer to use this park after 300 pm as the solarradiation at that time would not annoy them

33 Assessment of the Thermal Environment The subjectswere asked to report their thermal and wind sensationsaccording to a 7-point and a 5-point scale respectivelyFigure 2 shows the relative frequency distribution for ther-mal sensation votes while being surveyed 42 of the subjectsfelt the thermal conditions to be thermal neutral 28 feltslightly cool cool and cold and 30 felt slightly warmwarm and hot Figure 2 also shows the distribution for wind


75

32

12

4

1

6

7

10

13

12

9

11

10

6

28

48

54

3

13

10

7

9

10

8

11

25

32

21

9

5

0()

20 40 60 80 100

Very unsuitable

Unsuitable

General

Suitable

Very suitable

ColdCoolSlightly coolNeutral

Slightly warmWarmHot

(a)

11

1

1

2

14

16

22

9

8

14

35

63

79

77

71

30

14

10

11

1

8

2

2

Very unsuitable

Unsuitable

General

Very suitable

StillWeak Moderate

StrongVery strong

0()

20 40 60 80 100

Suitable

(b)

Figure 3 (a)Thermal sensation votes versus votes on fieldwork dayrsquos weather (b) wind sensation votes versus votes on fieldwork dayrsquos weather

sensation votes In wind assessment the majority of subjects(72) assessed the wind conditions as being moderate 14as still or weak and 14 as strong or very strong As shownin Figure 2 themajority of subjects considered the weather offieldwork days as suitable for outdoor leisure activities 22chose very suitable 51 suitable 22 general 5 unsuitableand 1 as very unsuitable

Patterns of thermal or wind sensation votes versus field-work day weather are examined in more detail in Figure 3As shown in Figure 3(a) when feeling the weather as suitableor very suitable for outdoor leisure activity about 70 ofsubjects were also satisfied with the thermal conditions atthe site with their votes falling in the three central categories(TSV = minus1 0 and +1) of the thermal sensation scale whereas30 were unsatisfied by voting extreme thermal sensations(TSV = plusmn2 plusmn3) Of the people feeling unsuitable or veryunsuitable 80 to 100 were not satisfied with the thermalconditions at the site In Figure 3(b) the distributions ofcross-examinations between wind sensation and votes on theweather fieldwork days revealed the same trend howeverwhen subjects felt ldquounsuitablerdquo or ldquovery unsuitablerdquo 35 and14 felt the wind was moderate respectively

4 Thermal Perception Analysis

41 Thermal Sensation versus Thermal Environment The re-lationship between thermal sensation and thermal envi-ronment was examined using linear regressions betweenthermal sensation votes and the thermo-physiological indexWBGT was selected as the thermal index in this studyProvided in ISO 7243 [16] as a simplified version of ETlowastfor the assessment of hot environments the WBGT foroutdoor environments with solar radiation is determinedfrom three single readings namely wet-bulb temperatureglobe temperature and dry bulb temperature As explained inthe introduction the WBGT seems suitable for practical use

by those unskilled in energy-balance modeling of the humanbody which is the reason this study decided to test WBGTas the basis for all subsequent analyses The WBGT indexcombines temperature humidity radiation and wind into asingle index which is determined as follows

WBGT = 07 times 119905wb + 02 times 119905119892 + 01 times 119905119886 (1)

where 119905wb is normal meteorological wet bulb temperatureshown by awet bulb thermometer 119905

119886is dry bulb temperature

and 119905119892is 150mm diameter black globe temperature

In the regression analysis the mean thermal sensationvotes in each temperature interval were used rather thanactual individual votes in order to eliminate the influenceof individual differences Thus all thermal sensation votesof the subjects were sorted in ascending order according toWBGT and are binned into 10∘C intervals of WBGT The1198772 of the model can be interpreted as an index of goodnessof fit The regression of the mean thermal sensation voteagainst WBGT is shown in Figure 4Thermal sensation votescorrelate strongly with WBGT thus the WBGT index isconsidered by this study as a suitable index without elaborateprocedures of calculations

42 Thermal Acceptability Generally the votes equal toldquoslightly coolrdquo ldquoneutralrdquo and ldquoslightlywarmrdquo are considered tobe of those who consider the thermal conditions surroundingthem acceptable Thus for each 1∘C interval of the WBGTthe percentage of thermal acceptability could be determinedfrom counting the total number of votes and the numberof votes falling into the three categories of ldquoslightly coolrdquoldquoneutralrdquo and ldquoslightly warmrdquo Figure 5 shows the histogramof the distribution of the acceptable votes as well as thepercentage of unacceptability due to coldness or hotnessThe percentage of hot unacceptability in each interval ofthe WBGT is derived from dividing the number of votesfalling into the categories of ldquowarmrdquo and ldquohotrdquo by the total


0

1

2

3

5 10 15 20 25 30 35

TSV

minus3

minus2

minus1

TSV = 01856 WBGT minus4454R2 = 094

WBGT (∘C)

Figure 4

100806040200

20406080

100

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Acce

ptab

le v

otes

()

AcceptableCold unacceptableHot unacceptable

Una

ccep

tabl

e vot

es (

)

WBGT (∘C)

Figure 5

number of votes while the percentage of cold unacceptabilityis derived from dividing the number of votes falling into thecategories of ldquocoolrdquo and ldquocoldrdquo by the total number of votesIt appears that the distribution of thermal acceptability rateand the distribution of thermal unacceptability rate dependon WBGT

The sigmoid distribution of unacceptability rates due tohotness or coldness suggests that the resulting percentageswithin each interval could be subjected to the probit analysis[17 18] The resulting models are depicted in Figure 6 Themaximum likelihood probit models for the percentages ofunacceptability due hotness and coldness are given in (2) and(3) respectively

For hotness

probit 119901hot = 438 timesWBGT + 2921198772 = 089 (2)

For coldness

probit 119901cold = minus411 times119882119861119866119879 + 1661198772

= 093 (3)

1

10

100

5 10 15 20 25 30 35 40

Una

ccep

tabi

lity

()

ColdWarmTotal

WBGT (∘C)

Figure 6

Then the sum of the probabilities of unacceptability dueto hotness and coldness is the total percentage of unac-ceptability with respect to a specific WBGT By inspectingthe curve of total unacceptability it can be noticed thatthe distribution of thermal unacceptability is approximatelysymmetrical around the ideal comfort temperature ForWBGT between 20∘C and 260∘C there are less than 20of subjects voting unacceptable that is more than 80 ofsubjects voting acceptable An ideal comfort condition atwhich theminimum value of thermal unacceptability occursis at the point of 232∘CWBGT

5 Behavioral Adaptation

According to the adaptive principle ldquoIf a change occurs andproduces discomfort people react in ways that tend to restoretheir comfortrdquo [19] For the case of this study the behavioraladaptations of clothing adjustments andmetabolic rates wereevaluated The air velocity and attendance of visitors wereused as means to measure the methods subjects used toachieve comfort

51 Clothing Level Adjusting clothing is the most importantpersonal behavioral adaptation to restore thermal comfortat different temperatures By plotting the value of clothinginsulation worn by the subjects it is easy to determine thecorrelation between the clo value and the outdoor thermalcondition Figure 7 shows how the clo value varies among thefieldwork days The scattered clo value was observed from aminimum of 03 clo on hot days to a maximum of 15 clo oncold days The regression in (4) shows that the correlationbetween average clothing insulation and average WBGT ona fieldwork days is robust

clo = minus0039 timesWBGT + 1541198772 = 096 (4)


0

5

10

15

20

25

30

35

00

05

10

15

20

25

Clot

hing

leve

l clo

CloWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 7

0

5

10

15

20

25

30

35

08

10

12

14

16

18

20

22

24

26

Met

abol

ic ra

te m

et

MetWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 8

A similar regression was conducted between the clothingand the instantaneous WBGT during interviews The linearregression gives


Results from the field studies demonstrate that individu-als use changes in clothing levels to try and achieve comfortand that a correlation exists between the clothing and theWBGT

52 Activity Level The plot of the activity levels of visitors onfieldwork days shows that the corresponding metabolic rateis nearly horizontal between 10 and 15 met Figure 8 Thisindicates that the visitorrsquos activity level is independent of thevalue of the WBGT

53 Air Movement Figure 9 shows the average wind speedand percentage of wind sensation votes in ldquostillrdquo and ldquoweakrdquo

00

20

40

60

80

100

120

0

20

40

60

80

6 10 14 18 22 26 30 34 38

Win

d sp

eed

(ms

)

Freq

uenc

y (

)

Still and weakStrong and very strongAir speed

minus40

minus20

WBGT (∘C)

Figure 9

categories or ldquostrongrdquo and ldquovery strongrdquo categories as a func-tion ofWBGT Inwarmer-than-neutral conditions (WBGT ≧240∘C) the percentage of subjects feeling the wind speed

to be ldquostillrdquo or ldquoweakrdquo increases dramatically from 10 at240∘C WBGT to 52 at 340∘C WBGT even though themean air speed varies in a narrow range of 09ndash15msA possible explanation is that subjects who exposed tohigh WBGT perceived the wind to be weak based on theirexperience that lower wind speed may contribute to hotconditionThat is they think stronger wind may release theiruncomfortable feeling so they might vote the wind speed asldquostillrdquo and ldquoweakrdquo to reflect their subconscious uncomfortableperceptionThe sharp rise in wind discomfort votes without asignificant change in wind speed and in accordance with therespective thermal conditions indicates that wind is actuallyperceived as a component of the thermal environment ratherthan as a separate environmental factor It should be notedthat the wind speed measured in this park is not strongdue to the high density urban forms in Taiwan and tallbuildings surroundingThe subjectsmay express a reasonableperception equivalent to actual wind speed once the windspeed is relatively high (eg gt10ms)

54 Avoidance of the Sun Thorsson et al [20] conducteda fieldwork study in Japan where the ideal beauty is fairskin and found that 80 of the visitors in the urban publicplaces sought shade at temperatures higher than 20∘C Acounterpart study done in Sweden [21] where the idealbeauty includes a suntan showed that only 14 of parkvisitors sought shade at temperatures higher than 20∘CWithrespect to attitudes toward the sun this study demonstratesthe relationship between the thermal environment in termsof the temperature difference (119905

119892minus 119905119886) between globe tem-

perature and dry-bulb temperature and the usage as shownFigure 10 Rather than the percentage of visitors in shade totalattendance is used in Figure 10 which results from the limitedamount of shade in the park As shown in Figure 10 themaximum of people in the park was observed at a situation


0

40

80

120

160

200

0 2 4 6 8 10 12 14 16 18

Num

ber o

f visi

tors

tg minus ta

N = exp[minus015(tg minus ta) + 519]

R2 = 092

Figure 10

For cool conditions

For warm conditions

020406080

100120140160180

5 10 15 20 25 30 35 40

Tota

l atte

ndan

ce

WBGT (∘C)

N = 770xWBGT minus 876R2 = 089

N = minus1151xWBGT + 4070

R2 = 073

Figure 11

where the temperature difference was less than 10∘C As the119905119892minus 119905119886increases the total attendance presents an exponential

decay The best-fitted regression equation is superposed inFigure 10 The 1198772 = 092 indicates a robust relation existsThis demonstrates that strong solar radiation intensity resultin people in Taiwan where the ideal beauty is also fair skintends to avoid the sun to a notable extent

55 Relation between Total Attendance and Thermal Condi-tions Figure 11 shows the relation between thermal environ-ments in terms of WBGT and the average total attendanceThis distribution of total attendance againstWBGT is a singlepeak model When the parkrsquos thermal condition is moderatethere are more than 120 people remaining in the study areaof the park and the total attendance in the park decreasesconsiderably to a level of less than 20 people staying in thestudy area The number of people decreases more rapidlywithWBGT in hot conditions than in cool conditions Linearregression analysis is used to fit the relation between thermalconditions and total attendance as shown in Figure 11 Therelation is found to be significant which indicates that themore comfortable the perceived thermal environment is thehigher the usage rate of the park will be

6 Conclusions

Urban outdoor thermal environmental evaluation is ofgreat significance in guiding the publicrsquos outdoor activitiesthe design of comfortable outdoor environments and theimprovement of urban climate Based on the data fromfield surveys this study used the WBGT as the thermo-physiological index to analyze outdoor thermal comfort Themajor achievements of this study are as follows

According to the respondentsrsquo thermal perceptionsWBGT as an index of the outdoor thermal conditions hasstatistical significance relationship with the thermal percep-tion of the respondents This suggested the reliability of itsapplication for analyzing outdoor thermal comfort Accord-ing to that relationship the lower and upper limits of comfortacceptability for 80 of acceptability were 20∘C WBGT and26∘C WBGT This study also found that the temperaturecorresponding to the lowest thermal unacceptable value is232∘CWBGT

The results regarding the adjustment behaviors and ther-mal environments suggested that the amount of clothingwas significantly correlated to WBGT However the activitywas not significantly correlated to WBGT When the WBGTincreases expectations for high wind speed rise rapidlyWhen theWBGT decreases expectations for low wind speedrise rapidly The research found that Taiwanrsquos residents hadthe apparent characteristics of avoiding sunlight With risingor falling of WBGT the number of visitors in the park woulddecline accordingly The WBGT range of most visitors wasapproximately consistent with the outdoor thermal comfort-able zone

Acknowledgment

The authors offer their sincere appreciation for assistance ingrant to the National Science Council of Taiwan (Project noNSC-99-2221-E-239-028-MY2)

References

[1] J Spagnolo andR J deDear ldquoAfield study of thermal comfort inoutdoor and semi-outdoor environments in subtropical SydneyAustraliardquo Building and Environment vol 38 no 5 pp 721ndash7382003

[2] K S Ahmed ldquoComfort in urban spaces defining the bound-aries of outdoor thermal comfort for the tropical urban envi-ronmentsrdquoEnergy and Buildings vol 35 no 1 pp 103ndash110 2003

[3] J Nakano and S Tanabe ldquoThermal comfort and adaptation insemi-outdoor environmentsrdquo ASHRAE Transactions vol 110pp 543ndash553 2004

[4] M Nikolopoulou and S Lykoudis ldquoThermal comfort in out-door urban spaces analysis across different European coun-triesrdquo Building and Environment vol 41 no 11 pp 1455ndash14702006

[5] S Oliveira and H Andrade ldquoAn initial assessment of thebioclimatic comfort in an outdoor public space in LisbonrdquoInternational Journal of Biometeorology vol 52 no 1 pp 69ndash842007

[6] H Andrade M-J Alcoforado and S Oliveira ldquoPerceptionof temperature and wind by users of public outdoor spaces


relationships with weather parameters and personal character-isticsrdquo International Journal of Biometeorology vol 55 no 5 pp665ndash680 2011

[7] V Cheng E Ng C Chan and B Givoni ldquoOutdoor thermalcomfort study in a sub-tropical climate a longitudinal studybased in Hong Kongrdquo International Journal of Biometeorologyvol 56 no 1 pp 43ndash56 2012

[8] S Kariminia S ShAhmadN Ibrahim andMOmar ldquoOutdoorthermal comfort of two public squares in temperate and dryregion of Esfahan Iranrdquo in Proceedings of the InternationalConference on Science and Social Research (CSSR rsquo10) pp 1266ndash1271 Kuala Lumpur Malaysia December 2010

[9] T-P Lin ldquoThermal perception adaptation and attendancein a public square in hot and humid regionsrdquo Building andEnvironment vol 44 no 10 pp 2017ndash2026 2009

[10] R-L Hwang T-P Lin M-J Cheng and J-H Lo ldquoAdaptivecomfort model for tree-shaded outdoors in Taiwanrdquo Buildingand Environment vol 45 no 8 pp 1873ndash1879 2010

[11] T-P Lin R de Dear and R-L Hwang ldquoEffect of thermaladaptation on seasonal outdoor thermal comfortrdquo InternationalJournal of Climatology vol 31 no 2 pp 302ndash312 2011

[12] T-P Lin A Matzarakis and R-L Hwang ldquoShading effect onlong-term outdoor thermal comfortrdquo Building and Environ-ment vol 45 no 1 pp 213ndash221 2010

[13] ISO ISO 7726 Ergonomics of the Thermal Environment-Instruments for Measuring Physical Quantities InternationalStandards Organization Geneva Switzerland 2003

[14] ISO ISO 7730 Ergonomics of the Thermal Environment-Analytical Determination and Interpretation ofThermal ComfortUsing Calculation of the PMV and PPD Indices and Local Ther-mal Comfort Criteria International Standards OrganizationGeneva Switzerland 2005

[15] ASHRAE ASHRAE Handbook Fundamentals (SI) AmericanSociety of Heating Refrigerating and Air Conditioning Engi-neering Atlanta Ga USA 2005

[16] ISO ISO 7243 Hot Environments-Estimation of the Heat Stresson Working Man Based on the WBGT-Index (Wet Bulb GlobeTemperature) International Standards Organization GenevaSwitzerland 2003

[17] E R Ballantyne R K Hill and J W Spencer ldquoProbit analysisof thermal sensation assessmentsrdquo International Journal ofBiometeorology vol 21 no 1 pp 29ndash43 1977

[18] J F Nicol and M A Humphreys ldquoA stochastic approachto thermal comfort occupant behaviour and energy use inbuildingsrdquo ASHRAE Transactions vol 110 no 2 pp 554ndash5682004

[19] M A Humphreys and J F Nicol ldquoUnderstanding the adaptiveapproach to thermal comfortrdquo ASHRAE Transactions vol 104no 1 pp 991ndash1004 1988

[20] S Thorsson T Honjo F Lindberg I Eliasson and E-MLim ldquoThermal comfort and outdoor activity in Japanese urbanpublic placesrdquoEnvironment andBehavior vol 39 no 5 pp 660ndash684 2007

[21] I Eliasson I Knez UWesterberg SThorsson and F LindbergldquoClimate and behaviour in a Nordic cityrdquo Landscape and UrbanPlanning vol 82 no 1-2 pp 72ndash84 2007

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Figure 1 Photograph of investigated Wen-Xin Park in TaichungTaiwan

responses and thus enable reliable predictions to be madebe used to replace such complex indictors to help architectsachieve better climatic design Thus the objectives of thisstudy were to select a thermo-physiological index that can bedetermined from simple readings to analyze outdoor thermalcomfort and to discuss the relationship between the publicrsquosoutdoor adaptive behaviors and the selected index

2 Materials and Methods

21 Description of Study Park This study was based on ques-tionnaire surveys and weather measurements performedsimultaneously in Taichung City the third largest city ofTaiwan (longitude 120∘401015840E latitude 24∘091015840N) which islocated in central Taiwan and has approximately 1200000inhabitants The city has a hot and humid climate with mildwinters and hot and humid summers

The field investigations were conducted in the openarea of Wen-Xin Park (see Figure 1) which is one of thethree metropolitan parks in downtown Taichung City Thispark is used for leisure and sport activities such as lyingsitting promenading jogging and kite flying particularlyduring weekends and holidays The surveyed area has pavedsidewalks and green areas with about 80 of the total areacovered by grass There are a few benches facing the greenareas along the sidewalks however most people use the grassareasThe trees that provide shade are around the sidewalk inthe middle of the surveyed area and cover about 20 of thearea

22 Instrumentations and Microclimatic Measurements Acombination of portable equipment which complies with therequirements of instruments for measuring physical quan-tities in ISO 7726 [13] was assembled to allow monitoringof the microclimate during questionnaire interviews DataLogger Center 314 was used to collect measurements of dry-bulb temperature globe temperature and relative humidityThe globe thermometer is a standard black-painted matteglobeThedry-bulb temperature and relative humidity sensor

were shielded from radiation by a highly reflective alu-minized top film but were subject to free-flowing ventilationAir speed was monitored with a separate data logger theomnidirectional anemometers Delta HD 2103Metabolic rateand the insulation of clothing [14] were estimated based onthe answers to the questionnaire The thermo-physiologicalindex WBGT was calculated in order to evaluate the com-bined effects of atmospheric variables on thermal sensationvotes (TSV) The wet-bulb temperature was obtained bysubstituting the measured dry-bulb temperature and relativehumidity into the equations in the Chapter of PsychometricsASHRAE Handbook of Fundamentals [15] Besides the mea-surements of condition nearby the respondents two sets ofinstruments were installed in sunlit and tree-shaded area forcontinuous measurements on fieldwork days Meteorologicaldata were also obtained from a nearby local official weatherstation which is located in another downtown metropolitanpark about 4 km away from the study park

23 Questionnaire Interviews and Observation A team ofthree research assistants performed the questionnaire inter-views and observations every fieldwork day two of themwereresponsible for questionnaire interviews and the remainingassistant for observations The interviews were performed inChinese and required 15 minutes to complete The question-naires used in this study were created by modifying thosedeployed in earlier studies [9ndash11] divided into two partsnamely BACKGROUND and PERCEPTION

BACKGROUND covered questions regarding demo-graphics current clothing garments metabolic activitiesliving or working in the neighborhood of park the reasonfor being in the park and the frequency and duration of timespent in the park

PERCEPTION had questions concerning the subjectrsquosassessment of their immediate thermal environment at thatpoint in time The subjects were asked to report theirsensations of thermal environment through a 7-point scaleand of air movement through a 5-point scale The thermalsensation scale was the ASHRAE 7-point scale ranging fromcold (minus3) to hot (+3) with neutral (0) in the middle Thesubjects assessed the wind sensation on a 5-point scale still(minus2) weak (minus1) moderate (0) strong (+1) and very strong(+2) The final question in the PERCEPTION part askedsubjects whether or not they considered the weather ofthe fieldwork day suitable for leisure outdoor activities Theprotocol for each interview was as follows (1) two researchassistants approach subject ask if time is convenient andpresent the questionnaire (2) one of them gives the subjecta brief explanation about the aim and the context of ques-tionnaire while the other settles the instrumentations nearbyto measure thermal environmental variables (3) subjectcompletes questionnaire survey (4) during the survey a 15-minute sample of the thermal environment is made and (5)subject leaves and the assistants seek the next subject 60ndash120subjects were surveyed daily on fieldwork days

The number of visitors and their activities within thestudy area were investigated by observations on fieldworkdays Observations on each day were performed every 30




dagger








01020304050607080

0 1 2 3

Freq

uenc

y (

)


Windsensation votes



Figure 2




75

32

12

4

1

6

7

10

13

12

9

11

10

6

28

48

54

3

13

10

7

9

10

8

11

25

32

21

9

5

0()

20 40 60 80 100

Very unsuitable

Unsuitable

General

Suitable

Very suitable



(a)

11

1

1

2

14

16

22

9

8

14

35

63

79

77

71

30

14

10

11

1

8

2

2

Very unsuitable

Unsuitable

General

Very suitable

StillWeak Moderate

StrongVery strong

0()

20 40 60 80 100

Suitable

(b)














0

1

2

3

5 10 15 20 25 30 35

TSV

minus3

minus2

minus1

TSV = 01856 WBGT minus4454R2 = 094

WBGT (∘C)

Figure 4

100806040200

20406080

100

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Acce

ptab

le v

otes

()


Una

ccep

tabl

e vot

es (

)

WBGT (∘C)

Figure 5



For hotness


For coldness


= 093 (3)

1

10

100

5 10 15 20 25 30 35 40

Una

ccep

tabi

lity

()

ColdWarmTotal

WBGT (∘C)

Figure 6







0

5

10

15

20

25

30

35

00

05

10

15

20

25

Clot

hing

leve

l clo

CloWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 7

0

5

10

15

20

25

30

35

08

10

12

14

16

18

20

22

24

26

Met

abol

ic ra

te m

et

MetWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 8






00

20

40

60

80

100

120

0

20

40

60

80

6 10 14 18 22 26 30 34 38

Win

d sp

eed

(ms

)

Freq

uenc

y (

)


minus40

minus20

WBGT (∘C)

Figure 9







0

40

80

120

160

200

0 2 4 6 8 10 12 14 16 18

Num

ber o

f visi

tors

tg minus ta


R2 = 092

Figure 10

For cool conditions

For warm conditions

020406080

100120140160180

5 10 15 20 25 30 35 40

Tota

l atte

ndan

ce

WBGT (∘C)



R2 = 073

Figure 11




6 Conclusions




Acknowledgment


References

































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in




dagger








01020304050607080

0 1 2 3

Freq

uenc

y (

)


Windsensation votes



Figure 2




75

32

12

4

1

6

7

10

13

12

9

11

10

6

28

48

54

3

13

10

7

9

10

8

11

25

32

21

9

5

0()

20 40 60 80 100

Very unsuitable

Unsuitable

General

Suitable

Very suitable



(a)

11

1

1

2

14

16

22

9

8

14

35

63

79

77

71

30

14

10

11

1

8

2

2

Very unsuitable

Unsuitable

General

Very suitable

StillWeak Moderate

StrongVery strong

0()

20 40 60 80 100

Suitable

(b)














0

1

2

3

5 10 15 20 25 30 35

TSV

minus3

minus2

minus1

TSV = 01856 WBGT minus4454R2 = 094

WBGT (∘C)

Figure 4

100806040200

20406080

100

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Acce

ptab

le v

otes

()


Una

ccep

tabl

e vot

es (

)

WBGT (∘C)

Figure 5



For hotness


For coldness


= 093 (3)

1

10

100

5 10 15 20 25 30 35 40

Una

ccep

tabi

lity

()

ColdWarmTotal

WBGT (∘C)

Figure 6







0

5

10

15

20

25

30

35

00

05

10

15

20

25

Clot

hing

leve

l clo

CloWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 7

0

5

10

15

20

25

30

35

08

10

12

14

16

18

20

22

24

26

Met

abol

ic ra

te m

et

MetWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 8






00

20

40

60

80

100

120

0

20

40

60

80

6 10 14 18 22 26 30 34 38

Win

d sp

eed

(ms

)

Freq

uenc

y (

)


minus40

minus20

WBGT (∘C)

Figure 9







0

40

80

120

160

200

0 2 4 6 8 10 12 14 16 18

Num

ber o

f visi

tors

tg minus ta


R2 = 092

Figure 10

For cool conditions

For warm conditions

020406080

100120140160180

5 10 15 20 25 30 35 40

Tota

l atte

ndan

ce

WBGT (∘C)



R2 = 073

Figure 11




6 Conclusions




Acknowledgment


References

































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


75

32

12

4

1

6

7

10

13

12

9

11

10

6

28

48

54

3

13

10

7

9

10

8

11

25

32

21

9

5

0()

20 40 60 80 100

Very unsuitable

Unsuitable

General

Suitable

Very suitable



(a)

11

1

1

2

14

16

22

9

8

14

35

63

79

77

71

30

14

10

11

1

8

2

2

Very unsuitable

Unsuitable

General

Very suitable

StillWeak Moderate

StrongVery strong

0()

20 40 60 80 100

Suitable

(b)














0

1

2

3

5 10 15 20 25 30 35

TSV

minus3

minus2

minus1

TSV = 01856 WBGT minus4454R2 = 094

WBGT (∘C)

Figure 4

100806040200

20406080

100

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Acce

ptab

le v

otes

()


Una

ccep

tabl

e vot

es (

)

WBGT (∘C)

Figure 5



For hotness


For coldness


= 093 (3)

1

10

100

5 10 15 20 25 30 35 40

Una

ccep

tabi

lity

()

ColdWarmTotal

WBGT (∘C)

Figure 6







0

5

10

15

20

25

30

35

00

05

10

15

20

25

Clot

hing

leve

l clo

CloWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 7

0

5

10

15

20

25

30

35

08

10

12

14

16

18

20

22

24

26

Met

abol

ic ra

te m

et

MetWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 8






00

20

40

60

80

100

120

0

20

40

60

80

6 10 14 18 22 26 30 34 38

Win

d sp

eed

(ms

)

Freq

uenc

y (

)


minus40

minus20

WBGT (∘C)

Figure 9







0

40

80

120

160

200

0 2 4 6 8 10 12 14 16 18

Num

ber o

f visi

tors

tg minus ta


R2 = 092

Figure 10

For cool conditions

For warm conditions

020406080

100120140160180

5 10 15 20 25 30 35 40

Tota

l atte

ndan

ce

WBGT (∘C)



R2 = 073

Figure 11




6 Conclusions




Acknowledgment


References

































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


0

1

2

3

5 10 15 20 25 30 35

TSV

minus3

minus2

minus1

TSV = 01856 WBGT minus4454R2 = 094

WBGT (∘C)

Figure 4

100806040200

20406080

100

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Acce

ptab

le v

otes

()


Una

ccep

tabl

e vot

es (

)

WBGT (∘C)

Figure 5



For hotness


For coldness


= 093 (3)

1

10

100

5 10 15 20 25 30 35 40

Una

ccep

tabi

lity

()

ColdWarmTotal

WBGT (∘C)

Figure 6







0

5

10

15

20

25

30

35

00

05

10

15

20

25

Clot

hing

leve

l clo

CloWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 7

0

5

10

15

20

25

30

35

08

10

12

14

16

18

20

22

24

26

Met

abol

ic ra

te m

et

MetWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 8






00

20

40

60

80

100

120

0

20

40

60

80

6 10 14 18 22 26 30 34 38

Win

d sp

eed

(ms

)

Freq

uenc

y (

)


minus40

minus20

WBGT (∘C)

Figure 9







0

40

80

120

160

200

0 2 4 6 8 10 12 14 16 18

Num

ber o

f visi

tors

tg minus ta


R2 = 092

Figure 10

For cool conditions

For warm conditions

020406080

100120140160180

5 10 15 20 25 30 35 40

Tota

l atte

ndan

ce

WBGT (∘C)



R2 = 073

Figure 11




6 Conclusions




Acknowledgment


References

































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


0

5

10

15

20

25

30

35

00

05

10

15

20

25

Clot

hing

leve

l clo

CloWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 7

0

5

10

15

20

25

30

35

08

10

12

14

16

18

20

22

24

26

Met

abol

ic ra

te m

et

MetWBGT

Percentile 95

Percentile 5

WBG

T (∘

C)

Sep

18

Sep

26

Oct

3O

ct 1

0O

ct 1

7O

ct 2

4O

ct 3

1N

ov 7

Nov

28

Dec

5D

ec 1

2D

ec 1

9Ja

n 9

Jan

16

Figure 8






00

20

40

60

80

100

120

0

20

40

60

80

6 10 14 18 22 26 30 34 38

Win

d sp

eed

(ms

)

Freq

uenc

y (

)


minus40

minus20

WBGT (∘C)

Figure 9







0

40

80

120

160

200

0 2 4 6 8 10 12 14 16 18

Num

ber o

f visi

tors

tg minus ta


R2 = 092

Figure 10

For cool conditions

For warm conditions

020406080

100120140160180

5 10 15 20 25 30 35 40

Tota

l atte

ndan

ce

WBGT (∘C)



R2 = 073

Figure 11




6 Conclusions




Acknowledgment


References

































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in


0

40

80

120

160

200

0 2 4 6 8 10 12 14 16 18

Num

ber o

f visi

tors

tg minus ta


R2 = 092

Figure 10

For cool conditions

For warm conditions

020406080

100120140160180

5 10 15 20 25 30 35 40

Tota

l atte

ndan

ce

WBGT (∘C)



R2 = 073

Figure 11




6 Conclusions




Acknowledgment


References

































Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in



























Volume 2014

Mining


Journal of



Geophysics







Journal of




Advances in











Geology Advances in

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