Landscape and Urban Planning 138 (2015) 99–109

Contents lists available at ScienceDirect

Landscape and Urban Planning

j ournal homepage: www.elsevier.com/locate/landurbplan

Research Paper

Effect of planting design and tree on human thermal

comfort in the

a,∗ a b

Loyde Vieira de Abreu-Harbich , Lucila Chebel Labaki , Andreas Matzarakis

a

School of Civil Engineering, Architecture and Urban Design, State University of Campinas, Rua Saturnino de Brito, 224, 13083-850 Campinas,

b

Faculty of Environment and Natural Resource, Albert-Ludwigs-University Freiburg, Werthmannstrasse 10, D-79085 Freiburg, Germany

h i g h l i g h t s

•

Single and clusters of are quantified on a quantitative manner.

•

Thermal comfort conditions are strong influenced by solar radiation and wind.

•

Must appropriate tree for the improvement of thermal comfort conditions are Caesalpinia pluviosa.

• ◦

Reduction of Tmrt can improve thermal comfort conditions about 16 C (PET) during summer condition.

a r t i c l e i n f o a b s t r a c t

Article history: Trees behave in different ways on microclimate due to mainly distinct features of each species and

Available online 12 March 2015

planting strategies especially in the tropics. This paper quantifies the daily and seasonal microclimate

behavior of various tree species with different planting design either individual or in clusters. This specific

Keywords:

knowledge is an important step in the development of urban design guidelines based on the shading of

Human thermal comfort

trees and climate adaptation in urban areas in the tropics. It focuses on human thermal comfort based

Physiologically equivalent temperature

on the physiologically equivalent temperature (PET) for different species. Twelve species were analyzed:

Mean radiant temperature

Handroanthus chrysotrichus (Mart. ex A.DC.) Mattos, Jacaranda mimosaefolia D. Don., Syzygium cumini

Tree planting design

L., Mangifera indica L., Pinus palustris L., Pinus coulteri L.; Lafoensia glyptocarpa L., Caesalpinia pluviosa F.,

Tropical climate

Spathodea campanulata P. Beauv., Tipuana tipu F., Delonix indica F. and Senna siamea L. The results show

Brazil (Campinas)

that shading of trees can influence significantly human thermal comfort expressed by (PET). The species

◦

C. pluviosa F. presents the best possibility in terms of PET because it can reduce between 12 and 16 C for

◦

individual trees cluster can reduce between 12.5 and 14.5 C. Appropriate vegetation used for shading

public and private areas is essential to mitigate heat stress and can create better human thermal comfort

especially in cities. The results can be seen as a possibility of improvement of outdoor thermal comfort

conditions and as an important step in order to achieve sustainability in cities.

© 2015 Elsevier B.V. All rights reserved.

1. Introduction characteristics of the various surfaces in urban spaces and their

behavior with respect to incident solar radiation have serious

An important characteristic of tropical cities is urban greenery impacts on the urban environment (Guderian, 2000). The study

that creates shading along streets and in residential areas and can of vegetation in the control of incident solar radiation, and as

assist in the development of adaptation possibilities against cli- a regulator of urban climatic changes involves qualifying and

mate change. It also acts as a carbon sink, relative to the amount quantifying the influence of trees on human thermal comfort

of green coverage (Abreu-Harbich, Labaki, & Matzarakis 2013a, (Abreu-Harbich, Labaki, & Matzarakis, 2012; Matzarakis, 2013;

2013b; Emmanuel, 2005; Emmanuel, Rosenlund, & Johansson, Matzarakis & Endler, 2010; Shashua-Bar, Pearlmutter, & Erell, 2009;

2007; Grimmond, 2007; Lin, Matzarakis, & Hwang, 2010). The Shashua-Bar, Potchter, Bitan, Boltansky, & Yaakov, 2010; Streiling &

Matzarakis, 2003; Yilmaz, Toy, Irmaka, & Yilmaz, 2007). Numerous

studies focusing on trees and their benefits in urban environment

∗ have been published (Bernatzky, 1979; Cardelino & Chameides,

Corresponding author at: Rua Saturnino de Brito, 224, Caixa Postal 6021, 13083-

1990; Dimoudi & Nikolopoulou, 2003; Heisler, 1977; Herrington,

852 Campinas, Brazil. Tel.: +55 0193521 2384; fax: +55 19 3788 2411.

1977; McPherson, Nowak, & Rowantree, 1994; Meyer & Bauermel,

E-mail address: [email protected] (L.V. de Abreu-Harbich).

http://dx.doi.org/10.1016/j.landurbplan.2015.02.008

0169-2046/© 2015 Elsevier B.V. All rights reserved.

100 L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109

1982; Montague & Kjelgren, 1998; Oke, 1989; Santamouris, 2001; Our aim was to quantify the daily and seasonal microclimate

Shashua-Bar & Hoffman, 2000; Shashua-Bar et al., 2010). Vari- behavior of various tree species in different planting configurations.

ous methodologies confirm that vegetation can influence urban Such knowledge is important in the development of urban design

microclimate, improve human thermal comfort, and decrease the guidelines based on the shading of trees and climate adaptation in

potential for health impairment of urban populations (Akbari, urban areas of the tropics. We have focused on thermal comfort of

2002; Akbari, Rosenfeld, Taha, & Gartland, 1996; Dimoudi & humans based on the PET for different tree species. We intend to

Nikolopoulou, 2003; Mayer, Salovey, & Caruso, 2008; Santamouris, quantify these affects by providing quantitative results, which can

2001; Streiling & Matzarakis, 2003). Arboreal species behave in be applied in tropical regions.

diverse ways in outdoor spaces, especially in terms of differences

in shade, with previous studies quantifying these benefits (Bueno-

2. Methodology

Bartholomei & Labaki, 2003; Lin et al., 2010; Shahidan, Shariff,

Jones, Salleh, & Abdullah, 2010; Shashua-Bar & Hoffman, 2000;

2.1. Study area

Shashua-Bar et al., 2009, 2010).

Urban trees can modify air temperature, increase air humid- ◦   ◦  

Our study was conducted in Campinas (22 48 57 S; 47 03 33

ity, reduce wind speed, and modify air pollutants (Streiling &

W; 640 m elevation), in the southeast of Brazil. It is one of the

Matzarakis, 2003). It has been confirmed that the positive effects

larger cities in the country, with 1.1 million inhabitants and a

on the bioclimatic conditions of a city, the mean radiant tempera- 2

very high population density of 1300/km (Brazil, 2010). The

ture (Tmrt) and the human biometeorological thermal index – the

Köppen-Geiger climate classification of the city is subtropical

physiologically equivalent temperature (PET), of single trees and

(Cwa; Kottek, Grieser, Beck, Rudolf, & Rubel, 2006), with less rain-

clusters are distinct because of differences between areas with

fall in winter, and rainy, warm-to-hot days in summer. Mean

trees and without trees. Local air temperature can be influenced ◦

annual air temperature is 22.3 C and annual rainfall 1411 mm.

by green coverage and area index (LAI), which are impor-

Rain is predominant from November to March, with dry peri-

tant arboreal characteristics (Tsutsumi, Ishii, & Katayama, 2003).

ods of 30–60 days in July and August. The summer period is

Some studies confirm that specific features of species, like struc-

from November to April, with average maximum temperatures

ture and density of the treetop, size, shape and color of , tree ◦

between 28.5 and 30.5 C and minimum temperatures between

age and growth, can influence the performance of solar radiation ◦

11.3 and 13.8 C. The warmest month is February, with an average

attenuated by canopy, air temperature and air humidity (Abreu- ◦ ◦ ◦

temperature of 24.9 C (maximum 30.0 C and minimum 19.9 C).

Harbich et al., 2012; Bueno-Bartholomei & Labaki, 2003; Correa,

The winter season is June, July and August, with maximum tem-

Ruiz, Canton, & Lesino, 2012; Gulyás, Unger, & Matzarakis, 2006; ◦

peratures between 24.8 and 29.1 C and minimum between 11.3

Scudo, 2002; Shashua-Bar et al., 2009). Tree canopies are able to ◦

and 13.8 C. The coldest month is July, with an average temper-

modify to microclimatic environments because of reflection, trans- ◦ ◦ ◦

ature of 18.5 C (maximum 24.8 C and minimum 11.3 C). The

mission and absorption of solar radiation and control wind speed

prevalent wind direction is southeast, with a mean annual speed

(Steven, Biscoe, Jaggard, & Paruntu, 1986). In tropical climates,

of 1.4 m/s. Annual sunshine duration is 2373 h, and the mean

the possibility of changing wind conditions and shade will modify 2

daily solar radiation is 4.9 kWh/m . Weather variations in Camp-

the microclimate and improve human thermal comfort (Lin et al.,

inas are caused by regional atmospheric circulation shifts and

2010).

diverse topography. There are tropical, equatorial continental,

In Brazil, it was recently concluded that outdoor thermal com-

tropical Atlantic (the most common) and polar (especially polar

fort is closely related to urban tree management (Spangenberg,

Atlantic) systems, and these modify the regional climate (Nunes,

Shinzato, Johansson, & Duarte, 2008). Various Brazilian researchers

1997).

have used PET, but these indexes need to be adapted to the local

climate (Monteiro & Alucci, 2010).

Studies have shown that shade and increase wind speed can 2.2. Sites and observations

improve human thermal comfort in tropical climates (Abreu-

Harbich et al., 2013a; Akbari & Rose, 2008; Akbari & Taha, 1992; The scales adopted in field measurement for this research

Lin et al., 2010). Therefore, planting trees is a good solution for were instantaneous and microclimatic, which allowed for assessing

improving thermal comfort in tropical cities. weather conditions and not climate. However, the “in loco” cli-

The shade cast by trees, and the amount of radiation filtered, is mate, mainly within 1 km, was influenced by local environmental

influenced by the form and density of the canopy. The amount of parameters (solar radiation, air temperature, relative humidity and

radiation intercepted depends on the density of the twigs, branches, wind speed), and by macroclimatic and mesoclimatic conditions. In

and leaf cover. These elements influence the overall characteristics studies concerned with qualifying and quantifying trees and their

of tree shape and density (Abreu-Harbich et al., 2012; Brown & benefits at the micro scale, similar surrounding conditions should

Gillespie, 1995; Scudo, 2002). Tree shade qualities are also influ- be considered: no shade from buildings or other trees; uniformity

enced by the individuality of trunks and of leaves, which should be of conditions around trees related to topography, lack of pavement

considered (Abreu-Harbich et al., 2012; Shashua-Bar et al., 2010). and buildings nearby; standardization of the surface at the measur-

As an example, tree species in Brazil can attenuate solar radi- ing points; and time of exposure, with few or no clouds. The criteria

ation from 76.3 to 92.8% in the summer months (Abreu-Harbich for the choice of species to be studied were those most used in tree

et al., 2012; Bueno-Bartholomei & Labaki, 2003). These results con- planting programs of the Campinas city government. Trees were

firm that the structure of the crown, and the dimension, shape required to meet the following conditions: mature; their physi-

and color of leaves influence the levels of reduction in solar radi- cal characteristics were representative of their species; they were

ation. It is important to observe the vegetation parameters which located in areas suitable for measurement; specifically unshaded

affect solar radiation and wind in relation to their thermal control by nearby trees or buildings; accessible topography and sufficient

strategies, and their different green elements (Table 1). It is also area for equipment around the species; and no interference by

important to quantify the thermal conditions of trees with field passers. The large gap of study different trees species is because

measurements, and to combine these results with the tree features they behave in different ways in microclimate. As well, it is neces-

to improve green design. Accordingly, planting the right trees in sary to consider the biodiversity for sustainability of urban green

the cities can improve and adapt the cities to climate change. on cities.

L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109 101

Table 1

Thermal control based in trees features.

Fig. 1 lists the date of measurements, and the tree species for 2.3. Measurement

each site in the urban area of Campinas. Twelve species were

selected and grouped accordingly: For each individual tree and tree clusters, air temperature and

humidity, wind speed, and global radiation were collected for in the

• shade and in the sun during summer and winter periods between

Single trees; Handroanthus chrysotrichus (Mart. ex A. DC.) Mattos,

2007 and 2010. The sampling interval was 10 min every hour over

Jacaranda mimosaefolia D. Don., Syzygium cumini L., M. indica L.,

a period from 6:00 AM to 6:00 PM Air temperature and humidity

Pinus palustris L., Pinus coulteri L.

• data were collected with a Testo data logger, model 175-1. Two

Single trees and clusters; Lafoensia glyptocarpa L., Caesalpinia plu-

tripods were fixed in the shadow and in the sun. Wind speed data

viosa F., Spathodea campanulata P. Beauv., Tipuana tipu F.

• were collected at a fixed site with a Testo anemometer, model

Clusters; Delonix indica F. and Senna siamea L.

0635-1549, connected to a multifunction recorder, model 445. The

sensors were positioned at a height of 1.1 m. All recordings were

In supplementary material, extra tables show individual and protected from solar radiation using special shelters designed for

clustered trees, along with characteristics such as crown, trunk outdoor measurements (Fig. 2).

and leaf. All measurement fields were situated in the urban area Solar radiation was measured using two tube solarimeters,

©

of Campinas. TSL (Delta-T Devices ). Sensors from the tube solarimeters were

102 L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109

Fig. 1. Studied trees and clusters.

©

connected to a logger, model DL2, also from Delta-T Devices . of trees, was obtained by the method of Bueno-Bartholomei and

2

The equipment measured average irradiance (W/m ) in situations Labaki (2003), where measurements of solar radiation in the shade

where the distribution of radiant energy was not uniform, such as and in the sunlight were made simultaneously, in accordance with

beneath tree crowns and greenhouses. The spectral response corre- the expression:

sponded to visible and near infrared radiation (350–2500 nm). For S − S

sun sh

= ×

individual and clusters trees, one of the solarimeters was positioned AT 100 (1)

Ssun

in the middle of the tree shadow, while the second was positioned

in sunlight. For the time interval considered, AT is solar radiation attenu-

2

ation (%), Ssun is the area (kWh/m ) for the total incident energy

2.4. Methods and analyses collected by the solarimeter in sunlight, and Ssh is the area

2

(kWh/m ) for the total incident energy in the shade.

Modern human biometeorological methods use the energy bal- The area index (PAI) describes the amount of foliage when

ance of the body (Höppe, 1993, 1999) to extract thermal indices for referring to all light-blocking elements (stems, twigs, leaves, etc.),

describing effects of the thermal environment on humans (Mayer, while the leaf area index (LAI) accounts only for leaves (Holst et al.,

1993; VDI, 1998). For this study, we used values of meteorological 2004; Nackaerts, Coppin, Muys, & Hermy, 2000; Neumann, Hartog,

data obtained every minute in the 10-min sampling time to calcu- & Shaw, 1989). Hemispherical photography (“fish-eye”) in orthog-

late PET (Mayer & Höppe, 1987). To quantify the thermal comfort onal projections was used for specific points below canopies for

provided by shade of trees, meteorological data (air temperature, each individual tree, and clusters of trees. These pictures look for

air humidity, wind speed and global radiation) collected from field sun gaps in the canopy layer where direct or diffuse radiation is able

measurements were used to calculate PET with the assistance of to reach the ground (Abreu-Harbich et al., 2012; Tsutsumi et al.,

RayMan software (Matzarakis, Rutz, & Mayer, 2007, 2010). PET 2003). To obtain the PAI of each analyzed tree, the Sky View Fac-

estimation was dependent on atmospheric influences, primarily tor (SVF) is calculated based on fish-eye pictures using RayMan Pro

clouds and other meteorological variables such as vapor pres- software, where the sky area is replaced by the area of branches

sure or particles. Tree morphologies acting as obstacles were also and green leaves.

included. The primary input parameters to RayMan in the study

were air temperature, air humidity, wind speed, and total solar 2.5. Applied model

radiation. The comfortable range that has been used is the Euro-

pean one (Matzarakis & Mayer, 1996) in combination of the tropical The RayMan model was applied to analyze the long-term

produced/adjusted for Taiwan by Lin and Matzarakis (2008). For changes in thermal bioclimate caused by differences in tree shad-

◦

European, the range of thermal comfort is between 18–23 C and ing. RayMan allows the calculation of Tmrt, which is used to calculate

◦

for tropical 26–30 C, and for extreme heat stress, higher than 41 thermal bioclimatic indices, or PET. Tri-dimensional models of veg-

◦

or 42 C. etation were designed based on features of the studied trees, and

The attenuation of solar radiation was dependent on tree fea- included height, crown radius, trunk length and trunk diameter. In

tures such as the density of the twigs and branches, and leaf cover. addition, the SVF of each individual tree, and cluster of trees, was

The percentage of radiation attenuated by each tree, or cluster included in the simulation.

L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109 103

Fig. 2. Field measurements equipment.

◦

PET was calculated for each tree during over 7 years pluviosa, T. tipu reduced the air temperature by 0.9–2.8 C between

(2003–2010). Meteorological data used in this simulation were 10:00 AM and 2:00 PM. Individual S. cumini exhibited the best shade

◦

obtained from an urban automatic agro-meteorological station behavior, with 2.8 C of cooling in the shade during this period. Clus-

© ◦

with a CR23X data logger (Campbell Scientific Inc. ) at the Agro- ters of C. pluviosa or T. tipu reduced the air temperature by 0.7–2 C

◦ 

nomic Institute of Campinas (IAC) on Santa Elisa Farm (22 54 S; during the same period.

◦ 

47 05 W; 669 m elevation). This site is in northern Campinas, 5 km In the winter, air temperature reduction results differed (Fig. 4).

from the city center. This station was not affected by surround- The air temperature in the shade, or in direct sunlight, for indi-

ing obstacles, and provided meteorological data representative of vidual trees (Handroanthus chrysotrichus, P. palustris, P. coulteri, L.

the study areas. The meteorological data provided were air tem- glyptocarpa, M. indica and S. campanulata) was not significantly

perature, relative humidity, wind speed, and solar radiation over a different. For S. cumini and C. pluviosa, the air temperature was

◦

7-year period (25 June 2003–31 December 2010). These data points reduce by 1.9–2.6 C from 10:00 AM to 2:00 PM. For clusters of

were sampled every 60 min. trees (C. pluviosa, S. campanulata and D. indica), the air tempera-

◦

ture was reduced by 0.1–2.4 C from 10:00 AM to 2:00 PM over

the same period. C. pluviosa exhibited the best cooling effects,

3. Empirical findings

whether individual or in clusters. With respect to individual trees

◦

of this species, the air temperature was reduced by 2.2–2.7 C in the

For the quantitation of thermal comfort provided by tree

shade during the warmest daylight hours; a cluster of these trees

canopies during different seasons, daily data results for air tem-

◦

reduced the air temperature until 2.0 C in the shade over the same

perature (Ta) in summer and winter are shown in Figs. 3 and 4,

period.

respectively. Daily data results for PET in summer and winter are

PET values observed for summer (Fig. 5) showed that the shade

presented in Figs. 5 and 6, respectively.

cast by individual trees, such as Handroanthus chrysotrichus, S.

Figs. 3–6 show the differences in temperature between sunlight

cumini, C. pluviosa, and T. tipu, reduced temperatures by as much as

and shade from 6:00 AM to 6:00 PM. The cooling effects of tree

◦

16 C. Shading from C. pluviosa and T. tipu tree clusters reduced the

shading were more evident from 10:00 AM to 2:00 PM compared

◦

air temperature by 11.2–14.4 C from 10:00 AM to 2:00 PM. C. plu-

with those in the early morning and evening.

viosa exhibited the best effects with respect to improving thermal

In the summer, the air temperature in direct sunlight and shade

comfort. An individual tree of this species reduced air temperature

for individual trees showed minor differences. The air tempera-

◦

by 12–16 C during daylight hours, while a cluster of these trees

ture for tree clusters however exhibited distinct patterns (Fig. 3).

◦

reduced air temperature by 12–14.4 C.

Individual trees such as Handroanthus chrysotrichus, S. cumini, C.

104 L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109

Fig. 3. Diurnal courses of air temperatures during the summer.

Fig. 4. Diurnal courses of air temperatures during the winter.

◦

Fig. 5. Diurnal courses of physiologically equivalent temperature (PET) ( C) during the summer.

L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109 105

◦

Fig. 6. Diurnal courses of physiologically equivalent temperature (PET) ( C) during the winter.

The PET values for winter (Fig. 6) show that individual S. cumini, pluviosa can attenuate solar radiation by 83.8% in summer, but only

M. indica, C. pluviosa and L. glyptocarpa provided the best results 69.5% during winter.

with respect to improvements in thermal comfort. These trees Deciduous species such as Handroanthus chrysotrichus, S. cam-

◦

resulted in a reduction of air temperature of 7.4–17.5 C from panulata and T. tipu are characterized by variation of leaves in

10:00 AM to 2:00 PM. Individual Handroanthus chrysotrichus with- the crown over a year. Native Handroanthus chrysotrichus, with an

out leaves exhibited the worst results in terms of cooling effects, orthotropic sympodial trunk, has a PAI of 47.7% and attenuation of

◦

with the air temperature reduced by only 0.6–1.1 C over the same solar radiation is 82.8% in summer and 46.4% in winter. When leaf-

period. A cluster of C. pluviosa and L. glyptocarpa trees had the less, this value drops to 51.4%. Exotic species (S. campanulata and T.

best cooling effects, with their shading reducing the air temper- tipu) are characterized by plagiotropic trunks, with PAIs of 78.1 and

◦

ature by 7.8–14.4 C. Clusters of other tree species did not result in 72.2%, respectively. Attenuation of solar radiation during summer

improvements for thermal comfort. was 76.3%, and over winter this was 55%.

A comparison of the summer and winter PET results showed that For clusters of trees, the PAI results for C. pluviosa, L. glyptocarpa,

the cooling effects of trees, either individual or in clusters, in the S. campanulata, T. tipu, D. indica and S. siamea were 99.3, 65.7, 77.5,

summer were greater than in the winter (Table 2). Using air tem- 98.8 and 91.3%, respectively. During the summer, the results of solar

perature as factors the differences between sun and shade are less radiation attenuation for C. pluviosa, T. tipu, D. indica and S. siamea

◦

2.8 C in summer. For PET the differences are much higher ranging were 94.8, 80.2, 73.5 and 89.2%, respectively. During winter, solar

◦

from 1 up to 16 C. For individual trees, the differences are higher radiation attenuation results for C. pluviosa, L. glyptocarpa, S. cam-

than for clusters because of the effect of wind on PET. This behavior panulata and D. indica were 92.5, 76, 82.4, and 72.3%, respectively.

can be explained by the phenology of each species. We have pre- Clusters of C. pluviosa had the best cooling effects for thermal com-

sented the attenuated solar radiation over the year, along with PAI fort. This can be explained by specific features of this species: they

(Fig. 7). are large trees with maximal coverage due to their height; they

For individual trees, the PAI results for the coniferous species P. have plagiotropic trunks; and small bipinate leaves. In addition,

palustris and P. coulteri, were 47 and 34% respectively. These trees the distance between the trees was proportional to the diameter

are characterized by a pyramidal crown, a narrow canopy, and a of the crown (10 m × 10 m), along with the number of trees in the

moderate area of sunny spots with 53 and 66% SVF for P. palustris cluster (n = 20), and the linear formation of the cluster contributed

and P. coulteri, respectively. The cooling effects can be explained to our findings.

by solar radiation attenuated by the crown (79.7 and 83.8% during

summer; 69.8 and 78.3% during winter). 4. Estimating cooling effects based on trees features

The PAI results for the perennial species S. cumini and M. indica

were 87.8 and 85%, respectively. These trees are characterized by The tridimensional model was based on tree features includ-

a dense canopy, a plagiotropic trunk, and produce relatively large ing height, crown radius, trunk length and diameter, and outdoor

tree coverage. This leads to high cooling effects in terms of thermal disposition. Meteorological data from 2003 to 2010 were used to

comfort, especially during the winter. The attenuation results for quantify the contribution of trees’ shade on built-up spaces using

solar radiation during the summer were 87.2 and 89.2%, and 89.1 PET.

and 88.6% during winter for S. cumini and M. indica, respectively. The results (Fig. 8) show that individual trees as M. indica, S.

Semi-deciduous species as J. mimosaefolia, L. glyptocarpa and C. campanulata, L. glyptocarpa, S. cumini, C. pluviosa provided the best

pluviosa can be characterized by their plagiotropic trunk, distinct results with respect to improvements in thermal comfort. These

◦

canopies, and considerable variation in PAI (26.9, 74.8, and 92.3% trees resulted in a reduction of air temperature of 5.5–7.4 C from

respectively), which can vary from sparse to dense during the year. 10:00 AM to 2:00 PM. Individual trees as P. coulteri and P. palus-

These native trees have a medium–large coverage and high cooling tris exhibited the worst results in terms of cooling effects, with the

◦

effects in terms of thermal comfort, especially during summer, due air temperature reduced by only 0.8–4.0 C over the same period.

to the quality of shading and access by wind. As an example, C. A cluster of S. siamea, C. pluviosa and T. tipu trees had the best

106 L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109

Table 2

Differences between results in the shade and in the sun.

◦

Trees species Disposition Season Differences of air Differences of PET ( ) in Solar radiation Plant area SVF

◦

temperature ( C) in the the sun and in the attenuated (%) index (PAI)

sun and in the shade shade during 10 AM–2

during 10 AM–2 PM PM

Pinus palustres Individual Summer 0.5–1.3 7.2–9.9 79.7 47% 0.53

Winter 0.1–1.0 4.6–9.1 69.8

Pinus coulteri Individual Summer 0.6–1.1 7.1–9.5 83.8 34% 0.66

Winter 0.8–0.9 6.6–9.3 78.3

Handroanthus Individual Summer 1.6–1.8 11.2–14.2 82.8 47.7% 0.52

chrysotrichus Winter (leafless) 0.3–0.7 0.6–1.2 46.4

Winter (with flowers) 0.1–0.2 2.6–3.6 51.4

Jacaranda mimosaefolia Individual Winter 0.3–1.3 4.1–11.7 63.8 26.9% 0.73

Syzygium cumini Individual Summer 1.5–2.8 10.8–13.9 87.2 87.8% 0.12

Winter 1.9–2.6 7.5–10.8 89.1

Mangifera indica Individual Summer 1.0–1.2 9.4–12.7 89.2 85.0% 0.15

Winter 0.9–1.1 13.0–17.5 88.6

Caesalpinia pluviosa Individual Summer 0.9–1.3 12.3–16.0 83.8 92.3% 0.07 Winter 2.2–2.7 7.4–11.0 69.5 0.01 Cluster Summer 0.9–1.3 12.5–14.3 94.8 99.3%

Winter 0.1–2.0 7.8–10.5 92.5

Lafoensia glyptocarpa Individual Winter 0.1–0.8 8.1–16.0 63.9 74.8% 0.25

Cluster Winter 0.2–1.1 8.8–14.5 76.0 65.7% 0.34

Spathodea campanulata Individual Winter 0.3–1.4 4.1–9.1 55.0 78.1% 0.21

Cluster Winter 1.0–2.5 0.9–2.6 82.4 77.5% 0.22

Tipuana tipu Individual Summer 1.0–1.8 9.8–12.8 76.2 72.2% 0.27

Cluster Summer 0.2–2.0 11.3–13.5 80.2 98.8% 0.012

Delonix indica Cluster Summer 0.2–0.7 0.6–2.7 73.5 91.3% 0.08

Winter 0.7–1.8 0.3–1.2 72.3

Senna siamea Cluster Summer 0.1–0.7 0–0.5 89.2 83.4% 0.16

cooling effects, with their shading reducing the air temperature by 5. Discussion

◦

5.9–11.5 C. These results demonstrate that clusters of trees can

mitigate temperatures to a greater extent compared with indi- Thermal bioclimate analysis with respect to air temperature,

vidual trees. As well, the planting design of clusters trees with 2 Tmrt, and PET, for Campinas, Brazil, was able to describe climate

lines and 5–10 trees in each line can provide more thermal com- change due to solar radiation attenuated by the shade of trees

fort than others analyzed. Tree height, canopy size, and shape (Abreu-Harbich et al., 2013a). However, the behavior of arboreal

are features that likely influence the improvement of the thermal species is affected by differences in growth conditions and tree

environment. features (Abreu-Harbich et al., 2012; Bueno-Bartholomei & Labaki,

Fig. 7. Comparison between plant area index and solar radiation attenuated by trees.

L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109 107

◦

Fig. 8. Diurnal courses of physiologically equivalent temperature (PET) ( C) for different for single trees and clusters of trees.

2003; Correa et al., 2012; Shahidan et al., 2010; Shashua-Bar et al., In outdoor spaces, urban greenery is able to control and improve

2010). thermal comfort, and mitigate air temperatures. For indoor areas,

◦

Air temperature reductions are 0–2.8 C for single trees and tree shading can reduce the incidence of solar radiation on building

◦

0.3–15.7 C for clusters of trees during the day (10:00 AM to 2:00 facades, improve thermal comfort, conserve energy spent on refrig-

PM) during the study period. The results of the PET are 0.84 to eration, and maintain a healthy environment (Emmanuel, 2005;

◦ ◦

17.5 C for single trees and 0.3 to 15.7 C for clusters of trees for Emmanuel et al., 2007; McPherson et al., 1994; Santamouris, 2001).

the same period. Most studies of vegetation influences in urban The shape and size of trees can modify the effect in different climate

microclimate have been focused in mitigation of air temperatures regions (Shashua-Bar et al., 2010; Streiling & Matzarakis, 2003).

(Akbari, 2002; Bueno-Bartholomei & Labaki, 2003; Santamouris, The evaluation of different commonly found arboreal species and

2001; Scudo, 2002; Shahidan et al., 2010; Shashua-Bar et al., 2010) their characteristics should be taken into account by profession-

instead of PET and Tmrt. The quantification of tree shading benefits, als of the urban built environment. This would improve outdoor

in terms of PET, provides an accurate measure of the real cooling thermal comfort, reducing the effect of heat islands and ensuring a

effects for thermal comfort. better quality of life for people in the urban environment (Abreu-

Comparing the results from single trees and clusters of trees, Harbich et al., 2013b; Correa et al., 2012; Shashua-Bar et al., 2010;

air temperatures for individual C. pluviosa and T. tipu were about Streiling & Matzarakis, 2003).

one third that of clusters. The PET results we obtained were similar.

Our findings suggest that clusters of trees, in different proportions, 6. Conclusions

function like a microclimate thermoregulator. The large coverage

provided by clusters of trees is able to mitigate PET through an From our findings it can be seen that the main influencing

umbrella effect (Emmanuel, 2005). parameter in the microclimate and urban environment is mostly

Our results suggest that cooling effects are influenced by the per- driven and controlled by changes in the Tmrt and wind speed, espe-

meability of the crown (Shahidan et al., 2010; Shashua-Bar et al., cially in tropical cities. The size and shape of the tree crown can

2010), and the capacity of shading in attenuating solar radiation improve thermal comfort in a microclimate, as can the size and

(Abreu-Harbich et al., 2012; Bueno-Bartholomei & Labaki, 2003). shape of the leaves, the trunk, and the permeability of the crown.

If the maximum mean temperatures of PET during the months of The semi-deciduous C. pluviosa exhibited the best results in terms

◦

May to September are 29 C (Abreu-Harbich et al., 2013a, 2013b), of PET for both individual and clustered formations. These partic-

◦

trees that can reduce the PET by greater than 15 C in the win- ular trees have small bipinate linear leaves, plagiotropic trunks,

ter, such as M. indica, could provide thermal discomfort. These large green coverage, and moderate crown permeability. The crown

findings confirm the results of Emmanuel (2005) and Lin et al. architecture for these trees promotes large green coverage that

(2010). filter solar radiation in accordance with the prevailing season,

Tree features such as tree height, green coverage, shape and and allow for the wind to permeate. The phenology of trees also

permeability of the crown can influence the thermal environment, needs to be considered. The shade of native species (Handroanthus

and their effects on microclimates could be observed through sim- chrysotrichus and C. pluviosa) which vary during all the year can be

ulation. The field measurements suggest that trunk and branching used for human thermal comfort adaptation.

structure, and size and shape of leaves contribute to cooling effects. Clusters of trees can increase the cooling effects of one tree;

C. pluviosa is tall, has large coverage, an elliptical crown, a pla- however, it is important to note how tree formation can promote

giotropic trunk, and small leaves that are bipinate and linear. These a large area of shade, especially for aligned clusters. For effective

features cannot be simulated on RayMan Pro. tree shading along a street, the distance between trees needs to be

108 L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109

relative to the diameter of the crown. Further studies can quantify Emmanuel, R., Rosenlund, H., & Johansson, E. (2007). Urban shading – A design

option for the tropics? A study in Colombo, Sri Lanka. International Journal of

the thermal comfort provided by different species of trees planted

Climatology, 27(14), 1995–2004.

in streets and open areas and the influence’s distances of these

Grimmond, C. S. B. (2007). Urbanization and global environmental change: Local

green areas in tropical cities. The optimal distribution of single effects of urban warming. Geographical Journal, 173, 83–88.

Guderian, R. (2000). Arten und Ursachen von Umweltbelastungen. In R. Guderian

trees, or clusters, to produce shading during the harshest condi-

(Ed.), Handbuch der Umweltveränderungen und Ökotoxikologie, Band 1A: Atmo-

tions is the main driver for improving human thermal comfort.

sphäre (pp. 1–60). Heidelberg: Springer-Verlag.

Besides thermal comfort, the ecological factor, economic, cultural, Gulyás, A., Unger, J., & Matzarakis, A. (2006). Assessment of the microclimatic and

thermal comfort conditions in a complex urban environment: Modeling and

and aesthetic aspects of urban planning must be considered.

measurements. Building and Environment, 41, 1713–1722.

Planning needs to be appropriate for recent climate conditions

Heisler, G. M. (1977). Trees modify metropolitan climate and noise. Journal of Arbori-

and future climate changes. Planting the appropriate trees around culture, 3, 201–207.

the buildings, in sidewalks, pedestrian ways, squares and parks Herrington, L. P. (1977). The role of the urban in reducing urban energy

consumption. Proceedings of the Society of American Foresters, 20–66.

can be helpful fighting climate change in micro scale. Evaluation

Holst, T., Hauser, S., Kirchgässner, A., Matzarakis, A., Mayer, H., & Schindler, D. (2004).

of different arboreal species commonly found, and tree-planting

Measuring and modelling plant area index in stands. International Journal

strategies during the urbanization of cities, is important informa- of Biometeorology, 48, 192–201.

Höppe, P. (1993). Heat balance modelling. Experientia, 49, 741–746.

tion for urban planning and maintaining an urban microclimate.

Höppe, P. (1999). The physiological equivalent temperature – A universal index

Additionally, tree planting with typical regional trees providing

for the biometeorological assessment of the thermal environment. International

mostly shade (C. pluviosa) is a practical and inexpensive solution, Journal of Biometeorology, 43, 71–75.

Kottek, M., Grieser, J., Beck, C., Rudolf, B., & Rubel, F. (2006). World Map of the

and is considered as an energy efficient alternative.

Köppen-Geiger climate classification updated. Meteorologische Zeitschrift, 15(3),

259–263.

Acknowledgements Lin, T. P., & Matzarakis, A. (2008). Tourism climate and thermal comfort in Sun Moon

Lake, Taiwan. International Journal of Biometeorology, 52, 281–290.

Lin, T. P., Matzarakis, A., & Hwang, R. L. (2010). Shading effect on long-term outdoor

This research was supported by São Paulo Research Founda- thermal comfort. Building and Environment, 45, 213–221.

Matzarakis, A. (2013). Stadtklima vor dem Hintergrund des Klimawandels [Urban

tion (FAPESP) research grant (08/05870-5), National Counsel of

climate in the context of climate change]. Gefahrstoffe – Reinhaltung der Luft, 73,

Technological and Scientific Development (CNPq) research grant

115–118.

(311641/2013-0), and research cooperation between Coordination Matzarakis, A., & Endler, C. (2010). Adaptation of thermal bioclimate under climate

change conditions – The example of physiologically equivalent temperature in

for the Improvement of Higher Education Personnel (CAPES) and

Freiburg, Germany. International Journal of Biometeorology, 54, 479–483.

German Academic Exchange Service (DAAD) research grant (BEX

Matzarakis, A., & Mayer, H. (1996). Another kind of environmental stress: Thermal

4234/10-3). stress. WHO Collaborating Centre for Air Quality Management and Air Pollution

Control. Newsletters, 18, 7–10.

Matzarakis, A., Rutz, F., & Mayer, H. (2007). Modelling radiation fluxes in simple and

Appendix A. Supplementary data

complex environments – Application of the RayMan model. International Journal

of Biometeorology, 51(4), 323–334.

Matzarakis, A., Rutz, F., & Mayer, H. (2010). Modelling radiation fluxes in simple

Supplementary data associated with this article can be found,

and complex environments: Basics of the RayMan model. International Journal

in the online version, at http://dx.doi.org/10.1016/j.landurbplan.

of Biometeorolology, 54(2), 131–139.

2015.02.008. Mayer, H. (1993). Urban bioclimatology. Experientia, 49, 957–963.

Mayer, H., & Höppe, P. (1987). Thermal comfort of man in different urban envi-

ronments. Theoretical and Applied Climatology, 38, 43–49. http://dx.doi.org/10.

References 1007/BF00866252

Mayer, J. D., Salovey, P., & Caruso, D. R. (2008). Emotional intelligence: New ability

or eclectic mix of traits? American Psychologist, 63, 503–517.

Abreu-Harbich, L. V., Labaki, L. C., & Matzarakis, A. (2012). Different trees and con-

McPherson, E. G., Nowak, D. J., & Rowantree, R. A. (1994). Chicago’s urban

figuration as microclimate control strategy in Tropics. In Proceedings of the

ecosystem: Results of the Chicago Urban Forest Climate Project. Department of Agri-

international conference on passive and low energy architecture, 2012 Lima, PE,.

culture, Forest Service, Northeastern Forest Experiment Station, Northeastern

Lima: PLEA.

Florest Experimental Station.

Abreu-Harbich, L. V., Labaki, L. C., & Matzarakis, A. (2013a). Thermal bioclimate as fac-

Meyer, F. H., & Bauermel, G. (1982). (Trees in the city) Bäume in der Stadt. Stuttgart,

tor in urban and architectural planning in tropical climates – The case of Camp-

Germany: Eugen Ulmer Verlag., 380 pp.

inas, Brazil. Urban Ecosystems, http://dx.doi.org/10.1007/s11252-013-0339-7

Montague, T., & Kjelgren, R. (1998). Urban tree transpiration over turf and asphalt

Abreu-Harbich, L. V., Labaki, L. C., & Matzarakis, A. (2013b). Thermal bioclimate

surfaces. Atmospheric Environment, 32(1), 35–41.

in idealized urban street canyons in Campinas, Brazil. Theoretical and Applied

Monteiro, L. M., & Alucci, M. P. (2010). Proposal of an outdoor thermal com-

Climatology, 115, 333–340. http://dx.doi.org/10.1007/s00704-013-0886

fort index for subtropical urban areas. Paper presented at the 3rd Passive &

Akbari, H. (2002). Shade trees reduce building energy use and CO2 emissions from

Low Energy Cooling for the Built Environment conference, Rhodes Island,

power . Environmental Pollution, 116, 119–126.

Greece.

Akbari, H., & Rose, L. (2008). Urban surfaces and heat island mitigation potentials?

Nackaerts, K., Coppin, P., Muys, B., & Hermy, M. (2000). Sampling methodology for

Human–Environment System, 11(2), 85–101.

LAI measurements with LAI-2000 in small forest stands. Agricultural and Forest

Akbari, H., Rosenfeld, A., Taha, H., & Gartland, L. (1996). Mitigation of summer urban

Meteorology, 101, 247–250.

heat islands to save electricity and smog. Atlanta, GA: Paper presented at the

Neumann, H. H., Hartog, G., & Shaw, R. H. (1989). Leaf area measurements based on

76th American Meteorological Society Annual Meeting, Report no. LBL-37787.

hemispheric photographs and leaf-litter collection in a deciduous forest during

American Meteorological Society.

autumn leaf-fall. Agricultural and Forest Meteorology, 45, 325–345.

Akbari, H., & Taha, H. (1992). The impact of trees and white surfaces on residential

Nunes, L. H. (1997). (Spatial and temporal distribution of rainfall in the São Paulo state:

heating and cooling energy use in four Canadian cities? Energy, 17(2), 141–149.

Variability, trends, processes involved) Distribuic¸ ão espac¸ o-temporal da pluviosi-

Bernatzky, A. (1979). Grünflächen und Klima [Green spaces and climate]. DBZ –

dade no Estado de São Paulo: Variabilidade, tendências, processos intervenientes

Forschung und Praxis, 080 DBZ 8/79, 1205–1209.

(Thesis). University of São Paulo, Geography Institute., 192 pp.

Brown, R., & Gillespie, T. (1995). Microclimate landscape design: Creating thermal

Oke, T. R. (1989). The micrometeorology of the urban forest. Philosophical Transac-

comfort and energy efficiency. New York: John Wiley & Sons.

tions of the Royal Society of London, B324, 335–349.

Bueno-Bartholomei, C. L., & Labaki, L. C. (2003). How much does the change of species

Santamouris, M. (2001). Energy and climate in the urban built. London: James & James.

of trees affect their solar radiation attenuation? Paper presented at the fifth inter-

Scudo, G. (2002). Thermal comfort in green spaces. In Green structures and

national conference on Urban Climate, Lodz, Poland.

urban planning. Milan. Accessed in: http://www.greenstructureplanning.eu/

Cardelino, C. A., & Chameides, W. L. (1990). Natural hydrocarbons, urbanization and

COSTC11/comfort.htm

urban ozone. Journal of Geophysical Research, 95, 13971–13979.

Shahidan, M. F., Shariff, M. K. M., Jones, P., Salleh, E., & Abdullah, A. M. (2010). A

Correa, E., Ruiz, M. A., Canton, A., & Lesino, G. (2012). Thermal comfort in forested

comparison of Mesua ferrea L. and Hura crepitans L. for shade creation and radia-

urban canyons of low building density. An assessment for the city of Mendoza,

tion modification in improving thermal comfort. Landscape and Urban Planning,

Argentina. Building and Environment, 58, 219–230. http://dx.doi.org/10.1016/

j.buildenv.2012.06.007 97(3), 168–181.

Shashua-Bar, L., & Hoffman, M. E. (2000). Vegetation as a climatic component in

Dimoudi, A., & Nikolopoulou, M. (2003). Vegetation in the urban environment:

the design of an urban street. An empirical model for predicting the cooling

Microclimatic analysis and benefits. Energy and Buildings, 35, 69–76.

effect of urban green areas with trees. Energy and Buildings, 31(3), 221–235.

Emmanuel, M. R. (2005). An urban approach to climate-sensitive design: Strategies for

http://dx.doi.org/10.1016/S0378-7788(99)00018-3

Tropics. London: E & FN Spoon Press., 172 pp.

L.V. de Abreu-Harbich et al. / Landscape and Urban Planning 138 (2015) 99–109 109

Shashua-Bar, L., Pearlmutter, D., & Erell, E. (2009). The cooling efficiency of urban Streiling, S., & Matzarakis, A. (2003). Influence of single and small clusters of trees

landscape strategies in a hot dry climate. Landscape and Urban Planning, 92(3–4), on the bioclimate of a city: A case study. Journal of Arboriculture, 29, 309–316.

179–186. http://dx.doi.org/10.1016/j.landurbplan.2009.04.005 Tsutsumi, J. G., Ishii, A., & Katayama, T. (2003). Quantity of plants and its effect on

Shashua-Bar, L., Potchter, O., Bitan, A., Boltansky, D., & Yaakov, Y. (2010). Microcli- local air temperature in an urban area. Paper presented at the fifth international

mate modelling of street tree species effects within the varied urban morphology conference on urban climate, Lodz, Poland.

in the Mediterranean city of Tel Aviv, Israel. International Journal of Climatology, VDI. (1998). VDI 3787, Part I: Environmental meteorology, methods for the human

57, 44–57. biometeorological evaluation of climate and air quality for the urban and regional

Spangenberg, J., Shinzato, P., Johansson, E., & Duarte, D. (2008). Simulation of the planning at regional level. Part I: Climate. Berlin: Beuth., 29 pp.

influence of vegetation on microclimate and thermal comfort in the city of Sao Yilmaz, S., Toy, S., Irmaka, M. A., & Yilmaz, H. (2007). Determination of climatic

Paulo. Revista SBAU, 3(2), 1–19. differences in three different land uses in the city of Erzurum, Turkey. Build-

Steven, M., Biscoe, P., Jaggard, K., & Paruntu, J. (1986). Foliage cover and radiation ing and Environment, 42(4), 1604–1612. http://dx.doi.org/10.1016/j.buildenv.

interception. Field Crops Research, 13, 75–87. 2006.01.017