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    整合微气候回应策略的都市公园设计:从设计前期看功能分区配置的影响
    2019-07-19  点击:[]

    整合微气候回应策略的都市公园设计:从设计前期看功能分区配置的影响

    Integrating Microclimate Response Strategy in Urban Parks’ Design: The Effect of Functional Zones Configuration

     

    林宝秀 褚汉威 *

    Bau-Show Lin,Han-Wei Chu *

     

    林宝秀 / 1976 年生 / / 台湾大学园艺暨景观学系副教授 / 研究方向为景观规划与设计、环境资源评估、都市绿地效益评估、生态系统服务

    LIN Baushow, who was born in 1976, is an associate professor in Department of Horticulture and Landscape Architecture, National Taiwan University. Her research directions include landscape planning and design, environmental resource assessment, benefit assessment of urban greenland, and ecosystem services.

    褚汉威 / 1989 年生 / / 台湾大学园艺暨景观学系硕士

    通信作者邮箱 (Corresponding author Email): doralin@ntu.edu.tw

    CHU Hanwei, who was born in 1989, is an M.A. in Department of

    Horticulture and Landscape Architecture, National Taiwan University.

    摘要:本文针对都市公园设计的前期,探讨整合微气候回应策略的影响,解析功能分区配置阶段导入微气候调节的影响,主要分三个阶段来进行:第一阶段为辨识都市公园必要分区与空间配置,第二阶段为微气候模拟模型验证,第三阶段为整合微气候调节策略功能空间配置方案的温度评估。结果显示,不同功能空间配置影响都市公园温度表现,以林荫区位于上风处、广场区位于下风处且中央功能分区为草坪区的公园空间配置温度较低。

    关键词:气温;ENVI-met;数值模拟

    Abstract: Aimed at early stage of landscape design, this thesis investigated the effect of integrating microclimate response strategy in urban parks’ design by arranging functional zones configuration. This study conducted a three-stage study: Stage 1 identified the required functional zones and configuration of functional zones, Stage 2 validated the performance of the model and developed scenarios, and Stage 3 assessed temperature performance of the scenarios. The results showed that functional zones configuration affected temperature performance of an urban park. An urban park which allocated a wooded zone in the upwind, a plaza zone in the downwind, and a lawn zone in the center had a lower temperature.

    Key words: air temperature; ENVI-met; the numerical simulation

    1 引言

    都市公园是民众日常休闲游憩的重要场所。随着都市人口日增,都市环境品质明显下降,致使都市公园的功能考量日益多元,尤其是都市环境议题的日增,使都市公园被称为缓解都市环境问题的重要途径。而众多都市环境议题当中,因都市化与都市扩张、建筑物与不透水面积增加、都市热排放等因素造成都市高温化的热岛现象,受到更多学者的关注。

    全市性的大型公园区域面积广且需提供多元的功能配置,其设施应尽可能满足大家的需求,包含生态、景观、防灾、游憩等。然而,不同空间其土地覆盖的材质、植栽绿覆程度有所差异,因而影响其降温效果。相关文献显示,公园周边建筑密度、公园绿覆率、人口密度、铺装密度、天空可视率、街道高宽比以及土地使用类型会影响公园的空气温度的表现[1-10],而风也是影响微气候的重要因子之一[11],风的流动会带动周边水池或植物的水气使空气湿度提升,进而降低空气温度[12]

    近年来,整合微气候回应策略的都市公园设计受到越来越多的关注,并通过实证研究作为引证设计的重要依据,而都市公园的多元功能需求,如何在不影响都市公园多样化使用功能的前提下,进行较佳的功能空间配置以满足现有使用,并提升更佳的温度调节表现,显得十分重要。因此,本研究主要针对都市公园设计前期,探讨整合微气候回应策略的影响,于功能分区阶段导入微气候调节的考量,透过数值模拟方式探讨都市公园功能空间配置与温度表现的关系,试图找出较佳降温效益的空间配置与准则,作为日后规划设计者的参考。

     

    2 研究方法

    本研究主要分为三个阶段:第一阶段为辨识都市公园必要的功能分区与空间配置,第二阶段为都市公园微气候模拟模型验证,第三阶段为整合微气候调节策略的功能空间配置方案的温度表现评估。详细内容说明如下:

    2.1 第一阶段:辨识都市公园必要的功能分区与其空间配置

    功能分区为都市公园设计前期的重要阶段,而功能分区会因基地本身条件、社会需求、法规规范等因素而受到影响。为了解全市性公园功能分区种类与空间配置,本研究透过文献搜集与个案公园分析,确认都市公园必要的功能分区及其空间配置。

    本研究以台北市、台中市、高雄市共16 座公园为个案研究对象,以法规规范分析、航拍影像图、Show Taiwan Google 街景,进一步确认功能分区种类与空间配置关系。

    三个城市的公园设计规范均指出公园需依据性质及环境需要设置相关设施,设施包括:景观设施、休憩设施、运动设施、游戏设施、社教设施、服务设施、管理设施等,而设施包含于功能分区中,故通过五位景观设计师将设施对应功能分区归类,包括:林荫区、草坪区、广场区、展演舞台区、水池区、儿童游戏区、运动区、服务及管理区八种功能分区。进一步绘制 16 座全市性公园功能分区图,再利用 Adobe Photoshop CS6 Image J 进行图面量化,以公园主次入口与中央的公园内部位置作为划分空间位置。

    功能分区统计结果显示如下(表1),16 座公园都设有广场、林荫、服务及管理的功能分区,15 座公园中设有草坪区与儿童游戏场区,9 座公园设有水池区,展演舞台区最少,仅有 4 座公园有设置;在配置方面,16 座公园中,有 8 座公园的中央设置草坪区,5 座公园设置广场区,3 座设置水池区。整体而言,主要设置于主入口附近的功能分区是广场、林荫区、草坪区、展演舞台区,主要设置于次入口附近的功能分区为广场、林荫区、草坪区、水池区、运动区、儿童游戏场与服务及管理区。

    以众数统计功能分区数量,结果显示多数都市公园在园内设置三个广场区,其余功能分区仅设置一个,故本研究将广场分为:主入口广场、公园中央广场、次入口广场,各分区平均面积比率为广场区(8%)、林荫区(38%)、草坪区(25%)、水池区(9%)、运动区(7%)、展演舞台区(2%)、儿童游戏场区(1%)、服务及管理区(6%),作为后续考量微气候方案发展的基础。

    1 全市性公园功能分区配置统计表

    Table 1 Functional Zones and Their Configuration in Urban Parks

     

    功能分区

    公园 数量

    配置

    公园功能   1

    分区数量

    平均面积 比率 (%)

    中央

    主入口

    次入口

    其他

    广场

    16

    5

    16

    13

    2

    3

    8

    林荫区

    16

    -

    4

    15

    9

    1

    38

    草坪区

    15

    8

    3

    9

    5

    1

    25

    水池区

    9

    3

    -

    4

    2

    1

    9

    运动区

    11

    -

    1

    10

    2

    1

    7

    展演舞台区

    4

    -

    2

    1

    1

    1

    2

    儿童游戏场区

    15

    -

    1

    13

    1

    1

    1

    服务及管理区

    16

    -

    7

    10

    4

    1

    6

    1:公园功能分区数量统计方式系分别统计各功能分区于公园的数量,并以众数为代表记录于本表,举例来说,广场的分区数量为3,代表公园最常出现3个广场。

    Note1: The statistical method for the number of park functional zones is to separately count the number of each functional zone in the park and record it in the table with mode as the representative. For example, if the number of plazas is 3, it means that there are usually three plazas in the park.

    Input Parameters


     

     

     

     

     

    Meteorological Data

     

    Wind speed, 10 m above ground

     

    2.93 m s-1

    Wind direction (0:N, 90:E, 180:S, 270:W)

    90°

    Roughness length

    0.1 m

    Initial   temperature atmosphere

    284 K

    Specific humidity in 2500 m [Water/air]

    7 g Kg-1

    Relative humidity in 2 m

    59.46 %

     

     

     

     

     

    Building Data

     

     

    Inside temperature

     

     

    295 K

    Heat   transmission walls

    3.778 W m-2 K-1

    Heat transmission roofs

    0.769 W m-2 K-1

    Albedo walls

    0.2

    Albedo roofs

    0.2

    2.2 第二阶段:都市公园微气候模拟模型验证

    本研究以大安森林公园为研究地点,建模与设定、模拟效度检验、方案发展说明如下:

    2.2.1 对环境和配置进行建模

    利用航拍图与数值地形图进行大安森林公园建模,网格设定为x = y = z = 4 m,模型网格数长 235 格、宽 165 格。各网格建模判定标准采用单位方格内比例最高的土地覆盖类型作为该方格的代表。

    以台北气象站监测数据为天候初始输入资料,日期为 2014 1 17日,粗糙度输入典型都市数值 0.1[13];建筑部分则以数值地形图显示建筑属性与建筑材质规范之数值输入(表 2)。

    植物层设定方面,根据现况调查,将乔木设定为10 m高,叶面积密度(LAD) LAD 1 LAD 4 为树干部位因此数值为 0LAD 5 LAD 10 为乔木冠幅,数值设定为 1.05,而根面积密度(RAD)则保持不变,草地高度设定为20 cm。铺面层设定方面,道路选用柏油路(S),广场、步道等铺面设为砖路(kk),舞台前座椅区与运动场地板等铺面设定为混凝土铺面(P),土壤则使用壤质土壤(l),人工生态池为水体(W),游戏地垫为RR

     

    2 模型气候与建筑参数设定表

    Table 2 the Meteorological and Building Parameter Settings in the Model

     

     

     

     

     

     

     

     

     

     

     

    2.2.2 ENVI-met 模型评价

    在进行正式模拟之前,必须先确定模型的有效性,可透过现地测量数据与模拟数据的比较检验准确度[14-17]

    故本研究于现地选择 8 处(图1),以 EL-USB-2+ 测量 2014 117日气温,以比较模拟值与测量值关系,结果显示各测点的气温模拟值与实测值的相关性介于 0.7 0.9 之间,与其他研究相比,本研究模型模拟结果可信。

    1 大安森林公园建置模型与监测测点点位图

    Figure 1 Building Model of Da 'an Forest Park and Bitmap of Monitoring Points

    方案一 方案二 方案三  方案四

    2 模拟方案图

    Figure 2 Simulated Scenario Diagram

     

    2.2.3 方案发展

    考虑不同功能空间组成元素致使功能空间的热表现有差别,且空间配置关系将影响公园整体热表现,故本研究基于功能空间与其出现的相关位置,以上下风处进行不同功能空间配置方案的发展。

    以夏季盛行西南季风将公园区分为上风处、下风处、公园中央,在各功能分区面积比例不变的情况下(表1),利用夏季盛行西南季风的上风处与下风处以及公园中央的空间位置概念,分配林荫区、草坪区与广场区的空间配置,共发展出四组模拟方案,方案一与方案二同为广场位于中央,而方案一上风处为林荫区、下方处为草坪区,方案二上风处为草坪区、下风处为林荫区;方案三与方案四同为草坪区位于中央,而方案三上风处为林荫区、下风处为广场区;方案四上风处为广场区、下风处为林荫区(图 2)。

    2.3 第三阶段:整合微气候调节策略功能空间配置方案的温度表现评估

    四组模拟方案,采集夏季 2014 5 14 日的气候数据:风速 2.90 ms-1、风向 225°(西南风)、初始温度 303.17 k(30.17℃)、比湿 7 g Kg-1、相对湿度 64.67 %进行模拟。于夏季热压力尖峰时段 10:00 - 14:00,每 30 分钟输出模拟结果。

    本研究所探讨的都市公园温度表现,其温度代表公园平均气温,根据每个功能分区所占公园的面积比率设定数据样本数量,每一个功能分区至少选取一点,且每增加5% 的面积比率增加一点,每个数据样本采用随机选取并记录其坐标位置,微气候模拟后根据坐标位置统计数据,并求取平均,作为该公园的代表温度,各分区面积比率与数据笔数如表 3

    3 分区数据使用量表

    Table 3 Data Usage for Each Functional Zone

    功能分区

    面积比率 %

    数据笔数

    林荫区

    38

    7

    草坪区

    25

    5

    广场

    8

    2

    水池区

    9

    2

    儿童游戏场区

    1

    1

    运动区

    7

    2

    展演舞台区

    2

    1

    服务及管理区

    6

    2

    3 结果

    3.1 方案的气温变化

    由方案气温变化分析图可知(图3),林荫区、草坪区、水池的温度较低,广场、展演舞台、运动区、儿童游戏场、服务及管理区温度明显较高。此外,公园周边为人工地盘为主的环境,故公园内部下风处受公园降温影响温度较低。

    3.2 各方案中各功能区气温变化情况

    八种功能分区在 10:00-12:00 时段温度上升快,并在 13:00-14:00 时段达到最高温并趋于稳定;八种功能分区的温度变动无明显不同。通过气温变化图可以发现不管是哪种模拟方案都是服务及管理区最高温,在 13:00 之前,水池区为最低温的功能分区,而在 13:00 过后,方案一的水池区与林荫区同为最低温的功能分区,至于方案二、方案三、方案四的在 13:00 过后的最低温为林荫区(图 4)。

    从功能分区的温度变动趋势来看可以发现方案三各功能分区彼此之间温差较小,方案四的服务及管理区则有明显高温的情形。

    3.3 功能区配置的影响

    由模拟结果可知,10:00-14:00 的温度随着时间而提高,进一步选用13:00-14:00 温度最高且趋于稳定的时段进行分析。

    单因子变异数分析检定结果显示,不同公园空间配置对公园温度具有显著影响(p<0.001),F值为 68.985。进一步以 post hoc Scheffe test 进行事后多重检定,比较不同方案的温度表现,依据温度高低,归类为 3 群,依序为:(a)方案三;(b)方案一;(c)方案四、方案二(表 4)。

    推测方案 3 表现较好是因为林荫区位于上风处,可增加公园入流风的湿度以降低空气温度,并透过风的带动将低温带到公园各处。

    3 模拟方案气温变化分析图

    Figure 3 Air Temperature Variations for Each Simulation Scenario

    4 公园配置方案与公园温度之单因子变异数分析表

    Table 4 One-way ANOVA of the Effect of Functional Zones Configuration On Air Temperature

     

    方案

    平均温度   (℃ )

    标准差

    27.91 a

    0.07

    28.14 b

    0.07

    28.28 c

    0.06

    28.31 c

    0.06

    F=68.985***

    ***p 0.001

    进一步分析不同上风处功能分区对公园温度的影响,以独立样本t检定进行检定,如下:

    比较方案一与方案二,两者公园中央功能分区同为广场,仅上风处与下风处的功能分区类型互换,方案一的上风处为林荫区,下风处为草坪区,而方案二则相反,上风处为草坪区,下风处为林荫区;当上风处为林荫区时,平均温度为 28.14℃,标准差为 0.06;当上风处为草坪区时,平均温度为 28.31℃,标准差为 0.06,独立样本t检定结果表示当公园中央为广场时,上风处功能分区不同对公园温度有显著影响,且林荫区温度低于草坪区(表 5)。

    5 上风处功能分区对于公园温度 t 检定分析表(方案一与方案二)

    Table 5 T-test of the Effect of Functional Zone That Be Allocated

    Upwind On Air Temperature (Scenario 1 and Scenario 2)

     

     

    上风处

    平均温度   (℃ )

    标准差

    林荫区

    28.14

    0.06

    草坪区

    28.31

    0.06

    t=-5.750***

    ***p 0.001

    比较方案三与方案四,两者公园中央功能分区同为草坪区,仅上风处与下风处的功能分区类型互换,方案三的上风处为林荫区,下风处为广场,而方案四则相反,上风处为广场,下风处为林荫区;当上风处为林荫区时,平均温度为 27.91℃,标准差为 0.07;当上风处为广场时,平均温度为 28.28℃,标准差为 0.06,独立样本t检定结果表示当公园中央为草坪区时,上风处功能分区不同对公园温度显著影响,且林荫区温度低于广场(表 6)。

    6 上风处功能分区对于公园温度 t 检定分析表(方案三与方案四)

    Table 6 T-test of the Effect of Functional Zone That Be Allocated

    Upwind On Air Temperature (Scenario 3 and Scenario 4)

    上风处

    平均温度   (℃ )

    标准差

    林荫区

    27.91

    0.07

    广场

    28.28

    0.06

    t=-11.579***

    ***p 0.001

    4 讨论

    本研究根据全市性公园空间配置形态,发现林荫区、草坪区与广场无特定配置规则,因此,透过此三个功能分区类型配合以上风处、下风处与中央的公园空间配置概念,研拟四个空间配置模拟方案经由单因子变异数分析检定。结果表示,不同空间配置对于公园温度具有显著影响,显示方案三(上风处为林荫区;下风处为广场;中央功能分区为草坪区)空间配置有最佳的公园温度表现,其次为方案一(林荫区在上风处;下风处为草坪区;中央功能分区为广场)的公园空间配置。在八个功能分区类型所占公园比例固定的情况下进行空间配置,经过单因子变异数分析检定结果发现四个空间配置方案彼此皆有显著差异,表示公园的确能通过空间配置的手法,在不影响公园基础功能的情况下能够有更好的降温效果。

    利用独立样本t检定进行分析检定。上风处功能分区对于公园温度表现具有显著差异,当公园中央功能分区同为广场时,上风处为林荫区、下风处为草坪区的公园温度与上风处为草坪区、下风处为林荫区的公园温度具显著差异(方案一、方案二),另外,当公园中央功能分区同为草坪区时,上风处为林荫区、下风处为广场的公园温度与上风处为广场、下风处为林荫区的公园温度具显著差异(方案三、方案四),从此研究结果可以推论,林荫区在上风处的降温效果佳,风可以带动林荫区的水气,增加空气湿度,并且能降低空气温度,而经由风的流动带入下风处,透过本研究等温图也可以发现低温度都会聚集在下风处位置。针对林荫区设置于公园上风处时,公园内部温度有较好的温度表现,此研究结果与前人研究相符[17-20]

    由本研究调查结果显示,林荫区在上风处、广场在下风处且草坪区在公园中央的空间配置为公园温度表现最佳的空间配置类型,公园中央的开阔型空间应使用草坪供民众户外活动使用,广场、服务及管理区、儿童游戏场、展演舞台等则尽量设置在公园的下风处或邻近水体及林荫区,除了不会造成公园内部温度的提升以外,林荫区位于上风处所带来的冷空气也能舒缓下风处的广场空气温度。因此,于都市公园设计前期,整合功能分区的降温配置考量能达到较低的温度表现,提升都市公园降温的能力。

    本研究由于时间与人力限制,在方案模拟方面,透过 16 座全市性公园的配置形态进行归纳,最后研拟出四个模拟方案,以中央、上风处、下风处作为空间配置的操作变项,利用林荫区、草坪区与广场进行配置,并固定各功能分区的所占面积比例进行微气候模拟,未来可尝试调整功能分区的面积比例与空间配置对于公园温度表现之关系;此外,水是降温的主要因素,未来可将水池纳入空间配置的项目之中,而功能分区的形状也可能影响温度表现,后续也可针对此点进行深入探讨。

     

    1 Introduction

    Urban parks are important places for people's daily leisure and recreation. With the gradual increase of urban population, the environmental quality of the city has decreased significantly, which leads to the functional consideration of urban parks becoming more diversified. In particular, with the popularity of urban environmental issues, urban parks have been called a crucial way to solve or relieve urban environmental problems. Among many urban environmental issues, the urban heat island phenomenon caused by urbanization and urban expansion, the increase of buildings and impervious areas, urban heat emission and other factors has attracted the attention of many scholars.

    Large parks in the whole city have a large area and need to provide multiple functions. Its setting should meet the needs of all people as much as possible, including open space with functions of ecological, landscape, disaster prevention, recreation, etc. However, the cooling effect will be affected because the land cover material and planting green cover degree are different in each space. According to relevant documents, the building density, green coverage rate, population density, paving density, sky view factor, aspect ratio of streets and land use type around the park will affect the air temperature of the park [1-10], and wind is also one of the important factors affecting the microclimate [11]. Wind flow will increase the air humidity by driving the moisture of surrounding pools or plants, thus reducing the air temperature [12].

    In recent years, integrating microclimate response strategy in urban parks’ design has received extensive attention and has become an important basis for evidence-based design through empirical research. However, for the multi-functional requirements of urban parks, it is particularly important how to make a better functional zone configuration to meet the existing use and improve the performance of temperature regulation without affecting the diversified use functions of urban parks. Therefore, aimed at early stage of landscape design, this study investigated the effect of integrating microclimate response strategy in urban parks’ design by arranging functional zones configuration, discussed the relationship between functional space allocation and temperature performance of urban parks through numerical simulation, so as to find out the space allocation and criteria for better cooling efficiency and provide reference for future planners.

    2 Research Method

    This study conducted a three-stage research: Stage 1 identified the required functional zones and configuration of functional zones, Stage 2 validated the performance of the model and developed scenarios, and Stage 3 assessed temperature performance of the scenarios. The details are as follows:

    2.1 Stage I:Identified the required functional zones and configuration of functional zones

    Functional zone is the core in the early stage of urban park design, and the types and configuration of functional zones will be affected by the base's own conditions, social needs, laws and regulations, etc. In order to understand the functional zone types and spatial allocation of parks in the whole city, this study confirmed the necessary functional zones and spatial allocation of urban parks by collecting literature and analyzing case parks.

    Taking Taiwan province’s three major urban areas: Taipei, Taichung and Kaohsiung, with a total of 16 citywide urban parks as case studies, this study further confirmed the relationship between functional zone types and spatial allocation by means of regulatory analysis, aerial photography, Show Taiwan and Google Street View.

    The park design codes of the three cities all point out that the park should be equipped with relevant facilities according to the nature and environmental needs, including landscape facilities, recreational facilities, sports facilities, game facilities, social education facilities, service facilities, management facilities, etc. The facilities are included in the functional zones, so the five landscape professionals classify the functional zones corresponding to the facilities, including eight functional zones: wooded zone, lawn zone, plaza zone, performance stage zone, pool zone, children's play zone, sports zone, service and management zone. The five professionals further produced 16 functional zone drawings of the city's parks, and then quantified the drawings by Adobe Photoshop CS6 and Image J. They divided the space between the primary and secondary entrances of the park and the internal location of the central park.

    The statistical results of functional zones are shown as follows (table 1): 16 parks are equipped with functional zones of plaza, trees, functional zones of service and management, 15 parks are equipped with lawn zones and children's play zones, 9 parks are equipped with pool zones, and only 4 parks are equipped with performance stage zones; In terms of configuration, 8 of the 16 parks have lawn zones in the center, 5 parks have plaza zones, and 3 parks have pool zones. As a whole, the functional zones mainly located near the main entrance are plaza zone, wooded zone, lawn zone and performance stage zone. The functional zones mainly located near the secondary entrance are plaza zone, wooded zone, lawn zone, pool zone, sports zone, children's playground and service and management zone.

    When using mode to count the number of functional zones, the results show that most urban parks have three plaza zones inside and only one for other functional zones. Therefore, this study divides the plaza into the main entrance plaza, the park central plaza and the secondary entrance plaza. The average area ratio of each district is: plaza zone 8%, wooded zone 38%, lawn zone 25%, pool zone 9%, sports zone 7%, perf

    ormance stage zone 2%, children's playground zone 1%, service and management zone 6%, which serve as the basis for subsequent consideration of the development of microclimate strategy.

    2.2 Stage II:Validated the Performance of the Model and Developed Scenarios

    Taking Da 'an Forest Park as the research site, the modeling and setting, simulation validity test and program development of this study are explained as follows:

    2.2.1 Modeling the Environment and Configuration

    Da'an Forest Park was modeled by using aerial photographs and digital topographic maps. The grid is set to x = y = z = 4 m. The length of the model grid number is 235 and the width of the model grid number is 165. The land cover type with the highest proportion in the unit grid is adopted as the representative of the grid by each grid modeling judgment standard.

    Taking the monitoring data of Taipei Meteorological Station as the initial input data of the weather, the date is January 17, 2014, and the typical urban value of 0.1 [ 13 ] is input into the degree of roughness. For buildings, it uses the numerical input of building attributes and building material specifications shown in the digital topographic map (table 2).

    Regarding the setting of plant layer, according to field investigation, arbor should be set to 10 m high. Since LAD1 to LAD4 belong to trunk parts, the values of the leaf area density (LAD) were set 0. LAD5 to LAD10 belong to arbor crown, so the value is set to 1.05. The root area density (RAD) remained unchanged and the height of the grassland was set at 20cm. Regarding pavement layer setting, asphalt roads are selected for roads (S), pavements such as plazas and footpaths are built into brick roads (kk), and pavements such as seating areas and sports areas in front of the stage are set as concrete pavements (P), which use loamy soil (L). Artificial ecological pool is used as water body (W) and game mat is RR.

    2.2.2 ENVI-met Model Evaluation

    Before the formal simulation, the validity of the model must first be determined. We can check the accuracy by comparing the field measurement data with the simulated data[14-17].

    Therefore, this study selected 8 sites (fig. 1) to measure the air temperature on January 17, 2014 with EL-USB-2+, and compared the relationship between the simulated value and the measured value. The results show that the correlation between the simulated temperature and the measured temperature is between 0.7 and 0.9. Compared with other researches, the simulation results of this research model are trustworthy.

    2.2.3 Programme Development

    Different functional zone components will lead to different thermal performance of the functional zone, and the overall thermal performance of the park will be affected by the spatial configuration relationship. Therefore, based on the functional zone and its relative location, this study develops different functional zone configuration scenarios the upwind and downwind.

    The park is divided into upwind, downwind and the center of the park by the southwest monsoon prevailing in summer. Under the condition that the zone proportion of each functional zone is unchanged (table 1), four sets of simulation schemes are produced by using the spatial location concepts of upwind, downwind and the center of the park under the influence of southwest monsoon prevailing in summer to allocate the spatial configuration of the wooded zone, lawn zone and plaza zone. Both scenario 1 and scenario 2 belong to the plaza zone and are located in the center. While, the upwind in scenario 1 belongs to the wooded zone, and the downwind in scenario 1 belongs to the lawn zone. The upwind in scenario 2 belongs to the lawn zone, and the downwind in scenario 2 belongs to the wooded zone. Both scenario 3and scenario 4 belong to the lawn zone and are located in the center. However, the upwind of scenario 3 belongs to the wooded zone, and the downwind of scenario 3 belongs to the plaza zone. The upwind of scenario 4 is the plaza zone and the downwind is the wooded zone (fig. 2).

    2.3 Stage III:Assessed temperature performance of the scenarios

    These four sets of simulation scenarios were carried out by using the climate data on May 14, 2014 in summer: wind speed of 2. 90ms-1, wind direction of 225 (south-west wind), initial temperature of 303.17k ( 30.17℃ ), specific humidity of 7 g Kg-1, and relative humidity of 64.67%. The simulation results are output every 30 min-utes from 10: 00 to 14: 00 during the peak period of summer thermal pressure. The temperature in the performance of urban park temperature discussed in this study represents the average temperature in the park. The number of data samples is determined by the area ratio of each functional zone in the park. At least one sample is selected for each functional zone, and one sample is added for each area ratio increasing by 5%. Each data sample is randomly selected and its coordinate position is recorded. After microclimate simulation, statistical data are obtained according to coordinate positions, and the average temperature is calculated as the representative temperature of the park. The area ratio of each zone and the data usage are shown in table 3.

    3 Results

    3.1 Temperature Changes in the Scenarios

    In figure 3, it can be concluded that the temperatures in the wooded zone, lawn zone and pool zone are relatively low. The temperatures in the plaza zone, perfor-mance stage zone, sports zone, children's play zone, service and management zone are obviously higher. In addition, the surroundings of the park are dominated by artificial sites, so the downwind temperature inside the park is relatively low due to the cooling effect.

    3.2 Temperature Variation of Functional Zones in Various Scenarios

    The temperatures of the eight functional zones rose rapidly from 10: 00 to 12: 00, and reached the highest temperature and stabilized from 13: 00 to 14: 00. The temperature changes of the eight functional zones are not significantly different. According to the temperature change map, it can be found that no matter what kind of simulation scenario, the service and management zone has the highest temperature. Before 13: 00, the pool zone is the functional zone with the lowest temperature. While after 13: 00, the pool zone and the wooded zone in scenario 1 are the functional area with the lowest temperature. After 13: 00, the wooded zone is the functional zone with the lowest temperature in scenario 2, scenario 3 and scenario 4 (fig. 4).

    According to the temperature change trend of the functional zones, it can be found that the temperature difference between the functional zones in scenario 3 is not obvious. The service and management zones in scenario 4 are in a state of marking high temperature.

    3.3 Impact of Functional Zone Configuration

    According to the simulation results, the temperature from 10: 00 to 14: 00 increases with time. We further select the period with the highest temperature and the temperature tends to be stable in the period of 13:00-14: 00 for the analysis.

    The results of one-way ANOVA shows that different park space configurations have significant effects on park temperature (p<0.001), and F value was 68.985. After rechecking with post hoc Scheffe test and comparing the temperature performance of different scenario, they can be divided into three types according to the temperature: (a) scenario 3; (b) scenario 1; (c) scenario 4 and scenario 2 (table 4). We speculate that scenario 3 performs better because the wooded zone is located at the upwind, which can increase the humidity of the park inflow wind to reduce the air temperature and bring the low temperature to the whole park through the wind.

    The author makes further analysis on the influence of different upwind functional zones on park temperature, and uses independent t-test for verification. The steps are as follows:

    Compared with scenario 1 and scenario 2, the functional zones of two central parks are both plazas, and only functional zones of upwind and downwind are different. The upwind in scenario 1 belongs to a wooded zone, and the downwind in scenario 1 belongs to a lawn zone. Different from the scenario 1, the upwind of the scenario 2 is the lawn zone, and the downwind is the wooded zone. When the upwind belongs to the wooded zone, the average temperature is 28.14℃ , and the standard deviation is 0.06. When the upwind belongs to the lawn zone, the average temperature is 28.31 ℃ , and the standard deviation is 0.06. The independent t-test test results show that when the center park belongs to the plaza zone, the functional zones at the upwind are different, which has a significant impact on the temperature of the park, and the temperature of the wooded zone is lower than that of the lawn zone(table 5).

    Compared with scenario 3 and scenario 4, the functional zones of two central parks are both lawn zones, and only functional zones of upwind and downwind are different. The upwind in scenario 3 belongs to a wooded zone, and the downwind in scenario 1 belongs to a plaza zone. Different from the scenario 3, the upwind of the scenario 4 is the plaza zone, and the downwind is the wooded zone. When the upwind belongs to the wooded zone, the average temperature is 27.91℃ , and the standard deviation is 0.07. When the upwind belongs to the plaza zone, the average temperature is 28.28℃ , and the standard deviation is 0.06. The independent t-test results show that when the center park belongs to the lawn zone, the functional zones at the upwind have significant impacts on the park temperature. The temperature of the wooded zone is lower than that of the plaza zone (Table 5).

     

    4 Discussion

    According to the city-wide park space allocation patterns, this study found that there are no specific allocation rules for wooded zones, lawn zones and plaza zones. Therefore, through the three types of functional zones and the park space allocation concepts in the upwind, downwind and central park, this paper has developed four space allocation simulation scenarios and verified them through One-way ANOVA. The results show that different spatial configurations have significant effects on park temperature. First of all, the space allocation of scenario 3: the upwind is the wooded zone. The downwind is the plaza zone. The central functional area is the lawn zone, which has the best park temperature performance. Secondly, the space allocation of scenario 1: the upwind is a wooded zone. The downwind is a lawn zone. The central functional area is a plaza zone. The space is configured under the condition that the proportion of the eight functional zoning types in the park is fixed. The results of one-way ANOVA show that there are significant differences among the four spatial allocation scenarios, which indicates that the park can really achieve better cooling effect without affecting the basic functions of the park through spatial allocation.

    Independent t-test was used for analysis and verification. Functional zone at the upwind has a significant impact on the park temperature performance. When the central functional zones of the two parks are both plaza zones, there are significant differences between the park temperature in which the upwind is the wooded zone, the downwind is the lawn zone, and the park temperature in which the upwind is the lawn zone, the downwind is the wooded zone (scenario 1 and scenario 2). In addition, when the central functional zones of the two parks are both lawn zones, there are significant differences between the park temperature in which the upwind is the wooded zone, the downwind is the plaza zone and the park temperature in which the upwind is the plaza zone and the downwind is the wooded zone (scenario 3 and scenario 4). According to the research results, it can be inferred that the wooded zone has a good cooling effect when it is in the upwind. The wind can drive the moisture in the wooded zone, increase the air humidity and reduce the air temperature. The flow of wind can bring moisture downwind. It can also be found that low temperatures are gathered at downwind through the isothermal diagram of this study. When the wooded zone is in the upwind of the park, the internal temperature of the park has a better temperature performance, and this research result is consistent with previous studies [17-20]. According to the survey results of this study, space allocation with the best park temperature performance: the wooded zone is the upwind, the plaza zone is the downwind, and the lawn zone is the center park. Open spaces such as lawns in the center park should be used for outdoor activities. The plaza zone, service and management zone, children's play zone and performance stage zone should be located downwind of the park or close to the pool zone and wooded zone. It can not only avoid raising the temperature inside the park, but also reduce the air temperature in the plaza zone downwind from the cool air brought by the upwind of the wooded zone. Therefore, in the early stage of urban park design, the cooling configuration considerations of integrated functional zones can achieve lower temperature performance and enhance the cooling capacity of urban parks. Limited by time and manpower, this study summarizes the configuration of 16 citywide parks in terms of scenario simulation. Finally, four simulation scenarios have been developed. Taking the center, upwind and downwind as the operation variables of spatial configuration, this study uses wooded zone, lawn zone and plaza zone for configuration, and carries out microclimate simulation by fixing the area proportion of each functional zone. In the future, it is possible to adjust the relationship between the area ratio of functional zones and the space allocation for the performance of park temperature. In addition, water is the main factor for cooling, and pool zones can be included in space allocation projects in the future. Moreover, the shape of the functional zone may also affect the temperature performance, which can be discussed in depth in the further studies.


     

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    (整理:赵迪 译:戴晨峪)

     

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