Landscape Elements in the Lhasa Residential Area

Landscape Elements in the Lhasa Residential Area: Comparison

Please note this is a comparison between Version 3 by LIXING CHEN and Version 2 by LIXING CHEN.

景观元素因其对热环境的直接影响而成为提高居民生活质量的重要手段，但景观元素的选择和表征在不同气候条件下对人体的热舒适度有不同的影响。本研究以西藏拉萨典型居民区为研究对象，采用正交试验方法制备实验方案，利用ENVILandscape elements have become an important means to improve the quality of life of residents because of their direct influence on the thermal environment, but the selection and configuration of landscape elements have different effects on human thermal comfort in different climate conditions. Therefore, in this study, in order to better understand the impact of residential landscape elements on the outdoor thermal environment and thermal comfort in a high-met进行模拟，探索高寒气候条件下绿色植被、水域、地面折射的侵入度，以及它们与冬夏热环境的相互作用。以生理当量温度（PET）为优化指标，确定了住宅景观元素协同效应的最优设计方案。结果如下。（altitude cold climate area, the typical residential area of Lhasa in Tibet was taken as the research object,the thermal environment of a residential area with different landscape element configurations was numerically simulated based on the orthogonal experimental design method. The PET was taken as the optimization objective, and the simulation results were analyzed with intuitive analysis and variance analysis. The main objectives were as follows:

(1）景观构象因子的顺序如下：绿色构象>水域面积>夏季叶面积指数>地面折射。在冬季，目>水域面积>地面反射率>叶面积指数（LAI）进行绿色构象。（) To clarify the primary and secondary effects and advantages of various landscape elements on an outdoor thermal comfort under high altitude and cold climate conditions.

(2）通过正交试验和数值模拟的结合驱动，确定了景观构件的最优方案，即“灌木草坪，水域面积比16%，地面折射率为0) To clarify the synergistic relationship between landscape elements and their interaction with outdoor thermal comfort under high altitude and cold climate conditions.5，LAI

(3) To put forward the experimental scheme and strategy of landscape =element 3 m2/m3”。（3）最后，针对拉萨居民区典型户外活动空间提出了景观构象的最优设计策略。allocation optimization in a residential area for the conditions of high altitude and a cold climate.

high altitude
landscape elements
outdoor thermal comfort
orthogonal experiment

1. Background

1. The plane of the city of Lhasa is distribu

Lhasa is located in the middle of the Qinghai Tibet Plateau, with an altitude of 3650 meters. The plane of the city of Lhasa is distributed in a belt from east to west. Two mountains (South Mountain and North Mountain of Lhasa) sandwich the city, and a river (Lhasa River) passes through the city. It is a typical axial development city. According to the Chinese standard meteorological data, the hottest month is June, and the coldest month is January. The monthly average maximum temperature is above 20°C, the monthly average minimum temperature is below −3°C, and the annual temperature difference is 18.1°C . Lhasa belongs to the cold region in China's architectural climate zoning, but because it is located in the Qinghai Tibet Plateau, the climate conditions of Lhasa are significantly different from those of Beijing, Xi'an, Lanzhou (cold climate region), and other cities. By comparing the enthalpy and humidity diagrams of the three cities , it can be seen that the annual temperature and the humidity of Lhasa are relatively lower, and the annual temperature difference is also relatively smaller. Beijing and Xi'an also have coexisting heat and humidity, but Lhasa has a dry climate, so there is no such phenomenon.

According to the sixth report of the Intergovernmental Panel on Climate Change (IPCC), global warming caused by human activities is 1.0 °C higher than before industrialization, global warming is continuing, and the risk of extreme weather events is further increasing [1,2]. The urban heat island effect (UHI) caused by climate change and anthropogenic changes in rapid urban development has directly led to the emergence of urban problems such as high temperature, drying, poor ventilation, and pollutant accumulation. These changes reduce the urban outdoor thermal environment and the thermal comfort of residents [3,4] and increase the energy consumption of urban buildings [5,6]. They also endanger human health, induce various health problems [7,8], and can even lead to death [9]. The China Climate Change Blue Book released by the China Meteorological Administration in 2021 pointed out that: “China is a sensitive area and a significant impact area of global climate change, and the heating rate is significantly higher than the global average in the same period [10]”. It has become crucial to take strong measures to improve the urban environment and improve the quality of the human living environment. There is already a large amount of research trying to find optimal solutions to mitigate the many challenges posed by the growing climate problem. From the perspective of urban planning, this is mainly reflected in two aspects: urban building layout and urban landscape (vegetation, water body, underlying surface, etc.). As a nature-based solution, urban landscapes are believed to play a key role in improving microclimates and mitigating heat island effects [11]. In addition to this, a good landscape environment can enhance residents’ well-being while improving residents’ comfort [12,13].

In this research, 60 residential areas were investigated and analyzed based on the following two factors . (1) Architectural layout: most of the architectural layout forms were the determinant at high south and low north as well as the mixed type of peripheral and determinant combination, and the number of building floors was mainly that for multilayer and small high-rise buildings. (2) The current situation of the landscape element allocations in residential areas, which is as follows: The common greening forms of green space are trees, shrubs, and grass. The types of underlying surfaces mainly include floor tiles, permeable bricks, gravel roads, grass planting bricks, permeable plastic, and lawns. The number of waterscape layout areas is small, the waterscape form is relatively single, and the shapes are mostly still water and fountains.

2. Literature Review

2.2. Characteristics of residents' behavior habits

确定如何基于自然的解决方案创造健康的户外热环境已成为一个热门的研究课题，改善居民区的室外热环境尤为重要，因为它们是许多户外活动的基础。与住宅区室外热环境和热舒适性密切相关的景观环境因素主要包括绿化、水体和地表。在绿化方面，在炎热和干旱地区，选择能够减少太阳辐射的树木是降低生理当量温度（PET）最有效的城市设计策略[14]。Middel等人的研究[15]证明，紧凑的建筑布局在白天对气温的影响大于绿化，在紧凑的低密度建筑区使用树木使温度降低了2°C，高密度建筑区的树木可以有效地将空气温度降低0.2-0.4°C[16]，但这在开罗的低密度建筑区无效[17]。在炎热潮湿的气候中，Srivanit等人[18]和Zhuang等人[19]的研究证实，树木可以影响太阳辐射并改变风环境，显着降低平均辐射温度（Tmrt）和PET。树冠的结构以及叶子的大小，形状和颜色影响了太阳辐射的水平[20]。在寒冷气候下，除了改善夏季的室外热环境[21]外，树木还可以通过调整树木的布局来有效改善冬季的室外风环境[22]。在温带气候下，Lee等人[23]证实，树木和草坪的组合形式对Tmrt和PET的影响比单独的草坪更显着。在水体方面，Lu等人[24]以潮湿炎热的气候为背景，证实水体在白天变暖阶段具有降温作用。此外，晚间降温阶段起到了保温作用，具有加湿和调节风速的作用。在寒冷的气候条件下，滨水居民区湿热环境的影响规模很大程度上取决于体积比、路堤高度和绿化[25]。此外，地面的特性是影响居民热舒适度的重要因素[26]。在潮湿炎热的气候下，Kwan等人[27]、郭等人[28]和宋等人的研究[25]发现，不透水表面的温度高于透水面的温度，天然的低垫面具有较好的冷却效果。在温和的气候下，Santamouris等人[29]表明，具有高反射率的材料可以显着影响人体的热舒适度，但Taleghani等人的研究表明，Tmrt和PET都随着反射率的增加而增加。

The Lhasa area is affected by strong radiation, and the demand for shade space in summer is greater than that in winter. There is also a greater objective demand for the comfort of the outdoor space thermal environment in summer and winter (Figure 3). In this study, through a questionnaire survey, we examined the behavioral characteristics of outdoor activities of the local residents in Lhasa. The content of the questionnaire mainly included two parts: (1) basic information about respondents (gender, age, name, and ethnicity); and (2) respondents' behavior habits (activity time, activity form, and preferred activity venue).

研究人员发现，景观元素对不同气候带区域热环境的影响之前已经研究过很多次，其研究结果也各不相同，但对各种景观元素之间协同作用机制的研究还比较缺乏。每个城市都处于特定的区域大气环境中，城市气候的差异影响景观要素对室外热环境的改善机制。中国西藏地区受到其特殊地理位置、气候条件和宗教文化的影响。景观元素对热环境的影响与其他气候带不同。当地居民每天进行大量的户外活动，频繁和长期的户外活动对户外环境提出了更高的要求。然而，对高海拔寒冷气候带的研究相对较少，很难为改善极寒气候下的生活环境质量提供理论支持。

2.3. Research framework

因此，本研究为了更好地理解高海拔寒冷气候区住宅景观要素对室外热环境和热舒适性的影响，以拉萨为例，基于正交实验设计方法，对具有不同景观要素构象的居民区热环境进行了数值模拟。以PET为优化目标，采用直观分析和方差分析对仿真结果进行分析。主要目标如下：

（he research framework of this study is shown in this Figure : (1）阐明高海拔和寒冷气候条件下各种景观元素对室外热舒适性的主要和次要影响和优势。

（) The landscape elements model of the residential area was grouped with the orthogonal design method to determine the experimental scheme. (2）阐明高海拔和寒冷气候条件下景观元素及其与室外热舒适相互作用的协同关系。

（) ENVI-met, a three-dimensional urban microclimate simulation software jointly developed by Michael Bruse and Heriberfleet of Bochum University in Germany, was used for numerical simulation. This study used ENVI-met version v4.4.3 for the calculation to study the influence degree and the order of different landscape elements and their interaction with the thermal environment in residential areas. (3）提出高海拔、寒冷气候条件下居民区景观要素配置优化的试验方案和策略。

) The experiment optimization scheme with the collaborative action of landscape elements in a residential area was determined by taking the PET as the test index, and finally, the optimal design strategy was put forward.