| 摘要: |
| 城市水体作为一种基于自然的解决方
案，被视为调节城市气候、改善城市热环境的重
要工具。研究水体的能量分配特征是认识和把
握水体对城市热环境影响的关键。然而，由于缺
乏系统的量化方法和充分的数据支撑，水体的
能量分配，即水体与周边环境能量交换的物理
过程，尚未完全明晰。基于能量平衡理论，以广
州荔湾湖为例，通过冬、夏两季的连续系统观
测，得到湿热地区城市湖泊各能量分项的分配
特征。结果表明：一、辐射通量在湖泊的能量平
衡中具有双重作用，在白天短波辐射是主要能
量输入源，在夜间长波辐射冷却是重要的散热
形式；二、各能量分项受天气条件的影响不同，晴朗少云的“理想”天中净辐射通量Q*
和潜热通量QE显著大于雨天和阴天多云等其他天气条件，
而显热通量QH在这三种天气条件下的差异较小；三、季节对湖泊能量分配有显著影响，在高温高
湿的夏季，蓄热通量Qs的平均日累计占比最大，即大部分净辐射分配给了蓄热；在凉爽干燥的冬
季，QE占比最大，即大部分能量输入转化为了潜热。可为考察城市静态水体能量分配特征提供研
究方法参考，并为认识和把握水体的气候调节效应提供湿热地区的数据支撑，进而推进基于蓝色
基础设施的气候适应型城市建设。 |
| 关键词: 水体 能量平衡 波文比法 湿热地区 |
| DOI：10.13791/j.cnki.hsfwest.20230602 |
| 分类号: |
| 基金项目:国家重点研发计划政府间国家科技创新合作重点专
项（2019YFE0124500）；广东省省级科技计划项目国
际科技合作领域（2018A050501007）；亚热带建筑
与城市科学全国重点实验室开放课题（2021ZB01）；
广东省基础与应用基础研究基金自然科学基金面上
项目 |
|
| Characteristics of Energy Partitioning of Static Urban Water Bodies in Hot-Humid Regions: A Case Study of Liwan Lake in Guangzhou |
|
YAO Lingye,XU Genyu,ZHAO Lihua
|
| Abstract: |
| Urban areas play a fundamental role in local- to large-scale planetary processes by altering
heat, moisture, and chemical budgets. As urbanization continues globally, it is vital to acknowledge
the consequence of converting natural landscapes into the built-up environment. Cities around the
world are experiencing elevated temperatures and extreme heat events due to the combined effects
of global warming and urbanization. Recognizing cities as primary responders to global change,
considerable efforts are currently dedicated worldwide to monitor and understand urban atmospheric
dynamics. Additionally, various adaptation and mitigation strategies aimed to offset the impacts of
rapid urban sprawl and urban overheating are being developed, implemented, and evaluated.
Urban surfaces can inf luence the near-surface urban climate through three primary
mechanisms, i.e., radiative exchange, sensible heat exchange between urban surface and ambient
air, and latent heat exchange via evaporation and transpiration. It is documented that urban surfaces
could drive up to 25% of variation in air temperature. Urban water bodies, hailed as a nature-based
solution, have emerged as an important potential strategy in tempering urban climates and enhancing
thermal environments to design sustainable thermally-safe cities. The cooling benefits of water
bodies have been widely investigated concerning their influence on surface and air temperatures.
However, a better metric of thermal behavior of water bodies requires the consideration of the overall
energy balance, including radiative energy exchange, convective heat transfer, evaporation, and heat
storage and release. Analyzing the characteristics of energy partitioning of urban water bodies is
the key to understanding and capturing the impacts of water bodies on urban thermal environment.
However, due to the lack of systematic quantitative methods and adequate data support, the energy
allocation of water bodies, i.e., the physical process of energy exchange between water bodies and
the surrounding environment, has not been investigated and elaborated thoroughly.
Based on the energy balance theory, this study has further developed the energy balance
observation methodology by integrating the Bowen ratio and energy balance equation. In comparison
to the methods such as the Bulk coefficient and Eddy correlation methods, the Bowen ratio method
offers a distinctive advantage in quantifying the energy components of water bodies, based on
routine meteorological observations, considering both daytime and nighttime, as well as the calm
wind conditions. In hot and humid regions of China, there is a dense network of rivers, streams,
and canals, and water systems are well developed, closely intertwined with human settlements. Simultaneously, hot-humid regions are characterized with consistently high temperatures and high humidity throughout the year. With the exacerbation
of global climate change, the urban heat environment issues in these regions are more severe than in other areas. Therefore, utilizing water bodies to
improve the urban thermal environment is of significant importance for the construction of climate-resilience cities in hot-humid regions. Additionally,
according to literature review, the thermal effects of water bodies vary by location. The response of water bodies in hot and humid areas to climate change
differs from other regions. Further analysis of its physical characteristics can be conducted from the perspective of energy partitioning. Given the context
above, the energy partitioning patterns of an urban lake located in the densely built-up areas of hot-humid regions, were obtained through continuous field
measurements in summer and winter based on the Bowen ratio energy balance method, taking the Liwan Lake in Guangzhou as a case study.
Results of this study demonstrated a multifaceted role played by the net radiation heat flux Q*
in the energy balance of urban lakes. It was observed that
the shortwave radiation functioned as the primary energy inputs during daylight hours, whereas longwave radiative cooling emerged as a significant heat
release during nocturnal periods. Weather conditions exhibited varying impacts on distinct energy components of the lake, with net radiation heat flux Q*
and
latent heat flux QE being greater on clear and cloudless ‘ideal’ days than on rainy and other days such as cloudy and overcast days. Conversely, sensible heat
flux QH displayed negligible variations across the three weather conditions. The seasonal dynamics emerged as a critical determinant governing the energy
allocation of the lake. In hot-humid summer, the heat storage flux Qs accounted for the highest percentage, indicating that a majority of the net radiation
was directed towards heat storage. Conversely, during cold-arid winter, a significant portion of QE was observed, signifying that a substantial fraction of the
energy inputs was converted into latent heat. These distinct seasonal trends underscored the adaptive nature of urban water bodies in redistributing energy
based on prevailing climatic conditions. Findings of this study can provide a methodological reference for assessing the energy partitioning of static urban
water bodies, provide data support of hot-humid regions for understanding the climate regulation effects of water bodies, and promote the construction of
climate-resilience cities based on blue infrastructure. |
| Key words: Water Bodies Energy Balance Bowen Ratio Method Hot-Humid Region |
