珠江三角洲地面风场的特征及其城市群风道的构建

利用珠三角20个观测站1964—1983年的风数据分析了珠三角城市群地面风场风向、风速分布与季节变化特征,并基于经验正交函数(EOF)进行了地面风场的空间分类。呈缺口盆地地形的珠三角风速较低,为3—2 m/s,整个区域风速南高北低;以伶仃洋为界,西岸高于东岸;西南部潭江谷地夏季多南风,冬季为北风,东岸东江谷底全年多东风,北江与西江河谷冬季盛行北风,夏季为东南风。综合风向与风速,结合地形,可将珠三角地面风场由南向北依次划分为较高风速区、中风速区和低风速区三类。根据空间尺度以及在区域中发挥的作用,珠三角城市群应构建多级风道,且风道还有常年与季节之别:伶仃洋(伶仃洋—虎门—狮子洋—广州水道)、西江(磨刀门—九江—三水)、潭江河谷应属于一级常年风道;北江(清远—三水)和东江(博罗—狮子洋)为一级季节风道。广州—三水段、黄埔—东莞段、中山—江门段以及伶仃洋段是影响整个珠三角大气环境质量风道的枢纽地段。城市群规划中对枢纽段超高建筑群进行风环境影响的评价,对枢纽段河道宽度、建筑物高度与密度的控制,将有助于提高珠三角城市群的空气质量,并防范下垫面粗糙度改变引起峡谷风的新风险。

Wind fields and the development of wind corridors in the urban metropolis of the Pearl River Delta

The application of wind field analysis and simulation can improve traditional urban planning and regional eco-environmental efforts. We analyzed the wind direction, wind speed and seasonal variation of the surface wind field, in combination with empirical orthogonal function (EOF) analysis to spatially classify the surface wind field of the Pearl River Delta based on the wind data from 20 observation stations collected from 1964 to 1983. The low average wind speed seldom exceeded 2-3m/s because of the gap-shaped basin topography, with relatively higher wind speeds in the south and low speeds in the northern part of the region. From the boundary of the Lingding Gulf, the wind speeds along the west coast are higher than wind speeds along the east coast. A south wind prevails in summer and a north wind in winter in the Tang River Valley in the southwestern part of the region. An east wind prevails during the entire year in the East River Valley along the east coast. A north wind prevails in winter and the southeast wind in summer in the West River Valley and North River Valley. The background wind direction and topography effect the surface windfield resulting in higher wind speeds in the south than in the north. Wind speed pattern is an important background factor influencing air quality in the Pearl River Delta. From 1964 to 1983, the wind speed decreased in the north and increased in the southern parts of the region, which increased the wind speed differences between these two areas. Based on the wind direction, wind speed and topography, we divided the surface wind field in the Pearl River Delta into three parts from south to north which we called the high, mid-range and low-wind speed zones. A wind corridor is the main air-flow channel within an urban metropolis area, which impacts near-surface atmospheric environmental quality. Based on the spatial characteristics of tall buildings and the regional topography, we need to manage and construct multi-level wind corridors for the Pearl River Delta metropolis. Based on the relationship between wind direction and the riverway direction, we divided the wind corridors into seasonal and annual wind corridors. The primary feature of the annual wind corridor is that the regional background wind direction is consistent with riverway direction. The annual wind corridor includes Lingding Gulf (Lingding Gulf-Humen-Shizi Gulf-Guangzhou), West River (Modaomen-Jiujiang-Sanshui) and Tang River Valley. So, the wind corridor of the Shangchuang Island-Gaohe-Sanshui creates a high speed area of wind in the Pearl River Delta and air fluently flows through it. But the North River (Qingyuan-Sanshui) and East River (Boluo-Shizi Gulf) belong to the first-level seasonal wind corridor because wind direction there is perpendicular to the valley direction during several months of a year. With the development of ultra-high buildings and an increase in building density the wind corridor is often blocked resulting in reduced ventilation and increasing levels of pollution and the creation of a heat island. Also, recently constructed high-rise buildings are located in or near the valley, which narrows the valley and some wind corridors are transformed into valley wind corridors. This increases the risk of disasters when the valleys and buildings combine to channel the wind during unusual weather events such as typhoons and other types of storms. The wind corridor of the Guangzhou-Sanshui, Huangpu-Dongguan, Zhongshan-Jiangmen and Lingding Gulf section is the hub of all the wind corridors, which impacts air quality of the entire Pearl River Delta. The Pearl River Delta currently has green belt and green corridor planning, but a complete ecological corridor should include a wind corridor, green belts and green corridors. The assessment of the wind environment for tall buildings is at the core of urban planning. When combined with the control of hub river width and building height and density, it will help improve air quality in the urban metropolis of the Pearl River Delta, protecting the valley wind corridor from changes at the surface. Limited statistical and simulation data is available, so the authors discuss the concept of wind corridors which needs to be the subject of massive experimentation in the future.