北京城市通风廊道研究Ⅰ:环境效应模拟

Ventilation Corridor in Beijing,Part Ⅰ:Simulation of Environmental Effects

采用耦合城市冠层模式UCM的中尺度气象模式WRF,利用北京市高分辨率地表类型、城市建筑及通风廊道规划方案等资料,针对2019年冬季和夏季各开展了为期1个月的百米尺度高分辨率敏感性模拟试验,并应用自动气象站网观测数据进行了验证。模拟试验结果表明:引入通风廊道后气象要素差异不仅限于廊道区,而是在整个研究区域都有体现。模拟的地面风速明显增大,热岛强度减弱,风的平流效应导致热岛范围发生偏移。引入廊道后北京城区月平均气温下降了0.14~0.17℃,平均风速及相对湿度分别增加了0.32~0.36 m/s和2.02%~3.37%。表明通风廊道对于改善城市密集区的风热环境,提高气候舒适性是有效的,背景风速越大,通风廊道的缓解效应越明显。气象要素差异的日变化分布显示,通风廊道对白天气象要素的影响要大于夜间。进一步分析显示,通风廊道对局地气象要素的影响主要来自于风速增大的平流效应及下垫面湍流通量改善两方面的贡献。

The construction of ventilation corridors is considered to be an effective measure which can promote urban air quality,alleviate heat island effect and improve urban living environment.Urban ventilation corridor is a kind of energy-saving and ecological method which makes the most efficient use of the natural weather conditions to improve the urban environment.It can make the clean air from the outskirts of the city into the interior of the city through the ventilation path because of the characteristics of air flowing.Meanwhile,it can make the exhaust-gas and waste-heat to be dilutedly discharged with the wind.Thus,the purpose of purifying urban air and improving urban environment can be achieved.Basing on the data such as surface type with high-resolution,the urban building and the urban ventilated corridor planning in Beijing,the coupled of urban canopy model with the mesoscale meteorological model WRF(Weather Research and Forecasting) is used in this paper.In addition,the sensitivity simulation tests with high-resolution of 200 m was conducted in January and July of 2019 respectively.And the WRF model is verified by applying of the observational data from automatic meteorological station network.Some results can be obtained through the simulation tests.After the urban ventilation corridors have been constructed,the difference of meteorological elements will be not limited to the corridor area,but the whole area studied.The surface wind speed will increase significantly,the intensity of urban heat island will weaken,and the range of the urban heat island will shift caused by the advection effect of wind.After the corridor has been finished,the average monthly temperature in Beijing will decrease by0.14-0.17℃,the average wind speed and the relative humidity will increase by 0.32-0.36 m/s and 2.02%-3.37% respectively.Through the analysis of the numerical simulation test results,the following conclusions can be drawn.The ventilation corridor is effective in improving the thermal environment and increasing the climate comfort in the city-intensive areas.And the greater the wind velocity is,the more obvious the mitigation effect of the ventilation corridor is.The diurnal variation distribution of the meteorological field shows that the influence of ventilation corridors on meteorological field is greater in the daytime than in the night.Further analysis indicates that the influence of ventilation corridors on local meteorological elements is mainly due to the advection effect caused by the increase of wind speed and the improvement of the quantity of the turbulence flux on underlying surface.