杭州市城郊生态带对城市气象特征的影响

The impact of Hangzhou suburb ecological zone on urban meteorological characteristics

城市生态带的局地气候特征及其影响是生态城市建设的重要内容.利用南京大学区域边界层模式(Regional Boundary Layer Model,RBLM),对杭州市城湖控制区2014年和2015年12d个例进行了两组数值模拟研究.在不同背景风下,分析杭州市城郊生态带对下游城区气象特征的影响.研究表明:城郊生态带山区表面是低温、高湿和大风速区域,当背景风为西北风时,山区对下游城区的温度、相对湿度和风速的影响范围分别为0.25km,0.75km和0.5km;在西南风下,山区对下游城区的温度、相对湿度和风速的影响更远,降温、增湿、风速增大范围分别达到3.5km,3km和2.25km,这主要是因为山区是西南-东北走向的原因.2014年4月15日城湖控制区有明显的山谷风环流,当日背景风风速较小,观测到这一天背景风向为偏东风,且风向没有明显转向,谷风出现时间为11:00-18:00,山风出现时间为19:00-次日07:00,18:00-19:00为谷风和山风的转换期,山谷风垂直厚度大约为300m.

Ecological zone can improve urban resilience,which is critical for sustained development of cities.To study the impact of Hangzhou suburb ecological zone on meteorological features under different background wind fields,a sensitivity simulation and a control experiment on 12 days from 2014 to 2015 were conducted by using Regional Boundary Layer Model（RBLM）developed by Nanjing University.In the sensitivity simulation,the land covers for mountain area were replaced by grassland and the mountain terrain elevation was removed.Results indicated that,when the background wind was southwest,the suburb ecological zone would cause cooling and humidifying effect on the downwind city,and the effect distance could extend to 3.5 km and 3 km,respectively.As well,the wind speedover the mountain was bigger than the surrounding area,and the wind speed in the downwind would be increased by the influence of the mountain within 2.25 km.When the background wind was northwest,the mountain would also cause cooling and humidifying effect on the downwind city,and the effect distance could extend to 0.25 km and 0.75 km,respectively.Meanwhile,the wind speed over the mountain was bigger than the surrounding area,and the wind speed in the downwind would be increased by the influence of the mountain within 0.5 km,which was shorter than the distance in southwest.The distance for cooling and humidifying effect in northwest was shorter than the distance in southwest,which was very likely that the mountain was going southwest to northeast.It was found that the mountain-valley circulation occurred in April 5,2014 and the wind speed in the background was very small.The wind direction of the day was easterly and the wind direction did not change significantly.The valley breeze prevailed at local time from 11：00 to 18：00 and the mountain breeze prevailed at local time from 19：00 to 07：00（the next day）.The valley breeze turned into mountain breeze during 18：00 to 19：00.