study on the effect of urban rivers on micro climate in surrounding region

(1)当风吹过河流时，内部边界层在河道中发展，风的下部在水面和洪泛平原上冷却。在我们的观测中，这种冷却效应达到30米高。这种冷风的侵入导致城市地区气温下降。(2)白天，大气和洪泛平原之间的热交换达到最大，海风吹的时候比陆风吹的时候热交换更大。此外，热量交换与城市河流周围地区的温度下降有关。(3)研究了城市河流漫滩和水面的热量收支。洪泛区以潜热为主，水面以热储存为主。这是河流冷却作用的主要过程。(4)在静水压力假设下，模拟了大气内边界层的流动。数值模拟预测风速，温度和湿度分布。预测结果与实测数据吻合较好。(5)感潮河流中，水体的运动对热量收支有很大的影响。由于潮汐的影响，温度在波动。据观察，潮汐河流的水温比湖泊更均匀。地表水和底层水的温差只有1.5摄氏度。这种微小的温差增加了河流的冷却效果。(6)提出了一个预测城市水面和绿地降温效果的数值模型。利用该模型进行的模拟可以对城市水面和绿地的布局提供建议。

(1) When wind blows across rivers, internal boundary layrs develop in channels and the lower portion of the wind is cooled on water surfaces and flood plains. This cooling effect reaches 30 m high in our observation. The intrusion of this cooled wind results in the drop of temperature in urban areas.(2) Heat exchange between the atmosphere and flood plains is maximized in the daytime, and it is larger when sea wind blows than land wind does. In addition, the heat exchange is correlated to the drop of temperature in urban areas around rivers.(3) Heat budget on flood plains and water surfaces in urban rivers is studied. Latent heat is dominant in flood plains, while heat storage is dominant in water surfaces. These are the main processes of the cooling effect of rivers.(4) Under the assumption of hydrostatic pressure, the atmospheric flow in the internal boundary layr is modeled. Numerical simulations are performed to predict wind velocities, temperature and humidity distribution. The predicted results agree well with the observed data.(5) In tidal rivers, heat budget is strongly effected by the movement of water body. The temperature is oscillating due to tides. It is observed that water temperature in tidal rivers is more uniform than lakes. The temperature difference between surface water and bottom water is as small as 1.5 degrees Celsius. This small difference of temperature increases the cooling effect of rivers.(6) A numerical model to predict the cooling effect of water surfaces and greenbelts in urban areas is proposed. The simulation using this model can suggest the arrangement of water surfaces and greenbelts in urban areas.