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

(1)当风吹过河流时，内边界层在河道中发展，下部风在水面和漫滩上被冷却。在我们的观测中，这种降温效应达到了30米高。这种冷风的入侵导致了城市地区气温的下降。(2)白天大气与洪泛平原之间的热交换最大，海风的热交换比陆风的热交换更大。此外，城市河流周边地区的热量交换与降温密切相关。(3)研究了城市河流泛滥平原和水面的热量收支。泛滥平原以潜热为主，水面以蓄热为主。这些都是河流降温效果的主要过程。(4)在静水压力假设下，模拟了内边界层中的大气流动。对风速、温度和湿度分布进行了数值模拟。预报结果与实测值吻合较好。(5)在感潮河流中，水体运动对热量收支有很大影响。由于潮汐的作用，气温在波动。据观察，感潮河流的水温比湖泊的水温更均匀。地表水和底层水之间的温差只有1.5摄氏度。这种微小的温差增加了河流的降温效果。(6)提出了预测城市水面和绿地降温效果的数值模型。利用该模型进行模拟，可以对城市水域和绿地的布局提出建议。

(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.