study of mitigation of heat environment by a large restoration of inner-city river -A case of Cheong-Gye Stream in Seoul-

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The authors observed the parameters of the physiological thermal indicator SET* (air temperature, relative humidity, wind speed, sky radiation, surface temperature) at five observation points within 100m from the restored zone and the stream in mid August in 2003-2006.They observed the surface temperature with a thermography camera, and upward sensible heat flux using a scintillometer. They further utilized the time series analysis of air pollutants observed by Seoul Metropolitan Government. Movement of cool air mass along the restored river was numerically simulated by applying a CFD model, taking into account swirls developing at road crossingsBased on observation with ultra-sonic anemometers in 2006, it was clarified that with the sea breeze along the Cheong-Gye Stream, cool air mass is able to spread approximately 80m from the restored zone.In the total monitoring in 2007, the objective was to prove the meteorological mechanism of the processes that convey the cool air from the river to urbanized area. The authors set up poles at the middle of the river and at the southern and northern riversides, where they measured air temperature and relative humidity.As for the cooling effects by water, air temperature gets lower and water vapor pressure gets higher at closer distances to the surface of the river. At the southern riversides, air temperature was relatively lower than at the northern riverside.On the other hand, at the northern riverside, air temperature near the surface is often higher during daytime. As the cause, it was considered that the surface of northern riverside was concrete pavement though southern riverside was vegetational pavement. These results therefore indicate that a layer of cool air was generated in the southern riverside.