Seoul city government is now adopting policies to mitigate the urban heat island by means of reducing the anthropogenic heat, reforming the artificial surface covers to diminish the sensible heat flux to latent heat flux ratio, and improving the urban structure to facilitate cold air passage. Specifically, the impacts of the restoration of inner-city stream called Cheonggye and urban development in the north-west region of Seoul were investigated in relation to the nature-friendly urban planning and development. The mitigation effects on urban heat island were studied by observing the spatiotemporal variations in temperature and humidity at the development sites. Although very helpful to quantifying the impacts on local meteorology, it was difficult to maintain the monitoring network for along period. Numerical models are very useful to the complement of such shortcomings in direct observation.

In this study, the spatial and temporal distribution of temperature and wind flow in the urban street canyons was analyzed to assess the impact on local meteorology due to the land use changes during the urban development. For the first step, five automatic weather stations (AWSs) around Eunpyeong new town area, which is under development, were selected to analyze the spatial and temporal distribution patterns of air temperature depending on the weather conditions from 1998 to 2008. Additionally, nine temperature loggers were installed inside the development area to investigate the fine structures of spatiotemporal changes of air temperature from March 2007 to February 2008. Then, a computational fluid dynamics (CFD) model was employed to simulate the changes in local wind speed and flow patterns due to the development in the north-west region in Seoul. The urban development, which started in February 2004 and scheduled to finish in October 2011, includes the changes in land use and terrain height over 3.4 square km. Guidance on urban planning in regard to the wind flow has been suggested based on the impacts of the development on air flow in street canyons and surrounding areas.