| The thermal environment change, represented by urban heat island (UHI) effect, is becoming an influential factor on the city environment along with the development of economy and expansion of city. China, as the largest developing country, is experiencing rapid urbanization. Researching on spatial-temporal evolvement of thermal environment in the cities, establishing the protection and improvement plan for high temperature condition in cities have already become critical tasks. Shanghai is a typical international metropolis characterized by high level urbanization and high population density. Researching on the characteristics and its evolvement of UHI in Shanghai will provide technical supports for improving the living environment, the urban planning and land use planning.Based on observed data provided by meteorological stations in Shanghai, the basic characters and evolvement of UHI have been studied, including annual variations, seasonal variations, diurnal variations and spatial distribution. Meanwhile, based on meteorological data provided by NCEP/NCAR, simulated the thermal environment in Shanghai by WRF, and analyzed the impact of the land use evolvement on UHI effect.The analysis based on observed data showed that, the urban-rural temperature gap has been ascending and became significant after 1990s. UHI in Shanghai is significant. During the year of 1987～2004, the UHI occurred in 86.0% days of a year with an average magnitude of 1.17℃, and UHI was most significant in autumn and least significant in summer. The annual mean UHI was evolving through years: low-magnitude UHI had a trend to evolve into mid-magnitude and high-magnitude UHI. The study on spatial character of UHI in 2007 showed that:the UHI in Shanghai was characterized by multi-center. The secondary UHI, represented by Songjiang district, was significant. Especially in summer and autumn, the magnitude of monthly secondary UHI in Songjiang district was higher than overall UHI in Shanghai. The simulation based on WRF model showed that, the central city is the high temperature center in Shanghai; Minghang district, center region in Jiading district, west Pudong district, northeast Songjiang district, and east Qingpu district composed secondary high temperature regions; west Qingpu district, Jinshan district, Fengxian district and Nanhui district composed low temperature regions. Simulations based on underlying surfaces in the year 1990 and 2007 showed that, expansion of urban has significant influence on expansion of high temperature regions. Especially, at night time, changes of underlying surface land use could significantly influence the temperature of surface layer. |
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