Analysis On Urban Heat Island Effect Based On The Dynamical Change Of Urban Surface Biophysical Descriptors

The dynamics of urban biophysical descriptors, represented mainly by impervious surface, vegetation and open water, can affect the quality of urban thermal environment (UTE). The study focuses on the quantitative relationship between impervious surface and land surface temperature (LST) because the impervious surface has for many years been recognized as an indicator of the intensity of the UTE and. with the advent of urban sprawl, become a key issue in urban habitat health. The city’s biophysical properties, e. g., impervious surface, vegetation and water, along with LST in1995.2002. and2009were retrieved from the Landsat TM/ETM+images of the corresponding years.(1) The results reveal the dynamics of the urban biophysical properties of the city in the14study years and their quantitative relationship to the UTE change. The main urban area and the impervious surface area greatly increased, while the water area was in decline. The main urban area had an increase from47.10km2in1995to200.75km2in2009,4.26times than before.(2) The rate of change of different land cover type in the urban area was significantly faster than the rate of change in study area. The main urban area increased speed was21.59%between1995and2002, which was1times than the speed between2002and2009. In1995-2002. the main urban areas of Ningbo city had a rapid expansion, the internal parts of the table cover type proportion did not changed significantly for the past14years.(3) The landscape structure of Ningbo city had a great change in the past14years. The cost of the increase in urban impervious surfaces was the considerable reduction of vegetation and open water coverage in the city area. In the research area level, the vegetation patch tended to be broken, and the fragmentation was getting higher, while the impervious surface patch on the contrary trend. In the main urban area level, it appeared contrary trend, which was the main reason of the decrease of heat island effect in this area.(4) The scope of heat island enlarged year by year,and the speed was accelerating, the heat island intensity increased gradually, but the speed slowed up. The main city’s heat island effect has decreased. The heat island mainly distributed in main urban area and Zhenhai District in1995. With the expansion of the city and the development of the surrounding villages and towns’ industry, the scope of heat island enlarged. Land use for industrial warehousing and transportation had strong contribution of heat island effect.(5) In summer the surface temperature of vegetation was2.6℃lower than impervious surface, and the surface temperature of water was4.16℃lower than impervious surface. The study also found that the contribution of impervious surface to LST could exceed that of the vegetation and water.