Modeling the spatial distribution of urban population density and its evolution in Hangzhou

The evolution of urban morphology in the process of urban growth is one of the theoretical frontier issues, while the spatial-temoral structure of the distribution of urban populationdensity is one of the important contents of urban growth. Combining with data of the previous censuses(the second census in 1964, the third one in 1982 and the fourth one in 1990), the author usesdata of the Fifth Census of Hangzhou to study the models of spatial distributionof population density and its evolution in Hangzhou for more than 30 years systematically. First of all, the author transforms data of population census into spatial data by using the map of Hangzhou, and extracts data of urban population density distribution of different years.Then seven kinds of models are tested, including the linear one, the exponential one, the logarithmic one, the power one, the lognormalone, the power-exponential one and the second degree exponentialone. With a viewpoint of the whole tendency, the power-exponential model, as an amended form of the negative exponential model, can describe spatial distribution of urban population density of Hangzhou well. The parameter σreflects the tendency of changes of information entropy of urban geographic system. The parameter σfluctuates, increases and approaches 1, indicating that the power-exponential distribution of urban population density evolves into the ideal Clark (negative exponential) one with the lapse of time. The analysis of urban growth and its spatial dynamics shows that the spatial complexity and the utility of Hangzhou's function unit increase, and that urban spatialstructure tends to be in a new order with the increase of urban ability as a self-organization and the development of suburbanization. As a result of regression, we can't get a model like that of Newling, and there isn't any tidal wave of expansion in the development of spatial distribution of population density in Hangzhou within the past several decades, so it is easy to draw a conclusion that there is a large gap between Chinese cities and western ones in multi-nucleus morphologyand process of suburbanization.