The Analysis Of Changes In Temperature And Built-up Areas In Urbanization In The Yangtze River Delta

In order to assess the impacts of urbanization on temperature variation and learn about the climatic effects of urbanization on the Yangtze River Delta region, China, based about that DMSP/OLS data have been widely used abroad to estimate the lighting of urban population, consumption, gross domestic product (GDP), analysis of the impact of urban expansion area of land resources, and analysis of urban heat island city monitoring, we analyzed the temperature data after homogenization adjustment from national weather stations in this paper A linear trend estimation method was used to conduct a preliminary analysis of the temperature variation in the region for the past two decades. Moreover, non-radiometric calibration nighttime lights data from the U.S. Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) was used to quantitatively describe the urbanization spatial evolution characteristics. Based on the research about the spatial expansion of urban built-up areas, some cities with rapid process of urban built-up areas expansion in YRD were selected and studied. To further verify the impact of urban built-up areas expansion on temperatures, land surface temperature (LST) data of these cities from MODIS was used to describe the annual evolution process of urban heat island in the whole year and four seasons. The main conclusions are as follows.(1) The Yangtze River Delta region experienced a rapid expansion process of urban land use type during1992-2007, and urban agglomeration merged, while there was great difference about the expansion. Shanghai had the highest level of urbanization, and the level of urbanization gradually decreased to the periphery of the region. The urban expansion was slower during1992-2000, while significantly faster during2000-2007. During1992-2007, urban land expansion mode of the sixteen cities in the Yangtze River Delta can be roughly divided into four categories:from "urban" to "urban and spots", from "urban" to "urban","urban and spots" to "form a huge" and from "urban and spots" to "simultaneous development of both".(2) The urbanization about the urban built-up areas in Yangtze River Delta region, to some extent, affected the temperature changes of the cities. In Nearly two decades (1989-2007), both the annual average temperature and season average temperature in the entire Yangtze River Delta region showed a general uptrend. The annual average temperature linear warming rate, the spring warming rate and the winter warming rate were0.84℃/10a,1.13℃/10a and0.47℃/10a, respectively.(3) The annual and seasonal average temperature linear warming rate of the16cities in the Yangtze River Delta were consistent with that of the Yangtze River Delta region in years1989-2007. The annual average temperature linear warming rates of16cities were between0.64～0.98/10a in years1989-2007, showing spatially inhomogeneousity; the rates between1989and1999years had large fluctuations, while showing small fluctuations between year2000and2007. The fluctuations presented non-uniform spatial distribution, which of the nearby city were similar to each other. The values and the fluctuations of seasonal average temperature linear warming rates for the16cities in the Yangtze River Delta presented non-uniform spatial distribution in years1989-2007. The fluctuations in spring, summer and autumn were larger in years1989-1999, while being smaller in years2000-2007. The winter average temperature linear warming rates in years1989-1996were slightly volatile, while being greatly volatile in years1997-2007.(4) Overall annual average temperature linear warming rate between2001and2007years was higher than that between1989and2000years. The spring average temperature warming rates of most cities between1989and2000were higher than those between2001and2007years, which were just opposite in spring and summer. The annual average temperature difference between the1989-2000period and the2001-2007period in the Yangtze River Delta region was0.79℃. Among the seasonal average temperature differences, the spring average temperature difference was the maximum (0.98℃) while the winter difference ranked minimum(0.58℃).(5) The variation of annual and seasonal average temperatures in the1992-2007and2000-2007periods showed its relation to the change in urban built-up areas. In the1989-2007periods, the main impact of urban built-up areas expansion in the Yangtze River Delta region was reflected by the spring average temperature increase. Meanwhile, the linear warming spring average temperature throughout the Yangtze River Delta region was1.13℃/10a. MODIS ground temperature data of the cities were used to describe the yearly evolution process of heat island of years and seasons from2001to2007. We can know that the heat island zone and transition zone of Jiangsu and Shanghai showed an increasing trend of fluctuation year by year; furthermore, the temperature in the lower zone was gradually decreasing, corresponding to the trend of urban built-up area expansion.