Nearly 15 Years In Beijing Urban Area Remote Sensing Monitoring Of Vegetation Cover And Its Thermal Environment

Beijing had rapid economic development in recent decades with huge changes included transformation of industrial structure, adjustment of urban functional structure and function layout and rapid expansion of urban space. Urban underlying surface (e.g. vegetation, impermeable layer) had been changed a lot because of rapid urban construction. Population density, industrial development and more anthropogenic heat emission resulted in the temperature of urban areas generally higher than rural areas. Now, people pay close attention to the ecological environment. As an important factor affecting the urban environment, urban heat island also causes much more attention. The relation between urban heat island and underlying surface has been the key point and the difficult point of academic research.The area within the Sixth Ring Road in Beijing whose urban surface had been changed a lot was chosen to be study areas. In order to provide data sources for the research on temporal and spatial variation of urban heat island, the mono-window algorithm was chosen to retrieve the land surface temperature based on Landsat TM/ETM+ data from 1996 to 2009. Meanwhile, the fuzzy c-means (FCM) method was chosen to extract vegetation coverage by improving the training sample selection method to obtain the end-member sample based on minimum noise transform (MNF), pixel purity index analysis (PPI), and N-dimensional visualization analysis.In addition, the surface parameters retrieved were used to analyze the spatial variation rule of urban heat island and vegetation coverage in Beijing by multi-angle. Land surface temperature profiles that run through northeast to southwest showed that the patterns look like a "hill". And Beijing Railway Station, etc. had appeared warming trend year after year. Using mean-standard deviation method to characterize the distribution of land surface temperature, sub-high temperature areas and high temperature areas were brought into heat island areas. From 1996 to 2005, heat island had expanded with area proportion increased from 34.3% to 36.0%. But it reduced in 2009. Because of heat island areas dispersing, its intensity was from 7.91 in 1996 down to 4.85 in 2005. (declined from 7.91 to 4.85) Vegetation coverage also had great changes from 1996 to 2009. The proportion of low coverage areas grew steadily; medium coverage areas reduced about 513.5km2 from 1996 to 2002, but had a slight increase about 0.26% from 2002 to 2009; high coverage and full coverage areas also declined, but it declined slowly in these recent years.With surface biophysical parameters in 2002, the research on the relationship of vegetation coverage and land surface temperature also carried out in this article. Based on landscape ecology and the way vegetation coverage affected the heat island, the author analyzed deeply according by landscape metrics of vegetation coverage. The results show that NP does not affect LST; CONTAG and LST has a strong negative correlation, when CONTAG value increased by 1, LST declined by 0.19℃; SHEI positively correlated with LST, when SHEI value increased by 0.1, LST declined by 1.3℃.