Study on land surface temperature vegetation cover relationship in urban region:a case in Shenzhen City
Received date: 2005-07-20
Revised date: 2006-03-17
Online published: 2006-06-15
Studies on urban heat islands(UHIs) have traditionally focused on relationship between vegetation fraction(Fv) and land surface temperature(Ts),which are important parameters to describe characters of ecosystem.The objectives of this study are:(1) to derive Ts and analyze their spatial variations using Landsat ETM+ thermal measurements;(2) to apply linear spectral mixture analysis to estimate Fv of urban vegetation abundance;and (3) to investigate the relationship between Ts and Fv derived vegetation abundance(using) conventional statistics and fractal analysis. Based on examination of a Landsat Enhanced Thematic Mapper Plus(ETM+) image of Shenzhen city,acquired on February 23,2004,the landscape classification of Shenzhen is conducted on supervised classification and interactive modification,and the applicability of Fv is investigated as an alternative indicator of vegetation abundance,and Ts is derived from ETM+ thermal infrared(TIR) data.To examine the spatial patterns of Ts and Fv,28 transects(profiles) are drawn across through the center of the city on the image.Since these transects pass over various landscapes with different environmental settings,an inquiry into the fractal characteristics of the profiles using the divider method will help to understand the factors shaping the city's thermal and vegetative landscape and lead to the development of UHIs.The use of fractals for analyzing TIR images will improve our understanding of the thermal behavior of different land cover types. Results demonstrate that Ts possessed a slightly stronger negative correlation with the Fv for all land cover types across the spatial resolution(30 to 960 m).Fractal analysis of image texture shows that the complexity of these images increased initially with pixel aggregation and peaked around 120 m,but decreased with further aggregation.Correlations reached the strongest at a resolution of 120 m,which is believed to be the operational scale of Ts and Fv.The spatial variability of texture in Ts is positively correlated with those in Fv.The interplay between thermal and vegetation dynamics in the context of different land cover types leads to the variations in spectral radiance and texture in Ts.It is suggested that the areal measure of vegetation abundance by unmixed vegetation fraction has a more direct correspondence with the radiative,thermal,and moisture properties of the Earth's surface that determines Ts.
Key words： land surface temperature; vegetation cover; Shenzhen
ZHANG Hsiao-fei, WANG Yang-lin, WU Jian-sheng, LI Wei-feng, LI Zheng-guo . Study on land surface temperature vegetation cover relationship in urban region:a case in Shenzhen City[J]. GEOGRAPHICAL RESEARCH, 2006 , 25(3) : 369 -377 . DOI: 10.11821/yj2006030001
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