The Study Of Urban Heat Island Effects Using Multi-source Remotely Sensed Data

With the increasing of urban environment issuses, scientists have paid more attention on Urban Heat Island(UHI)research. Therefore, how to monitor, analyze, and evaluate UHI effect quantitatively has become one of the prime impormant research aomong current urban climate and environment research. With the development of remote sesing technology, it has become an important approach to UHI researches. In this paper, combined with the multi-source remote sensing data(MODIS and Landsat TM/ETM data), the improvement on the method for land surface temperature(LST)retrieval from single thermal remote sensing data have made successfully. Taking Changsha-Zhuzhou-Xiangtan metropolis area as a case study area, the author studied UHI effect at regional and local level. The main conclusions are as follows:(1) Retrieval of LST with multi-source remote Sensing DataIn order to get the atmospheric parameter of LST retrieval by single channel thermal infrared data, this paper calculated firstly the distribution of atmospheric water vapor content at pixel level using MODIS near infrared data. Then, LST is retrieved by using the thermal infrared band of Landsat TM/ETM+ and atmospheric water vapor content based on generalized single-channel method. The exploited approach was applied to Changsha and Wuhan city. The results show that the combination of multi-source remote sensing data is effective for retrieving LST and estimates reasonably land surface temperature. The most advantage of this approach is to obtain the atmospheric parameter of LST retrieval rapidly and accurately.(2) UHI study of Changsha-Zhuzhou-Xiangtan area at regional levelLST in Changsha-Zhuzhou-Xiangtan area was retrieved by split window algorithm based on multi-season MODIS data. The seasonal characteristics of UHI and its factors were analyzed quantitatively in Changsha-Zhuzhou-Xiangtan area. The result indicated that there was a clear UHI effect in the spring and summer, but this did not happen in the winter and autumn; land cover affected urban heat island clearly, the distribution of UHI presented a obvious negative correlation with the vegetation in spring, summer and autumn in Changsha-Zhuzhou-Xiangtan area, especially in summer, the correlation coefficient R~2 between LST and NDVI has reached 0.8193 in summer, that is, the higher vegetation cover, the less urban heat island was. Therefore, the vegetation has an important effect on alleviating urban heat island.(3) UHI study of Changsha city at local levelFirstly, LST was retrieved by single channel algorithm based on multi-temporal Landsat TM/ETM+ data. Then NDVI, MNDWI, NDBI and NDBaI indices were calculated to classify the land use/cover types by decision tree method in the study region. Finally, the spatial and temporal changes of UHI and the relationship between UHI and land use/cover change in Changsha city was studied quantitatively. The results show that with the expansion of built-up area in Changsha city, the extent of UHI was increasing. The change of land use/cover types would change the spatial distribution of LST. Bulit-up area and bare land were the maijor contribution factors of UHI intension, while water body and froest land has a good function of reducing LST. The regression analysis shows that there were significant correlations between LST and four indices, and there was a great difference of LST in different land use/cover types.