Study on thermal environmental distribution in coastal city using ASTER data

The ASTER instrument consists of three subsystems divided by the spectral range: the visible and near infrared (VNIR), the short-wave infrared (SWIR) and the thermal infrared (TIR), with spatial resolutions from 15 m to 90 m. Hence, both urban biophysical descriptors and thermal features can be extracted from them. In this study, the thermal environment of urban in the city of Beihai, Guangxi, which located on the southern coast of China, was analyzed by using the ASTER data acquired on October 7, 2003. The ASTER TIR bands were used to retrieve land surface temperature (LST), and the ASTER VNIR and SWIR bands were used to calculate the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI). Correlation and regression analyses were further conducted to explore the relationship between LST, NDVI, and NDWI in the urban environment. The spatial pattern of LST, NDVI and NDWI demonstrated the spatial variation on the thermal effect in Beihai city. In the urban area, the NDVI and NDWI are low and the LST is high, while in the rural area, the NDVI and NDWI are high and LST is low. City center areas are the hot spots and appear to be 3-4 K higher than the surrounding rural areas, 8 K higher than the sea surface. This fact may be attributed to the intense human being activities and industrial activities. It can be concluded that the integrated method of retrieve LST from ASTER TIR data provide a good way to study the distribution of thermal environment in the city. Using ASTER data to extract the thermal environment information can obtain more precise results and will have a perspective future.