Investigation of Vegetation Changes and Its Effect on Surface Temperature Changes (Case study: SarpolzahabCity)
Mostafa Dastorani
1
(
University of hakim sabzevai
)
Keywords: Vegetation, SarpolzahabCity, Landsat, Temperature Changes, remote sensing,
Abstract :
The present research was conducted in order to measure the changes of urban surface heat islands in 3 time periods of 1984, 1998 and 2016 using vegetation indices, urban built-up areas index and land surface temperature index. For this purpose, after determining the boundaries of the area, pre-processing steps including radiometric and atmospheric corrections of images, arrangement of bands, mosaicing and cropping of images based on the study area were carried out on TM and ETM+ Landsat 8 sensor images. Then, NDVI, SAVI and NDBI indexes were applied on the images and through the difference of the images, temporal and spatial monitoring of vegetation cover was started and changes were studied in the form of three types of decrease, increase and no change. Also, to calculate the surface temperature index (LST), thermal bands 10 and 11 of Landsat 8 and band 6 of Landsat 5 were used. The results showed that the two indices NDVI and SAVI had a decreasing trend, but the NDBI index had an increasing trend so that the amount of changes in the first period decreased from 77% to 63% in the SAVI index and in the NDVI index from 45% to 41%, while the NDBI index was 51% in the first period and increased to 57% in the second period. In the same period, the LST index has had a heterogeneous trend, but it seems that the distribution of this index has changed from a widespread state to a patchy state, which means that in the future, heat waves will occur locally in areas of the city that have ventilation problems and It can reduces the quality of life and provides the basis for related diseases. Therefore, built-up urban areas have intensified urban heat islands and the density of vegetation has moderated urban heat islands.
