Spatial-temporal Analysis of urban heat island of Mashhad city according to the city expansion and land use/ cover changes

The aim of this study was to evaluate changes in temperature and expansion of the urban heat island, in the city of Mashhad in recent decades is the result of the expansion of the city. In this study using multi-temporal Landsat images (TM 1987, ETM + 2000 and OLI / TIRS 2014) and the application of the threshold NDVI and Planck's law for images TM and ETM +and split-windows algorithm for images OLI / TIRS, land surface temperature were extracted. Then land surface temperature was normalized and were examined its relationship with fraction vegetation cover and land use /cover changes. The results showed that about 2,500 hectares of agricultural land and green space change to built-up land use that almost equal to the increase in area of very hot temperature class. This shows that the decrease in vegetation cover is the most important factor in the development of heat islands in Mashhad. With the loss of vegetation cover in and around the city, very cool temperature class has been replaced by normal temperature class. Also by manipulating the surrounding of city, their temperature is increased and change to the hot and very hot temperature classes. Results of this research showed that the use of multi-temporal satellite data and combine traditional methods of retrieval UHI (spatial-temporal analysis of UHI associated with urban growth, land use/cover changes and fractional vegetation cover) can be provide comprehensive view of the formation and expansion of urban heat islands.