Change-point Detection of Annual Temperature by using the Grey Relational System for Analyzing Mashhad's Heat Island

Heat island forming in big cities is one of the modern environmental hazards due to the uncontrolled urban development. The global temperature is increasing slowly from the 19th century. The heat islands of big cities have two components: global warming and urban development (population growth, urban development, land use changes and etc.). The purpose of this paper is to study these components in Mashhad city with 127 years of long-term temperature data. Change point of Mashhad annual temperatures was achieved with Grey relational patternin 1980. Mean annual temperatures before and after 1980 are respectively 13.5 and 15.1 by difference 1.6 which shows increasing trend. This increasing is about 3 degree end to 2013. The linear trend line equation for Mashhad after change-point has coefficient of determination and the trend test statistic is 0.0993 (show trend), While this statistic before change point is 0.0035 (show no trend). Moreover annual temperatures of three stations: Kortian, Bar and Olang-Asadi which located outside of Mashhad and adjacent to it analyzed for comparing heat island too. The grey relational pattern showed that change points of the three stations are between the years of 1976 to 1980.This analysis showed that the increasing in annual temperature of Mashhad and suburb are nearly at the same time.The slop of Mashhad's trend line compared with Olang-Asadi. The reason of choosing Olang-Asadi is that its elevation similar with Mashhad and it is being adjacent to Mashhad.The final result showed that the heat island in Mashhad began from 1981 with a slope of 0.093. The annual difference temperature of Mashhad is degree from 1981 to 2013. The relation of temperature difference and population growth provided to a standardized pattern that confirms the existence of heat islands.