Evaluating the effects of urban heat island resulting from local pollutions on climate parameters (A case study in Mashhad)

Urban expansion and pollution growth and development of major industrial activities in metropolitan areas have impacted the local climates of the cities. Transforming large cities into heat islands is one of the most important results of this microclimate change. In this research variations of some important climate factors (precipitation, temperature, relative humidity and percentage of cloudiness) have been reviewed in order to study the microclimate changes. Mashhad city was chosen to study as a metropolitan area. Study was done by comparing the climate parameters of Mashhad city with the neighboring regions which were placed in the same climate classification. According to the effective role of precipitation in urban weather modification and decreasing the pollutions, precipitation variation becomes more important. The results of this study imply that precipitation variation follows the change of temperature trend. A significant correlation between temperature and precipitation changes shows the effect of heat island on urban climate parameters. The urban heat island phenomenon increases the warm seasons precipitation while has decreasing effect on cold seasons one.