evaluating the effects of uhi on mashhad precipitation

abstract urban expansion, pollution augmentation, and extention of major industrial activities in metropolitan areas impacted local climates of major cities. transforming big cities into heat islands is one of the most prominent results of such a micro-climate change. in this study, variation of precipitation, temperature and some other important climatic parameters including relative humidity, and percentage of cloudiness were reviewed in order to study micro-climate change. the city of mashhad selected for this study, as metropolitan area. the study was performed by comparing the climate parameters of this city with the neighboring regions, which were identified as the same climate category. due to the effective role of rainfall in the urban weather modification and decreasing of pollution, rainfall variation is more important and crucial. the result of this research showed that the rainfall variation followed the temperature trend. a significant correlation between temperature and precipitation change showed the effect of heat island on urban climate parameters. the urban heat island phenomenon increase the hot season rainfall while its effects on cold season rainfall decrease.