The Effect of Heat Island Phenomenon on the Local Climate Change in Ahwaz Metropolis

Vertical and horizontal extension of cities and growing trend of industrial activities in them has resulted in wide changes on ground physical properties, released energy, air pollution, temperature and as a result change of local climate in metropolises. Cities are often warmer than their environment. This phenomenon is determined by the difference between cities’ energy and their environment’s energy. Synoptic climatology data of Ahvaz and Dezfool in a 44- year period was surveyed and studied to specify these changes in Ahvaz metropolis. The results showed that annual average minimum temperature of Ahwaz in this period has a total increasing trend of 3.375 °C and (0.077 °C/1yr) yearly, whereas the corresponding parameter was without any changes in Dezfool. Temperature increasing trend in Ahwaz in comparison with Dezfool as indicated by the results which is resulted by the heat island effect in Ahwaz and the lack of development of Dezfool with time. The greatest increase rate of Ahwaz average minimum temperature is 4.14 °C and (0.094 °C/1yr) yearly in Azar monthly in this period and the smallest is 2.07 °C and (0/047 °C/1yr) yearly in Esfand monthly. Usually the extent and extension of the city are known as the most important factors in the severity of heat island effect, and population growth is among the serious factors which cause the increase of its severity and finally result in the change of local climate of metropolis. Population is considered as
parameter which is explanatory of city’s size. In this study, a relationship has been developed for the average intensity of heat island effect in Ahwaz and the logarithm of population.