بررسی تغییرات لکه‌های داغ شهر تهران و اقمار براساس نوع کاربری اراضی و نقش آن در مخاطرات حرارتی شهری

شهرنشینی و فعالیت‌های بشری بر روی اقلیم شهرها و به وضوح بر روی دمای هوای نزدیک به سطح اثر مهمی دارد. در تهران و اقمار آن عواملی از قبیل منطقه اقلیمی، فصل، زمان روز و رژیم‌های باد، توپوگرافی،وسعت محیط شهری،تراکم جمعیت،فعالیت ساکنین ساختار پوشش گیاهی و فرم فیزیکی شهری در شکل‌گیری جزایر حرارتی شهری نقش اساسی دارند. جزیره حرارتی بعنوان یکی از مخاطرات محیطی، گروههای آسیب پذیر را درمعرض خطر قرار می دهد. هدف از این پژوهش بررسی تاثیر نوع کاربری اراضی و پوشش زمین بر جزیره حرارتی تهران و اقمار آن می‌باشد. به منظور بررسی فضایی یاخته‌های بدست آمده و استخراج جزیره حرارتی، از تحلیل نقشه‌های لکه‌های داغ و تولید نقشه‌های کاربری اراضی با 7 کلاس و رابطه آن‌ها باهم برای سال‌های 2015-2001 استفاده شد. نتایج نشان داد تهران با وجود داشتن بیشترین مساحت مناطق مصنوع، در مقایسه با شهرستان‌های ری، رباط‌کریم و اسلامشهر از جزایر حرارتی کوچکتر و تعداد لکه‌های داغ کمتری برخوردار است. از سوی دیگر پراکندگی و وسعت سطوح سرسبز در مقایسه با ایجاد سطوح جنگلی و درختکاری شده به صورت محدود در یک مکان، نقش موثرتری در کاهش جزیره حرارتی دارد.

The assessment of hot spots changes in Tehran and satellite based on land use and its role in urban heat hazards

Evaluation of hot spots changes in Tehran city and satellite based on land use and its role in urban heat hazardsExpanded abstractProblem statement: Urbanization and human activities affect the urban climate and clearly affect the air temperature close to the surface. In Tehran and its satellite, factors such as climatic region, season, time of day and wind regimes, topography, urban environments, population density, residentschr('39') activity, vegetation structure and urban physical form play an important role in the formation of urban heat islands. The purpose of this research is to determine the type of spatial distribution of heat islands of Tehran metropolis and satellite cities using land use and land cover. Replacing natural land cover with impervious surfaces due to urban development has negative environmental, social and economic impacts, in addition to beneficial aspects. Most of the albedo belong to the built areas and the bare land and the smallest of the Albedo belong to the aquatic areas and vegetation. In this research, the hypothesis is whether the suburbs may have higher temperatures than urban areas depending on the type of land use? In fact, it is examined the spatial distribution of the heat island of Tehran and its satellites, in which the use of land and land cover are analyzed as a factor contributing to the creation, intensification or reduction of the thermal island.Methodology: Extraction and preparation of imagery data through the Landsat 7 Satellite ETM + sensor over the years 20012015 and selection of June as the hottest month of the study area. These images were extracted from Route 164 and Row 35 of the USGS. An assessment was carried out through the accuracy of ground surface temperature data by Landsat satellite images and obtained temperatures from the weather stations in the area based on the Taylor diagram. In order to investigate the spatial structure of the cells obtained in each map, each containing surface temperature and heat island extraction, it used the methods of world spatial autocorrelation (high and low clustering, spatial correlation) and local (Cluster and Outlier analysis, hot spot analysis). The high and low clustering statistics show how the concentration of high or low values ​​in the region. In the next step, the results of analysis of Anselin Local Moran and hot spots were compared in map format. Hot spots were analyzed in all studied regions and in all 7 cities. The area of ​​hot spots was investigated over the course of 15 years and the results were presented in table and diagram form.Land use was surveyed for every 7 county. In the last section were studied, the relationship between hot spots in each city and type and land use changes over 15 years.Surface spatial analysis of the surface temperature of the area showed that the cells follow a cluster pattern and their trend towards clustering. Any kind of land cover and land use will create special features in a place that can be increased or decreased with a specific microclimate.Explaining and results: After selecting the years 2001, 2005, 2010, and 2015 as the sample and survey of the temperature of each land use in that year, it was determined that artifact, pasture, bare lands, forest, aquatic areas, agriculture and green spaces were respectively have the highest to the lowest temperature in the area. On the other hand, in the area of heat island in a region are Rabat Karim, Ray, Islamshahr, Tehran, Shahriar, Karaj and Shemiranat, respectively.In spite of the reduction of aquatic areas and even bare lands, because of the large impact of green space or agricultural land was reduced the extent of heat islands during the statistical period, and on the contrary, the reduction of green space and agricultural land in places where even their forest areas have grown, has increased the levels of heat islands. This suggests that the dispersion and extent of green spaces has a more effective role in reducing the heat island compared with the creation of limited forest and planted surfaces in one place. Hence, in Tehran despite the significant growth of artifacts, due to the increasing growth of green space, the heat islands has been reduced compare with the Ray, Robatkarim and Islamshahr cities, which are exactly on its suburbs. Keywords: Heat Island, hot spots, land use, Tehran, satellite cities.