Mostafa Tahani Yazdly; Sayyed Mohammad Hosseini; Farahnaz Khoramabadi; Mohammad Mohtaram
Abstract
IntroductionIn recent decades, along with the physical development of cities and population increase due to immigration, Heat islands, which are mainly the result of human made activities, have gained significant importance. So that; The reduction of vegetation cover, the high consumption of fossil fuels, ...
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IntroductionIn recent decades, along with the physical development of cities and population increase due to immigration, Heat islands, which are mainly the result of human made activities, have gained significant importance. So that; The reduction of vegetation cover, the high consumption of fossil fuels, the emission of greenhouse gases and the use of inappropriate materials in urban construction have created the microclimate of a heat island above the metropolis of the world. Finally, it causes an increase in the land surface temperature, atmospheric stability, persistence and stabilization of pollutants and an increase in respiratory diseases. Today, by using remote sensing methods and using digital satellite images, it is possible to examine the land surface temperature with high accuracy and in a short period using MODIS sensor and Terra satellite images. Therefore, the main objective of the current research is to analyze the temporal and spatial variations of heat islands of Isfahan using the principal component analysis method. With this technique, it is possible to identify the seasons and months when increased the land surface temperature and the heat island.Materials and methodsIn this regard, the present research considers analyzing the temporal and spatial variations of this phenomenon in Isfahan during period of 20 years (from 2000 to 2020 AD). To achieve this purpose, was used the land surface temperature (LST) data extracted by MODIS sensor and Terra satellite. These data are available for the whole world with a time resolution of 8 days and a spatial resolution of 1x1 km in a sinusoidal grid with dimensions of 1200x1200 km. Therefore, for Isfahan, 913 images extracted from the MODIS sensor. Then, with the principal component analysis (PCA) method, the seasons and months that have the most influence on the occurrence of heat islands identified and in order to analyze the trend of this phenomenon, were used the Mann-Kendall test and the Kolmogorov-Smirnov test.Results and discussionThe findings of the research indicate that, the land surface temperature in the last 20 years in Isfahan had an increasing trend with rate of 4%. Although this trend in the population and urban centers has been completely different from the surrounding areas of Isfahan. In terms of spatial distribution, the highest occurrence of heat island in the eastern and southeastern parts (including Hassan Abad and Jolgeh) due to its proximity to the hot deserts of Kavir-Lout, proximity to Sepiddasht, Varzaneh, Shahrak Ramsheh industrial towns and changing in the land use of agricultural to industrial and residential has been registered. also in the North-West region (including Mahmudabad and Isfahan city) due to the increase in man-made heating caused by the increase in the consumption of fossil fuels, the growth of residential, industrial and commercial units, temperature has risen. In addition, the results showed that the intensity of the heat island in winter is more than in summer, and the most intense time of its occurrence recorded in January and the least in November.ConclusionIsfahan is integrally affect by global climate conditions, but depending on the geographical location of each part of this province, the land surface temperature and the occurrence of heat islands are different, so that, eastern and central parts, adjacent to Kavir-Lout and close to industrial towns, have an increasing trend. Moreover, the southern parts have a decreasing rate of temperature and heat islands due to less urban population, larger agricultural lands and more vegetation. The increase in urbanization, migration, and the increase in fossil fuel consumption, the decrease in vegetation, the aggravation of drought, and the change of land use have a fundamental role in increasing the occurrence of this phenomenon.
Faezeh Alizadeh; Samereh Falahatkar; Afsaneh Afzali
Abstract
Introduction: In the past three decades, dust has become a global concern for global societies. Due to Iran’s location in an arid region, it is severely influenced by this phenomenon. This phenomenon usually carries a huge mass of particle matters that can be clearly detected by satellite images. ...
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Introduction: In the past three decades, dust has become a global concern for global societies. Due to Iran’s location in an arid region, it is severely influenced by this phenomenon. This phenomenon usually carries a huge mass of particle matters that can be clearly detected by satellite images. The purpose of the present study was to investigate the time series changes of absorbing aerosol index using satellite images at a national scale. Material and methods: In order to study the trend of monthly changes in dust phenomena in Iran, the data of Absorbing Aerosol Index (AAI) of SCIAMACHY sensor, which was taken during 2002-2012, and GOME-2 during 2007-2017 were evaluated using non-parametric Man-Kendall test. The variation rates for different sectors were estimated using Theil-Sen slope. Results and discussion: The results showed an increasing trend in the western, southwest, center, and northeastern regions of Iran during 10 years based on Z statistics SCIAMCHY. The results also showed an increasing trend of GOME-2 Aerosol Absorbing Index in some parts of Markazi, Isfahan, Hamedan, and Fars provinces, and Lake Urmia and completely in Chaharmahal & Bakhtiari, and Kohgilouyeh & Boyerahmad provinces. Also, Golestan and Semnan provinces didn’t show any specific trends. According to P statistic, the trend of change in most regions of Iran was significant. Based on the results of Theil-Sen slope, the western, southern and central regions of Iran showed the most changes in atmospheric aerosol concentration. Conclusion: The high compatibility between the present results and the reports of meteorological stations showed the high capability of satellite data, which we used in this study, in order to identify the areas that encountered to dust phenomenon at a national scale. Accordingly, it is recommended that this technology be used for the macro-management of the natural resources in Iran.
Nader Barani; Ayatollah Karami
Abstract
Introduction: Climate change is exacerbated by natural factors such as aridity and drought or human activities. Identifying and revealing the changes in each factor and what cause them is considered the first step in the study of the process of climatic elements. The trend analysis might be due to natural ...
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Introduction: Climate change is exacerbated by natural factors such as aridity and drought or human activities. Identifying and revealing the changes in each factor and what cause them is considered the first step in the study of the process of climatic elements. The trend analysis might be due to natural changes, such as drought or human activities e.g. increasing greenhouse gas emissions. However the trend in the climatic factors of each area might be normal, its continuity in the coming years may have more significant effects on the economic and social components. Climate change in a region can be detected by investigating the changes in the average rainfall and temperature. This research was carried out in order to identify the time variation of climate parameters (temperature and precipitation) in decuple agroecology regions of Iran. Material and methods: For this study, data on temperature and precipitation variables were extracted annually from all provinces of the country during the period 1985-2015 from the Meteorological Organization of Iran. Since the distribution of a number of climatic parameters such as temperature and precipitation climatic series is not normal, the non-parametric Mann-Kendall method was used for analyzing their distribution. To determine the level of significance in variables and to determine the trend of annual changes, Mann-Kendall test was used with XLSTAT extension software. Results and discussion: The results showed that temperature variable in Central, Northwest, Caspian Coastal Plain, Khuzestan, Central Zagros, Arid Southern, Khorasan, Southern Coastal Plain Arid Central zones had an upward trend and no trend in Southern Zagros zone. Precipitation variable was decreasing in Khuzestan and Khorasan. Precipitation variables in Central, Northwest, Caspian Coastal Plain, Central Zagros, Arid South, Arid Southern, Arid Central and Central Zagros zones were not trendy. The increase in temperature will lead to a significant increase in the annual evapotranspiration rate (which is already higher than annual precipitation in most parts of Iran). The Intergovernmental Panel on Climate Change regards this issue as a serious challenge to arid and low rainfall regions, including Iran, and as a consequence, predicts that the production of strategic products in Iran will decrease compared to the current level of production. The vastness of Iran, along with its geographic location, and the location of heights, prevent the region from fully absorbing the atmospheric humidity. The existence of such conditions causes an inhomogeneity in the amount and pattern of precipitation that has crystallized in the temporal and spatial behavior of the climatic factors. This could be a warning to a country like Iran that is heavily in need of water, and will face water scarcity in the future. Conclusion: The results of the research showed that the mean annual temperature significantly increased in all stations. However, there is no particular trend for the rainfall situation Due to the arid and semi-arid climate of Iran; Iran is one of the countries facing water shortage. Obviously, this shortage will greatly affect agricultural production.
