آشکارسازی تأثیر تغییرات کاربری اراضی بر توزیع فضایی گردوغبار در شمال غرب ایران مرکزی

Dust storm is a natural event that forms in parts of the world that have arid and semi-arid areas. This phenomenon is one of the climatic disasters and its occurrence has many adverse effects. Dust storm dramatically reduces air quality and endangers human health. The main objective of this study was to investigate the relationship between the land use change variations and spatial variations of the MODIS optical depth index in northwestern central Iran. The study area includes the provinces of Tehran, Alborz, Qom, Qazvin, Markazi province. In this research, data has been used. The first batch of data is data from Landsat satellite imagery that was used to derive a land use map for the period 2000 and 2016. The second group of data used is the data for the MODIS Aqua and Terra Optical Depth Sensor, which has been obtained for the last two years as an average of 3 years. These data are powered by a spatial resolution of 10x10 km, and are used monthly. To characterize land cover variations, the satellite-controlled satellite sorting method has been used with maximum similarity algorithm. Two precision measurement indicators including general health index and kappa coefficient have been used for classification classification validation. By using the supervised classification method of maximum similarity, 9 land use categories such as field lands, grasslands, gardens, agriculture, water zones, urban areas, shore lake, desert, forest, has been identified which is the most commonly used for the rangelands, which in each two years More than 50% of the area is covered by the area, the least is forest use. Also, 35% of land and 35% of meadows have fallen by 11% compared to 2000. In 2000, rangelands and then agriculture, respectively, with 56% and 24% of the area of the study area, had the most applications, and the lowest level of use was related to the water zones, which accounted for 0.008 of the area of the study area. While In 2016, two rangelands and then agriculture, respectively, with 50% and 27% of the area of the study area, have the most applications, and forest areas as users that have the lowest area of the study area are distributed in a sporadic way In the northwest of the region. The results of classification validation showed that the classification accuracy based on the Kappa index for the two years 2000 and 2016 was 85% and 86%, respectively. Also, the results indicate that in 2000 the average spatial value of AOD index in the surveyed area was 0.65, which means almost average dust. In 2016, the average spatial value of the AOD indicator in the surveyed area was 72%, indicating an increase in dust accumulation in the entire surveyed area. In 2000, the eastern regions of the region, which are mostly based on salvation and desert coatings, have the highest AOD  value of 0.88 to 0.89. The northern and southern regions of the surveyed area had the lowest AOD index this year, which was less than 0.5. In 2016, the spatial extent of areas with high values of the optical depth index has increased, and the numerical magnitude of this index has increased. In 2016, it reached 0.8 to 0.92 in the eastern regions, indicating an increase in dust concentration in this part of the surveyed area than in 2000. This year, the maximum dust was found in the eastern part of the country and is based on saline and desert areas and the most desert dust fields. Agricultural landscapes, quality rangelands and forests are the lowest in the AODs for each year, which is less than 0.5 and, to a lesser extent, below 0.3. The results of the research also showed that in the area under study, the maximum dust index is for uses such as saline and desert, which during the 17 year period, these two growth surface coatings were equal to 0.95. In spite of the spatial growth of these two users, in addition to the increase in the mean spatial depth of the optical depth of the aerosols (from 0.65 in 2000 to 0.72 in 2016), the spatial extent of the maximum dust level observed in the eastern regions of the year 2016 is about 2.1times more than in 2000, and the AOD index has increased from 0.8 to 0.92 in 2016.