sohrab jamalpour bergai; hassan ahmadi; Aboalfazl Moeini; mohammad faraji
Abstract
Dust storms is one of the most important environmental hazards, especially in arid and semi-arid climates, which causes irreparable damages to the various dimensions of the environment. The aim of this study was to identify dust sources in south-east Ahwaz, using a remote sensing technique and fuzzy ...
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Dust storms is one of the most important environmental hazards, especially in arid and semi-arid climates, which causes irreparable damages to the various dimensions of the environment. The aim of this study was to identify dust sources in south-east Ahwaz, using a remote sensing technique and fuzzy logic. For this purpose, the satellite images of dust events of Ahwaz City were investigated and the wind characteristic of the study area were studied by plotting the storm rose of Ahvaz Synoptic Station. In the next step, the criteria were categorized into two categories: soil moisture, land surface temperature and vegetation constitute the main layers and land use, spatial data of soil, climate, slope and sedimentology were used as constraint layers. The main layers were extracted from Landsat OLI-TIRS satellite images. The Boolean method were used to standardize the constraint layers, and the fuzzy membership functions were used to standardize the main layers. Also, main layers weighting was done using fuzzy analytic hierarchy process. Finally, the dust sources map was obtained by overlapping the layer. To validate the results, 44 ground control point were selected from the study area that showed high accuracy (81.8%) for identified areas. Based on investigating of satellite image and storm rose of Ahvaz Synoptic Station, the south-east of Ahwaz was recognized as dust-generating source and 145162.01 ha of lands are dust generating sources from which 69343/01 ha (47.77%) belongs to destroyed rangelands and 335.99 ha (0.23%) belongs to Canebrake, contains the highest and lowest level of sources of dust production in the study area, respectively.
Nader Jalali; Fazel Iranmanesh; Mohammadhadi Davoodi
Abstract
Generally, satellite images and climatological and environmental data are used simultaneously in dust storm studies. Most of the processing techniques are limited to a few indices such as brightness temperature differences, normalized dust density index, aerosol optical depth, false color composite and ...
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Generally, satellite images and climatological and environmental data are used simultaneously in dust storm studies. Most of the processing techniques are limited to a few indices such as brightness temperature differences, normalized dust density index, aerosol optical depth, false color composite and visual image interpretation. Since the reliability of the above-mentioned methods are varied, so an attempt was made to increase the reliability of automatic spatial image clustering by contributing the expert knowledge via visual image interpretation. Therefore, the required satellite images were collected for a period of 2005 to 2008, in Mesopotamian, Syria and south-western provinces of Iran. For doing this, the MODIS color composite images were decomposed into their ordinary bands and then used for further analysis. In this research, spatial image clustering followed by visual image interpretation (hybrid classification) was applied for accurate mapping of geographical extents of dust storm with different intensities. The sources of dust storms were also identified through visual image interpretation by considering the interpretation criteria such as shapes and patterns. Comparison of the previous results and obtained by this research, indicated critical conditions in terms of dust storm occurrence in the region. Image clustering and hybrid classification led to daily dust persistence over the region and then those images compiled in order to prepare annual total heavy dust persistence map. The result of using brightness temperature difference method verified similarity and reliability of obtained results. Therefore, this simple method could be proposed for identification of dust sources, related plumes and their affecting areas, when raw image data are not available.
Mansour Jahantigh
Abstract
Duststorms occur generally in Sistan region. So, it limits the development of the region. Many factors play especial role on duststorms such as removal of vegetation cover due to automobile transportation. The aim of this research was to identify car transportation role in producing dust storm. For this ...
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Duststorms occur generally in Sistan region. So, it limits the development of the region. Many factors play especial role on duststorms such as removal of vegetation cover due to automobile transportation. The aim of this research was to identify car transportation role in producing dust storm. For this reason, three sites with different characteristics were chosen and in each area, two sites of 600 and 300 m length and wide respectively were selected with and without car transportation. Three soil samples were taken randomly from the first, mid and the end of the sites of each location and they were analyzed for pH, EC, CaCO3, organic carbon, moisture, calcium and vegetation cover. The soil erosion measured according to the Universal Soil Loss Equation. The results showed that the car transportation areas have less amount of clay, vegetation cover, topography, soil surface roughness, organic carbon, but, they have an increase in soil small particles with less than 0.84 mm in diameter, pH, EC, CaCo3and land length which they have especial effect on wind erosion of the region. Results also show that the amount of soil erosion is 15.8-216.3 tonsperhectare in study area.
