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.
Ebrahim Borooshke; Seyed Ahmad Hosseini
Abstract
Construction activities on the river branches and the middle areas of the watersheds can lead to changes on the river bed morphology of down streams. Understanding the river bed morphology changes and its effects on the lands next to river is essential to rehabilitate and stabilize the bed and banks. ...
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Construction activities on the river branches and the middle areas of the watersheds can lead to changes on the river bed morphology of down streams. Understanding the river bed morphology changes and its effects on the lands next to river is essential to rehabilitate and stabilize the bed and banks. This study aim to identify the river bed morphology changes over the past five decades in Zarrinehrud River. In this research a range of 25 km at the end of Zarrinehrud River in West Azerbaijan province was studied using aerial photos of year 1334 and 1346, topographic maps of year 1375 and SPOT satellite image of year 1382. Results showed that morphological changes of the river bed and the surface area of adjacent lands were reduced from 561.1 ha to 221.3 ha. The sand dam area at river bed in 1346 was 13.8 ha and at 1382 was 2.7 ha, this result represents a large discharge fluctuations and changes in the hydrological and hydraulic conditions of the river. Meander form of River morphology also has been changed. Number of Meanders reduced from 4 to 3. The effective factors on the morphological changes were, changes in the hydrological regime due to dam construction, runoff reduction and sediment deposition in the river bed.
