Dust storms are yet quite frequent in various parts of the world, particularly ancient Mesopotamia (approximately corresponding to most parts of Iraq as well as certain surrounding regions toward its north). To add to the ongoing difficulty, monitoring dust patterns has been proven to be a rather difficult endeavor given the absence of reliable ground-based monitoring stations in the corresponding area. Additionally, western provinces of Iran, especially Khuzestan in the southwest of Iran, have been severely affected by dust storms carried by the westerly winds, blown through neighboring countries in ancient Mesopotamia. This study proceeds to employ aerosol optical depth (AOD), extracted from the MODerate-resolution Imaging Spectroradiometer onboard the Terra spacecraft, to assess spatial dust variations between 2001 and 2017 over the Khuzestan province and ancient Mesopotamia. The variations were also correlated with the temporal dust changes in the Khuzestan province. Frequency of occurrence for AOD?>?1 was used to identify and categorize major dust sources in the aforementioned regions. The findings were indicative of an increasing trend in the annual AODs of the Khuzestan province, which eventually led to a significant increase from 2008 toward the end of 2012, but decreased again in the following years. Correspondingly, the entire time period (2001–2017) was further divided into three sub-periods: the first time period spanning from 2001 to 2007, followed by the second from 2008 to 2012 and finally a third time period from 2013 to 2017. Dust source identification was speculative of numerous dust spots in Iraq, Syria, Kuwait and also the southern parts of Khuzestan province which have become more active in recent years. Additionally, a large active dust spot was pinpointed between the northwest Iraq and eastern Syria border which has become extremely active during the second time period, possibly due to a severe drought in the Fertile Crescent.
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Evidence for Mountain Glacier Changes in Semi-arid Environments based on Remote Sensing Data 总被引：1，自引：0，他引：1
Neamat Karimi Manuchehr Farajzadeh Ali Moridnejad Soodabeh Namdari 《Journal of the Indian Society of Remote Sensing》2014,42(4):801-815
Countries like Iran, which are geographically situated in a rather arid and warm regions, will suffer more from global warming than countries located in humid and semi-humid regions. In such environments, analyzing the variations of mountain glaciers can reveal several aspects of climate change patterns more efficiently in comparison to the other geo-indicators. The present study reports some evidence of changes for Alamkouh glacier between 1955 and 2010 based on several mediums to high-resolution satellite images. Considering that most part of the Alamkouh glacier is covered by debris and delineating its actual area is not possible, planimetric change analysis was restricted to the clean-ice regions. The object-oriented classification approach was used to estimate the clean ice areas. This technique takes into account the shapes of the features along with their spectral patterns. Results revealed that clean ice regions of Alamkouh glacier shrank since 1955 with an overall area reduction of about 59 %. Although the general observed trend is a clean ice area reduction, some advancement was detected over the period from 2000 to 2010. During 1992–2000, the maximum reduction in the clean ice area was observed (0.08 km2.a?1). However, clean ice area of the case study has partially increased about 0.028 km2.a?1 from 2000 to 2010. Supra-glacial lake change analysis illustrated that at the surface of the glacier, lakes have been enlarged remarkably in the past 55 years (about 4.75 times greater). In addition, clean ice area and the surface area of supra-glacial lakes oscillated in compliance with each other. The findings revealed that the maximum expansion of supra-glacial lake occurred during 1992–2000, which demonstrate the glacier maximum reduction during this period. This shrinkage in the Alamkouh glacier caused an extensive glacial lake outburst flood in Jun 2011. The results of this study agree with documented changes in other mountain glaciers located in arid and semi-arid environments and they also confirm the application of mountain glaciers in climate variations monitoring over such regions. 相似文献
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Hamed NAJAFI Alireza KARIMI Gholam Hosain HAGHNIA Farhad KHORMALI Shamsollah AYOUBI Hossein TAZIKEH 《山地科学学报》2019,(7)
The objective of this study was to characterize the morphological and magnetic properties of Sari loess-paleosol section in northern Iran for paleopedologic and paleoenvironmental interpretation. The section consisted of a modern soil(MS) and three paleosols(PS_1, PS_2, PS_3) separated by loess layers(LS_1, LS_2 and LS_3). Based on particle size distribution, clay mineralogy, carbonates distribution and size of secondary carbonates, pedogenic development of the soils was in order of PS_3PS_2PS_1=MS. Presence of redoximorphic features in PS_3 was attributed to alternate stagnic saturation due to local water or high precipitation. Dominance of smectite and vermiculite as well as large carbonated dolls in PS_3 indicated suitable environment and sufficient time for pedogenic development. Magnetic properties(χ~(lf) and χ~(fd)%) were distinctly higher in MS, PS_1 and PS_2 when compared to loess layers. The Lowest magnetic properties values were observed in PS_3 which can be the result of ferrimagnetic minerals destruction under hydromorphic conditions. The highest Fe_d content occurred in PS_3, however, low χ~(lf)/Fe_d ratio indicated that majority of the iron minerals in PS_3 are not magnetic. In conclusion, the particle size distribution, clay mineralogy and carbonates features were indicative of pedogenesis intensity, whereas, magnetic properties were useful to characterize the pedogenic environment. 相似文献
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This study reports on the clean ice area and surface elevation changes of the Khersan and Merjikesh glaciers in the north of Iran between 1955 and 2010 based on several high to medium spatial resolution remote sensing data.The object-oriented classification technique has been applied to nine remote sensing images to estimate the debris-free areas.The satellite-based analysis revealed that the clean ice areas of Khersan and Merjikesh glaciers shrank since 2010 with an overall area decrease of about 45% and 60% respectively.It means that the dramatic proportions of 1955 glaciers surface area are covered with debris during the last five decades.Although the general trend is a clean ice area decrease,some advancement is observed over the period of 1997-2004.During 1987-1991 the maximum decrease in the clean ice area was observed.However,the clean ice area had steadily increased between 1997 and 2010.To quantify the elevation changes besides the debris-free change analysis,several Digital Elevation Models(DEMs) were extracted from aerial photo(1955),topographic map(1997),ASTER image(2002) and Worldview-2 image(2010) and after it a 3-D Coregistration and a linear relationship adjustments techniques were used to remove the systematic shifts and elevation dependent biases.Unlike the sinusoidal variation of our case studies which was inferred from planimetric analysis,the elevation change results revealed that the glacier surface lowering has occurred during 1955-2010 continuously without any thickening with the mean annual thinning of about 0.4 ± 0.04 m per year and 0.3 ± 0.026 m per year for Khersan and Merjikesh glaciers,respectively.The maximum thinning rate has been observed during 1997-2002(about 1.1 ± 0.09 per year and 0.96 ± 0.01 mper year,respectively),which was compatible partially with debris-free change analysis.The present result demonstrates that although in debris-covered glaciers clean ice area change analysis can illustrate the direction of changes(retreat or advance),due to the high uncertainty in glacier area delineation in such glaciers,it cannot reveal the actual glacier changes.Thus,both planimetric and volumetric change analyses are very critical to obtain accurate glacier variation results. 相似文献
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Mohammad Saeed SEIF Ebrahim JAHANBAKHSH Roozbeh PANAHI Mohammad Hossein KARIMI 《海洋工程》2009,(3):517-528
High speed planing hulls have complex hydrodynamic behaviors. The trim angle and drafts are very sensitive to speed and location of the center of gravity. Therefore, motion simulation for such vessels needs a strong coupling between rigid body motions and hydrodynamic analysis. In addition, free surface should be predicted with good accuracy for each time step. In this paper, velocity and pressure fields are coupled by use of the fractional step method. On the basis of integration of the two-phase viscous flow induced stresses over the hull, acting loads (forces and moments) are calculated. With the strategy of boundary-fitted body-attached mesh and calculation of 6-DoF motions in each time step, time history of ship motions including displacements, speeds and accelerations are evaluated. For the demonstration of the software capabilities, circular cylinder slamming is simulated as a simple type of water slamming. Then, a high-speed planing catamaran is investigated in the case of steady forward motion. All of the results are in good concordance with experimental data. The present method can be widely implemented in design as well as in performance prediction of high-speed vessels. 相似文献
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