Seyed Saeid Nabavi; Hamidreza Moradi; Mohamad Shrifikia
Abstract
Extended Abstract Introduction There has been an increase in the occurrence of dust storms in the Middle East in recent years. The World Meteorological Organization has introduced dust storms as the result of atmospheric turbulence, which injects a large amount of dust into the atmosphere and makes the ...
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Extended Abstract Introduction There has been an increase in the occurrence of dust storms in the Middle East in recent years. The World Meteorological Organization has introduced dust storms as the result of atmospheric turbulence, which injects a large amount of dust into the atmosphere and makes the horizontal visibility less than 1000 meters. Iran is involved in dust storms due to its geographical location and weather conditions. Long-term evaluation of statistical data, identifying the origin and routing dust storms can be effective in identifying the time and location of this event. Materials & Methods In this research, the temporal distribution of Khuzestan dust storms from 2000 to 2015 was investigated at five synoptic stations including Ahvaz, Abadan, Aghajari, Safi Abad and Mahshahr. Given the World Meteorological Organization’s codes on the dust storm incidents, and in order to minimize human error, the information related to the event was extracted using the Linux operating system. Furthermore, Mann-Kendall test and Pearson and Spearman correlation coefficients were used to evaluate the trend of the temporal changes of dust storms and the rate of the correlation of the effective factors with the frequency of dust storm occurrence, respectively. Regression models were used to determine the rate of the effectiveness and the prioritization of the factors affecting storms. The entire statistical analyses were performed using the SPSS 20 software. Results & Discussion According to the results obtained, out of 1507 recorded dust storms, the Ahvaz station with 509 (34%) and the Aghajari station with 156 (10%) recorded events, have had the highest and the lowest number of recorded dust storms, respectively. The temporal variations trend of dust events at the study stations was not significant at the 1 and 5% levels. However, the frequency of dusty days in the Ahvaz and Abadan stations was positively correlated with the frequency of days with the region’s prevailing wind speed and direction at the 99% confidence level (p<0.01). There was also no significant correlation between soil texture and type. The results of linear regression model showed that there is a positive relationship between the frequency of dusty days with the frequency of days with the region’s prevailing wind direction at all stations at the 99 and 95% levels. Based on the standardized regression coefficient, at most stations, the occurrence frequency of the prevailing wind at the study stations has the highest impact on the occurrence frequency of dust storms. Conclusion: About 65 percent of dust events have occurred in two cities of Ahvaz and Abadan, located in the center and southwest part of the Khuzestan province. This could be due to the further proximity of these two stations to the local and regional dust sources. Another reason could be the flow of atmospheric circulations in different regions of the province. In this regard, the northwest-southeast winds which carry dust, hit Ahvaz and Abadan more frequently. The highest number of dust storms were recorded during summer and spring. A downward trend of dust events has been observed at all studied stations since 2008. Nevertheless, the problems caused by this event have become more apparent and have affected the lives of people. For this reason, the general view is that the number of dust storm events has increased. The high concentration and the higher persistence of dust storm events could be the reason of such an idea as well. These possible causes could be addressed in future studies in analysis and control of dust storm events.
Siavosh Shayan; Gholamreza Zare; Mojtaba Yamani; Mohammad Sharifikia; Mohsen Soltanpour
Abstract
Meanders are one of the typical geomorphological forms that is frequently observed on the southern coasts of Irandue to the availability of environmental conditions. These dynamic and active landforms have strong spatial variations under the influence of the dynamics of the rivers and the ...
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Meanders are one of the typical geomorphological forms that is frequently observed on the southern coasts of Irandue to the availability of environmental conditions. These dynamic and active landforms have strong spatial variations under the influence of the dynamics of the rivers and the gentle slopes of the deltas, in a short period of time. It’s been tried in this paper to extract and analyze the morphological changes of the Mond River bed over a period of 57 years in five time periods of (1955, 1985, 1994,
2000, and 2012) using remote sensing data and field surveys. The results of this research showed that the morphological changes of the Mond river bed have been very high during the years 1955 to 2012, so that, a nearly 3.5 kilometer displacement of the bed was observed on the estuary. Spatial comparison of the river bed in 1955 and 2012 indicated that 42.52 square kilometers were added to the left bank of the river, while on the right riverside, this amount was calculated to be 33.8 km2.The gentle slope of the delta (reduction of water speed and the sedimentary deposition on the river bed), vegetation cover on the riverside and on the river bed (trapping sediments in the river bed) and humans (building dams on the Mond river basin, constructing bridges and protection platforms on the bottom of the river bed and the transferring of water to the shrimp breeding sites) are among the important factors in changing the Mond river bed.
