تحليل مطالعات مخاطره گرد و غبار در جنوب غرب ايران در دوره 22 ساله (2017- 1996)

(The analysis of dust hazard studies in southwest region of Iran in 22 years (1996-2017

توفان گرد و غبار يك رويداد طبيعي است كه در مناطق خشك و نيمه خشك شكل مي گيرد و پيامدهاي نامطلوب بسياري را به همراه دارد. از آنجا كه غالب پژوهش هاي انجام شده بصورت موردي است و پژوهش جامع مروري كه مجموعه گسترده اي از پژوهش هاي موجود را مورد ارزيابي قرار داده و به نتايج كلي برسد، در منطقه جنوب غرب ايران وجود ندارد؛ لذا در اين پژوهش به مرور جامع منابع موجود پرداخته شده است كه شامل مروري بر مطالعات در زمينه تغييرات زماني-فضايي، مدل سازي و آشكارسازي گردوغبار و سلامت در جنوب غرب ايران است.. بررسي سابقه مطالعات توفان گردوغبار از منابع اطلاعاتي نشان داد كه بيشتر محققان (61/40 درصد) از روش آماري- سينوپتيكي براي مطالعه توفان هاي گردوغبار استفاده كردند و مهمترين شاخص هايي كه در ويژگي هاي فيزيكي مورد توجه پژوهشگران قرار گرفت، فراواني و تراكم بود كه به ترتيب 34/21 و 34/21 درصد از مطالعات را به خود اختصاص داده اند. بررسي مطالعات در مورد روش هاي آشكارسازي پديده گرد و غبار نشان مي دهد كه صرفاً استفاده از باندهاي حرارتي و يا انعكاسي نمي تواند پديده گرد و غبار را با دقت بالا آشكارسازي نمايد، بنابراين بايد مدلي توسعه دهند كه از تركيب باندهاي انعكاسي و حرارتي براي اين منظور بكار رود، بعبارتي استفاده از تركيب طيف هاي انعكاسي و حرارتي MODIS مي تواند در تشخيص توفان هاي گردوغبار در منطقه مورد مطالعه نتايج بهتري ارائه دهد. بررسي ها نشان مي دهد كه منشا اكثر توفان ها در خارج از ايران است. همچنين در معرض قرار گرفتن به آلاينده هاي هوا، به ويژه هنگام رخداد گرد و غبار خاورميانه، منجر به افزايش بيش از حد بستري شدن در بيمارستان است. بطوري كه در زمان پديده گردوغبار، مراجعات بيماران ريوي به مراكز درماني با رشد 70 درصدي روبرو بوده است. مرور مطالعات شبيه سازي مسير حركت ذرات گردوغبار نشان مي دهد كه اغلب مسيرها از مناطق شمالي و مركزي عراق و سوريه گذشته و منشاء توفان هاي گردوغبار، مناطق كويري و خشك شمال و مركز عراق و سوريه هستند. نتايج بررسي ها نشان مي دهد كه منطقه مرزي بين سوريه و شمال غرب عراق، غرب و جنوب غرب عراق به همراه شرق و شمال شرق عربستان كانون هاي اصلي گردوغبار براي منطقه مورد مطالعه هستند و شرايط همديدي همزمان با رخداد گردوغبارهاي برخاسته نشان از نقش بارز سيستم هاي سيكلوني در رخداد و انتقال اين پديده است، چرا كه همزمان با رخداد اين پديده در دوره گرم، تقويت قابل توجه سيستم كم فشار عراق بهمراه شكل گيري تراف در زاگرس سبب شكل گيري و انتقال گردوغبار به منطقه مورد مطالعه مي شود.

The analysis of dust hazard studies in southwest region of Iran in 22 years (1996-2017) Dust storms are natural hazards that mostly occur in arid and semi-arid regions and there are many harmful consequences. According to the topographic-climatic conditions in Iran and the significant increase in the number and severity of dust storms occurrence in recent decades، especially in the West and Southwest regions where the dust storms are the most important environmental crisis. Studying this phenomenon is necessary for better management its harmful effects. Since most of the research are implemented as different case studies، and there is no comprehensive study that review a wide range of existing researches with overall results in the southwestern parts of Iran، in this study a comprehensive overview of available literature reviews are addressed including dust spatio-temporal variations، modeling، detection، and health issues. This research is based on a library research and search of valid national and international scientific articles about the dust crisis and no data-processing. We attempted to analyze temporal and spatial variations in the south and southwest of the country using the available studies and the challenges of this phenomenon in the past and present to provide a new perspective to apply a comprehensive land management and managing environmental hazards in Iran with all the problems. A review of the history of dust storm studies from information sources showed that most researchers (61.40%) used a synoptic method to study dust storms، and the most important indicators that were considered by the researchers in physical properties were frequency and density، 34.21% and 34.21% of the studies respectively. Dust detection methods show that the use of thermal or reflective bands cannot detect dust phenomena with high precision، therefore، a model which applies both bands simultaneously should be developed. In other words، applying a combination of reflective and thermal spectra of Military Origin Destination Information System (MODIS) could offer better results in detection of dust storms in the study area. Studies indicate that most of the storms originate outside of Iran. Moreover، exposure to airborne contaminants، especially when the dust storms occur in the Middle East، can lead to an increase in the related diseaseoutbreak in the study area. For instance، there was a 70% increase in referring to medical centers for lung related problems when a dust phenomenon occurred. The Results showed that in cold seasons where low height and western waves is formed on the European and Mediterranean Sea، due to the heaviness، cold air in these days، can penetrate low latitudes and their trough is located over the Middle East area. Under warming condition، the front of rough is formed as ridge، then engendered turbulence and wind. In the warm seasons، thermal low pressure is rapt to ward in the high latitude، and severe dryness of the area is also due to the fact that the dusty phenomenon is intensified in the area. Dust storm occurrence in the summer due to bareness of the land، transparency of the atmosphere، dryness of the air and the vast plains، which can reduce the formation of local instability in the case of a sharp rise in air temperature. The dispersal of deserts and sand sea is mainly in the northwest of Khuzestan province، especially in Fakkeh and Moussan which are located in the western borders of Iran with Iraq، which cover most of the Azadegan plain and west of the Karkheh and Mollasani and Maroon Rivers، and ultimately end in the Omidiyeh and Aghajari regions. Results show that the border between Syria and northwest Iraq، west and southwest of Iraq to east and northeast of Saudi Arabia are the main sources of dust in the studied region . Synoptic conditions considering simultaneously with the occurrence of dust storms showed the significant role of cyclonic systems in the occurrence and transfer of this phenomenon. With the phenomenon occurrence during the warm period، the significant strengthening in low pressure of Iraq along with the trough formation in Zagros causes the formation and transfer of dust towards Southwest Iran. Simulation studies of dust particles movement paths have shown that most of the paths are from the northern and central parts of Iraq and Syria and the source of dust storms are deserts and dry regions of the northern and central parts of Iraq and Syria. In addition، the study of the transmission paths of particles in dust storms indicates the presence of a lower level jet، which causes horizontal displacement of dust particles in a shallow layer and prevents its vertical propagation in the higher layers of the atmosphere. In general، although the dust phenomenon is transnational and uncontrollable، it can introduce limitations in terms of circulation patterns and statistical properties at different time intervals to the different planners via its time and scope which will necessitate appropriate programs for combating and adaptation.