fa تحلیل همدیدی و دینامیکی پدیده گرد و غبار و شبیه سازی آن در جنوب غرب ایران در تابستان 1384 تخصصي Special پژوهشي Research <p dir="RTL" style="margin-right: 28.55pt; text-align: justify;"><span style="font-size:16px;"><span style="font-family: nasimyw;"><strong>یکی از مشکلات زیست محیطی کشور ما وقوع رخداد توفانهای گردوغبار به ویژه در استانهای غربی و جنوبغرب کشور است. در این مطالعه، به بررسی توفان شدید و فراگیر مرداد ماه 1384 می پردازیم که در آن بخش وسیعی از کشور تحت تأثیر این توفان قرار گرفت. </strong><strong>ملاک انتخاب روزهای گرد و غباری شاخص، گزارش گرد و غبار در اکثر ایستگاهها، حداقل دید و حداکثر تداوم می&shy;باشد.</strong><strong> ابتدا جدول حداقل دید افقی روزانه با کمک داده های سازمان هواشناسی در 5 شهر غربی کشور ارائه می</strong><span dir="LTR">‌</span><strong>شود. سپس نقشه‌های همدیدی مربوط به این پدیده از وبگاه </strong><span dir="LTR">NOAA</span><strong> استخراج&nbsp; می‌شود و تفسیر همدیدی و</strong> <strong>دینامیکی آنها&nbsp; انجام می شود. سپس تصاویر سنجده </strong><span dir="LTR">MODIS</span><strong> ماهواره </strong><span dir="LTR">Aqua </span><strong>&nbsp;و میانگین غلظت جرمی ذرات گردوغبار این سنجنده در پدیده مورد نظر مورد بررسی قرار می</strong><span dir="LTR">‌</span><strong>گیرد. سپس با کمک </strong><strong>مدل لاگرانژی </strong><span dir="LTR">HYSPLIT</span><strong> مسیر ذرات گردوغبار ردیابی می‌شوند. </strong><strong>پس از مسیریابی پس گرد ذرات گردوغبار، مناطق بیابانی کشور سوریه بعنوان کانون شکل گیری گردوغبار</strong> <strong>شناسایی شدند.</strong> <strong>در آخر، خروجی</strong><span dir="LTR">‌</span><strong>های غلظت گردوغبار مدل </strong><span dir="LTR">WRF-Chem</span><strong> مورد بررسی قرار می‌گیرد. به منظور صحت سنجی، خروجیهای مدل در&nbsp; شهر تبریز این خروجیها با داده</strong><span dir="LTR">‌</span><strong>های غلظت سازمان محیط زیست&nbsp; و داده‌های دید افقی سازمان هواشناسی کشور مقایسه می‌شود. نتایج خروجیهای مدل به خوبی روند افزایش گردوغبار و روز حداکثر گردوغبار را نشان می‌دهد، اما این خروجیهای غلظت گردوغبار تفاوت چشمگیری با مقادیر واقعی دارد.</strong></span></span></p> <p style="text-align: justify;"><span style="font-family:times new roman;"><span style="font-size: 16px;">Dust particles consist of important aerosols and resulting in blowing strong winds on the surface of desert areas. These particles enter the atmosphere under the influence of different factors including: weather condition (wind, precipitation and temperature), land surface (topography, humidity level, roughness and vegetation), soil features (texture, density, composition and land use (agriculture).</span></span></p> <p style="text-align: justify;"><span style="font-family:times new roman;"><span style="font-size: 16px;">Today powerful dust storm destroys people lives and causes severe damages to their life and also causes financial problems in most regions of the world especially in west and southwest of Asia. Dust storm is one of the most important natural phenomena and also a kind of severe natural disaster that influence Iran and its west and southwest part. The location of Iran on the desert belt is accompanied by frequent increasing of sand and dust storm. Integral prediction of dust storm phenomena can be useful in decreasing damages caused by these storms. So synoptic-dynamic analysis of dust storms and their simulation play an important role in achieving to this goal.</span></span></p> <p style="text-align: justify;"><span style="font-family:times new roman;"><span style="font-size: 16px;">In this research, we investigate severe dust storm in August 2005 that affected a large area of our country. Select of dusty days were based on minimum visibility and maximum durability of that dust storm. At first, we show the minimum of daily visibility table. These data has been provided by Meteorological Organization in 5 western cities. The synoptic maps were related to these phenomena derived from NOAA website and synoptic and dynamic interpretation has been done. We have got the data with resolution of 2.5 degree from NOAA website.</span></span></p> <p style="text-align: justify;"><span style="font-family:times new roman;"><span style="font-size: 16px;">Then 700 hpa relative vorticity maps were drawn. We investigate MODIS images instrument on Aqua satellite and evaluate the amount of mass concentration of dust particles. Then the Lagrangian Integrated Trajectory Model has been used to determine the backward trajectory of dust particles. We run HYSPLIT model by GDAS data with a resolution of 0.5 degrees. At last we investigate the output of the WRE-CHEM model. This model was run to simulate dust storms in 7-10 August and FNL data with a resolution 1 degree use for initial and boundary conditions. WRF-CHEM is used to simulate dust condition and transmission. As a part of WRF model, its main application is the study of atmosphere chemistry.</span></span></p> <p style="text-align: justify;"><span style="font-family:times new roman;"><span style="font-size: 16px;">At 500 hpa a very strong ridge entered Iran from the southwest. It covered all areas of our country which prevents the transference of dust to high levels of atmosphere. In 700 hpa relative vorticity maps show one day before dust storm reach to Iran a Positive voriticity is located in Iraq and Syria. So dust comes up to higher levels of the atmosphere and in dusty days in our country. There is a negative voriticity located in our country and because of downside movement of the air, dust storm happen in Iran.</span></span></p> <p style="text-align: justify;"><span style="font-family:times new roman;"><span style="font-size: 16px;">Dust loading and friction velocity of outputs of the model has been drawn in dusty days. The time series of dust concentration of output models for Tabriz are compared with the concentration data of Environmental Organization of visibility data. Result show that a low pressure system is located over the Oman sea that its blaze has been extended to the northwest of Iran. On the other hand a high pressure center is located in the Europe that extended to the east of Mediterranean. So strong pressure gradient were in Iraq and Syria and they caused the creation of strong winds in their deserts which caused dust emission.</span></span></p> <p style="text-align: justify;"><span style="font-family:times new roman;"><span style="font-size: 16px;">Friction velocity related to the model outputs show that the velocity of wind is high in dusty days in Iraq and Syria. So conditions are suitable for dust raining. Satellite images showed that WRF/CHEM model is simulated very well in emission, source, diffusion and the extent of the areas covered with dust. Comparing MP10 concentration of the model output with and Environment Organization data of Tabriz city show that WRF/CHEM model forecast daily changes well. But model underestimate significantly in quantity of concentration. This error may be due to a model considering only dust quantity but other pollutants affected on visibility. In general it can be said that in this event, dust concentration has been underestimated by WRF/CHEM model especially in maximum amount of PM10 concentration.</span></span></p> توفان گردوغبار, مدل WRF-Chem, تصاویر ماهواره, غلظت گردوغبار, دید افقی dust storms, WRF-CHEM model, satellite images, dust concentration, visibility 91 102 http://jsaeh.khu.ac.ir/browse.php?a_code=A-10-3-42&slc_lang=fa&sid=1 nasim hossien hamzeh نسیم حسین حمزه nasim_hh@yahoo.com 10031947532846001105 10031947532846001105 Yes ebrahim fattahi ابراهیم فتاحی 10031947532846001106 10031947532846001106 No Mjtaba Zoljodi مجتبی ذوالجودی 10031947532846001107 10031947532846001107 No Parvin Ghaforian پروین غفاریان 10031947532846001108 10031947532846001108 No abbas ranjbar عباس رنجبر 10031947532846001109 10031947532846001109 No