فهرست مطالب

  • سال چهل و پنجم شماره 3 (پاییز 1398)
  • تاریخ انتشار: 1398/09/01
  • تعداد عناوین: 12
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  • حمید خسروی، غلام جوان *، محمد تاتار، مهدیه سفری صفحات 487-505

    در ساعت 10:39:10 صبح روز 16/1/1396 (مطابق با 6:09:10 به وقت جهانی روز 05/04/2017) زمین لرزه ای با بزرگی ML=6 روستای دوقلعه در 46 کیلومتری شمال شرقی فریمان از توابع خراسان رضوی را تخریب کرد. رو مرکز این زمین لرزه در 81/35 درجه عرض شمالی و 36/60 درجه طول شرقی و عمق 13 کیلومتری محاسبه شد. پس از وقوع زمین لرزه اصلی پس لرزه های فراوانی به وقوع پیوست که بزرگ ترین آنها حدود 14 ساعت بعد از زمین لرزه اصلی با بزرگی ML=5.5 خراسان رضوی را به شدت لرزاند. با توجه به پیشینه لرزه خیزی تاریخی و دستگاهی، علی رغم اینکه پهنه خراسان از مناطق فعال و لرزه خیز ایران است اما در منطقه فریمان به جز چند مورد، زمین لرزه بزرگی گزارش نشده است. بلافاصله پس از وقوع این زمین لرزه یک شبکه موقت محلی با توانمندی 16 ایستگاه لرزه نگاری و سه ایستگاه شتاب نگاری به مدت 36 روز توسط پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله در منطقه نصب شد و فرصت مناسبی برای بررسی توزیع مکانی پس لرزه ها، شناخت گسل مسبب و ویژگی های زلزله شناختی این زمین لرزه که در ایالت لرزه زمین ساختی کپه داغ قرار دارد را فراهم آورد که در این پژوهش پس از به دست آوردن نسبت سرعت موج P به S به روش واداتی، بهینه سازی مدل یک بعدی اولیه انجام گرفته و پس لرزه ها مجددا تعیین محل شده اند. سازوکارهای به دست آمده از روش ترکیبی پلاریته و نسبت دامنه بیانگر این است که روند گسل مسبب آنها غالبا به صورت شمال غربی-جنوب شرقی است. توزیع پس لرزه ها نیز روندی شمال غربی-جنوب شرقی نشان می دهد که در ادامه گسل مزدوران و هم راستا با گسل فریمان می باشد اما با توجه به اینکه نوع سازوکارها غالبا فشاری و فشاری با مولفه امتداد لغز بوده است لذا احتمال اینکه گسل مسبب گسل مزدوران باشد بیشتر است. نمودار توزیع عمقی پس لرزه ها بیانگر آن است که عمده پس لرزه ها در محدوده 8-4 کیلومتر از سطح زمین رخ داده اند. علاوه بر آن با ترسیم پروفیل هایی در راستا و عمود بر روند پس لرزه ها مشاهده شد که عمق غالب پس لرزه ها کمتر از 10 کیلومتر همراه با به خط شدگی کاملا واضح با شیب به سمت شمال شرقی می باشد. نتایج کلی این مطالعه نشان می دهد که فعالیت لرزه ای گسل پی سنگی در عمق کمتر از 10 کیلومتر صورت گرفته است بنابراین ضرورت رعایت دقیق مقررات ساخت وساز بر اساس معیارهای فنی استاندارد در طراحی و ساخت بناهای مسکونی و صنعتی در منطقه فریمان برای کاهش آسیب های وسیع ناشی از زلزله های مخرب آتی اجتناب ناپذیر است.

    کلیدواژگان: زمین لرزه دوقلعه فریمان، شبکه موقت لرزه نگاری، کپه داغ، گسل مزدوران، سازوکارکانونی
  • رامین ورفی نژاد*، سعید پرنو، ابوالقاسم کامکار صفحات 507-521

    آشکارسازی سازه های زیرسطحی همواره یکی از مسائل مورد بحث در تامین امنیت و نگهداری تاسیسات مدفون و برخی اکتشافات ژئوفیزیکی بوده است. بنابراین نیاز ضروری به روش های غیر مخرب برای آشکار سازی این گونه اهداف زیرسطحی کاملا مشهود می باشد. از این رو برای تهیه نقشه این سازه ها می توان از روش های ژئوفیزیکی مناسب، بدون هرگونه تخریبی در سطح زمین بهره گرفت. با وارون سازی داده های ژئوفیزیکی می توان پارامترهای هندسی مانند عمق، موقعیت افقی و خواص فیزیکی مانند خودپذیری مغناطیسی بی هنجاری های زیرسطحی را تعیین کرد. در روش مغناطیس سنجی، مساله وارون سازی دارای عدم یکتایی جبری و عدم یکتایی تئوریکی است. همچنین تغییرات کم در مقدار داده ها به دلیل وجود نوفه، باعث تغییرات شدیدی در تخمین پارامترهای مدل می شود. برای رفع این مشکلات می توان از قیدهای مختلف و اطلاعات اولیه بهره گرفت. در این پژوهش، الگوریتم وارون سازی کمینه طول وزن دار منظم سازی شده و دو قید فشردگی و وزن دهی عمقی استفاده شده است. برای بررسی کارایی الگوریتم، از داده های مصنوعی حاصل از مدل دایک قائم و مدل دو دایک شیب دار استفاده شده است. نتایج به دست آمده، دلالت بر تفکیک پذیری بالای الگوریتم مورد نظر داشته به نحوی که شیب و تباین چگالی آن نزدیک به مدل اصلی هستند. برای بررسی کارایی عملی الگوریتم پیشنهادی، این الگوریتم بر روی داده های برداشت شده لوله انتقال گاز در منطقه قلعه شوکت شهرستان شاهرود و داده های آثارباستانی ناحیه ای از شهر سوخته پمپئی اعمال شده است. نتایج حاصل از وارون سازی با استفاده از این الگوریتم، بازیابی قابل قبولی از واقعیت زیر سطح را نشان می دهند.

    کلیدواژگان: مغناطیس سنجی، وارون سازی، قید فشردگی، وزن دهی عمقی، مدل مصنوعی
  • سودابه کارگر، عباس غلام زاده*، محسن فرخی صفحات 523-535

    در این مطالعه ساختار سطحی پوسته در ناحیه فاریاب، استان کرمان، با استفاده از توموگرافی دو بعدی امواج لاو، مورد بررسی قرار گرفته است. با استفاده از روش تک ایستگاهی 437 پس لرزه ثبت شده در 9 ایستگاه شبکه موقت محلی، مورد تجزیه و تحلیل قرار گرفت. منحنی پاشندگی برای هریک از رویدادهای ثبت شده در ایستگاه ها محاسبه شده است. پس از تعیین منحنی پاشندگی، سرعت گروه امواج لاو، در بازه 0/1 ثانیه تا 10 ثانیه با استفاده از وارون سازی خطی، به دست آمد. در پریودهای کمتر از 3 ثانیه محدوده سرعت گروه امواج لاو از 0/5 تا 3 کیلومتر بر ثانیه است در حالی که برای پریودهای بیشتر از 3 ثانیه سرعت گروه امواج لاو بین 2/0 تا 1/5 کیلومتر بر ثانیه است. بر این اساس به نظر می رسد در این منطقه با دو نوع پوسته اقیانوسی و قاره ای مواجه باشیم. وجود پوسته اقیانوسی با شواهدی از حضور سنگ هایی در سطح زمین شامل پریدوتیت و گابرو و افیولیت تقویت می شود. با توجه به کاهش سرعت گروه در پریودهای بیشتر از 3 ثانیه، به نظر می رسد در زیر پوسته اقیانوسی با رسوبات نرم پوسته قاره ای مواجه باشیم. بر این مبنا به نظر می رسد امواج لاو که دارای پریود بین 3 تا 9/5 ثانیه هستند از سنگ هایی عبور کرده اند که زیر این پوسته اقیانوسی قرار دارند. یک توده پر سرعت با سرعتی در حدود 2/5 کیلومتر بر ثانیه در بخش میانی منطقه مورد مطالعه دیده می شود. این آنومالی از پریود 0/1 ثانیه قابل مشاهده است اما در پریودهای بیشتر وسعت و محدوده آن واضح تر دیده می شود.

    کلیدواژگان: امواج لاو، توموگرافی دوبعدی، ساختار سطحی، سنندج-سیرجان، فاریاب
  • بهزاد ملکی، حبیب رحیمی*، وحید ملکی صفحات 537-552

    با توجه به اهمیت مقادیر شتاب در دوره بازگشت های بلندمدت و تاثیر آن در طراحی طیف ویژه ساختگاه، انتخاب مناسب توابع توزیع بزرگا برای چشمه های لرزه ای مهم بوده و تاثیر قابل توجهی در نتیجه تحلیل خطر لرزه ای دارد. در گستره شمال غرب ایران، گسل شمال تبریز به دلیل خصوصیات لرزه خیزی منحصربه فرد و تاریخچه جنبش آن از اهمیت ویژه ای برخوردار است و با توجه به مطالعات دیرینه لرزه خیزی صورت گرفته و بررسی رفتار این سامانه گسلی، احتمال لغزش سرشتی در بخش میانی آن تایید شده است. حال اگر این سامانه گسلی رفتاری سرشتی داشته باشد، با انتخاب مدل سرشتی توزیع بزرگا برای محدوده میانی گسل، تحلیل خطر زمین لرزه به روش احتمالاتی انجام شده و نتایج بررسی شده است. تاثیرات انتخاب این مدل از توزیع بزرگا بر مقادیر پارامتر شتاب جنبش نیرومند زمین در دوره بازگشت های مختلف بررسی شده است. در نتایج تحلیل خطر، با در نظر گرفتن مدل سرشتی برای این بخش از گسل شمال تبریز، نقشه مناطق هم شتاب برای سنگ بستر با 5 درصد میرایی برای مولفه افقی تهیه شده و مقدار آن برای محدوده شهر تبریز در دوره بازگشت 475 سال از g 0/28 تا g 0/5 متغیر می باشد. همچنین پارامتر شتاب حاصل از جنبش زمین برای محدوده گسلی شمال تبریز با دو مدل توزیع بزرگای نمایی و سرشتی، در دوره بازگشت های بلندمدت و کوتاه مدت محاسبه و مقایسه شده است. شتاب حاصل از انتخاب مدل سرشتی توزیع بزرگا برای این بخش از گسل، در دوره بازگشت های بلندمدت بیشتر از مدل نمایی بوده و برعکس، برای دوره بازگشت های کوتاه مدت کمتر می باشد.

    کلیدواژگان: برآورد خطر زمین لرزه، مدل سرشتی، مدل نمایی، چشمه بالقوه زمین لرزه، گسل شمال تبریز
  • کامل آزرم، عباس مفیدی*، علی محمد خورشیددوست صفحات 553-573
    در پژوهش حاضر ضمن تحلیل الگوی گردش مقیاس همدید، با بهره گیری از یک مدل اقلیمی منطقه محدود، سازوکار میان مقیاس حاکم بر وقوع بارش های بهاره در شمال غرب ایران بررسی شد. در این راستا، نقش واداشت های دینامیکی وگرمایش محلی در وقوع بارش ها با استفاده از داده های ایستگاهی، داده های رقومی باز تحلیل NCEP-NCAR و ERA-Interim و خروجی اجرای مدل RegCM4 بررسی شدند. یافته ها بیانگر آن است که نمی توان بخش قابل توجهی از بارش های فصل بهار در شمال غرب ایران را به طور مستقل وکامل «بارش همرفتی» نامید. در واقع، بارش های بهاری با مشخصه همرفتی در شمال غرب ایران، اصطلاحا نوعی «همرفت واداشته» محسوب می شوند. بدین معنی که، در صورت عدم وجود واداشت های دینامیکی در مقیاس همدیدی، از قبیل ناوه تراز میانی وردسپهر، بخش قابل توجهی از بارش های همرفتی شمال غرب ایران به وقوع نخواهند پیوست. همچنین، گرمایش محلی به تنهایی به دلیل نبود رطوبت کافی در منطقه و عدم کفایت آن جهت فراهم سازی نیروی شناوری، قادر به ایجاد ناپایداری مورد نیاز برای وقوع بارش نخواهد بود. تحلیل مقادیرگرمایش بادررو نشان داد که فرارفت افقی گرما از دامنه های کوهستانی به عنوان یک واداشت محلی، در تامین گرما و انرژی دسترس پذیر و تکوین همرفت و بارش همرفتی نقش مهمی دارد. همچنین، بررسی گرمایش محلی نشان دادکه چشمه های گرمایی بر روی دامنه های جنوبی و غربی و چاهه های گرمایی بر روی دامنه های شمالی و شرقی ارتفاعات مشاهده می شوند. یافته کلی آنکه، حضور گذرای واداشت های دینامیکی مقیاس همدیدی در فصل بهار، در ترکیب با حضور پایدار و پیوسته فرارفت افقی و قائم گرما، ناشی از گرمایش محلی بر روی دامنه های جنوبی و غربی ارتفاعات در ساعات روز، وقوع بارش با مشخصات همرفتی را در پی خواهد داشت.
    کلیدواژگان: بارش همرفتی، تحلیل میان مقیاس، شمال غرب ایران، گرمایش بادررو، فرارفت افقی، مدل RegCM4
  • شادی ارفع، محسن ناصری* صفحات 575-597
    در این تحقیق، روش کاهش مقیاس آماری تک ایستگاهیSDSM  و DMDM و همچنین یک روش چندایستگاهی مبتنی بر رگرسیون چند متغیره متشکل از دو مدل وقوع و مقدار با استفاده از جداسازی مقدار تکینه (SVD) در بخشی از استان تهران، شامل ده ایستگاه بارا ن سنجی معمولی و سینوپتیک مورد ارزیابی قرار گرفته و سپس به شبیه سازی سناریوهای تغییر اقلیم (RCP2.6, RCP4.5, RCP8.5) بارش در بازه زمانی 2021-2050 متاثر از تغییر اقلیم اقدام شده است. در اولین گام به بررسی رفتار های روزانه مدل های مورد اشاره اقدام شده است. نتایج گویای تطابق بلند مدت بهتر میانگین در مدل SDSM و افزایش دقت (کاهش خطای محاسباتی) در روش چندایستگاهی و مدل DMDM است. همچنین با از این روش با هدف بازتولید اطلاعات ایستگاه های جدید نیز استفاده شده که در ابتدا مدل DMDM و پس از آن نتایج مدل چندایستگاهی عملکرد مناسبی را ارائه می کند. در گام بعد به بررسی رفتار حدی روش های مورد بررسی پرداخته شده است. در این مرحله، با استفاده از توزیع آماریGEV  و خروجی های سه مدل کاهش مقیاس فوق، منحنی شدت مدت فراوانی (IDF) با دوره بازگشت های 2 الی 100 سال در ایستگاه سینوپتیک مهرآباد محاسبه شد. همچنین ارزیابی عدم قطعیت گویای پایداری مطلوب تر روش DMDM نسبت به سایر روش های مورد استفاده است. مقایسه نتایج حاصل از منحنی IDF تجربی موجود، گویای برتری مدل DMDM و پس از آن روش چندایستگاهی در مقایسه با روش SDSM در تخمین مقادیر حدی بارش است.
    کلیدواژگان: کاهش مقیاس، SDSM، DMDM، عدم قطعیت، کاهش مقیاس چندایستگاهی، GEV، IDF
  • هادی داوری *، بیژن فرخی صفحات 599-607

    با استفاده از روش ذره در سلول رفتار غبار پلاسمایی در شرایط جو زمین و تاثیر میدان مغناطیسی بر فرآیند باردارشدن ذرات غبار توسط ذرات پلاسما شبیه سازی و موردبررسی قرار گرفت. واکنش برخوردی الکترون ها با ذرات پلاسما و غبار شامل یونیزاسیون، برانگیختگی و برخورد کشسان فرض شد. تاثیر تفاوت در چگالی اولیه پلاسما و میدان مغناطیسی متفاوت شبیه سازی و نتایج آنها باهم مورد مقایسه قرار گرفت. در فرآیند باردارشدن ذرات غبار زمان رسیدن به حالت اشباع و میزان بار اشباع متفاوت به دست آمد. همچنین مشاهده شد که افزایش میدان مغناطیسی لزوما به معنای افزایش بار الکتریکی ذرات غبار و یا کاهش زمان رسیدن به حالت اشباع نیست. یافتن حد این میدان که مطمئنا به خصوصیات فیزیکی پلاسما بستگی دارد می تواند در برخی از مسائل مثلا در شرایط پلاسمای جو در فضا و یا آزمایشگاه مفید و راه گشا باشد. همچنین نتایج این شبیه سازی می تواند در مدل های شبیه سازی آینده که در رابطه با ترابرد ذرات غبار و تاثیر آن بر کل غبار پلاسمایی تمرکز دارد مورداستفاده قرار گیرد.

    کلیدواژگان: غبار پلاسمایی، شبیه سازی ذره در سلول (PIC)، بار الکتریکی غبار، میدان مغناطیسی
  • عباسعلی داداشی رودباری، محمود احمدی* صفحات 609-623
    هدف از این پژوهش وردایی زمانی-مکانی و نقطه تغییر شاخص هواویز (AI) فصلی در ایران است. در این راستا داده های سنجنده TOMS دو ماهواره Nimbus 7 (1979-1992) و Earth Probe (1996-2005) و سنجنده OMI (2005-2015) ماهواره EOS Aura اخذ و از آزمون Buishand برای شناسایی نقطه تغییر شاخص هواویز استفاده شد. نتایج نشان داد بیشینه شاخص هواویز در دوره گرم سال و بهار به دلیل کاهش میزان رطوبت خاک و فعال شدن چشمه های گردوخاک، بیشینه شاخص هواویز فصلی را دارا می باشد. همچنین فصل زمستان به دلیل اثر کنترلی بارش مقدار هواویز کمتری را دارا است. گردش منطقه ای وردسپهر نیز نقش شایان توجهی در وردایی هواویزها در ایران دارند به طوری که  باد شمال تابستانه، الگوهای دینامیکی و گرمایی غرب آسیا و کم فشار گرمایی سند بیشترین نقش را در افزایش هواویزهای ایران دارند. همچنین شاخص هواویز (AI) حساسیت بالایی به ارتفاع لایه مرزی وردسپهر دارد چرا که بیشینه ارتفاع لایه مرزی با مناطقی است که شار گرمایی قابل ملاحضه ای وجود داشته باشد و شار گرمای نهان به علت فقدان پوشش گیانی و منابع آب کم است. میانگین شاخص هواویز (AI) پس از نقطه تغییر بیشتر از پیش از نقطه تغییر بوده است که نشان دهنده افزایش شاخص هواویز در ایران است. سال های 1983، 2000 و 2007 به ترتیب برای ماهواره های Nimbus7، EP و Aura به عنوان سال های میانگین جهش در سری زمانی تشخیص داده شدند که می توان این سه سال را به عنوان گرانیگاه دوره فعال و غیرفعال شاخص هواویز در ایران در دوره مورد مطالعه یاد کرد.
    کلیدواژگان: شاخص هوایز (AI)، سنجنده TOMS، سنجنده OMI، آزمون Buishand، ایران
  • محمود احمدی*، عباس علی داداشی، طیبه اکبری، جمال کرمی صفحات 625-644

    پدیده گرمایش جهانی در سال های اخیر مشکلات بسیاری را برای سامانه زمین به همراه داشته است و ایران به دلیل اینکه کشوری خشک است، مطالعه شرایط آینده می تواند برای برنامه های مدیریتی مفید باشد. هدف این پژوهش کارایی مدل HadGEM2-ES از سری مدل های CMIP5 مبتنی بر روش ریزگردانی دینامیکی CORDEX و وردایی نابهنجاری دمای فصلی در ایران است. در این راستا داده های روزانه دمای هوا از 45 ایستگاه همدید طی دوره آماری (2005-1970)، داده های دمای روزانه مدل HadGEM2-ES و ریزگردانی شده با استفاده از روش CORDEX و سناریوهای RCP برای دو دوره تاریخی (2005-1960) و پیش بینی شده طی سه دوره آینده نزدیک (2040-2011)، آینده میانی (2070-2041) و آینده دور (2099-2071) استفاده شد. برای ارزیابی کارایی مدل نیز از شش روش R2، MAE، MBE RMSE، t-Jacovides و نسبت t-Jacovides/R2 استفاده شد. نتایج نشان داد که مدل از عملکرد مناسبی برخوردار است. نابهنجاری دمای فصلی در تمام فصول، سناریوها و دوره های زمانی مورد مطالعه مثبت و فصل زمستان بیشینه نابهنجاری دما را در بین فصول نشان داده است که یک تهدید بزرگ برای منابع آب کشور تلقی می شود. بیشینه نابهنجاری فصلی دمای ایران در فصول زمستان و بهار منطبق بر ارتفاعات و عرض های جغرافیایی بالاست که شمال غرب به عنوان کانون نابهنجاری ها شناخته شد. در تابستان ارتفاعات و ایران مرکزی بیشینه نابهنجاری دمای هوا را نشان داده اند. فصل پاییز نماینده بیشینه نابهنجاری دما در سواحل جنوبی ایران و نوار شرقی کشور است. همچنین، یک پاسخ فصلی از عملکرد مدل و تغییرات فضایی دمای هوا در ارتباط با ارتفاع و توزیع ناهمواری ها در کشور دیده می شود.

    کلیدواژگان: نابهنجاری دما، مدل HadGEM2-ES، روش ریزگردانی دینامیکی CORDEX، CMIP5، سناریو های RCP، ایران
  • سید حامد فنایی، فرهنگ احمدی *، علیرضا محب الحجه صفحات 645-666

    الگوی دورپیوند شرق اطلس/غرب روسیه (EA/WR) در وضع هوای پاییز و زمستان اروپا و جنوب غرب آسیا نقش حائز اهمیتی دارد. هدف پژوهش حاضر شناخت نحوه اثرگذاری این دورپیوند بر گردش های جوی و تبادلات انرژتیک چرخندها در فازهای بحرانی (قوی) مثبت و منفی آن است. ابتدا با استفاده از داده های باز تحلیل NCEP/NCAR از سال 1950 تا 2014 برای زمستان 4 ماهه (نوامبر تا فوریه)، تحلیل دینامیکی از میانگین همادی و بی هنجاری کمیت های هواشناختی در فازهای بحرانی این دورپیوند ارائه می شود و سپس با به کار بردن رهیافت انرژتیک، تاثیر قطار موج این دورپیوند بر مسیر توفان های اطلس و مدیترانه و آثار آن بر جنوب غرب آسیا بررسی می شود. انرژی جنبشی پیچکی در غرب مدیترانه و جنوب اروپا در فاز منفی (مثبت) EA/WR افزایش (کاهش) شدید نشان می دهد، حال آنکه شمال و شرق اروپا و غرب روسیه کاهش (افزایش) انرژی جنبشی دارند. در نتیجه، در فاز منفی (مثبت)، مسیر جنوب شرق سوی (شمال شرق سو) توفان اطلس به سمت جنوب (شمال) اروپا تا شرق مدیترانه (شرق اروپا و جنوب غرب روسیه) نیز می تواند گسترش یابد. در هردو فاز، در ترازهای میانی و زبرین وردسپهر بی هنجاری متضاد کمیت ها بین شمال غرب و جنوب شرق دریای مدیترانه مشاهده می شود. جنوب غرب آسیا و شرق مدیترانه بی هنجاری گردش های جوی مشابه بی هنجاری غرب روسیه دارند که پیامد آن در فاز منفی (مثبت) کاهش (افزایش) جملات تولید و تبدیل کژفشاری، شارهای گرما و رطوبت، تضعیف (تقویت) جت جنب حاره ای جنوب غرب آسیا و امکان تضعیف (تقویت) چرخندزایی شرق مدیترانه و کاهش تعداد چرخندهای عبوری به سمت جنوب غرب آسیا و ایران است.

    کلیدواژگان: دورپیوند شرق اطلس، غرب روسیه، بی هنجاری، فازهای بحرانی، رهیافت انرژتیک، جنوب غرب آسیا، مدیترانه
  • پریسا رون، حسام احمدی *، آرمین سروشیان صفحات 667-686

    خشک شدن سطح وسیعی از دریاچه ارومیه و تشکیل مناطق مستعد به فرآیندهای فرسایش بادی و رخدادهای گرد و غبار می تواند باعث گسیل ذرات معلقی شود که بر شیمی جو و ترکیبات آب باران این حوضه آبریز تاثیرگذار باشند. جهت پایش آلودگی هوا و بررسی تغییرات کمی و کیفی آب باران از نظر عناصر با منشا دریاچه ای، 6 نمونه آب باران از مهرماه 1396 تا مهرماه 1397 از رخدادهای هم زمان به صورت رسوب تر از 13 ایستگاه اطراف دریاچه ارومیه شامل ایستگاه های ارومیه، برده سور و گلمانخانه در غرب دریاچه، باری، چوپانلوی سلماس و خوی در شمال دریاچه، آق گنبد، ایلخچی و تبریز در شرق دریاچه، آغداش، میاندوآب و کشاورز در جنوب و جزیره اشک در مرکز دریاچه ارومیه در جهت ها و فاصله های مختلف از حوضه آبریز دریاچه ارومیه جمع آوری شد. نتایج آماری حاصل از تجزیه واریانس داده های به دست آمده اختلاف معناداری را بین 13 ایستگاه از نظر غلظت عناصر با منشا دریایی شامل سدیم (Na)، منیزیم (Mg)، کلسیم (Ca) و پتاسیم (K) نشان داد؛ به گونه ای که ارتباط بین عناصر سدیم، منیزیم و کلسیم نشان دهنده منشا انتشار یکسان این عناصر بوده است. با توجه به نتایج به دست آمده بیشترین پراکنش عناصر مورد مطالعه در محدوده حوضه آبریز دریاچه ارومیه در اولین حلقه شعاعی (حداقل فاصله از بستر دریاچه ارومیه) و بیشتر در جهت های جغرافیایی غرب و شمال دریاچه ارومیه مشاهده شد.

    کلیدواژگان: ذرات گرد و غبار، ذرات معلق جو، پهنه بندی مکانی، ترکیب شیمیایی آب باران، حوضه آبریز دریاچه ارومیه
  • احد وظیفه، عباس علی علی اکبری *، مجید مزرعه صفحات 687-704

    در این مطالعه توزیع منطقه ای و ویژگی های جت سطوح پایین (LLJ) در منطقه کویر مرکزی واقع در جنوب رشته کوه البرز شامل گستره افقی و قائم و تغییرات زمانی آن بررسی شده است. علاوه بر این سازوکارهای مختلف شکل گیری جت سطوح پایین (LLJ) بررسی شده و ویژگی های  LLJروی دشت کویر و شباهت های آن با سایر پدیده های مشابه در شرق و جنوب غرب کشور مقایسه شده است. در پژوهش حاضر از داده های بازتحلیل ERA-Interim (ERA-I) برای بازه زمانی 1979-2017 استفاده شده است. با استفاده از داده های مشاهداتی داده های بازتحلیل از نظر کیفی ارزیابی و ملاحظات به کارگیری داده های بازتحلیل برای مطالعه  LLJ در شبکه منظم ارائه شده است. با به کارگیری شاخص های مرتبط با تغییرات زمانی و تغییرات قائم (نیم رخ) سرعت باد در محور جت و با استفاده از داده های بازتحلیل، ابزاری تهیه شد که ضمن آشکارسازی  LLJدر هر نقطه از شبکه دامنه مورد مطالعه روی کویر مرکزی، میانگین بلند مدت (1979-2017) فصلی و ماهیانه سرعت باد در محور جت برایماه های تابستان محاسبه و تعیین شود. نوسان شبانه روزی جت با استفاده از داده های بازتحلیل نشان می دهد که مطابق تعریف بلکادر (1957) جت روی کویر مرکزی جزء دسته LLJها طبقه بندی می شود و بررسی ساختار افقی و قائم نشان می دهد که محور جت (سرعت بیشینه باد) در ارتفاع حدود 850 میلی بار قرار می گیرد و بر اساس داده های مورد استفاده با تفکیک زمانی 6 ساعت، بیشینه و کمینه سرعت باد در این تراز به ترتیب در ساعت UTC 00 و UTC 12 است که علت اصلی آن تشکیل وارونگی دما در لایه های زیرین جو در هنگام شب و کاهش قابل ملاحظه نیروی اصطکاک سطحی و همچنین از بین رفتن تلاطم گرمایی ناشی از خورشید در هنگام شب در لایه های زیرین جو است. میانگین سرعت باد در محور جت در ماه ژوئن بیشینه و در ماه اوت کمینه است. زمین بررسی موردی ساختار قائم شیو دمای پتانسیلی و چینش باد نشان داد که انتقال تکانه از محور جت به سطح زمین سبب خیزش گردوخاک در مناطق مستعد کویر و انتقال آن به شهرهای حاشیه ای کویر مانند تهران، قم و کاشان می شود.

    کلیدواژگان: جت سطوح پایین، نوسان لختی، اثر بلکادر
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  • Hamid Khosravi, Mohammad Tatar, Mahdieh Safari, Gholam Javan * Pages 487-505

    The Mw 6.0 Do-Ghaleh Fariman earthquake occurred at 10:39 local time (06:09 GMT) on 2017 April 5, in 46 km away from Fariman city of Khorasan Razavi province in northeast Iran (Figure 1). The mainshock had a maximum Mercalli intensity of VIII (Severe) (Ahmadzadeh et al., 2018), and was felt by many people a radius of 200 km in eastern part of Iran. Despite the low population density, the earthquake caused widespread destruction, killing 2 people and injuring a further 100 people. Although many historical and instrumental destructive earthquakes have occurred in Great Khorasan, no evidences from large earthquakes reported in Fariman region. Immediately, after Do-Ghaleh Fariman earthquake, International Institute of Earthquake Engineering and Seismology (IIEES) decided to design an intensive seismic network around epicenter for monitoring aftershocks and seismological aspects studies. The IIEES local seismic network contains 16 velocitymeter (Lenartz 20 Sec) and 3 accelerometers (CMG-5TD Guralp with ±2g sensitivity) that deployed in the region for 40 days (Figure 1). The sampling rate of waveform data have been chosen at 200Hz for all seismic stations. Data acquisition is leading to 1500 aftershocks with high quality waveforms in this area. The IIEES velocity model is used as initial velocity model in Lotus12 program for optimizing velocity model in Fariman region. The optimum derived velocity model (as shown in table 4) is used for relocation of aftershocks. Figure 3 shows the location map of relocated aftershocks and seismic stations. The cross sections of well relocated events show a NW-SE dip direction (Figure 3).  To relocate the mainshock and to derive the fault plane solution we have retrieved all waveforms from seismic stations, both Iran Seismic center (ISC) belong to Institute of Geophysics at University of Tehran (IGUT) and Iran National Center of Broadband of Seismic Network belong to IIEES. For fault plane solution the first P-wave polarity method (Snoke et al., 1984) is used. The result of our relocation and fault plane solution of the main shock is shown in figure 5 & table 5 in comparison with other seismic agencies reports. To estimate the fault plane solutions of well-relocated aftershocks, we extracted 120 aftershocks with azimuthal gap less than 160°. The results of our fault plane solutions of 38 aftershocks with high quality are shown in figure 6 that have azimuthal gap less than 120° and recorded at least in 16 seismic stations. Focal mechanisms of 15 aftershocks are reversed which is numbered from 1 to 15 as shown in figure 6 and table 7. However, the rest of fault plane solutions show reverse mechanisms with strike slip component. Generally, the total average trend of reactivated fault, show NNW-SSE direction based on our study that is in good agreement with the trend and focal mechanism of Mozdoran fault (figure 6). Therefore, reactivation of the Mozdoran fault can be considered as main source of Do-Ghaleh Fariman Mw6 earthquake on April 5 2017. It should be noted that in some technical reports (e.g. Naimi, 2017) and old geological maps the final section of the Mozdoran fault is termed in Chah-Mazar fault.

    Keywords: Do-Ghale Fariman Earthquake, Seismic network, Kope-Dagh, Mozdoran Fault, Focal mechanism
  • Ramin Varfinezhad *, Saeed Parnow, Abolghasem Kamkar Pages 507-521

    Magnetic surveys have been used for a wide range of studies such as oil and gas exploration, mining applications and mapping bedrock topography. Inversion of magnetic data is the most important step in the interpretation of magnetic anomalies. Due to the existence of 2-D geological structures such as fracture zones, faults, dikes, rift zones and anticlines, 2-D inversion of magnetic data is very practical. Magnetic data inversion has two main problems about non-uniqueness and instability of the solution which can be obviated by using constraints and a priori information. Non-uniqueness is the consequence of two ambiguities: I) following Gauss theorem, there are many equivalent sources that can produce the same known field at the surface (theoretical ambiguity), II) since the parameterization of the problem is such that there are more unknowns than observations, the system does not provide enough information in order to uniquely determine model parameters (algebraic ambiguity). Every measurement of data on the earth’s surface contains some noise which imposes a large amount of changes on the inverse solution, therefore the problem is also ill-posed. There are many constraints including compactness, minimization of inertia around an axis or a point, depth weighting etc. Different combinations of these constraints in the objective function lead to different algorithms each of which are appropriate for some cases. In this paper, an inversion algorithm based on inserting a combination of compactness and depth weighting constraints in the regularized weighted minimum length solution is introduced. Compactness constraint, introduced by Last and Kubic, tries to minimize the area of the anomalous body in 2-D. Depth weighting function, introduced by Li and Oldenberg, is utilized to counteract the natural decay of kernel, so all the cells have an equal probability during the inversion. The subsurface is discretized into many horizontal prisms with infinite length in one direction, which is required for 2-D modeling, and the susceptibility of each prism is assumed to be constant. Model parameters, susceptibilities contrast, is also limited between a lower and upper bound. This algorithm was programmed in MATLAB software and its efficiency was investigated by applying it on synthetic models and real data. The first synthetic model is a vertical dyke and inversion process was done for free-noise and noisy data and in both cases recovered models were satisfactory. The second model was composed of two parallel dip dykes in different depths which is a complex synthetic case. Inverting free-noise data leads to the well recovering true model. Reconstructed model obtained from noisy data actually represented an acceptable model. Therefore, results of synthetic cases were promising enough and convince us in order to apply the algorithm on real cases. Finally, the algorithm was applied on two real data sets: i) real data of the buried metallic pipes for gas transmission in Qaleh-Showkat area, Shahrood, ii) an archeological data profile of an area in old Pompeii city near Naples in Italy. This profile intersects three walls. Inversion result of the first data set using this algorithm represents an anomaly at 35 m from the start point of profile with depth to top of about 1 m and its high recovered susceptibility value was suggestive of iron or steel pipe. The derived model from archeological data were suggestive of four anomalies: the first weak anomaly was not related to any of the three walls, the horizontal and vertical extensions of the second and third anomalies were in good agreement with the first two walls and the fourth one at the end of the profile has a great difference range depth with the third wall. One main reason can be related to the imperfect profile at the end where it is not being backed to the background value.

    Keywords: magnetometry, inversion, compactness, depth weighting, synthetic model
  • Abbas Gholamzadeh *, Mohsen Farrokhi, Soudabeh Kargar Pages 523-535

    The Sanandaj-Sirjan Zone (SSZ) extends ~1500 km from the northwest (Sanandaj) to southeast (Sirjan) parallel to the Zagros Fold Thrust belt with average width of 150–200 km. This zone is a metamorphic–magmatic belt, associated with the Zagros Orogen and part of the Alpine-Himalayan orogenic system in Iran. Its limits on either side are marked with discontinuously preserved ophiolites including the following: (1) the Neyriz-Kermanshah ophiolite situated on the northern edge of the Zagros Mountains and (2) the Khoy and Nain-Baft ophiolite complexes to the northeast (Stöcklin, 1981). The rocks in this zone are the most highly deformed of the Zagros belt and share the NW–SE trend of surrounding structures. The zone is dominated by Mesozoic rocks; Palaeozoic rocks are generally rare but are common in the southeast (Berberian, 1995). The SSZ is characterized by metamorphosed and complexly deformed rocks associated with abundant deformed and undeformed plutons, as well as widespread Mesozoic volcanic. The ophiolites are generally regarded as preserving a record of an ocean basin or basins that lay between these elements in Mesozoic through mid-Cenozoic time, as a whole referred to as the Neotethys Ocean, with the Eurasian continent to the north, and Gondwana-land to the south (e.g., Stöcklin, 1974; Sengör, 1979; Berberian and King, 1981; Stampfli and Borel, 2002; Agard et al., 2011). Faryab region in the Sanandaj-Sirjan zone is located in a very tectonically active zone, materialized by highly deformed metamorphic rocks, colored melange and ultramafic-mafic complexes. An earthquake with magnitude Mw 6.0 occurred on the Faryab region, on the southeastern part of Sanandaj-Sirjan, on February 28, 2006. Aftershocks of this earthquake were used to study Love wave's group velocity. Seismic surface wave tomography of short-period dispersion curves is a useful method for studying the shallow structures of the Earth. The main aim of this study is to apply the group velocity dispersion to Faryab region, southeast of Sanandaj-Sirjan zone, to calculate the two-dimentional Love wave group velocity tomography. We have analyzed surface wave dispersion curves of 2616 waveforms of 437 aftershocks, (figure 1). These aftershocks were recorded by a local temporary network including 9 short period station that were installed by International Institute of Earthquake Engineering and Seismology (IIEES) during 28 Feb. 2006 to 30 Mar. 2006. The temporary stations were equipped with Guralp CMG-6TD velocity seismometer with flat frequency response between 0.1 – 50 Hz. The epicentral distance and magnitude of earthquakes were less than 50 km and larger than 1.5, respectively. The dispersion curves were calculated in the period range between 0.1 seconds to 10 of seconds, which corresponded to the shallow structure of upper crust including sedimentary layers. Surface wave tomography was also performed to estimate the two-dimensional group velocity maps of Love waves in the Faryab region. The isolated surface wave fundamental modes (and group velocity dispersion curves) have been analyzed using linear inversion method for estimation of 2D tomography maps (Yanovskaya-Ditmar; 1990). Based on the ray coverage inside the 2 × 2 km cells in the region, the estimated minimum dimension of distinct heterogeneities was about 5 km. There are numerous anomalies in tomography maps. The range of Love waves velocity has two part: in periods shorter than 3 seconds, the velocity ranges from 0.5 to 3 km/s, and in periods above 3 second, the velocity ranges are 0.2- 1.5 km/s. It seems that in this area we are faced with two different crusts: oceanic and continental crust. Waves with a period shorter than 3 seconds pass shallower part of the crust, seem to be related to the oceanic crust that confirmed by evidence of some rocks such as Gabbro, peridotite, and ophiolites, that are exposed on the surface (figure 4). Under this oceanic layer, there is some soft sediment of continental crust. Waves with a period more than 3 seconds travel through these soft materials.

    Keywords: Love wave, 2D tomography, shallow structure, Sanandaj-Sirjan zone, Faryab region
  • Behzad Maleki, Habib Rahimi *, Vahid Maleki Pages 537-552

    Iranian plateau is a part of Alpine-Himalayan active Mountain, which caused occurring major earthquakes across Iran. Hence, the estimation of seismic hazard parameters is required to design building and structures properly. Importance of acceleration parameter in the long-term return period, consequently affects the on site-specific design spectra for building standard law of countries (ASCE7-5, ASCE7-10, IBC, 038 code and Iranian Seismic Code 2800), so in seismic hazard analyses, selecting recurrence model is an important issue in hazard assessment. North Tabriz Fault (NTF) is one of the most seismotectonically active faults in Iran and it attracts the attention of numerous researchers because of obvious morphologic features and historical seismicity. Probability characteristic slip in intermediate of fault, documented by paleoseismic studies of Hessami et al. (2003), also the mathematical probability density function of the exponential model, are not suitable for sources of repeated large earthquakes. Exponential model is just able to estimate recurrence of small to moderate earthquakes, while recurrence of large magnitude earthquakes is much higher than the extrapolated exponential model. This difference lead to the development of the characteristic earthquake model (Schwartz and Coppersmith, (1984)). In this study, seismic hazard parameters around Tabriz city based on characteristic recurrence model has been investigated. First step in all hazard studies is determining the seismotectonic of the province. Based on this definition, Mirzaei et al. (1998) divided Iran in five major seismotectonic provinces. The covered area in this study is located in Alborz-Azerbaijan Seismic province. In order to have more information regarding the seismic hazard analysis, seismotectonic map of study area is prepared up to a radius distance of 150km from site. In this study both areal and linear seismic source model are considered. The reason for selecting areal seismic source model is due to the lack of enough information about dip and geometry of the fault. Recurrence models are defined for linear seismic sources, for those that there are enough data about them. In this study North Tabriz fault is considered as three separated segments, in which the characteristic recurrence model are used to define the intermediate segment of seismic source. Seismic hazard assessment requires the estimation of strong ground motion. The estimation of peak ground acceleration regard to recurrence model of source, magnitude, source-to-site distance, tectonic properties and source type using attenuation relationships that are the main part of seismic hazard assessment process. Estimation of peak ground motion acceleration in this study for horizontal component is based on the next generation of attenuation relationships for the west 2 project (NGA West 2).In this study, we used attenuation equation reported by Campbell-Bozorgnia (2014) NGA West 2, Kamai et al. (2014) NGA West 2, Idriss (2014) NGA West 2, Chiou-Youngs (2014) NGA West 2 and Boore et al. (2014) NGA West 2. The estimated results show that the segment which modeled by characteristic recurrence model in higher recurrence period, have higher value of acceleration.

    Keywords: Characteristic Magnitude Distribution, Exponential Model, North Tabriz Fault, Seismic Hazard Assessment
  • Kamel Azarm, Abbas Mofidi *, Ali Mohammad Khorshiddoust Pages 553-573
    Due to the challenges coming from numerical modeling, measurements, observations, lack of data in some regions, not enough investigations, many aspects of the mechanism for the occurrence of precipitation are not well understood. These challenges are shown clearly in mountainous studies. This is particularly the case for the occurrence of precipitation in the warm season in mid-latitudes, which is controlled by convective processes at small spatial scales while cloud belts are associated with cyclones and atmospheric fronts at larger scales. Iran, and especially North-West of it, is a mountainous area. Due to mountainous conditions, the temporal and spatial variations of precipitation in this region are large. In this region, the significant of spring precipitation is the most important characteristic of the precipitation regime. Therefore, on average, over 40% of the total annual precipitation is falling in the spring season. According to studies and evaluation of available data, most of the total annual precipitation in the North West of Iran (NWI) is occurring by convective systems (thunderstorms). To study the mechanism for the occurrence of spring precipitation in the NWI, the main consideration of researchers focused on synoptic patterns, especially on mid-tropospheric trough. Thus, there is still a poor understanding regarding the dynamical, thermo-dynamical and mechanical processes which occur in mountainous area in mesoscale over the NWI. In this study, the occurrence of spring precipitation in the NWI is investigated using a combination of data to clarify the dynamical and thermo-dynamical processes which are governing the springtime precipitation events. Both synoptic patterns and mesoscale phenomena are considered along with a numerical simulation. A regional climate model (RegCM4) is used to evaluate the role of local topography and meso to regional scale processes on the occurrence of spring convective precipitation. A combination of data including station data, reanalysis and model outputs are used to clarify the role of the mountains, as well as local and regional thermal and mechanical forcing for the occurrence of convective precipitation in the NWI. The results indicate that, in the spring, western waves do not completely leave the NWI. The results also demonstrate that the large-scale positive vorticity advection in the mid-troposphere is associated with a local forcing from surface heating and surface fluxes (i.e. moisture convergence, latent and sensible heat fluxes) that are the main factors for formation and development of these convective systems. Therefore, unlike previous studies, in the absence of large scale dynamical forcing, such as the mid-tropospheric trough, convective precipitation will not have occurred in the NWI. In fact, local heating alone, due to lack of sufficient moisture in the area and inadequacy to provide buoyancy, cannot to create the required instability for the occurrence of precipitation. Calculating diabatic heating for the NWI is demonstrating that the horizontal advection of heat from the mountain slopes is playing an important role to formation and development of meso-scale convective systems. While the western and southern slopes of the mountains are playing as an elevated heat source, the eastern and northern slopes are playing as a sink. Therefore, the heating on southern and western slopes of the mountains as a local forcing plays an important role in providing the available heat and energy for the development of convection and convective precipitation. As a result, the responsible mechanism for the occurrence of convective precipitation in the NWI is due to an interaction between the mesoscale and synoptic/large scale processes over the region. In other words, none of the above-mentioned factors, alone or in the absence of other factors, cannot be able to create springtime heavy convective precipitation in the NWI. In fact, in the springtime, we face certain rain generating systems that their instability, ascent and humidity advection, on the one hand, are due to large-scale/synoptic-scale forcing and on the other hand, due to surface local heating. Thus, they are not entirely similar to rain generating systems in the monsoon region of India, Western Africa or Brazil which fully utilizing thermodynamic conditions and internal heating and not similar to mid-latitudes rain generating systems which are merely a result of the large scale advection of humidity and heat and the general ascent of the westerly waves.
    Keywords: Convective Precipitation, Diabatic Heating, Mesoscale Analysis, North West of Iran, RegCM4, Horizontal Advection
  • Shadi Arfa, Mohsen Nasseri * Pages 575-597
    Extreme weather conditions have an important role on strategic planning of water resource and developing adaptation plans and natural disaster management. Therefore, it is necessary to present a detailed perspective of upcoming extreme patterns of rainfall events. In the context of climate change, pattern extraction of extreme events can only be achieved by using of daily downscaling methods. In the current paper, two single site downscaling methods SDSM, DMDM and a multisite approach based on Singular Value Decomposition (SVD) technique are used and their results are evaluated. The case study is located on Tehran province with over 10 precipitation and synoptic stations in the period 1985 to 2005. The used climate change scenarios were generated for (2021-2050) period. In addition, the daily NCEP/NCAR dataset and results of climate change scenarios (RCP2.6, RCP4.5, and RCP8.5) were achieved from the Canadian Centre for Climate Modeling and Analysis. For each downscaling models, based on their own concepts, suitable predictors have been selected via backward stepwise regression as a preprocessing step (Hessami et al. 2008). The implemented multisite approach is based on combination of two multiple regression models to simulate precipitation amount and occurrence and also using SVD to capture stochastic behavior of precipitation to preserve accurately the space–time statistical properties of daily precipitation (Khalili and Nguyen, 2017). Beside the SDSM as a regression based downscaling method (Wilby et al. 2002), DMDM as a regression based tool box including Multiple Linear Regression (MLR), Ridge Regression (RR), Multivariate Adaptive Regression Splines (MARS) and Model Tree (MT) have been used as well (Tavakol et al. 2013b). To achieve the goal of the current research, temporal downscaling method to simulate extreme precipitation values is needed. In this regard, numerical model based on scaling invariant concept is used to do temporal downscaling (Nguyen et al. 2007). The sub daily extreme rainfall, are estimated from daily downscaled rainfalls by analyzing the non-central moments of observed rainfalls, single time regime (from 6 h to 24 h) and using scaling factor. Finally, as the major output of this study, Intensity Duration Frequency (IDF) curve is calculated affected by climate change in the period 2020 to 2050. The results based on statistical assessment both in calibration and validation periods of daily precipitation show the effectiveness of SDSM and DMDM models, respectively, in terms of long-term monthly average, and multisite model in preserving the trend of computed information in comparison with observed values. Based on uncertainty assessments results, DMDM provided the most precsion results versus the other methods over the study area. In addition, the models performance rank in estimating unseen station belong to the DMDM and multisite and SDSM methods, respectively. In the second step, quantities of IDF curves for return periods of (2-100) years and durations of (6, 12, 24 hour) at Mehrabad station are estimated using the results of coupled three different spatial downscaling and GEV distribution. Results show higher accuracy of DMDM and SDSM models respectively in comparison with multisite model. Based on the linear structure of SDSM and Multisite downscaling models versus the complex structure of DMDM, it seems that limitations of linear methods cause DMDM to be superior to the other ones. In addition, evaluation of the results of extreme values by three different climate change scenarios based on the DMDM downscaling model indicates an increase in rainfall intensity using scenario RCP8.5 and a decrease under scenarios RCP4.5 and RCP2.6.
    Keywords: Downscaling, SDSM, DMDM, Multi site downscaling, IDF, GEV, Uncertainty
  • Bijan Farrokhi, Hadi Davari* Pages 599-607

    The electric charge of dust particles plays an important role in the study of laboratory plasma, atmosphere plasma, and interplanetary plasma. Often, dust particles are present naturally in space plasma and some laboratory devices. Sometimes they are added to the system as desired in the laboratory for the production of dusty crystalline plasma or to study the dusty plasma behavior. This type of plasma consists of neutral atoms, ions, electrons, and dust particles. Dust particles are usually made of ice, silica, carbon, metal conductors, with different dielectrics, and their sizes range from a few hundred nanometers to several millimeters. The mass of these particles, in comparison with the electron and ion mass, makes it possible to observe many of the dynamic effects of the dusty plasma over a millisecond or longer. The study of how these particles are charged and the effect of their electrical potentials on the plasma properties, has always been a matter of interest. The dust particles are initially without charge, but after a while, with the collision of the electrons and the ions with the dust layer (most of the particles stick to the dust after contact) they become electrically charged. The behavior of dust particles, electrons, and ions in plasma is different in the presence or absence of a magnetic field, and research in this field is of great interest. Almost all laboratories use a magnetic field to control the plasma and enclose it. The use of a static magnetic field and a magnetic field caused by electromagnetic waves (variable with location and time) is also common. Theoretical, empirical, and simulated study of dusty plasma has a relatively long history. The use of computer simulation method is very popular due to its vast and inexpensive facilities (compared to empirical experiments). The code of particle-in-cell (PIC) simulation was used to simulate dusty plasma and the effect of magnetic field on the process of dust particle charging by plasma particles under earth’s atmosphere plasma conditions. The electric field was self-consistently solved from the Poisson equation. Electron-neutral elastic scattering, excitation and ionization processes were modeled by Monte Carlo collision methodology. The effects of the difference in the initial density of the plasma and the different magnetic field were simulated. During dust particle charging, the time to reach saturation and saturation load were compared. It was observed that increasing the magnetic field does not necessarily mean that the charge of the dust particles was increased or that the time to reach the saturated state was reduced. Finding the limit of this field, which certainly depends on the physical properties of the plasma, can be useful in some issues, for example, in earth’s atmosphere or laboratory plasma conditions. It was observed that, depending on the initial density of the plasma, the time to reach the saturated stated varied from 15 nanoseconds to 150 nanoseconds. The time to reach the saturated state is inversely proportional to the initial density of the plasma and the radius of dust particles. Also, the results of this simulation can be used in future simulation models that focus on the transportation of dust particles and their effects on the entire plasma.

    Keywords: Dusty plasma, electric charging, particle in cell method (PIC), earth atmos-phere’s plasma, magnetic field
  • Abbas Ali Dadashi Roudbari, Mahmoud Ahmadi * Pages 609-623
    Aerosols are solid or liquid particles in the air with a typical radius of 0.001 to 100 μm, which have a significant and harmful effect on human health. Aerosols come from both natural and human sources, and in recent years, human activities associated with urbanization and industrialization have led to a steady increase in the amount of these particles in the airborne state. Since the effect of aerosols on airborne processes is more intense in the ultraviolet group, the Aerosol Index (AI) is a useful and accurate method for detecting ultraviolet absorbing humus, such as soot and dust. The positive AI indicator represents aerosols, clouds are close to zero, and negative values are the absence of humus or due to the presence of non-absorbent particles in the UV group. The aim of this study was to investigate the spatio-temporal retrieval of the TOMS and OMI sensors in Iran. The results of this research can be useful in identifying seasonal sources of dust, critical areas and ultimately its feedback in the climate system for future studies. TOMS Nimbus 7 (TOMSN7L3 v008) data was used during the period 1979 to 1992; TOMS EP (TOMSEPL3 v008); 1996 to 2005; and OMI (OMTO3d v003) for the period of 2005 to 2015. In this research, the change of AAI index was studied using the Buishand test. After decoding the necessary data and calculations, the maps of each in the ARCGIS environment were mapped using the inverse distance-weighted method (IDW) with the least amount of Root Mean Square Error (RMSE). For each of the three satellites data, spring and summer, the highest amount of statistical data is the mean and maximum. The range of changes also increases naturally in the seasons with the mean peak, which is the maximum range of spring and summer changes. Seasonal changes of the amount of AI in Iran is due to a synergy in terms of emissions and atmospheric conditions. Winter AI has its non-alternating pattern synoptic systems that affect Iran during the cold season, especially winter is mainly, due to significant rainfall and humidity that, reduce AI. This is the most important factor that has caused the regions of central Iran to have fewer highs than those of the southeast to southwest of Iran. Therefore, the height of the boundar layer in very dry areas and the central regions of the desert naturally is higher than wetland areas of the desert, resulting in a higher value of Aerosol index (AI). So, in none of the three satellites data set studied after the average change point was less than before the change point, which indicates a significant increase in the aerosol in Iran's airspace. The results of the study have shown that in each of the three satellites data set studied, the warm- period has the maximum Aerosol index (AI). Seasonal variation of the aerosol index in Iran is due to the mixing of airborne aerosol the spring it has been shown  the activation of the regional dust sources. The minimum amount of Aerosol Index (AI) occurred in winter, possibly due to increased precipitation in the studied area. Rainfall has two important control effects on dust storm activity. 1-From soil moisture and 2-vegetation. Dust loads in the vast area of Iran can be classified into three general categories: 1-Urban/industrial activities and biomass burning (mainly in Isfahan, Tabriz, Tehran and Khuzestan), 2. Dust transport of desert areas and semi-arid (mainly arid and semiarid areas of Iraq, Syria, Saudi Arabia and North Africa) and 3) marine environments. The regional role of the atmosphere in the release and transport of aerosols to Iran plays a significant role, in the middle of spring until late summer, a small area of thermal low is formed inside Iran and Saudi Arabia, and this leads to strong pressure gradient responsible for the creation of northwesterly winds. The point of change in the annual Aerosol Absorption Index (AAI) by the Buishand test has shown that the Aerosol Index has been upgraded based on three satellite data and two sensors, so that the mean Aerosol Index (AI) after the change point in every three  satellite and the two sensors data surveyed that have more the change point than before.
    Keywords: Aerosol Index (AI), TOMS Sensor, OMI Sensor, Buishand Test, Iran
  • Mahmoud Ahmadi *, Abbas Ali Dadashi, Tayebeh Akbari, Jamal Karami Pages 625-644

    Global warming is considered as a major challenge for food security and in recent years, it has attracted attentions, especially in arid areas. The Middle East and the Mediterranean are known as sensitive areas to climate changes. It is essential to understand the condition of climate changes, firstly at regional scales and secondly at large scales to adopt appropriate policies. Although the variety of seasonal temperature anomalies by the CMIP5 through the use of statistical downscaling model has not been thoroughly investigated. The aim of this research is to evaluate the diversity of seasonal temperature anomalies which are extracted from RegCM2-ES as the CMIP5 collection model based on the dynamic regression method by CORDEX model for the first time in Iran. In this study, the HadGEM2-ES model has been applied as one of the CMIP5 collection models to investigate the seasonal temperature anomaly by the use of CORDEX dynamic regression downscaling method under the Representative Concentration Pathway (RCP) scenarios. This model was operated for the period (1970-2005) and for a predicted future period (2011-2099) under three RCP scenarios (RCP2.6, RCP4.5, RCP8.5). In order to achieve better evaluation of global warming at the next step, the model data was divided into three time intervals comprises near future (2011-2040), middle future (2041-2070), and far future (2071-2099). The model was validated using data based on 31 synoptic stations and by applying six statistics of deterministic coefficient (R2), mean absolute error (MAE), mean bias error (MBE), root mean square error (RMSE), t-Jacovides, and t-Jacovides/R2 ratio. According to statistical results of validation, the HadGem2-ES model proves that it has appropriate ability to reconstruct the seasonal temperature anomalies. Results show that the seasonal temperature anomalies are positive during the study of time intervals under the used RCP scenarios and it is high in winters which is considered as a significant threat to the water resources in Iran. The reconstructed maximum seasonal temperature anomalies indicate that it matchs well in high regions and high latitudes during winters and springs. Subsequently the northwest of Iran is known as the center of maximum temperature anomalies. In summer, the mountains and central Iran indicate the maximum temperature anomalies while in autumn, anomalies are recognized on the coastal regions in the south and east border of Iran. Furthermore, there is evidence for a seasonal response to performance of the model and spatial diversity based on different topography in Iran. Based on the results, it can be concluded that the most seasonal temperature anomalies based on the HadGEM2-ES model and dynamical downscaling CORDEX method is evident in high latitudes and mountainous regions of Iran. There is a different pattern of maximum positive anomalies in southwest, south, southeast, and east of country during autumn. Not only was the temperature anomaly positive in all of seasons but also it was positive in each of scenarios and time periods of study. Consequently, it is a major threat to natural water resources in Iran. The temperature anomaly extracted from HadGEM2-ES Model comparing to the temperature ranges of different models proves that according to global warming, there is a reduction in the cold extreme events in Iran. Moreover, the spatial variation of temperature in Iran depends on the complex environment topography which causes a specific response of the model to surface forcing. It is concluded that the existence of snow is the main reason for increasing the temperature anomaly in the highlands of northwest of Iran.

    Keywords: Temperature anomaly, HadGEM2-ES model, CORDEX, CMIP5, RCP scenarios, Iran
  • Seyed Hamed Fanaei, Farhang Ahmadi*, Ali Reza Mohebalhojeh Pages 645-666

    The teleconnection pattern (EA /WR) plays an important role in the fall and winter weather of Europe and Southwest Asia (SWA). The purpose of the present research is to find out how critical (strong) phases of this teleconnection influences atmospheric circulation and consequently affects weather of EurAsia by investigation of eddy energy fluxes and different conversion terms in the tendency of eddy kinetic energy (EKE) equation. First, by applying the monthly indices of EA/WR which are taken from the Climate Prediction Center (CPC), we derived 37 critical positive months (CPM) and 38 critical negative months (CNM). Then by using NCEP / NCAR reanalysis data of the years 1950-2014 for the 4-month of November to February (NDJF), we computed the ensemble mean (averaging over CPM and CNM separately) and anomalies of different meteorological quantities with respect to long mean (65-year period). The energetic terms which have been investigated include baroclinic conversion (BCC), barotropic conversion (BTC), conversion of total energy flux (CTF), ageostrophic flux (CAF) and baroclinic generation (BCG). The ensemble mean and vertical average of the energetic terms in a domain of 90W to 90E and 20N to 80N were computed. The first part of the paper is devoted to dynamic analysis of the ensemble mean and anomalies of the meteorological quantities in the critical phases of EA/WR. In the second part, an energetic approach is employed to study the effects of the wave train anomalies on the North Atlantic and Mediterranean storm tracks along with its effects on the SWA. As the subtropical cyclonic activities in the latter region is so much dependent on the strength and position of subtropical jet stream, the wind speed at 250 hPa level as well as BTC of energy between EKE and the mean kinetic energy have a key role in this topic. The results obtained indicate that EKE of the Eastern Mediterranean is not significantly different in the two phases, but in the negative (positive) phase of EA/WR there is a marked increase (decrease) of EKE in the south of Europe and the west of Mediterranean regions. Also, in the north and east of Europe and in the west of Russia in the negative (positive) phase the EKE decreases (increases). As a result, the south-east (north-west) pathway of the North Atlantic storm track to the south (north) of Europe is strengthened in the negative (positive) phase, which can spread to the southwest of Russia (east of Mediterranean). So the connection of the Mediterranean storm track to the Atlantic storm track is stronger in CNM compared to CPM. In the both phases, in the middle and lower troposphere a see-saw anomaly pattern was observed between the northwest and the southeast of the Mediterranean Sea. Anomalous atmospheric circulations of SWA and the Eastern Mediterranean Sea are similar to that in the center of West Russia. In the positive (negative) phase of the EA/WR, the cyclonic (anticyclonic) circulation in the Middle East increases (decreases) the BCG and BCC as well as heat and humidity fluxes and intensifies (weakens) the subtropical jet. These features would result in the possibility of strengthening (weakening) of cyclonic activity in the Eastern Mediterranean. In addition to the above characteristics, in the CPM, the formation of strong total energy flux divergence in the east of Mediterranean could act as a source of energy for downstream propagating waves and therefore enhance the activity of Eastern Mediterranean storm track towards Iran. In Iran, despite of the existence of intense jet in the southern part, BTC anomaly is negative, while in the north of Red Sea (the southern flank of the jet) it is positive which may be a result of less cyclone passage towards the south of the jet and more dissipation in comparison to the long mean in the northern flank of the jet. In the CNP, although based on the analysis of energitc terms the connection of the Eastern Mediterranean with the storm track of the North Atlantic is well established, but the formation of anticyclonic circulations in the SWA results in weakening of the activity, the passage of the cyclones and thereby the possibility of "downstream development" in the SWA. In this phase, the divergence of the ageostrophic flux (negative CAF) and increase in BCG (generation of the eddy available potential energy) can make the Mediterranean center as a source of eddy energy for the northeast of Africa and the Eastern Mediterranean. The dynamic anomalous circulations of the EA/WR pattern and EKE diagnostics confirm that in the positive phase, in contrast to the negative phase, the stretch of the Eastern Mediterranean storm track through the Middle-East is more active.

    Keywords: East Atlantic, West Russia teleconnection, anomalies, critical phases, energetic approach, Southwest Asia, Mediterranean
  • Parisa Ravan, Hesam Ahmady*, Armin Sorooshian Pages 667-686

    Due to the presence of elements such as Ca, Na, Mg and K, lakes can play an important role in the chemical properties of rainwater due to the evaporation of water droplets in the atmosphere. These marine aerosols can be transmitted by wind to areas far from their original source. Therefore, monitoring of the quality of rain water due to the transfer and sedimentation of marine aerosols as the best parameter for monitoring chemistry of the atmosphere has been important in extensive studies. This phenomenon occured with the drying of Lake Urmia, with the loss of 90 percent of its water volume and the formation of salt desert on its bed. This situation can overcome climate change in this area, increase respiratory diseases and, consequently, the lives of people living in these areas. Therefore, the present study intends to map the spatial variations of rainwater chemistry in terms of sodium, magnesium, calcium and potassium (as a representative of marine resources) by collecting rainwater from simultaneous events in 13 stations around the Lake of Urmia and damages are determined from the most acceptable area in terms of the impact of marine elements. This study selected the Lake Urmia watershed as the study area. About 129 rainwater samples were collected from 13 stations around Lake Urmia over a one year period. These stations are located in the four main geographical directions of north (Khoy, Bari and Chopanloo Salmas), southern (Aghdash, Miandoab and Keshavarz), East (Tabriz, Ilikhchi and Agh Gonbad) and West (Golmankhaneh, Urmia and Bardehsor) and the center of th lake )Ashk Island). Sampling from each event with the same volume of 250 ml at points away from contamination and then stored at 5-4°C to prevent physico-chemical changes. The analysis of the elements was measured using the ICP-MS model 8800 in ppb. In the present study, the meteorological data in two categories of wind speed and wind direction (meteorological glaciers) were considered for 13 study stations. the mapping of the studied elements were generated by the IDW method in the Arc GIS software version 10.4. One-way ANOVA and Pearson correlation coefficient were used in SPSS software version 18 to examine the changes and correlation between the elements. The highest concentrations of Na and Mg were obtained at Golmankhaneh station. Also, the highest concentration of Ca element was observed at Golmankhaneh station, which in the second Bardehsor,Ashk Island, and Tabriz stations had the largest concentration. The study of windrose showed that stations located south of the lake and stations in the west were affected by very low wind speeds from the lake but the stations located on the north and east of the lake have been affected by relatively fast winds from the lake side. The mapping showed that the highest concentrations of the studied elements were in the north and west stations, as demonstrated by the one-way ANOVA results. The correlation results showed that there is a significant correlation between sodium, magnesium and calcium, indicating that these elements are likely to have the same source of propagation and originate from salt salts and have strongly  been affected by suspended particles with the origin of the lake, considering the climatic data of stations in the north of Lake Urmia (Khoy and Salmas stations). By investigation of rainwater samples in terms of concentration of studied elements and their spatial variations at different distances from Lake Urmia showed that the highest concentrations of the elements studied at nearby stations (Golmaneh, Barry, Tak Island and Agh Gonbad), it was observed that in the Lake Urmia  relatively large amounts of these elements are found at Salmas and Khoy stations that in general, it can be said that this distribution is more than a few kilometers to the lake and shows that the impact of Lake Urmia is currently high on nearby stations. As a general conclusion, the western and northern regions of the lake are more susceptible to dust and suspended particles from the dried-up areas of Lake Urmia. Investigating the distance factor on the concentration of lake origin elements showed that the concentrations of these elements with increasing distance from the lake and the coastline are mainly  decreasing. Strong and positive correlation between sodium, magnesium and calcium elements is likely to indicate the sources of the same or close distribution of these elements, although this correlation is observed with a lower content of calcium element with sodium and magnesium elements, indicating enrichment calcium is a part of limestone and marl formation around the catchment area of Lake Urmia.

    Keywords: Atmospheric particulates, Aerosol, Spatial mapping, chemical composition of rainwater, Lake Urmia basin
  • Ahad Vazifeh, Abbas Ali Aliakbari*, Majid Mazraeh Pages 687-704

    Nocturnal low-level jets (NLLJs) occur frequently in many parts of the world. These low level jets are important in heat, dust, moisture and even insects transport for long distances; hence their characteristics have been the subject of many studies. There are many regions in mountainous areas of Iran that experience NLLJs for which the NLLJ over the Dashte Kavir (DK) is an important one that occur in summer months. The occurrence and other detailed characteristics of NLLJs over the DK in the north desert region of Iran and south of the Alborz chain are not well known. There are not much observational wind profiles available to study the jet in the region. So, we have used the ERA-Interim Reanalysis data that provide long enough historical grid data that can be used for this kind of studies. This paper climatologically presents the occurrence of NLLJs and its characteristics over the DK by analyzing multi-year ERA-Interim reanalysis. We have compared the reanalysis data with surface observations from 11 synoptic stations in the DK region in the long period (1979-2017) and also a 40m tall observation platform to find correspondence between the two. It is found that the ERA-Interim data set can capture the real atmospheric parameters and thus can be used to study NLLJs’ features in the region. The NLLJs occur in most of the summer nights, which are primarily easterly to northeasterly. The jet core typically appears at 850 hPa at the top of the surface inversion layer with monthly average speed of 9 to 14m/s in its core. Based on the Inertial oscillation theory or Blakadar (1957) effect, most NLLJs are located above the nocturnal inversion during the warm season nights, while during the cold season, the wind regime changes and weak westerly winds dominate in lower levels in this area. Based on the 6 hours’ resolution of the available reanalysis data, NLLJs above the inversion have strong daily oscillations and the maximum wind speed occurs at 00 and the minimum at 12 UTC and an annual cycle with a mean monthly maximum speed in June. We quantified mean monthly NLLJ parameters using some definitions and construct magnitudes of the NLLJ in every grid point in the DK region. The magnitude of the momentum in the lower atmosphere from the top of the surface layer to the top of the mixed layer is large for NLLJs of the warm season and using the bulk Richardson number, in a few case studies, the downward momentum transfer in weak stability conditions leads to dust rising in the region. The winds below the NLLJ core to the desert surface gain strength in summer, and these summer winds are coincident with an enhancement of rising dust that reduces visibility in the cities in the desert margins. The nocturnal jet seems to flow along the southern mountain range of Alborz that extents far west even to the Tehran greater plain. Such strong flow may have implication for air pollution ventilation of the Tehran area in summer. This phenomena can be interesting subject for future study in this area (Tehran) that suffers from acute air pollution episodes.

    Keywords: Nocturnal Low Level Jet, Inertial Oscillation, Blakadar Effect, Dashte Kavir, Iran