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پژوهش های جغرافیای طبیعی - پیاپی 99 (بهار 1396)

فصلنامه پژوهش های جغرافیای طبیعی
پیاپی 99 (بهار 1396)

  • تاریخ انتشار: 1396/03/21
  • تعداد عناوین: 10
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  • مقاله علمی پژوهشی
  • محمدحسین رامشت*، امیر صفاری، امیر کرم، عبرت محمدیان صفحات 1-20
    تغییر بینش پژوهشگران نقطه عطفی در تغییر ادبیات، منطق حاکم بر پژوهش، و حتی نوع ریاضیاتی است که آن ها در پژوهش‏های خود به کار می‏گیرند. بنابراین، شناخت ریشه های نظری روش‏ها کمک موثری است در درک بهتر پژوهشگر دارد. نسبی‏گرایی از مفاهیمی است که ابعاد مفهومی متعددی دارد. به‏ طور کلی، دیدگاهی است در شناخت‏شناسی که الزام قطعیت را نفی، دلالت را جایگزین علیت، و دال و مدلول را جایگزین اصل علت و معلول می‏کند. نسبی‏گرایی همان اندازه در اندیشه سوفسطائیان و هرمونتیست‏ها مطرح است که در میان دانشمندان علوم تجربی، معرفت‏شناسی سیستمی، ترامتنیت، و عرفان و اشراق دیده می‏شود. این مطالعه برگرفته از رساله‏ای در دانشگاه خوارزمی است. در این مطالعه، با روش تحلیل گفتمان، دیدگاه هفت شخصیت‏ برجسته در حوزه معرفت هرمنوتیک، علمی، سیستمی، ترامتنیت، و عرفان و اشراق درباره نسبی‏گرایی باز‏خوانی و با آنچه گیلبرت در ژئومورفولوژی نسبی‏گرایی نامیده، مقایسه شده است. نتایج این پژوهش نشان می‏دهد:
    کلیدواژگان: ژئومورفولوژی، سیستم، گیلبرت، نسبیت، نسبی گرایی
  • حسین محمدی، قاسم عزیزی، فرامرز خوش اخلاق، فیروز رنجبر* صفحات 21-37
    یکی از اثرهای تغییر اقلیم بروز بی نظمی در چرخه هیدرواقلیمی کره زمین است. این تغییرات در عدم موازنه تراز سطح آب در منابع آب زیرزمینی، سطحی، دریاچه ها و همچنین تغییر در توزیع مقدار و زمان بارش‏ها و جریان رودخانه نمود پیدا می‏کند. تحقیق حاضر به منظور شناخت روند تغییرات شاخص‏های حدی بارش روزانه ایران انجام گرفته است. بدین منظور، از داده های بارش 24ساعته 47 ایستگاه سینوپتیک طی دوره 1982 2012 استفاده شده است. برای استخراج روندها از شاخص‏های تیم کارشناسی آشکارسازی و نمایش تغییر اقلیم و شاخص‏های ETCCDI با استفاده از نرم افزار RClimDex تحت زبان برنامه نویسی Rبهره‏گیری شده است. نتایج این تحقیق نشان می‏دهد در دوره مورد مطالعه همه شاخص‏های حدی بارش در ایران دارای تغییر و روند است. در بیشتر ایستگاه ها، بارش سالانه کاهش (شامل حدود 92 درصد از ایستگاه ها) و تعداد روزهای خشک (CDD) افزایش یافته است (شامل حدود 72 درصد از ایستگاه ها) و فقط در برخی از ایستگاه ها در نواحی مرکزی و دامنه های زاگرس تعداد روزهای خشک روند کاهشی دارد. از نظر بارش‏های سنگین و نیمه‏سنگین و همچنین روزهای مرطوب و فوق‏العاده مرطوب، سهم تغییرات در ایستگاه های واقع در سواحل شمال و جنوب بیشتر است.
    کلیدواژگان: ایران، بارش، تغییر اقلیم، روند، شاخص های حدی
  • بهروز سبحانی، مسعود گنجی، اکبر گل دوست* صفحات 39-53
    در این پژوهش به تعیین و بررسی تاریخ‏های آغاز و پایان یخبندان‏های زودرس بهاره و دیررس پاییزه و چند ویژگی آماری آن در ایستگاه های استان اردبیل ‏پرداخته شده است. همچنین ویژگی هایی از جمله تاریخ‏های آغاز و پایان، تداوم، شدت و تواتر و ویژگی احتمالی این مولفه ها محاسبه می‏شود. روش مورد استفاده دانش احتمالات و زنجیره مارکوف است. نتایج نشان می‏دهد روند کلی روز‏شمار تاریخ‏ شروع یخبندان‏‏ها در ایستگاه پارس‏آباد کاهشی و در اردبیل و خلخال افزایشی است. روند روز‏شمار تاریخ‏های پایان یخبندان‏‏ها کاهشی است. شروع یخبندان‏ها (یخبندان‏های زودرس) در ایستگاه پارس‏آباد در ماه نوامبر و در ایستگاه های اردبیل و خلخال در ماه اکتبر است. یخبندان‏ها (یخبندان دیررس) در پارس‏آباد در ماه آوریل و در اردبیل و خلخال در ماه می پایان می‏یابد. در ایستگاه خلخال تداوم یخبندان‏ها بیشتر از ایستگاه های دیگر است. در ایستگاه خلخال تعداد یخبندان‏های شدید با احتمال رخداد 37/2 درصد در ماه اکتبر بیشتر از ایستگاه های دیگر است. از نظر تواتر، در یخبندان‏های زودرس بیشترین احتمال رخداد مربوط به حالت یخبندان بعد از یخبندان بوده که در خلخال با احتمال 31/63 درصد است و در یخبندان‏های دیررس بیشترین احتمال رخداد مربوط به حالت یخبندان بعد از حالت بدون یخبندان با احتمال 54/61 درصد در ایستگاه اردبیل است.
    کلیدواژگان: اردبیل، تداوم، تواتر، شدت، یخبندان
  • زینب جعفریان*، وحید بشتر، عطاالله کاویان صفحات 55-69
    فرسایش و هدررفت خاک امروزه به یکی از معضلات مهم زیست محیطی بشر تبدیل شده است. بنابراین، اجرای عملیات اصلاح و احیا برای کاهش آن ضروری است. هدف از این تحقیق برآورد میزان فرسایش خاک و سپس شبیه‏سازی اثر عملیات اصلاح و احیای مراتع بر میزان هدررفت خاک در منطقه لار استان مازندران است. نخست به مکان‏یابی طرح‏های اصلاح و احیای مناسب برای منطقه اقدام شد. سپس، با استفاده از معادله تجدیدنظرشده جهانی هدررفت خاک نقشه خطر فرسایش منطقه تهیه شد. سرانجام، با استفاده از این مدل، تغییرات فرسایش بعد از اجرای عملیات اصلاح و احیای فوق پیش‏بینی شد. میانگین بار رسوب سالیانه در منطقه مورد مطالعه 52 تن در هکتار در سال محاسبه شد. همچنین، مساحت اراضی ای که ‏بایست در آن ها عملیات اصلاح و احیا انجام شود به ترتیب شامل 378 هکتار بذرکاری، 246 هکتار میان کاری، و 176 هکتار کپه‏کاری است. نتایج شبیه‏سازی پس از عملیات یادشده نشان داد که فاکتور‏های P و C به ترتیب به 8/0 و 31/0 خواهد رسید. بنابراین، میزان متوسط فرسایش بعد از عملیات اصلاح و احیا نیز به 34 تن در هکتار در سال کاهش خواهد یافت که معادل کاهش 34 درصدی میزان فرسایش است.
    کلیدواژگان: احیای مرتع، درصد پوشش گیاهی، فرسایش خاک، مدل RUSLE
  • همت الله رورده*، طاهر صفرراد صفحات 71-83
    در پژوهش پیش رو ارتباط بین اختلاف درجه حرارت سطح دریا و هوا بر بارش‏های سنگین و فراگیر سواحل جنوبی خزر طی فصل پاییز بررسی شده است. داده های روزانه بارش ایستگاه های سینوپتیک آستارا، بندر انزلی، رشت، رامسر، بابلسر، قائم‏شهر، و گرگان طی سال‏های 1986 تا 2013 گردآوری شد. روزهایی که مقدار بارش آن ها حداقل در پنج ایستگاه بیشتر از صدک 95 آن سال بود به عنوان روزهای بارش‏ سنگین و فراگیر تعریف شد. مشخص شد که افزایش در بخش‏های جنوبی خزر بارش های سنگین و فراگیر را فقط در بخش شرقی منطقه مورد مطالعه به صورت معناداری افزایش می‏دهد. با بهره‏گیری از روش ادغام وارد و محاسبه همبستگی بین داده ها، سه خوشه تشخیص داده شد: خوشه اول بیشینه شیو در راستای شمال‏ غرب به جنوب شرق؛ خوشه دوم در راستای شمال به جنوب؛ و خوشه سوم در راستای غرب به شرق را بیان می‏کنند. ایستگاه های واقع در شرق منطقه مورد مطالعه در خوشه دوم بارش بیشتری داشتند؛ برعکس، ایستگاه هایی که در غرب قرار داشتند طی خوشه سوم بیشترین بارش را دریافت می‏کردند. بر اساس واکاوی همدیدی خوشه ها، استقرار هسته پرفشار در شمال غرب دریای خزر سبب ریزش هوای سرد از عرض‏های شمالی‏تر و ایجاد بارش های سنگین و فراگیر در منطقه می‏شود.
    کلیدواژگان: اختلاف درجه حرارت دریا و هوا، بارش سنگین و فراگیر، سواحل جنوبی خزر، فصل پاییز
  • غلامعلی مظفری، شهاب شفیعی* صفحات 85-100
    در این پژوهش تحلیل فضایی فراوانی رودبادهای مرتبط با بارش‏های فرین و فراگیر در غرب ایران با بهره‏‏گیری از رویکرد محیطی به گردشی انجام شده ‏است. بارش روزانه 69 ایستگاه سینوپتیک و اقلیم شناسی (1961 2010) انتخاب شد و 119 روز بارش‏های فرین و فراگیر منطقه بر اساس توزیع تعمیم‏یافته مقادیر فرین از میان آن ها برای بررسی انتخاب شد. فراوانی رودبادها در چهار تراز 250، 300، 400، و 500 هکتوپاسکال بررسی شد. نتایج بررسی ها نشان می‏دهد رودبادها در تراز 250 هکتوپاسکال فراوانی بسیار زیادی را نشان می‏دهند. نقشه های میانگین سرعت رودبادها از یک ‏سو منطبق بر رخداد بیشینه فراوانی رودبادها و از دیگر سو مقارن با وقوع بیشینه سرعت رودبادها در پهنه مورد مطالعه است و از قرارگیری ربع دوم هسته رودباد (که با افزایش تاوایی مثبت و همچنین واگرایی سطوح فوقانی و همگرایی سطوح پایین جو همراه است) بر روی غرب ایران حکایت دارد. ترسیم بیضی استاندارد در همه سطوح به جز سطح 250 هکتوپاسکال نشان داد که غرب ایران در نیمه اول بیضی قرار گرفته است. نحوه عملکرد دینامیکی هسته رودباد در ورودی راست و خروجی چپ، که همراه با واگرایی بالایی است، هم زمان با همگرایی در غرب ایران، بارش‏های فرین را در پی دارد.
    کلیدواژگان: بارش فرین، بیضی استاندارد، رودباد، غرب ایران، ناپایداری جوی
  • عطا عبداللهی ودی * صفحات 101-111
    از ویژگی های منحصربه‏فرد دریای خزر تغییرات سریع تراز آن نسبت به تراز دریاهای آزاد است. این تغییرات سریع بین سال‏‏‏‏‏های 1929-1995 به وسیله ایستگاه های اندازه‏گیری تراز آب و از سال 1992 به وسیله داده های آلتی‏متری با دامنه در حدود سه متر به ثبت رسیده و اثرهای درخور توجهی در مورفولوژی ساحل داشته است. با وجود این، آثار تغییرات تراز پیش از ثبت تراز آب مبهم است و نتایج گوناگونی ارائه شده است. بنابراین، پیش‏بینی تراز بسیار پیچیده و اغلب با اشتباه توام است. بر اساس داده های رادیو کربن به دست آمده از مناطق مختلف دریای خزر، دو دوره را می‏توان در اواخر هولوسن تفکیک کرد که در مورفولوژی دریای خزر اثرهای بسیار مهمی به جا گذاشته اند. این دو دوره تقریبا منطبق بر دوره های سردند و به عنوان دوره های سرد 2600 سال پیش و دوره سرد کوتاه در اروپای شمالی شناخته می‏شوند. در این مطالعه سعی شده است اثرهای دو دوره با استفاده از داده های میدانی، عکس های هوایی، و نتایج رادیو کربن از مناطق مختلف دریای خزر بررسی شود. نتایج نشان می‏دهد سواحل شرقی به دلیل شرایط توپوگرافی و مورفولوژی بیشترین تاثیر را در برابر افزایش تراز در دو دوره سرد هولوسن داشته است.
    کلیدواژگان: پیشروی و پسروی، تغییرات سریع دریای خزر، دریای خزر، دلتای سفیدرود
  • حسن لشکری *، عباس علی داداشی رودباری، زینب محمدی صفحات 113-133
    تروپوپاز لایه انتقالی از وردسپهر به پوش سپهر است. این لایه تعیین کننده حد بالایی و ضخامت وردسپهر است. در پژوهش حاضر از داده های ژرفاسنج مادون قرمز اتمسفری (AIRS) سنجنده مودیس آکوا ماهواره (EOS) استفاده شد. این محصول به شکل پارامترهای ژئوفیزیکی است و در شبکه ای به ابعاد 1×1 درجه قوسی توزیع شده است. این داده ها از 180- تا 180 طول جغرافیایی و 90 تا 90 عرض جغرافیایی موجودند که از سامانه تطبیقی پردازش مودیس (MODAPS) دریافت شدند. پس از بارگیری تصاویر مربوط به سال های 2003 تا 2015 میلادی، داده ها وارد نرم افزار MATLAB شد و مقادیر ارتفاعی تروپوپاز برای ماتریسی به ابعاد 12×155 برای هر سال محاسبه شد (155 معرف مقادیر شبکه های محاط در مرز ایران و دوازده ماه های سال اند). نتایج حاصل از پردازش های تصویر وارد محیط نرم افزار ArcGis10.2 شد و نقشه های هر ماه با استفاده از روش کریجینگ به واسطه کمترین مقدار خطا تهیه گردید. نتایج نشان داد در ماه فوریه بیشترین اختلاف ارتفاع بین جنوب و شمال کشور رخ می دهد. تقریبا در همه پهنه کشور منحنی هم ارتفاع موازی و مداری اند. در ماه های گرم سال ارتفاع تروپوپاز در جنوب شرق کاهش می یابد و بالاترین ارتفاع تروپوپاز در مرکز کشور رخ می دهد.
    کلیدواژگان: ارتفاع لایه تروپوپاز، ایران، تروپوپاز، نیمرخ ارتفاعی تروپوپاز
  • علی فتح زاده*، مریم اسدی، روح الله تقی زاده مهرجردی صفحات 135-149
    در این پژوهش کارایی شاخص‏های ماهواره‏ای و پارامترهای ژئومورفومتری در برآورد بار رسوبی با استفاده از مدل‏های مبتنی بر هوش مصنوعی و داده‏کاوی به چالش کشیده شده است. بدین منظور، نخست مدل‏ها به کمک پارامترهای ژئومورفومتری مستخرج از مدل رقومی ارتفاعی و شاخص‏های ماهواره‏ای بهینه‏سازی شد و نزدیک‏ترین داده های دبی و رسوب به زمان تصاویر ماهواره‏ای خروجی مدل درنظر گرفته شد. پس از اجرای الگوریتم‏ها، به وزن‏دهی پارامترها و تعیین میزان تاثیرشان در پیش‏بینی بار رسوبی معلق پرداخته ‏شد. نتایج نشان داد عملکرد مدل‏ها با ورودی های مختلف گوناگون است. مقادیر RMSE مدل‏ها بیانگر آن است که در صورت استفاده از پارامترهای ژئومورفومتری به ‏عنوان ورودی مدل مقدار RMSE بیشتر است و در مقابل با استفاده از برخی شاخص‏ها به‏ عنوان ورودی مدل‏ها میزان RMSE کاهش می‏یابد؛ به ‏طوری که در مدل فرایند گوسی با ورودی پارامترهای ژئومورفومتری مقدار10/35 RMSE= و در صورت ورودی شاخص‏های تصاویر ماهواره‏ای مقدار 7/513RMSE= است. با تلفیق پارامترهای ژئومورفومتری و شاخص‏ها میزان دقت همه مدل‏ها افزایش یافته و مدل فرایند گوسی با 026/5RMSE= بیشترین دقت را داشته است. نتایج حاصل از وزن‏دهی نیز نشان داد که شاخص‏های Clay index (average) و b5 (average) و NDVI (max) دارای بیشترین وزن بوده و بیشترین تاثیر را در پیش‏بینی بار رسوبی معلق داشته‏اند.
    کلیدواژگان: پارامترهای ژئومورفومتری، تصاویر ماهواره ای، داده کاوی، مدل رقومی ارتفاع
  • محمد عیسی زاده *، منیر شیرزاد، مجید رضایی بنفشه صفحات 151-168
    تبخیر مولفه‏ای اساسی در چرخه هیدرولوژی است و نقش مهمی در مدیریت منابع آب دارد. در این تحقیق عملکرد مدل‏های شبکه عصبی مصنوعی (ANN) و ماشین بردار پشتیبان (SVM) در تخمین تبخیر روزانه ارزیابی شده است. داده های روزانه هواشناسی میانگین دما، سرعت باد، فشار هوا، رطوبت نسبی، بارش، دمای نقطه شبنم، و ساعت آفتابی ایستگاه های سینوپتیک تبریز و مراغه، به منزله ورودی مدل‏های ANN و SVM، برای تخمین تبخیر روزانه استفاده شد. نخست ده ترکیب مختلف از هفت ورودی و سپس ورودی های منفرد به منظور تخمین تبخیر به‏کار گرفته شدند. نتایج مدل‏های استفاده‏شده نشان داد که هر دو مدل ANN و SVM عملکرد قابل قبولی در تخمین تبخیر دارند. ارزیابی نتایج استفاده از ورودی های تکی نشان داد که به‏ترتیب کاربرد پارامترهای میانگین دما و ساعت آفتابی‏ نسبت به پارامترهای دیگر نتایج بهتری در تخمین تبخیر هر یک از ایستگاه ها داشته است. بررسی های این تحقیق نشان می‏دهد که اگرچه تفاوت معنی‏داری بین نتایج سه تابع کرنل ماشین بردار پشتیبان وجود ندارد، تابع کرنل پایه شعاعی در مقایسه با توابع کرنل دیگر از دقت زیاد و عملکرد بهتری در تخمین تبخیر روزانه برخوردار است.
    کلیدواژگان: تبریز، تخمین تبخیر، شبکه عصبی مصنوعی، ماشین بردار پشتیبان، مراغه
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  • Mohammad Hosein Ramesht *, Amir Saffari, Amir Karam, Ebrat Mohammadian Pages 1-20
    Introduction
    One of the important issues in the development of any kind of knowledge including Geomorphology is the introduction of new viewpoints and special conceptualization in that field. Introduction of relativism in philosophy, language and sociology has brought about deep evolutions in the epistemology of the research methodology and the utility of these sciences. Although this viewpoint was traditionally introduced in Geomorphology first by the American scientist G.K. Gilbert one hundred and thirty years ago, temporal conditions did not provide for the development and understanding of the depth of his conceptions for others. Recognition of Gilbert’s views and its comparison with relativism concepts in this age can familiarize us with Gilbert’s thought and the evolutions it made in relativism concept. Besides, it can prevent us from considering Gilbert’s relativism to be in parallel with many concepts introduced by others.
    The purpose of this article is recognition of the depth of Gilbert’s transcendental meditation and the difference of his opinion with the dominant scientific thinking in the era of Davis. Obviously, to know the angles such insights can enrich new ways in the epistemological and theoretical literature of Geomorphology.
    Materials And Methods
    To recognize the concept of Relativism and compare it with Gilbert’s opinion. It is necessary to check the works of prominent persons in different fields of knowledge on this subject. After theoretical basic review of Relativism, four characters in this field having quite clear and obvious ideas were selected. They were: Hans Gadamer (Hermeneutics), Albert Einstein (Physics), Ludwig Bertalanffy (Systems), and Mulla Sadra (Mysticism and illumination). Then their original texts about the concept of Relativism were separated and their views were analyzed. Finally, we compared them with Gilbert’s opinion and extracted their differences and similarities.
    Results And Discussion
    Relativism has not been expressed in the fields of knowledge and methodology nor even as a skill in a common concept. In general, it can be mentioned in ten whole meanings. Some try to limit it to philosophical issues and others treat it as method.
    A. Relativism in the view of Sophists
    In this Relativism, the principle of non-contradiction, diverse readings and multi-voice are recognized and it is based on denying the existence of truth and fact.
    B. Hermeneutics
    Every commentator understands the effect of his/her experiences different from these of the others. In other words, understanding and interpretation are a function of semantic horizon of the commentator, and this is nothing is except "Relativism" in understanding.
    C. Sapir-Whorf’s Relativism
    This theory explains another aspect of relativism. Based on this, people do not take an equal understanding from a single external mental phenomenon, unless they are similar Language background.
    C. Scientific Relativism (Einstein)
    Concepts such as time, place and gravity are considered different based on the physical condition they are supervised in. They are regarded to have a changeable nature. In other words, based on this theory, there is no absolute time, and consequently, nor any absolute temporal coincidence. Moreover, time is not the same in the two systems that are not connected to each other (Shaleh, 1346:137).
    D. Relativism systemic in epistemology
    The external existence of phenomena and their objectivity are authenticated. Frist special totality is supposed as the system. Then each of the elements is evaluated are with the others or with the whole system.
    Q. Allometric
    In this field, effort of the researcher is focused to understand the relation of the phenomena with each other.
    E. Divine Relativism
    This Relativism expresses how a phenomenon and its emanation are effective in the observer’s understanding.
    F. Genette relativism
    This Relativism expresses that a researcher is not affect in the recognition phenomenon.
    G. Relativism in scale
    This technique consider the view point of cognition within the framework of special relativity and uses it to describe the reality of object.
    J. Gilbert’s of Relativism in Geomorphology
    The understanding of a phenomenon depends on the observer and his/her thought, and cognition cannot be treated as rigid and absolute matter. According to the researcher’s previous take of science, his/her conclusion differs from a phenomenon would differ.
    Comparison between 9 relativism trends and Gilbert’s relativism resulted in the following findings (similarities and differences between each trend and Gilbert’s relativism): Comparison between Sophistēs’ relativism and Gilbert’s relativism
    - Human’s thought background is the criterion for knowledge.
    - They acknowledge objective and experimental realities.
    Comparison between hermeneutists’ relativism and Gilbert’s relativism
    - Introduction of “mental background” and researcher “outcome” in the knowledge of phenomena is emphasized.
    Comparison between Sapir–Whorf’s relativism and Gilbert’s relativism
    - Researcher “outcome” is influential in the knowledge of phenomena.
    Comparison between scientific relativism and Gilbert’s relativism
    - Different objective data derived from a single phenomenon result in relativism in knowledge.
    Comparison between relativism in systemic epistemology and Gilbert’s relativism
    - Relationship between phenomena is by its own an expression of relativism.
    - They also believe in the denial of the necessity of structure in the phenomena.
    Comparison between relativism in Allometry and Gilbert’s relativism
    - Relationship between phenomena is apart from the supervisor’s mind.
    Comparison between Sacred relativism and Gilbert’s relativism
    - Part of the knowledge in the person who knows is related to what is known.
    Comparison between Genetic relativism and Gilbert’s relativism
    - In Gilbert’s viewpoint, knowledge depends on the researcher.
    Comparison between Relativism in scale and Gilbert’s relativism
    - In Gilbert’s view, relativism is not digital and numerical.
    Conclusion
    The results show that:• Gilbert is the first Geomorphologist who has applied the concept of relativism a transcendentally and deeply in his methodology 130 years ago (1886).
    • Ten independent concepts of epistemic relativism have been used in various systems.
    Keywords: Geomorphology, Gilbert, Systems, Relativity, Relativism
  • Hossin Mohammadi, Ghasem Azizi, Faramarz Khoshahklagh, Firouz Ranjbar * Pages 21-37
    Introduction
    Climate change caused some changes in the global climate in recent decades. One of the climate change impact is the disturbance of the hydro- climatic cycle and discipline in the world. The effects of climate change on the hydrological cycle are including changes in groundwater levels, lakes, as well as changes in the distribution of the amount and timing of rainfall and river flows.
    Intensity and frequency of extreme precipitation events and the risk of floods and droughts are increasing due to the climate change in the large parts of the world.
    The impact of climate change on spatial and temporal characteristics of precipitation and extreme events, affected people's life. Hence, study on trend and changes of precipitation extreme can reveal the occurrence every related hazard. Studies around the world have shown that global warming and climate change impact and the precipitation condition has changed in different regions. The main objective of this study is evaluating of daily precipitation indices trend over Iran.
    Methodology
    In order to analysis of daily precipitation indices trend, 47 synoptic stations were used to investigate the precipitation extreme events over Iran during the 1982- 2012 (11323 consecutive days). The RClimDex software was applied to extract daily precipitation trend.
    The list of precipitation indices include the following:• RX1day: Monthly maximum 1-day precipitation
    • Rx5day: Monthly maximum consecutive 5-day precipitation
    • R10: Annual count of days when PRCP>=10mm
    • R20: Annual count of days when PRCP>=20mm
    • CDD: Maximum number of consecutive days with RR=1mm
    • R95p: Annual total PRCP when RR>95th percentile
    • R99p: Annual total PRCP when RR>99th percentile
    • PRCPTOT: Annual total PRCP in wet days (RR>=1mm)
    Results And Discussion
    On Average, the amount of precipitation in climatic stations such as Bam, Zabul, Yazd, Tabas, Jask and Zahedan was less than 80 mm whereas Bandar Anzali, Rasht, Ramsar and Noshahr stations have experienced above 1000 mm of precipitation during the period 1982- 2012. Among of all studied stations, Anzali and Zabol stations have had about 1763 and 52 mm of precipitation during the studied statistical period, respectively. Investigation of total index of annual precipitation in Iran represents that the slope of precipitation in most of the stations is negative during the 1982- 2012. Averagely, the annual precipitation of Iran has decreased about 2.5 mm during the 1982- 2012.
    Generally, results illustrated that the trend of CWD index in some regions was negative, in some regions was positive and in some regions there wasn’t any trend during the 1982- 2012. Among all studied stations, the CWD index had positive trend for 11 stations including Kashan, Semnan, Ramsar, Mehr Abad, Dooshan Tapeh, Zahedan, Khorram Abad, eastern Isfahan, Anzali and Abadeh. There was no trend in Arak, Bandar Lengeh and Shahrood stations and negative trend was observed in other stations. According to the results, the CDD index was increasing in most studied stations during the period 1982- 2012. Approximately, in %72.5 of the stations the index was raising and in %27.5 of stations showed decreasing trend. The trends showed that the number of days without precipitation is increasing. The greatest changes have experienced on the coast of the Caspian Sea and the Persian Gulf. Results showed, indices R 10 mm, R 20mm, R 25 mm, at most of the stations has decreased and R 10 mm index had more negative trend.
    The trends indicated that the number of days without precipitation is increasing. Among the studied stations, Ramsar station has experienced the highest downward slope of R95p index with 6.4 mm annually. From this point of view, Saghez, Rasht, Sanandaj and Bandar Abas stations had the highest downward slope in very wet days. moreover, Gorgan station with 2.7 mm have experienced the most increasing trend among all stations annually and Shiraz, Esfahan and Chabahar with higher than one mm are in the next rank, respectively.
    Conclusion
    The results illustrated that all Precipitation Extreme Indices has been changed over Iran during the 1982-2012. There were negative trends in more stations. In most of studied stations, annual rainfall has decreased and the number of dry days (CDD) has increased, only a few stations in the central regions and the foothills of the Zagros have had positive trend.
    Keywords: Precipitation, climate change, Extreme Indices, Trend, Iran
  • Behruz Sobhani, Masood Ganji, Akbar Goldust * Pages 39-53
    Introduction
    Freeze is one of the serious climatic phenomena that influences different aspects of human life including agriculture, transportation and energy. Effects of freeze in agriculture section are more than other sections. Effects of freezes in agriculture section appeare more than its earliness or lateness aspects. In Ardabil Province, in most years, early and late freezes have caused serious damages to agricultural products. For example, in Farvardin 1393, gardens of Ardabil Province recompensed more than 4 billion Rials due to late spring cold. Due to this cold, 21000 Hectares of gardens of this province recompensed.
    Of the causes of extensions of recompenses resulted from climatic phenomena like freezes is unknown remaining of dimensions and nature of this phenomenon. In occasions of occurrence of early and late freezes, to decrease recompenses resulting from it, it is needed to have a coherent management program; that to prepare this program, it is needed to know different aspects of this phenomenon. In this research, it is tried to determine beginning and end dates of early and late freezes and to investigate several cases of properties of these freezes along with its possibility.
    Materials And Methods
    Data used in this study is minimum temperature as daily in 15-year statistical period (from 1996 to 2010) in stations of Ardabil Province. After collecting and setting data, series of data were planed as Juliuseous date that first day-counting of data was considered October and beginning and end dates of freezes (lack of temperature to zero and under zero Centigrade) were analyzed. In this research, knowledge of possibilities and also an approach called Markov’s Chains were used.
    Accordingly, continuity and possibility of occurrence of early and late freezes are considered in different continuities of, various intensities of early and late freezes and possibility of its occurrence and possibility of succession of different states freezes are investigated.
    Results And Discussion
    Analyzing beginning and end dates of occurrence of freezes shows that general trend of day-counting of beginning date of freezes in Parsabad Station is decreasing and moves toward hot season. In stations of Ardabil and Khalkhal, this trend is increading. In Khalkhal Station, beginning dates of freeze moves toward cold season with intensity of 1.07 day per year and has started later.
    Investigating end dates of freezes according to regression analysis shows that general trend of day-counting of dates was decreasing by 0.517 day per year in Parsabad Station and was increasing by about 0.29 and 0.14 day per year in stations of Ardabil and Khalkhal, respectively.
    Early freezes start in November in Parsabad Station and in October in stations of Ardabil and Khalkhal.
    Continuity of early freezes in Parsabad Station in less than other stations so that in this station freezes have not lasted more than 2 days. In Khalkhal Station, continuity of freezes is more than other stations so that in Khalkhal Station continuity of freezes has been less.
    In Parsabad Station, due to lower height temperature was higher than other stations and intensive freezes are not observed. In Khalkhal Station, number of freezes is more than other stations. In this station, 11 intensive freezes lower than -3 centigrade have occurred that there is 2.37 per cent of possibility of its occurrence in October.
    Conclusion
    The most important results resulting from above-mentioned topics are as follows: - Day-counting trend of beginning of early freezes is decreasing in Parsabad Station and is increasing in stations of Ardabil and Khalkhal. Day-counting trend of end of late freezes is decreasing.
    - Early freezes begin in November in Parsabad Station and in October in stations of Ardabil and Khalkhal. Late freezes are in April in Parsabad Station and in May in stations of Ardabil and Khalkhal.
    - Continuity of early freezes in Parsabad Station is less than other stations and in Khalkhal Station, continuity of freezes in more than other stations. In late freezes in Khalkhal Station, continuity of freezes has been less.
    - In terms of intensity of freezes, early intensive freeze has not happened in Parsabad Station. In this area, due to low height, temperature is more than other stations and intense freezes are not observed. In Khalkhal Station, number of intensive freezes with possibility of occurrence of 2.37 per cent in October is more than other stations.
    - In terms of succession of different states of freeze and without freeze, in early freezes there is the highest possibility of occurrence of freeze after freeze in Khalkhal Station with 63.31 per cent, and in late freezes in Ardabil Station, occurrence of freeze is with 61.54 per cent after the state of without freeze.
    Keywords: possibility, Continuity, Succession, early, late, Intensity
  • Zeinab Jafarian *, Vahid Beshtar, Ataollah Kavian Pages 55-69
    Introduction
    Rangelands are natural ecosystems whit native plant species cover and are suitable for grazing. Water, soil and vegetation have fundamental role in maintaining natural ecosystems such as rangelands, so, performing the researches that lead to the preservation of natural environment and human’s environment is essential. Proper and allowable utilization of rangelands in the range management projects is the important scientific and technical measure in the range management of Iran. Range management projects as improvement - restoration and reclamation guideline have particular importance in the natural resources’ organization. On the other hand, today, erosion and soil loss and sediment production has become one of the main problems in the human environment. Restoration of vegetation and its effects on reduce of erosion have been studied by Li, 2006, Zhou, et al. 2008, Zhanga et al. 2004, Abdelkrima, et al. 2013. Goal of improvement - restoration operations in natural ecosystems is recovery plant compositon and cover for more protection of water and soil and decrease of erosion soil, finally increase forage yield. Therefore, soil management for optimal utilization and reduce its degradation is essential. Mapping the rate of erosion and sediment yield and areas prioritization according to it is effective step for organization, the protection and utilization of the soil. The purpose of this study was estimating amount of soil erosion and then simulate the effects of improvement and restoration on soil loss in the Lar area (Mazandaran).
    Material and
    Methods
    Revised universal soil loss equation (RUSLE) was used within GIS. The parameters this model are consists of R, K, LS, C and P, respectively, that are calculated with using the data of rainfall, soil maps, digital elevation models and remote sensing techniques, respectively. Suitable location of improvement - restoration projects was determinate based on maps of slope, elevation vegetation, pedology and rangeland condition. Then, by combining theses maps and applying basic principles of range management for suggest appropriate methods, was offered rangeland management model for improving or maintaining the optimal status. Then erosion risk map was prepared using revised universal soil loss equation. Finally change of amount of erosion after restoration and reclamation operations was predicted using this model in GIS.
    Results And Discussion
    The results showed that the mean values of parameters R, K, LS, C and P for study area was 67.143, 18.0, 52.5, 37.0 and 1, respectively. Average of yearly sediment load was estimated 51 ton/ha/year. Also the areas that to be allocated restoration and reclamation operations including 378 ha seeding, 246 ha inter seeding and 176 ha planting pile. Also cultivation on contour lines with seeding and strip cultivation with inter seeding was suggested and simulated. Simulation results after the suggested operations showed that the P and C factor will 0.8 and 0.31 respectively, therefore erosion mean will be reduced to 34 ton/ha/year and following that is equivalent 34% reduction. RUSLE model were used by many researchers in Iran and out of Iran (Asadi, et al. 1389, Vaezi, et al. 1389, Fiona, et al. 2010, Nijel, et al. 2010, Zangh, et al. 2010) and was confirmed its performance according this research. Results showed that areas with low slop had sediment rate than other areas. Average of yearly sediment load was zero to 595 ton/ha/year in study area. Soil erosion was more in eastern south parts of watershed rather than other parts, similar to results of Asadi, et al. 1389. Restoration and reclamation operations have changed C factor that can caused reduction of erosion. After simulation these operations had reduced erosion amount zero to 464 ton/ha/year, similar to results of Ligdi & Morgan, 1995, Terranva, et al. 2009, Stevens, et al. 2009.
    Conclusion
    Simulation results after the suggested operations showed that the P and C factor will 0.8 and 0.31 respectively, therefore erosion mean will be reduced to 34 ton/ha/year and following that is equivalent 34% reduction that indicates the importance of improvement - restoration projects within rangelands. Combination of GIS with sediment and erosion models is the effective method for determination of spatial distribution of sediment and erosion. Suggested improvement – restoration operations in addition to protection of water and soil will caused increase of forage product and following it increase of livestock product and increase of household income.
    Keywords: soil erosion, RUSLE Model, vegetation cover, Rangeland Reclamation
  • Hematollah Roradeh *, Taher Safarrad Pages 71-83
    Introduction
    With the onset of fall season, the temperature of air and Caspian Sea diminishes, but due to the difference in the specific heat capacity of air and water, the rate of reduction of temperature in air is far greater than that of sea. Therefore, the surface of Caspian Sea water remains warmer than air. Establishment of dynamic high-pressure centers or diffusion of Siberian high pressure system over Caspian Sea especially during fall results in development of southward air stream over Caspian Sea. Caspian Sea as the first supplier of humidity resources for heavy precipitation and especially ultra-heavy precipitation of its southern coasts, plays a principal role in explanation of occurrence of precipitations in these coasts. The changes in Caspian Sea water temperature can result in variations in the precipitation in southern coasts of Caspian Sea. However, as stated by Alijani, only the seawater temperature is not sufficient for the precipitations of the southern coasts of Caspian Sea and the air temperature over the sea should also be taken into consideration. The sea-air temperature difference (ΔT) has attracted the attention of researchers as humidity intake index, to such an extent that it has become the most important thermodynamic factor in development of abundant and heavy precipitations in the southern coasts of Caspian Sea. Gradual elevation of the sea surface temperature in its proper arrangement from the north to the south and intake of humidity from the sea (ΔT index) have been mentioned as necessary for development of heavy and ultra-heavy precipitations in the southern coasts of Caspian Sea.
    Materials And Methods
    To do this research, the daily precipitation data of seven synoptic stations of Northern provinces of the country have been collected from 1968 to 2013. The threshold of heavy precipitations was defined as the day in which its precipitation level is greater than the percentile 95 of that year. Next, all of the days in which at least five stations have recorded heavy precipitation simultaneously were extracted and considered as regional heavy precipitation days. By extracting the air temperature at 2 meter above the sea level (Air2m) and the sea surface temperature (SST), the ΔT value was calculated as follows:∆T=SST-Air2m
    Benefiting from Ward linkage method and calculation of the correlation between the data, ΔT values were clustered in days in which regional heavy precipitation had occurred in the northern stations of the country. In each of the clusters, the day that had the greatest correlation with other days was chosen as the sample. For the sample days, SLP, VWnd, Uwnd, and HGT data in 1000 HPa for plotting and analysing synopsis conditions leading to regional heavy precipitation were extracted from http://www.esrl.noaa.gov. The relationship between regional heavy precipitation in the stations and ΔT was analysed through which the extracted clusters were interpreted and analysed.
    Results And Discussion
    With the onset of fall season, the air temperature declines more rapidly than seawater temperature. Therefore in this season, the sea will be warmer than air.
    The relationship between regional heavy precipitation and ΔT was investigated in the studied stations. Unexpectedly, direct relationship between ΔT in the south of Caspian Sea and regional heavy precipitation does not exist in all of the stations and this relationship only applies to the stations located in the East, whereas in the stations situated in the West, this relationship was seen to be inverse.
    Benefiting from Ward linkage method and calculating the correlation between the data, three clusters were recognized and in each of the clusters, the day that had the greatest correlation with other days was chosen as the representative of the cluster. The first cluster is representative of days with regional heavy precipitation in conditions where ΔT gradient reaches its maximum from North West to the south east. The second cluster represents incidence of regional heavy precipitation in conditions where the maximum ΔT gradient is from the north to the south. Eventually, the third cluster can be considered as the greatest ΔT gradient is observed from the West to the East (also Southwest to Northeast).
    Investigation of synopsis maps resulting in regional heavy precipitation in the selected days suggests their similar synoptic conditions such that establishment of high-pressure center in the northwest of Caspian Sea leads to influx of cold-air from more northern latitudes and over Caspian Sea towards southern latitudes. Passage of cold air over a warmer sea results in injection of humidity and modification of its temperature, such that by reaching the Caspian southern coasts, it becomes instable, eventually causing heavy precipitation in these coasts. The stations located in the east of the studied region, will receive greater precipitation when ΔT reaches its maximum level in the southern coasts of Caspian Sea (the second cluster). In contrast, the stations located in the West, will receive greater precipitation when ΔT gradient increases from the east to the west (the third cluster).
    Conclusion
    With the increase in ΔT in the southern parts of Caspian Sea, regional heavy precipitation grow significantly only in the eastern part of the studied region. The results obtained from ΔT clustering unveiled three clusters, where the first, second, and third clusters represented the maximum ΔT gradient from the Northwest to the southeast, north to the south, and west to the east, respectively. The stations located in the east of the studied region will have greater precipitation when ΔT reaches its maximum in the southern coasts of Caspian Sea (the second cluster). In contrast, the stations located in the West will receive the maximum precipitation when ΔT gradient increases from the east to the west (the third cluster). These results were in line with the results obtained from investigating the correlation between ΔT and regional heavy precipitation. The analysis of synoptic maps indicated that in all of the three clusters, establishment of high-pressure center in the northwest of Caspian Sea results in infusion of cold air from more northern latitudes and over Caspian Sea towards southern latitudes.
    Keywords: regional heavy precipitation, sea-air temperature difference, Southern coasts of Caspian sea, Autumn
  • Gholamali Mozafari, Shahab Shafeie * Pages 85-100
    Introduction
    In all weather maps, without exception belt or wind tape at high speed are seen to have drawn very long distances. As defined by the World Meteorological Organization, whenever the tape speed is faster than 30 meters per second, the jet stream is created (Alijani and Kavyani, 1379: 291). However, according to the definition in the dictionary of weather and climate extreme horizontal winds with speeds of over 50 knots, or about 26 meters per second, above the planetary winds blow, refers jet stream (Hitch, 1961). In fact, the jet stream, the core of which are fast moving and in the context of long and short waves, as they are areas of convergence and divergence (Alijani, 1381: 82). The core of the jet stream speed is also reduced from the core center around which this reduction to the poles to the equator volubility or positive, or negative anti cyclone.
    Materials And Methods
    Experimental basic research with an inductive approach. Geographical zones studied western regions of Iran. The data base that environmental to circulation approach involves two variables. The daily precipitation data of 69 synoptic stations and climate West of Iran (Hamedan, Kurdistan, Kermanshah, Lorestan and Ilam) in the interval from 2010 to 1961 as the database environment event was received from the National Weather Service. The second group of variables including wind component-oriented data and meridional wind component in order to draw jet streams at levels 250, 300, 400 and 500 hp were taken from the website of Noaa , data extraction was performed using the software Grds. According to the event database environment, enjoying updated daily rainfall 18624 West Iran interpolation method was Kriging. or this purpose, an interpolation of rainfall per day, the study area the size of 2.5 × 2.5 km in 1367 became cells, resulting in the formation of an array of daily precipitation database with dimensions of 1367 × 18624 West was Iran. Selected. Perform calculations on the data, was conducted using MATLAB software. The resulting calculation is presented in the form of maps. Maps arches were used for mapping software The number of rainy days inclusive extreme studied stations cover 30% of the 119 days that were analyzed. One of the most common parameters in spatial analysis in relation to the distribution points around the center Average used, the standard deviation ellipse. Since the situation may be occurring phenomena, has deviated directional arrow and oval standard deviation of the probability distribution may well show (Asgari, 1390: 89), as well as in-order to display the deviation of the distribution points, the standard oval used. Standard oval on the frequency jet stream was applied in each pixel.
    Results And Discussion
    Frequency jet stream at 250 hPa level spatial analysis showed that the most frequent jet stream is from the Southern Red Sea to the south of the Mediterranean, in other words more than 70% of the formation, establishment and cross Jetstream’s West's influence on rainfall in this area is, which is the main route from the Red Sea, which leads to water injection system precipitation from the Red Sea to the West Iran.% of the formation and establishment of the jet stream. Frequency jet stream at 400 hPa level spatial analysis showed that during the study period was the most common jet streams northeastern extension of the Red Sea to the west over Irans. The actual zones in this area in more than 50% of the formation and establishment of the jet stream. By reducing the height of the territory of jet streams and their influence has waned. Spatial analysis showed that the frequency jet stream at 500 hPa level jet stream during the study period was the most common variety of the northeastern Red Sea to the west of Iran in the covers. The actual zones in this area in more than 50% of the formation and establishment of the jet stream. The results of the standard oval jet stream in the range of activities on Iran's western regions, respectively. Given that, the event shows the dispersion ellipse fitting, oval shows the pattern of the jet stream of high activity in the West of Iran.
    Conclusion
    The results show that the jet stream at 250 hPa level, show a high frequency. Maps of average speed jet stream jet stream and on the other hand, in accordance with the highest frequency of occurrence coinciding with the maximum speed jet streams in the study area, and reflects the core jet stream wrapping the second quarter (by increasing positive vortices and upper level divergence and low levels of the atmosphere is mobile convergence) on the West Iran.
    Keywords: Jet Stream, atmospheric instability, extreme precipitation, Standard Deviational Ellipse, West of Iran
  • Ata Abdollhai Kakroodi * Pages 101-111
    Introduction
    The Caspian Sea (CS) can be subdivided into three parts: North, Middle and south parts (Figure 1). The CS experienced many cycles of Sea-level changes with vast emerged and submerged area. In the Khvalyn terraces in Dagestan two major phases have been distinguished. The Early Khvalyn transgression is represented by five successive marine terraces between and 0 m at absolute height (Kroonenberg et al, 1997). Furthermore, at the boundary of Late Pleistocene and Holocene a -50 (Kakroodi et al., 2015) and by other researcher a -113 sea level record has been identified. This is why many researchers call it as a capricious level due to great sea level changes (Krooenebreg et al., 2007). Recent sea-level changes also got attention, experienced around 3 m sea-level changes between 1929 and 1977 and rose back in 1995. Five late Holocene have been identified which reached at least up to -22 absolute elevation. Present work aims at showing two phases of transgression and its impact on Iranian coast by Arial photograph and radiocarbon dating, a 2600 BP and Littlie Ice age.
    Radiocarbon dating: Radiocarbon dating results are available now from all over the CA along the Iranian coast. Further radiocarbon dating is also needed to achieve better understanding of sea level change. The crucial thing is the samples must be not reworked and then it is important the marine environment to take samples. Otherwise the results are not accurate and sometimes in a wrong way. The marine environment far away from the wave is the best target to take the samples. The absolute elevation is also important, unreported elevation of the samples might indicate different data and should consider the same coordinate systems for all data. In this work, nearly all sample elevations have been measured by DGPS device based on the mean sea –level of the Persian Gulf. Table 1 indicates the radiocarbon dating data along the three parts of the CA Sea, East, Middle and West parts.
    The southeastern part of the CS: The south-eastern part of the CS is one of the best targets to reconstruct the sea-level curve and coastal evolution. An overall study of the past and recent sea-level changes have been done in this part as a PhD thesis (Kakroodi et al., 2012). The dominated coastal features in this part are characterized by Barrier-Lagoon and delta deposits. This part is so sensitive to sea level changes due to low angle coast and any minor sea-level change will have its own impact on the coast.
    Based on Arial photograph and filed data two highstands at -22 and -24 are distinguishable, Old Miankaleh spit and old delta deposits (Fig 2, 3). Linear old shoreline and old Gorgan delta is well preserved by aerial photograph and confirmed by field work. They are placed at absolute elevation of around -24 (Fig 2, 3).
    In the southern part of Gorgan Bay, the Bagho outcrop presents marine deposits similar to present Minaklaeh spit characterized by crossbedding, medium to coarse sand and Caspian fauna. Eastward, it has been buried by Qareh Su and Gorgan Rivers.
    The middle part of the CS: Because of short distance of the Alborze Mountains and the sea and high energy environment, the coast is characterized by gravel and coarse sand which is known as erosional coast and also not sensitive to sea level changes as observed at the eastern part. However, there is a small old elongated lagoon indicating a Lagoon- barrier system in this part. Also, Results of a core study indicates a lagoonal deposits further south at the foot of Alborz mountains and overlaid now by fluvial and organic rich layer. This organic layer was dated around 500 BP which probably is an evidence of little ice age highstand (Ramezani et al., 2016). The lower part of the mentioned core, also Lagoonal deposits, at the depth of 3.6 m a dated sample around 2500 BP was reported. Totally two highstands at -24 and 19 absolute elevations were identified in this part.
    The Western and East of Sefidrud delta part : The impact of sea-level change in this part is more studied than the other part of the CS. Sefidrud delta is the biggest river in the southern part of the CS originating from Zagrous Mountains and cross Alborz mountains providing around 70 sediment supply within the CS (Lahijani et al., 2009). Due to high sediment supply, the impact of sea-level change is different than the other parts.
    Recent study of sea-level rise between 1977 and 1995 indicates even with 3 m sea level rise the coast has not been changed and in some part it prograded instead of landward shift (Kakroodi et al., 2014). This is because the coast will be developed in 3 dimensional not just a simple linear trend. Therefore accommodation space resulted by sea level rise is compensated by sediment supply and other process like longshore currents. Many papers have been published recently and most of them concentered on Little Ice Age impact on the coast (Leory et al., 2011; Naderi et al., 2013, Haghani et al., 2015. Present morphological features include a series of beach-barrier (Fig. 6, b), Lagoons, modern delta and old delta (Fig. 6).
    Discussion and
    Conclusion
    Rapid sea level change is unique in the Caspian Sea and therefore coast response against this sea- level change got attention for many researchers. A real observation of coastal response to sea-level change instead of using mathematical model enable us to predict coastal behavior. The CS experienced many cycles and in the late Holocene, two highstands had strong impact on the coast, a 2600 BP and Little Ice age respectively. These two highstands synchronized with cooling periods of Northern hemisphere. Now the level of the Caspian is situated around -28 below sea level and considering the elevation -24 and -22 at the periods of two mentioned highstands, large area of the southern Caspian were subemerged at those periods. Any model should consider this these highstands.
    Keywords: the Caspian Sea, Rapid Sea level change, Sefidrud Delta, transgression
  • Hassan Lashkari *, Abbasali Dadashi Roudbari, Zinab Mohamadi Pages 113-133
    Introduction
    Tropopause transitional layer of the troposphere is to stratosphere. This layer determines the upper limit of the troposphere and somehow expresses the spatial and temporal variations in the thickness of the layers and the layer crystallization thermodynamic changes. Short and long-term atmospheric layer that all phenomena occur in it. In other words, this layer determines the thickness of the ceiling (upper limit) layer is the troposphere. Iran in terms of Geographical location is on the north side of the trading range Hadley cells in the general circulation of the atmosphere. That’s why when handling the extremely cells have modified the climate of this country. That's why the country is in the range of atmospheric systems important effects such as (anticyclone Saudi Arabia, the Siberian anticyclone, the anticyclone of the Azores, Mediterranean cyclones are low pressure Sudan. The land is adjacent to the vast deserts of the Arabian Peninsula and the vast deserts of Siberia is located. Two great ranges of Zagros and Alborz in the country's northern and western bar and the Dasht-e Kavir and Dasht-e Lut in Central and South East is also remarkably effective at the entry and transit systems and mechanisms. The sum of these factors makes the country highly subject to changes in time and space troposphere and the tropopause crystallized in the works. According to the tropopause layer height changes in response to seasonal or yearly changes that are occurring in the lower layer of the atmosphere. At the same time the top layer by layer to the stratosphere as well. If these changes can be estimated that the annual seasonal trends or changes in the troposphere layer has been and can be changed and the results of its possible to estimate and predict. For this purpose maps of the height of the tropopause layer altitude on the slope of Iran in the period 2015-2003 is examined in each of the months of the year.
    Materials And Method
    In this study, data from the Atmospheric Infrared depth (ATMOSPHERIC INFRARED SOUNDER) Moderate-resolution imaging spectroradiometer(MODIS), Aqua, Earth Observing System (EOS) the product(AIRSÄ) V006 (AIRX3STD) at GES DISC used. This product series of MODIS data in the form of geophysical parameters in the network have been distributed, 1 × 1 ° arc. The data from -180 to 180 longitude and latitude -90 and 90 are available from bases http://modaps.nascom.nasa.gov are available. After loading the images from 2003 to 2015, data compiled MATLAB software, and using the World Meteorological Organization Tropopause height values for the matrix of size 12 × 155 was calculated for each year (155 networks were introduced and 12 months of the year are inscribed on the Iranian border). The results of image processing software environment was ArcGis10.2 and maps of each month using the least amount of errors were prepared by Kryjng. The next step is to draw longitudinal profile of the height of the tropopause in 3D Analyst software plugin named slice of the North West (to a maximum height of the tropopause) to the South East of the country (as a minimum altitude of the tropopause) drawn and corresponding graphs for each of the months of the year were drawn.
    Results And Discussion
    The results showed that the tropopause height is matched to the south and north of the country in January. In February, the maximum difference in height between the southern and northern happened. In almost every area of the country and oriented parallel curves are the same height and the slope is not too unlike the last month in the West and South West. Changes in the year troposphere height in the range of Iran's normal response to many comments by atmospheric circulation. For example troposphere low in cold season can be caused by Eddies smaller and thinner linked cells Ferrell. The spring equinox in the country's highest tropopause height that generally belongs to the South East is about 16475 meters and the lowest elevation in North West Iran, striking a height of 11008 meters decreased So great altitudinal gradient between the south and north of the country there is this difference, amounting to 5700 meters, which is as thick as the middle troposphere.
    Conclusion
    The height of the tropopause layer Iran has seasonal fluctuations, yet the intensity of the incoming topography and activity of the system. But the impact of the tropopause height changes more pronounced in the input system from the effects of topography. Although in July reaches its peak height of the tropopause. But fluctuations in tropopause height between the south and north of the country is minimal. In the other months of the year maximum height of the tropopause in the south and north of the country is minimal. While the height of the tropopause in the month of August in the center of the country. In the other months of the year maximum height of the tropopause in the South East are the lowest in the North West. During the cold period in the northern slope of the layer to its minimum. And vice versa during the warm southern slope of the tropopause layer is minimized. This phenomenon has spread south polar vortex in the Siberian high pressure and cold period of year as well as the expansion of the subtropical high pressure north of Saudi Arabia during periods of warm harmonious. The study also showed that during the months of monsoon activity in the South East of extremely reduced height of the tropopause layer.
    Keywords: Tropopause, height of the tropopause layer, Iran, tropopause height profile
  • Ali Fathzdeh*, Maryam Asadi, Rohollah Taghizadeh-Mehrjardi Pages 135-149
    Introduction
    During recent decades in water resources engineering sciences, the prediction of suspended sediment load particularly in flood areas was highly regarded. Nowadays Methods and artificial intelligence techniques to predict hydrologic have become very popular. In recent studies of various parameters such as the spectral reflection bands of satellite images, land use, geology and climatic data have been used. Landsat satellite images according to their high resolution has good spatial resolution. Da Silvia (2015: 53) spectral calibration multispectral satellite images to assess their suspended sediment concentration. Their results showed that the concentration of suspended sediment has been strongly influenced by seasonal rainfall. The yellow river sediment using landsat satellite images by Zhang et al (2014:136) were evaluated. The results showed that, using the modified algorithm and recovery appropriate climate models, TM / ETM can be used to quantify the concentration of suspended sediment at the mouth of the yellow river. In this study, mining indices satellite images and watersheds geomorphometry parameters that derive from the characteristics of the basin surface to evaluate and compare the performance of these parameters to predict suspended sediment has been studied. In this study, methods such as artificial neural networks, linear regression, K nearest neighbor, Gaussian processes, support vector machine and evolutionary support vector machine selected and with purpose check the role of these parameters were used to predict suspended sediment load,to detection of the impact of these parameters is to improve the assessment models.
    Materials And Methods
    Study Areas
    There were 68 catchment areas located in the provinces of Gilan and Lorestan from Iran
    Data processing
    Data mining geomorphometry
    After determining the area of study geomorphometry parameters were extracted. Geomorphometry parameters was extracted from 30 meter area digital elevation model
    The modeling process
    In this study the input parameters in the prediction of suspended sediment load of data mining models such as linear regression, Gaussian processes, neural networks, k-nearest neighbor, support vector machine and evolutionary support vector machine was used.
    Linear regression
    Linear regression to model the value of a quantitative dependent variable that is based on a linear relationship with one or more independent variables used.
    Artificial Neural Network
    Artificial neural networks including computational models that can be used even if the relationship between inputs and outputs of a physical system is complex and nonlinear, with a network of interconnected nodes that are all are joined together.
    K-Nearest Neighbor
    K-Nearest Neighbor algorithm including the selection of a specific number of vector data then randomly from the set for the simulation period following is a given period.
    Gaussian process
    A Gaussian process is a stochastic process which consists of random values at any point in space or time domain so that each of the random variables are normally distributed.
    Support Vector Machine
    Support vector machines are a class of supervised learning methods for classification and regression problems applied.
    Evolutionary Support Vector Machine
    Evolutionary vector machine model use of an evolutionary strategy to optimize its. It offers an evolutionary algorithm to solve the problem of dual optimization a support vector machine.
    Evaluation Model
    In order to evaluate the algorithms applied to the data, the evaluation criteria Root mean squared error (RMSE), relative error (Re), Correlation coefficient (r), Absolute error (AE) was used.
    Weighting parameters
    In this study, for the weighting input parameters of support vector machine algorithm used, this algorithm
    coefficients a normal vector of linear support machine as the weight of characteristics determines.
    Results
    At first the different algorithms on the data geomorphometry parameters were applied. The results showed that with using geomorphometry parameters Gaussian process model with RMSE = 10.35 and R = 0.986 is the best model to predict suspended sediment load. In the next phase models, were used on the input data indices satellite images. Then index satellite images and geomorphometry parameters as input been togather and models were run on them. Also results showed the Gaussian process model RMSE= 5.026 and R=0.99 has highest accuracy in predicting suspended sediment load.
    Discussion and
    Conclusion
    The use of indices satellite images and geomorphometry parameters as model input cause increases the accuracy of data mining algorithms to predict suspended sediment load. The results of the study indicated that satellite imagery indices has been more effective in predicting suspended sediment load and using these indicators increase the accuracy of models more effective than geomorphometry parameters. Therefore, considering the indices of satellite images, Gaussian Process Model with RMSE =7.513 and also, if using the geomorphometry parameters of the Gaussian process model with RMSE =10.35 has Highest accuracy. By combining geomorphometry parameters and indicators has increased the accuracy of all models and Gaussian process model with RMSE =5.026 had the highest accuracy. The results of weighting also showed influence of indices satellite images to predict suspended sediment load.
    Keywords: Data mining, Satellite Images, Geomorphometry Parameters, Digital elevation model
  • Mohammad Isazadeh*, Monir Shirzad, Majid Rezaei Banafsheh Pages 151-168
    Introduction
    Evaporation is a fundamental component of the hydrology cycle and has an important role in water resources management. Daily evaporation is an important variable in reservior capacity, rainfall-runoff modeling, crop management and water balance. Measurement of actual evaporation is almost impossible, but evaporation can be estimated using several methods. There are two general viewpoint to estimation of evaporation: direct and indirect methods (Tezel 2015, Terzi 2013). It is inoperative to measure the evaporation by direct methods in all locations. Direct methods usually used proximate reservoirs or irrigation projects. The indirect methods of evaporation estimation need to various input data that are not easily available. Moreover, the evaporation have very complex and nonlinear process that simulation of its complex process using simple methods is impractical. In recent years, the artificial intelligent methods such as Artificial Neural Network (ANN) and Support Vector Machine (SVM) have been successfully utilized to modeling the hydrological nonlinear process such as rainfall, precipitation, rainfall-runoff, evaporation, temperature, water quality, stream flow, water level and suspended sediment, etc (Tezel 2015). Therefore this research evaluates the performance of ANN and SVM models in daily evaporation estimation.
    Materials And Methods
    The daily climatic data, air temperature, wind speed, air pressure, relative humidity, rainfall, dew point temperature and sun shine hours of Tabriz and Maragheh synoptic stations are used as inputs to the ANN and SVM models to estimate the daily evaporation. For this purpose, 75 percent of the daily evaporation data were selected to calibrate the models and 25 percent of the data were used to validate the models. Different combinations of seven input and then individual inputs applied in order to evaporation estimation.
    ANNs are parallel information processing systems consisting of a set of neurons arranged in layers. These neurons provide suitable conversion functions for weighted inputs. In this study, we used Multilayer feed-forward perceptron (MLP) network. The MLP trained with the use of back propagation learning algorithm. The back-propagation training algorithm is a supervised training mechanism and is normally adopted in most of the engineering applications. The neurons in the input layer have no transfer function. The logarithmic sigmoid transfer function was used in the hidden layer and linear transfer function was employed as an activation function from the hidden layer to the output layer, because the linear function is known to be robust for a continuous output variable. The optimal number of neuron in the hidden layer was identified using a trial and error procedure by varying the number of hidden neurons from 1 to 20. In recent years, SVM as one of the most important data-driven models, has been considered in this regards. This model is a useful learning system based on constrained optimization theory that uses induction of structural error minimization principle and results a general optimized answer. The SVM is a computer algorithm that learns by example to find the best function of classifier/hyperplane to separate the two classes in the input space. The SVM analyzes two kinds of data, i.e. linearly and non-linearly separable data. For a given training data with N number of samples, represented by (x_1,y_1 ),…,(x_N,y_N) , where x is an input vector and y is a corresponding output value, SVM estimator (f) on regression can be represented by: f(x)=w.∅(x)
    Where w is a weight vector, b is a bias, “.” denotes the dot product and ∅ is a non-linear mapping function. Typically, three kernel functions, radial basis, polynomial and linear are applied in SVM that use of each function with various parameters for evaporation estimation may have different results. Therefore, it is necessary to evaluate the accuracy of each of these functions and select the appropriate kernel function for evaporation estimation. Two performance criteria are used in this study to assess the goodness of models fit, which are: Correlation Coefficient (CC) and Root Mean Square Error (RMSE).
    Results And Discussion
    In this paper, ten different combinations of seven inputs and then individual inputs applied in order to estimate the evaporation. Results of evaporation estimation in Tabriz station indicate that the first and eighth combinations have minimum RMSE and maximum CC in test period of ANN and SVM models, respectively. Also results of evaporation estimation in Maragheh station indicate that the first and Seventh combinations have minimum RMSE and maximum CC in test period of ANN and SVM models, respectively. The ANN model using first combination including air temperature, wind speed, air pressure, relative humidity, rainfall, dew point temperature and sun shine hours climate data, achieves to the amount of 2.12 (mm) and 0.78 for RMSE and R statistics in test period for Tabriz station. The SVM model using eighth combination including wind speed, air pressure, relative humidity, rainfall, dew point temperature and sun shine hours climate data, achieves to the amount of 2.17 (mm) and 0.78 for RMSE and R statistics in test period for Tabriz station. Evaporation estimation of Maragheh station using ANN and SVM models, respectively achive to 1.62 (mm) and 1.43 (mm) for RMSE statistic in test period. In next step, individual input results show that ANN model has better estimation of evaporation values in Tabriz station and SVM model in Maragheh station. Also results indicate that the SVM and ANN models have better estimation of evaporation values using individual inputs including average temperature and sun shine hours compaired to other inputs, respectively.
    Conclusion
    The results of used models indicate that both ANN and SVM models have acceptable performance in evaporation estimation. Evaluation results show that the average temperature is better input than other six parameters in estimation of evaporation. The investigations of this study indicate that although there is no significant difference in the results of three kernel functions of support vector machine, but the Radial Basis kernel function has high accuracy and better performance in estimation of daily evaporation in comparison to other kernel functions.
    Keywords: Artificial neural network, Evaporation Estimation, Maragheh, Support Vector Machine, Tabriz