نوع مقاله : پژوهشی

نویسندگان

• محمود خسروی ¹
• تقی طاوسی ²
• کوهزاد رئیس‌پور ³
• محبوبه امیدی قلعه محمدی ⁴

¹ دانشیار گروه آب و هواشناسی، دانشگاه سیستان و بلوچستان

² استاد گروه آب و هواشناسی، دانشگاه سیستان و بلوچستان

³ استاد یار گروه آب و هواشناسی، دانشگاه زنجان

⁴ دانشگاه سیستان و بلوچستان

چکیده

چکیده
استان چهار­محال و بختیاری یکی از مناطق برفگیر کشور بوده و نزولات برفی آن نقش بسیار زیادی در وضعیت منابع آبی تأمین­کننده­ی آب منطقه مرکزی و جنوبی کشور دارد. در این پژوهش سعی شده است تا تغییرات سطوح پوشش برف در ارتفاعات زردکوه بررسی گردد. بدین منظور از تصاویر ماهواره­ای لندست TM و ETM+ در ماه­های آوریل و سپتامبر در سال­های 1991،2003 و 2011 استفاده گردید. نتایج نشان می­دهد که سطوح پوشش برف در ارتفاعات زردکوه بختیاری طی دوره­ی آماری (2011 نسبت به 1991) روندی کاهشی داشته است. برای بررسی روند تغییرات سال 1991 را سال مبنا قرار داده، که مقدار سطوح پوشش برف در ماه آوریل 1991 میلادی، 07/1758 کیلو متر مربع بوده، این مقدار پوشش در ماه آوریل در سال 2003 میلادی، به 43/1128 کیلومتر مربع رسیده، مساحت سطوح برف در آوریل 2011 میلادی 83/979 کیلومتر مربع بوده که نسبت به سال 1991 میلادی 24/778 کیلو­متر مربع کاهش پیدا کرده است. مقدار سطوح پوشش برف در ماه سپتامبر 1991میلادی برابر با 86/802 کیلومترمربع بوده، مقدار این سطوح در ماه سپتامبر 2003 به 83/615 کیلومترمربع رسیده که از ماه سپتامبر سال 1191 تا سپتامبر 2003 میلادی 06/187 کیلومترمربع کاهش پیدا کرده، مساحت پوشش برف در ماه سپتامبر 2011 میلادی برابر با 83/601 کیلومتر مربع بوده که نسبت به ماه سپتامبر 2011 میلادی به 03/201 کیلومتر مربع کاهش پیدا کرده است.

کلیدواژه‌ها

• سطح پوشش برف
• سنجش از دور
• لندست
• ENVI
• زردکوه بختیاری

20.1001.1.23833254.1396.4.12.2.5

عنوان مقاله [English]

A Survey on Snow Cover Variation in Mount Zardkooh-Bakhtyare Using Remote Sensing (R.S)

نویسندگان [English]

• Mahmood Khosravi ¹
• Taghi Tavousi ²
• Kohzad Raeespour ³
• Mahboobeh Omidi Ghaleh mohammadi ⁴

¹ Associate Professor of Climatology, Depatrment of Physical Geography, University of Sistan and Baluchestan

² - Professor of Climatology, Depatrment of Physical Geography, University of Sistan and Baluchestan

³ - Associate Professor of Geography and Climatology, University of Zanjan

⁴ Master of Applied Climatology, University of Sistan and Baluchestan

چکیده [English]

Extent Abstract
Introduction
In some parts of Iran, especially in its highlands, the predominant precipitation is snow. The large part of the snow cover is located in the mountainous and impassable areas. Consequently, it is almost impossible to study and investigate the snow point using traditional methods and snowflake stations. Chaharmahal-Bakhtiari province is one of the snowiest areas of Iran, and snowfall has a great role in the status of the water resources supplying the water of its central and southern regions, especially the Karun and Zayandeh Rood Rivers.
Methodology
 Regarding the role and importance of Mount Zardkouh heights and its rivers in the region, the purpose of this study was to investigate the changes in the snow cover levels in Mount Zardukh altitudes. Therefore, remote sensing data, due to its provision of better results, is used with the aim of obtaining detailed information on snow cover. Today, remote sensing technology and revolutionary satellite imagery are created in the field of snow cover study so that wide-area snow measurements are dramatically more accurate over time. The occurrence of the recent droughts, the severe decrease of water resources, and the role and importance of snowfall in the supply of groundwater resources in mountainous areas needs to maximize the use of available resources by making the necessary arrangements.
Discussion
The process of these changes was measured using landsat satellite data, TM and ETM + sensors. In addition, the ndsi index was used to analyze the changes in the snow cover level of April (Farvardin) and September (Shahrivar), which were the peak months of the snow cover.  The peak time of the snow cover melting in the region, Zardkouh Bakhtiari heights, during 1991, 2003, and 2011 (time spans of approximately 10 years) was also investigated to study the changes in the snow cover levels. Pre-processing steps including examining changes in the snow cover levels using the normalized differential snow index (NDSI) and corrections (radiometric, geometric, etc.), processing, classification, and after classification on the selected images using the ENVI software were taken. The NDSI index was applied based on the maximum snow cover per pixel of images (April & September).
Conclusion
 Finally, the values, or maps, derived from the above indicators were classified into two classes of snow cover and snowless surfaces. After this classification, the areas of ​​both classes were summed up for the investigation of the changes in snow cover and snowless cover during the studied years. The results showed that while the amount of the snow cover level in April 1991 was 1758.07 km², it became 1128.43 km² in April 2003. In other words, there was a decrease of 529.64 km² between the years 1991 and 2003. In addition, it was 979.83 km² in April 2011 and there was a decrease of 778.24 km², compared to 1991. Moreover, while it was 802.86 km² in September 1991, it became 615.83 km² in September 2003. In other words, there was a decrease of 187.06 km² between September 1991 and September 2003.  In addition, it was 601.83 km² in September 2011 and there was a decrease of 201.03, compared to September 1991.

کلیدواژه‌ها [English]

• Snow level
• remote sensing
• Landsat
• ENVI
• Mount Zardkooh Bakhtiari