تحلیل سری زمانی شاخص‏های خشکسالی SPTI, SPI, SPEI با استفاده از روش‏های SOFM شبکۀ عصبی و مقایسۀ عددی در استان چهارمحال و بختیاری

نوع مقاله: پژوهشی

نویسندگان

1 استادیار، دانشکدۀ علوم و فنون نوین، دانشگاه تهران

2 کارشناس ارشد اکوهیدرولوژی، دانشکدۀ علوم و فنون نوین، دانشگاه تهران

چکیده

تحلیل و مقایسۀ شاخص‏های خشکسالی از‏جمله مطالعات مورد نیاز به‌منظور پایش و ارزیابی صحیح خشکسالی توسط شاخص‏های متعدد است. تا کنون شاخص‏های متعددی به منظور پایش این پدیده معرفی و به کار برده شده است. مقالۀ حاضر به مقایسۀ کارایی سه شاخص خشکسالی SPEI، SPI و SPTI به منظور پایش خشکسالی در استان چهارمحال و بختیاری پرداخته است. اساس کار مقایسۀ شاخص‏ها، استفاده از شبکۀ عصبی SOFM است که با استفاده از نتایج توپولوژی این شبکه می‏توان نتیجه گرفت آیا مقادیر شاخص‏ها در یک رستۀ داده‏ای قرار گرفته‏اند یا خیر؟ پس از آن، به تحلیل فراوانی طبقات خشکسالی و انواع تحلیل زمانی خشکسالی پرداخته شده است. نتایج نشان ‏داد هر دو روش مقایسۀ عددی و شبکۀ عصبی SOFM با دقت زیاد می‏توانند خروجی‏های شاخص‏های خشکسالی را مقایسه و ارزیابی کنند. همچنین، براساس نتایج به‌دست‌آمده، در هر سه شاخص خشکسالی مد نظر، براساس تعداد وقوع خشکسالی به صورت ماهانه، بین سال‌های 1988 تا 1990 شدیدترین دورۀ تداوم خشکسالی اتفاق افتاده است. از سوی دیگر، شدیدترین خشکسالی رخ‌داده در مطالعۀ حاضر در سپتامبر 2003 براساس شاخص SPEI در ایستگاه بهشت‏آباد با مقدار 9/5- روی داده است. از دیگر نتایج مقالۀ حاضر، می‌توان به حساسیت بسیار زیاد شاخص خشکسالی SPEI نسبت به دو شاخص خشکسالی در برآورد سایر طبقات خشکسالی اشاره کرد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Analyzing time series of SPI, SPEI and SPTI drought indices by using artificial neural network SOFM method and numerical comparison in chaharmahal va bakhtiari

نویسندگان [English]

  • Mohammad Hossein Jahangir 1
  • Leila Noorazar 2
  • Ehsan Azimi 2
1 Assistant Professor, Faculty of New Sciences & Technologies, University of Tehran
2 University of Tehran
چکیده [English]

Analysis and comparison of drought indices are several of the studies needed to monitor and evaluate drought by multiple indicators. Drought evaluation is typically performed using climatic and hydrological parameters.
So far, several indices have been introduced to the analysis of this phenomenon. This paper in order to monitor drought in Chaharmahal and Bakhtiari province is compared to the Performance of three drought indicators, SPEI, SPI and SPTI. The basis of the comparison of indices is the use of the SOFM neural network, which by use of the results of the topology of this network, is resulted that the drought indices are in one category or not? Subsequently, the frequency analysis of drought classes and all types of drought analysis have been done. The results show that both numerical and SOFM methods can analyze and evaluate the outputs of drought indices, accurately. Also, according to the obtained results, the most severe period of drought had been occurred during the period between 1988 and 1990 in all three drought indices. On the other hand, the most severe drought was happened in this study in September 2003 based on the SPEI index at Behesht Abad Station with a value of -5.9. From other results of this paper can also be referred to the high sensitivity of the SPEI than two other drought indices in calculations.

کلیدواژه‌ها [English]

  • SPI
  • SPEI
  • SPTI
  • Chaharmahal va bakhtiari
  • Time Series Analysis
 

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