کاربرد شاخص کمبود توام (JDI) در تحلیل خشکسالی‌های حاشیه جنوبی دریای خزر

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری مهندسی منابع آب دانشکدة علوم آب دانشگاه شهید چمران اهواز

2 استادیار گروه مهندسی آب دانشکدة کشاورزی دانشگاه شهرکرد

3 استادیار گروه مهندسی منابع آب دانشکدة علوم آب دانشگاه شهید چمران اهواز

چکیده

خشک‌سالی پدیده‌ای اقلیمی است که به‌کندی شروع می‌شود و طبیعتی پنهان دارد. مدت زمان وقوع آن طولانی است و خسارت‌های ناشی از آن در بخش‌های مختلف، مانند کشاورزی و محیط ‌زیست و اقتصاد، به صورت تدریجی ظاهر می‌شود. پایش و پیش‏بینی خشک‌سالی‏ها، به‌ویژه تعیین دقیق زمان شروع و تداوم آن، در مدیریت منابع آبی و برنامه‏ریزی جهت کاهش آثار مخرب خشک‌سالی اهمیتی ویژه دارد. در این مطالعه، خشک‌سالی‏های سه استان گلستان، گیلان و مازندران (استان‏های حاشیة دریای خزر) با استفاده از شاخص کمبود توأم (JDI) ارزیابی شد. همچنین عملکرد شاخص JDI با دو شاخص بارش استانداردشده (SPI) و SPI اصلاح‌شده () مقایسه شد. بدین منظور، از داده‏های بارش ماهیانة پنج ایستگاه سینوپتیک بابلسر، بندرانزلی، رامسر، گرگان، و رشت، در دورة آماری 1971 تا 2011، برای محاسبة شاخص‌های مورد بررسی استفاده شد. نتایج نشان داد در سال‏های اخیر تعداد ماه‏های خشک در منطقة مطالعه‌شده افزایش یافته است؛ طوری که در همة ایستگاه‏ها (به جز بابلسر) درصد ماه‏های خشک به بیش از 50 درصد در دَه سال اخیر (2002ـ 2011) رسیده است. بر اساس محاسبات انجام‌شده برای شاخص‏های JDI و SPI و ، هر چه فاصلة ایستگاه‏ها از دریای خزر بیشتر می‏شود مقدار خشکی‏ها و کمبود بارش نیز افزایش می‏یابد. همچنین، نتایج نشان داد شاخص JDI، علاوه بر توصیف علمی وضعیت کلی خشک‌سالی، قابلیت مشخص کردن ظهور (آغاز) خشک‌سالی‏ها و نیز خشک‌سالی‏های طولانی‌مدت را دارد و ارزیابی وضعیت خشک‌سالی را به صورت ماه‌به‌ماه میسر می‏سازد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Application of Joint Deficit Index (JDI) for Analyzing Droughts over the Southern Margin of the Caspian Sea

نویسندگان [English]

  • Farshad Ahmadi 1
  • Rasoul Mirabbasi Najafabadi 2
  • Fereydoon Radmanesh 3
1 Ph.D Candidate, Water Resources Engineering. Shahid Chamran University, Ahvaz, Iran
2 Assistant Professor, Water Engineering Department, Shahre Kord University, Shahre Kord, Iran
3 Assistant Professor, Water Engineering Department, Shahid Chamran University, Ahvaz, Iran
چکیده [English]

Drought is a climatic phenomenon that slowly and gradually emerges, and is of a latent nature. It lasts long, damaging the different sectors of agriculture, environment and consequently the society. Monitoring and prediction of droughts, especially accurate determination of their times of emergence, and duration, are very important in water resources management and in planning for drought mitigation strategies. Throughout the present study, drought conditions in three provinces (Golestan, Guilan and Mazandaran) located in the southern margin of the Caspian Sea, were evaluated by means of Joint Deficit Index (JDI). The performance of JDI was compared with two other drought indices, Standardized Precipitation Index (SPI) and Modified Standardized Precipitation Index (SPImod). To follow the purpose, monthly precipitation data from 5 synoptic stations, namely: Babolsar, Bandareanzali, Ramsar, Rasht and Gorgan during the period of 1971 to 2011 were used for calculating the drought indices. Results showed that in recent years, the number of dry months across the study area had increased, significantly, as for all the considered stations (except Babolsar) the percentage of dry months had increased to more than 50% during the recent 10 years of 2002-2011. Based upon the calculated JDI, SPI and SPImod values, it becomes evident that the dry condition (along with deficit in precipitation) increase with an increase in the distance from the Caspian Sea. The results also indicate that JDI provides for a comprehensive assessment of droughts and that it is capable of reflecting both emerging and prolonging of the droughts in an accurate manner, allowing for a month-by-month drought assessment.

کلیدواژه‌ها [English]

  • Copula Functions
  • Drought
  • Caspian Sea
  • Joint Deficit Index

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