بررسی روند دوره‌های خشکی سالانه با استفاده از شاخص های AMDSL ، ANDSPS و SPI

نوع مقاله: مقاله پژوهشی

چکیده

شناخت تغییرات رژیم­های بارش در مدیریت صحیح منابع آب اهمیت بسزایی دارد. در این تحقیق، به­منظور تحلیل وضعیت بارندگی و دوره‌های خشک سالانه، روند تغییرات شاخص SPI سالانه و نیز دو شاخص حداکثر طول دوره خشک سالانه (AMDSL) و تعداد دوره‌های خشک سالانه (ANDSPs) مورد بررسی قرار گرفت. برای این کار آمار روزانه بارندگی پنج ایستگاه‌ سینوپتیک شمال‌غرب کشور (ارومیه، تبریز، اردبیل، خوی و مراغه) که دارای آمار 34 ساله (2014-1981) می‌باشند، مورد استفاده قرار گرفت. پس از بررسی همگنی و نرمال بودن داده‌ها، وجود خودهمبستگی معنی‌دار در هرکدام از سری‌ها مورد آزمون قرار گرفت و در صورت معنی‌دار بودن حذف گردید. اعمال آزمون من- کندال بر هریک از سری‌های مورد استفاده، نشان داد هر سه شاخص در اغلب ایستگاه‌ها دارای روند کاهشی هستند. روند نزولی دو شاخص AMDSL و ANDSPs بیانگر بهبود وضعیت تعداد و طول دوره­های خشک در منطقه بوده، ولی سیر کاهشی شاخص SPI حاکی از کاهش میزان بارندگی می‌باشد. می‌توان نتیجه گرفت که علی‌رغم کاهش میزان بارش در منطقه، پراکندگی آن در طول سال بهبود یافته است. روند کاهشی دو شاخص SPI و ANDSP در ایستگاه مراغه معنی‌دار تشخیص داده شد که آماره من- کندال (Zm)آنها در سطح 05/0 به ­ترتیب 622/3- و 408/2- می‌باشد. به­منظور شناسایی نقاط آغاز روند از تکنیک من- کندال دنباله‌ای استفاده شده است. نتایج نشان‌دهنده وقوع جهش‌های نزولی شاخص‌های SPI و ANDSP در ایستگاه مراغه می‌باشد. در سایر ایستگاه­ها جهش معنی­داری ملاحظه نشد.

کلیدواژه‌ها


عنوان مقاله [English]

Studying Trends in Annual Dry Periods Using the AMDSL, ANDSPs and SPI Indices

چکیده [English]

Study of the changes in precipitation regimes is very important in proper water resources management. In this research, in order to analyze the state of precipitation and annual dry spell periods, the trends of SPI, Annual Maximum Dry Spells length and Annual Number of Dry Spell Periods indices were studied. For this purpose, daily precipitation data of five synoptic stations in northwest of Iran (Urmia, Tabriz, Ardebil, Khoy and Maragheh) having a 34-year data record (1981-2014), were used. After examining the homogeneity and normality of the data, the significance of autocorrelation in each of the time series was tested. According to outcome of Mann-Kendall test, all three indices had a decreasing trend in the most of stations. Decreasing trend in the two AMDSL and ANDSPs indices reflects improvement of spell and number of dry periods, and decreasing trend of SPI index indicates reduction of precipitation. So, we can conclude that despite of the reduction in precipitation in the region, rainfall distribution has improved over the years. Decreasing trend of the two SPI, and ANDSP indices is significant in Maragheh and Mann-Kendall test criteria (Zm) for SPI, and ANDSP indices were -3.622 and -2.408 respectively (P<0.05). In order to identify the change points of the trends of series, sequential Mann-Kendall technique were used. The results indicated the occurrence of significant jump in Maragheh station.

کلیدواژه‌ها [English]

  • AMDSL
  • ANDSPs
  • Drought
  • Mann-Kendall Test
  • SPI
  • Trend Analysis
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