تحلیل روند شدت بارش سامانه‌های سودانی ورودی به ایران (مطالعه موردی:مسیرهای مستقل ورودی استان‌های خوزستان، بوشهر و هرمزگان)

هدف پژوهش حاضر، تحلیل روند شدت بارش سامانه‌های سودانی ورودی به ایران، از سه مسیر مستقل استان‌های خوزستان، بوشهر و هرمزگان است. به این منظور ابتدا براساس شاخص‌های مورد نظر(1ریزش حداقل یک میلی‌متر بارش در50 درصد ایستگاه‌های هر مسیر. 2 حداقل در یکی از ایستگاه‌ها بارش پنج میلی‌متر و بیشتر رخ داده باشد. 3 در ایستگاه نماینده ورود هر مسیر بارش رخ داده باشد و یا از آن‌جا شروع شده باشد.)، و با استفاده از داده‌های بارش روزانه هر مسیر در دوره‌ی 2017-1995، سامانه‌های سودانی استخراج و سپس معدل بارش آن‌ها، به تفکیک سالانه، ماهانه و دوره‌ی تداوم بارش، برای مسیرهای سه گانه استخراج گردید. در نهایت پس از آماده‌سازی و صحت سنجی داده‌های بارش، با استفاده از روش‌های آماری خط بهترین برازش، من-کندال و تخمین‌گر شیب سن، روند و شیب تغییرات شدت، در سطح اطمینان 95 درصد بررسی گردید. نتایج نشان داد که شدت بارش سامانه‌های سودانی(به تفکیک معدل سالانه، ماهانه و دوره‌های‌ تداوم بارش) در مسیرهای سه‌گانه، علی‌رغم وجود شیب تغییرات کاهشی و افزایشی بسیار جزئی((کم‌تر از 0/6± میلی‌متر طی دوره)، فاقد روند و شیب تغییرات قابل توجه و معنی‌داری است که بتوان آن را به تغییرات آب و هوایی نسبت داد. اما در کل بارش سامانه‌های سودانی در منطقه مورد مطالعه عمدتاً کوتاه مدت(دو روزه )و به ندرت بارش‌های آن‌ها در دوره‌های تداوم پنج روز و بیشتر رخ می‌دهد از این رو بارش‌های سامانه سودانی در منطقه مورد مطالعه(جنوب وجنوب‌غرب ایران)، عمدتاً کوتاه مدت و شدید است.

Analysis of precipitation intensity trend of Sudanese systems entering Iran(Case study: Independent entry routes to Khuzestan, Bushehr and Hormozgan provinces)

Analysis of precipitation intensity trend of Sudanese systems entering Iran(Case study: Independent entry routes to Khuzestan, Bushehr and Hormozgan provinces)Extended AbstractIntroduction:Rainfall is the most important source of water supply in the south and southwest of Iran. The Sudanese system is the most important cause of rain in these areas, which occurs mainly in the short and severe. Optimal survival is directly and indirectly related to the quantity and quality of these precipitations. As mentioned earlier, one of the most important characteristics of Sudanese systems in the south and southwest of Iran is their intensity. In the study of rainfall regime in the south and southwest of Iran, The lack of study of the intensity of rainfall in Sudanese systems, especially in recent decades, is quite evident. Therefore, in the present study, the trend of rainfall intensity of Sudanese systems from three independent input routes of Khuzestan, Bushehr and Hormozgan, which corresponds to the three main routes (A, B and C) of Lashkari (2002) research, is investigated. To use its findings in the management of water resources and atmospheric events such as floods and droughts.Research Methods:In the present study, in order to analyze the trend of rainfall intensity of Sudanese systems in the triple routes of Khuzestan, Bushehr and Hormozgan, first 43 study stations were separated in the form of three routes. In the entrance route of Khuzestan included: 23 stations from the provinces of Khuzestan, Ilam, Kohgiluyeh and BoyerAhmad, Chaharmahal and Bakhtiari and Lorestan, in the entrance route of Bushehr included; 15 stations from Bushehr, Fars, Kohgiluyeh and BoyerAhmad provinces and at the entrance of Hormozgan, including; 7 stations of the province itself. Then, based on the rainfall incidence index of 1 mm and more in 50% of the stations of each route, the frequency of annual, monthly and continuous rainfall periods of Sudanese systems were identified using daily rainfall data (19952017) and then their average rainfall was extracted. Finally, after validating the data, the trend of rainfall intensity in Sudanese systems (20171995), using the methods; line of best fit, ManKendall and Sen’s slop estimator and based on the annual average, monthly and rainfall continuity periods, at 95% confidence level, it was checked in Visual Basic Excel environment and SPSS softwareResults and conclusion:Sudanese systems operate in the cold period of the year in Iran (from the entrance routes of Khuzestan, Bushehr and Hormozgan). The rainfall of these systems in the triple routes is more 1 to 3 days, and rarely have rainfall of 5 days or more. The study of the trend of rainfall intensity of Sudanese systems (19952017) in the triple routes showed; the trend of rainfall intensity of these systems based on the annual average in the triple routes has a slope of decreasing changes of 0.04 to 0.1 mm during the period .However, these trends and the slope of changes are significant only in the rainfall of Bushehr route systems with a slope of very small decreasing changes (0.1 mm during the period). The trend of rainfall intensity in Sudanese systems based on the monthly average of rainfall in the triple routes, is decreasing in some months and increasing in some. The slope of changes in these trends is in most cases zero and in some cases from 0.55 to 0.58 millimeters during the period, fluctuating. But in the meantime, only the increasing trend of November in Bushehr entrance route (0.55 one mm during the period) and the decreasing trend of February in Khuzestan entrance route (0.21 mm during the period) is significant. The trend of rainfall intensity of Sudanese systems in the three routes is based on the average rainfall of different periods of continuity, in most cases decreasing and in some cases increasing. The slope of changes in these trends is in most cases zero and in some cases from 0.12 to 0.43 mm during the period. But in the meantime, only the decreasing trend of 2day systems of Bushehr route with a slope of changes of 0.26 mm during the period is significant.Conclusion: Despite the trend and slope of decreasing and increasing changes in the rainfall intensity of Sudanese systems, but due to the lack of significant trends and slope of changes (less than 0.6 ∓ one millimeter during the period), it can be concluded; The rainfall intensity of Sudanese systems in the entrance routes of Khuzestan, Bushehr and Hormozgan, lacks the trend and slope of significant changes at the 95% confidence level. But in general, Sudanese systems in most cases have short and heavy rainfall, and rarely light and long rainfall. As a result, the occurrence of heavy rains caused by Sudanese systems in the entrance routes of Khuzestan, Bushehr and Hormozgan should still be accepted as a principle. Therefore, floods are still one of the most important threats facing the study areas.Keywords: Trend, precipitation intensity, Sudanese‌‌ Systems, ManKendall, Sen,s Estimator, Iran.