تحلیل آماری - همدید بارش‌های سنگین دو حوضه آبریز کرخه و دز Journal Article

بارش‌های سنگین به عنوان عامل مخاطره انگیز در بروز حوادث طبیعی نظیر سیل هستند. بنابراین شناسایی و پیش‌بینی وقوع آنها از جمله اقداماتی است که می‌تواند خسارت‌های ناشی از آن را کاهش داد. این مطالعه با هدف تحلیل و تبیین بارش‌های سنگین با استفاده از روش‌های آماری – همدید انجام گرفت. بدین منظور از داده‌های بارش 14 ایستگاه سینوپتیکی و باران‌سنجی دو حوضه کرخه و دز در بازه زمانی 60 ساله (2019 – 1959) استفاده شد. در این رابطه ابتدا با استفاده از تابع توزیع احتمالات حد نهایی تیپ یک (گامبل) آستانه بارش سنگین تعیین شد. نتایج بدست آمده از آستانه‌های بارش سنگین مشخص کردند که به‌طور متوسط بارش بیش از 7/40 میلی‌متر در حوضه کرخه و متوسط بارش بیش از 47 میلی‌متر در حوضه دز به عنوان بارش سنگین محسوب می‌شوند. تعداد روزهای بارش سنگین حوضه کرخه متوسط 118 روز و حوضه دز 81 روز است. آستانه سیلاب‌خیزی حوضه کرخه کمتر از حوضه دز است. بنابراین بارش‌های کرخه ناگهانی‌تر و نامنظم‌تر رخ می‌دهد در حالی بارش‌های حوضه دز از سری‌های زمانی به‌هنجارتری برخوردار است. در نتیجه حوضه کرخه از نظر افزایش بارش‌های سنگین منجر به سیلاب آسیب‌پذیرتر از حوضه دز است. نتایج حاصل از تحلیل همدید نشان داد در تمام الگوها همدیدی سامانه‌های سودانی و سامانه ادغامی سودانی – مدیترانه نقش ﻣﺆثری در ایجاد بارش سنگین همزمان در هر دو حوضه کرخه و دز داشته‌اند. همچنین عمیق شدن ناوه مدیترانه در ترازهای میانی جو سبب فعال شدن سامانه کم‌فشار مرطوب بر روی سودان و دریای سرخ می‌شود. سامانه سودانی به واسطه حرکت به سمت شمال و شمال شرقی ناوه مدیترانه بر روی منطقه مورد مطالعه سبب ایجاد بارش سنگین می‌شود. منبع اصلی ﺗﺄمین رطوبت این بارش از دریای عرب، دریای عمان، دریای سرخ و مدیترانه است.

Heavy rains are a risk factor for natural disasters such as floods. Therefore, identifying and predicting their occurrence is one of the measures that can reduce the damage caused by it. This study was with purpose analyze and explain heavy rainfall using statistical-synoptic methods. For this purpose, precipitation data from 14 synoptic and rainfall stations of Karkheh and Dez basins in a period of 60 years (1959-2019) were used. In this regard, first, using the probability distribution function of the final limit of type one (Gamble), the heavy rain threshold was determined. The results obtained from heavy rainfall thresholds showed that the average rainfall of more than 40.7 mm in Karkheh basin and the average rainfall of more than 47 mm in Dez basin are considered as heavy rainfall. The average number of days of heavy rainfall in Karkheh basin is 118 days and Dez basin is 81 days. The flood threshold of Karkheh basin is lower than Dez basin. Therefore, Karkheh rains occur more suddenly and irregularly, while the rains in the Dez basin have more normal time series. As a result, Karkheh basin is more vulnerable to floods than Dez basin in terms of increased heavy rainfall. The results of synoptic analysis showed that in all models, synoptic systems of Sudanese and Sudanese-Mediterranean integration systems have played an effective role in creating heavy rainfall simultaneously in both Karkheh and Dez basins. The deepening of the Mediterranean submarine also activates the humid low-pressure system on Sudan and the Red Sea. The Sudanese system causes heavy rainfall by moving north and northeast of the Mediterranean coast over the study area. The main source of moisture is the Arabian Sea, the Oman Sea, the Red Sea and the Mediterranean. Heavy rains are a risk factor for natural disasters such as floods. Therefore, identifying and predicting their occurrence is one of the measures that can reduce the damage caused by it. This study was with purpose analyze and explain heavy rainfall using statistical-synoptic methods. For this purpose, precipitation data from 14 synoptic and rainfall stations of Karkheh and Dez basins in a period of 60 years (1959-2019) were used. In this regard, first, using the probability distribution function of the final limit of type one (Gamble), the heavy rain threshold was determined. The results obtained from heavy rainfall thresholds showed that the average rainfall of more than 40.7 mm in Karkheh basin and the average rainfall of more than 47 mm in Dez basin are considered as heavy rainfall. The average number of days of heavy rainfall in Karkheh basin is 118 days and Dez basin is 81 days. The flood threshold of Karkheh basin is lower than Dez basin. Therefore, Karkheh rains occur more suddenly and irregularly, while the rains in the Dez basin have more normal time series. As a result, Karkheh basin is more vulnerable to floods than Dez basin in terms of increased heavy rainfall. The results of synoptic analysis showed that in all models, synoptic systems of Sudanese and Sudanese-Mediterranean integration systems have played an effective role in creating heavy rainfall simultaneously in both Karkheh and Dez basins. The deepening of the Mediterranean submarine also activates the humid low-pressure system on Sudan and the Red Sea. The Sudanese system causes heavy rainfall by moving north and northeast of the Mediterranean coast over the study area. The main source of moisture is the Arabian Sea, the Oman Sea, the Red Sea and the Mediterranean. Heavy rains are a risk factor for natural disasters such as floods. Therefore, identifying and predicting their occurrence is one of the measures that can reduce the damage caused by it. This study was with purpose analyze and explain heavy rainfall using statistical-synoptic methods. For this purpose, precipitation data from 14 synoptic and rainfall stations of Karkheh and Dez basins in a period of 60 years (1959-2019) were used. In this regard, first, using the probability distribution function of the final limit of type one (Gamble), the heavy rain threshold was determined. The results obtained from heavy rainfall thresholds showed that the average rainfall of more than 40.7 mm in Karkheh basin and the average rainfall of more than 47 mm in Dez basin are considered as heavy rainfall. The average number of days of heavy rainfall in Karkheh basin is 118 days and Dez basin is 81 days. The flood threshold of Karkheh basin is lower than Dez basin. Therefore, Karkheh rains occur more suddenly and irregularly, while the rains in the Dez basin have more normal time series. As a result, Karkheh basin is more vulnerable to floods than Dez basin in terms of increased heavy rainfall. The results of synoptic analysis showed that in all models, synoptic systems of Sudanese and Sudanese-Mediterranean integration systems have played an effective role in creating heavy rainfall simultaneously in both Karkheh and Dez basins. The deepening of the Mediterranean submarine also activates the humid low-pressure system on Sudan and the Red Sea. The Sudanese system causes heavy rainfall by moving north and northeast of the Mediterranean coast over the study area. The main source of moisture is the Arabian Sea, the Oman Sea, the Red Sea and the Mediterranean.