مخاطرات سیل و خشکسالی در مناطق خشک و نیمه خشک تحت شرایط تغییر اقلیم: شمال استان فارس

نویسنده

چکیده

محدوده مورد مطالعه در شمال استان فارس قرار دارد و عمدتا دارای اقلیم خشک تا نیمه خشک (طبقه بندی دومارتن) است. در این مطالعه داده‌های روزانه ?? مدل گردش عمومی برای ? ایستگاه هواشناسی توسط مدل آماری LARS-WG برای دوره ????-???? ریز مقیاس شده اند. نتایج نشان میدهد که دمای متوسط سالیانه ?/?، ?/? و ?/? درجه نسبت به دوره مشاهداتی ????-???? تحت سه سناریوی RCP?.?، RCP?.? و RCP?.? افزایش و بارش سالیانه ?/??، ?? و ?? درصد کاهش خواهد یافت. بر اساس نتایج شدت بارشهای با دوره بازگشت ? سال در منطقه افزایش خواهد یافت. شدت بارشهای با دوره بازگشت ? سال بدون تغییر ولی شدت بارشهای با دوره بازگشت ?? و ?? سال کاهش خواهد یافت. بنابراین افزایش شدت بارشهای با دوره بازگشت ? سال موجب افزایش رخداد سیلاب و فرسایش در شمال استان فارس خواهد شد. همچنین نتایح حاصل از بررسی دوره های ترسالی و خشکسالی حاکی از آن است که در آینده نزدیک (????-????) تعداد سالهای ترسالی و نرمال افزایش ولی تعداد سالهای خشکسالی کاهش خواهد داشت، اما در آینده دورتر (????-????) شرایط متفاوت بوده، بطوریکه دوره های ترسالی و نرمال تقریبا بدون تغییر بوده ولی تعداد سالهای خشکسالی افزایش و شدت آن بیشتر خواهد شد.

کلیدواژه‌ها


عنوان مقاله [English]

The flood and drought events over arid and semi-arid regions under climate change: Northern Fars province

نویسنده [English]

  • Mostafa Naderi
چکیده [English]

Abstract
Introduction:
The melted ices, reduced snow covers, increased air temperature, change in frequency and duration of droughts and change in precipitation patterns are evidences of the climate change (Ehsani et al., ????; Huber and Knutti, ????; IPCC, ????). Different alternatives of driven factors (population and economic growth, technology efficiency and type of used energy) are considered in the ??st century to project the greenhouse gasses in the Representative Concentration Pathways (RCPs). These assumptions lead to the three RCPs, including a stringent mitigation scenario of RCP?.?, an intermediate scenario of RCP?.? and, a very high greenhouse gasses emission scenario of RCP?.? whose radiative forcing is +?.?, +?.?, +? and +?.? W/m?, respectively in the year ???? relative to pre-industrial values. The global warming is +?, +?.?, +?.? and +?.? ?, respectively at the end of the ??st century (????-????) relative to ????-???? (IPCC, ????). The study of the temporal variability of the observed precipitation and temperature in southern Iran showed that the precipitation and temperature trends are negative and positive, respectively (Tabari and Talaee ????a, ????b; Kousari and Asadi Zarch ????; Tabari et al. ????; Kousari et al. ????). There are large dams such as Dorudzan and Molasadra and natural lakes of kaftar, Arzhan and Parishan over the study area which may adversely affected due to climate change in future. Therefore, the objective of this study is to find how the climate variables of precipitation and temperature, drought duration and intensity of extreme storms will change under climate change.

Methods:
The six climatic stations are selected based on the longest common daily records of precipitation and temperature data (????-????) to investigate the climate change in the study area. In this study, the daily outputs of the ?? CMIP? models are applied for climate change study. The LARS-WG is used to downscale each GCM-predicted data in ? stations. The observed daily data during the ??-year period of ????-???? are inputted to the LARS-WG to calibrate it for each station. Then, to verify the LARS-WG at each station, the ??-year daily precipitation, minimum and maximum temperature are generated and statistical characteristics of the generated data (statistical distributions and mean values) are compared with observed ones at significance level of ?.?? using Kolmogorov–Smirnov (K-S) and Student’s t-test (Semenov and Barrow, ????). The verification results imply that the LARS-WG reproduces the daily data well in ? stations. The change factors are calculated using the given GCM data and relevant grid box to downscale that GCM output for each climatic station. the change factors are calculated using a transient approach in which ?-year future time windows shifted forward by ?-year.
Results:
The downscaling results in Abadeh station indicate that the mean annual temperature will increase from ??.? ? during the period ????-???? to ??.?, ??.? and ??.? ? under the RCP?.?, RCP?.? and RCP?.?, respectively, leading to the warming by +?.?, +?.? and +?.? ?, respectively. The downscaling results show that the mean annual precipitation will decrease from ??? mm during the observation period (????-????) to ???, ??? and ??? mm under the RCP?.?, RCP?.? and RCP?.?, respectively, leading to precipitation reduction by ??.?%, ??% and ??%, respectively. The intensity of extreme storms with different return period are estimated using the maximum annual series during the observation period and three RCPs. The goodness of fit on statistical distributions of Exponential (?P and ?P), Gamma (?P and ?P), General Gamma (?P and ?P), Log-Gamma (?P), General Extreme Value, Normal, Log-Normal (?P and ?P), Pearson (?P and ?P) and Log-Pearson (?) shows that the General Extreme Value is the best-fitted statistical distribution on maximum annual series. Then, the intensity of ?, ?, ?? and ??-year return period storms are determined using the fitted statistical distribution. The results indicate that the ?-year return period storms will be intensified, the ?-year storms will not be changed, but the intensity of the ??-year and ??-year storms will decrease in future due to climate change. The ??-month SPI analysis indicates that the wet and normal periods will slightly increase while droughts will decrease in the period ????s under the three RCPs. The SPI analysis in the second period (????s) show that the wet periods will not change, the normal periods slightly increase, but drought conditions may be intensified especially in RCP?.? and RCP?.?.

کلیدواژه‌ها [English]

  • Climate change
  • rainfall intensity
  • drought
  • northern Fars province