توسعه یک مدل پیش بینی ریسک خشکسالی هواشناسی (مطالعه موردی: زیرحوضه آبریز افین)

خشکسالی به عنوان پیچیده ترین، اما کمتر شناخته شده ترین خطر در میان تمام خطرات طبیعی است که نسبت به هر خطر طبیعی دیگر، درصد بیشتری از مردم را تحت تاثیر قرار می‌دهد. خشکسالی یکی از پدیده های طبیعی و مکرر اقلیمی است؛ تجزیه و تحلیل ریسک خشکسالی ترکیبی از تجزیه و تحلیل خطر خشکسالی و تجزیه و تحلیل آسیب پذیری خشکسالی است. در این مطالعه سعی شده است چشم انداری از تغییرات ریسک خشکسالی هواشناسی در آینده نشان داده شود. مطالعه به صورت موردی برای زیرحوضه افین (واقع در استان خراسان جنوبی) انجام شده است. دوره آماری استفاده شده برای دوره پایه 33 سال (2015-1983) می باشد. داده های آینده براساس سه مدل از پروژه cordex بدست آمده است. دوره آتی، به سه دوره 27 ساله شامل، آینده نزدیک (2046-2020)، آینده میانی (2073-2047) و آینده دور (2100-2074) تقسیم شده است. به منظور محاسبه ریسک خشکسالی، مخاطره خشکسالی براساس سه شاخص خشکسالی spi، spei و erdi برای دوره پایه و دوره های آتی و پس از آن آسیب پذیری تعیین شد. افزایش شدت خشکسالی ها در دوره های آتی از دیگر نتایج حاصل از این مطالعه است. خروجی های ریسک بدست آمده از روش مستقیم محاسبه ریسک که با داده های cordex و نیز روش استفاده از مدل پیش بینی ریسک که در این مطالعه بدست آمد، نشان از افزایش تعداد وقایع خشکسالی و بدنبال آن افزایش وقایع ریسک خشکسالی در منطقه دارد. همچنین، مشاهده شد شدت ریسک خشکسالی ها براساس سناریوی انتشار rcp8.5 بیشتر از rcp4.5 می باشد

Development of Weather Meteorological Drought Forecast Model (Case Study: Sub-basin Afin Watershed)

Introduction: Drought is the most complex, but less wellknown risk among all natural hazards, which affects more people than any other natural hazard. Meteorological and seasonal hydrological drought is a common phenomenon in tropical countries and is expected to increase further in the future. Drought is one of the natural and frequent climate phenomena; Drought risk analysis is a combination of drought risk analysis and drought vulnerability analysis. Drought risk assessment methods can be calculated either by remote sensing methods or by statistical methods or by combining both methods. Drought risk assessment shows a more Suitable and accurate view of the drought because, in addition to drought severity is simultaneously Includes the probability of occurrence of drought and the impact this phenomenon on the environment and the region. In this study, has been made to illustrate Visionary of Changes in future meteorological drought risk.;Materials and methods: The study was conducted as a case study for the Afin subbasin The average of minimum temperature, mean of maximum temperature, average temperature at 2 meters above ground level and rainfall data in this research have been used. The statistical period used for the base period is 33 years (19832015). Future data is derived from three models of the cordex project. The upcoming period is divided into three 27year periods including the near future (20202046), the middle term (20472073) and the distant future (20742100). In order to investigate the drought in future periods was prepared a combination model of three climatic models using the Bayesian method. Then, the future values of the meteorological parameters were calculated. Drought risk for the upcoming periods was calculated by direct method and modeling method. Finally, a comparison was made between the two methods in order to determine the appropriateness of the predicted model.;Results and discussion: In the survey of the intensity of SPI and SPEI drought indices during the base time period for time scales studied, the SPEI and SPI drought indices showed that both, drought events were the same during the studied period, while the indicator SPEI drought shows more mild and moderate droughts, and the SPI index has shown intense intensity on some scales. In future periods, according to the RCP8.5 scenario, the number of drought events in each period does not differ from the RCP4.5 scenario, but the intensities are higher than RCP4.5. By completing the questionnaire and using exploratory and confirmatory factor analysis methods, the drought vulnerability was determinated 53%. ARIMA (0,0,0) , The appropriate time series model was used to predict the level of risk. In the drought risk prediction section, the results showed that according to the SPI drought index in the upcoming periods, the number of drought events relative to the base period is relatively higher, thus the number of drought events (including four drought conditions) will increase in the far future than the two upcoming middle and nearer periods. According to prediction models of risk, rainfall parameter for all time scales of SPI index and for four time scales of spring, autumn, winter and annual drought index SPEI, is an effective parameter in drought estimation and effect on drought occurrence in the study area.;Conclusion :The results of this study indicate an increase in temperature in future periods based on both RCP emission scenarios. Increasing the severity of droughts in future periods is another result of this study. The risk outcomes obtained from the direct riskmeasurement method, which was obtained with CORDEX data as well as the method of using the riskpredictive model obtained in this study,Showed strong correlation and no significant difference in mean, which indicates the model apos;s appropriateness for risk prediction (hazard and after that risk) in the future.Also,The risk outcomes obtained from the direct Risk calculation method, which is based on CORDEX data with the method of using the risk prediction model obtained in this study, indicates an increase in the number of drought events followed by an increase in drought risk events in the region. also, it was observed that Severity of drought risk according to the RCP8.5 release scenario is higher than RCP4.5. For more more accurate results, it is suggested that more models (more than three models) be used from the sixth report of the Intergovernmental Panel on Climate Change.