ارزیابی اثرتغییر اقلیم بر بارش در مناطق فاقد آمار مشاهداتی با استفاده از بسته نرم‌افزاری Cct مطالعه موردی: حوضه دریان

این تحقیق با هدف ارزیابی تغییرات مکانیزمانی بارندگی تحت تاثیر احتمالی تغییر اقلیم در سطح حوضه دریان در شمال دریاچه ارومیه انجام گرفته است. باتوجه به عدم وجود ایستگاههای هواشناسی با دوره آماری بلندمدت در نزدیکی منطقه مطالعاتی، امکان استفاده از داده‌های (cru) به‌عنوان داده‌های مشاهداتی با بررسی وجود همبستگی بین این داده‌ها با داده‌های ایستگاه‌های هواشناسی سینوپتیک موجود در منطقه انجام گرفت. نوسانات آتی بارش در دوره (20202050) با استفاده از پنج مدل‌های اقلیمی(gcm) و در قالب دو سناریوی انتشارrcp2.6 وrcp8.5 با استفاده از بسته نرم‌افزاری cct پیش‌بینی شده است. انتخاب مناسب‌ترین مدل اقلیمی هر ایستگاه براساس مقدار rmse انجام گرفت. نقشه‌های توزیع مکانی بارندگی در دوره‌های پایه و آتی به روش idw در محیط gisتهیه شده است. وجود همبستگی معنی‌دار در سطح اطمینان 0.01 داده‌های (cru) با ایستگاه‌های هواشناسی سینوپتیک مجاور آنها، بیانگر امکان استفاده از آنها به عنوان داده‌های مشاهداتی بالاخص در مناطق فاقد ایستگاه هواشناسی می‌باشد. پیش‌بینی می‌شود درصد تغییرات وزنی بارش حوضه دریان در سناریوی rcp2.6 و rcp8.5 به ترتیب (6.3+) (16.4-) نسبت به دوره پایه پیشبینی شده است. متوسط وزنی بارش حوضه دریان در دوره پایه و سناریوهای یاد شده به ترتیب 312.7، 319 و 296 میلیمتر در سال برآورد گردید. علیرغم وجود عدم قطعیت در مطالعات تغییر اقلیم، نتایج حاصله در این تحقیق می‌تواند تصویر کلی از روند آتی بارندگی منطقه ارائه کرده و این اطلاعات می‌توند در برنامه‌ریزی منابع آب منطقه که ارتباط مستقیمی با حجم بارندگی‌ها دارند مفید واقع شود.

assessment the impact of climate change on precipitation in non-observed data using the cct toolkitcase study: daryan sub basin

introduction climate change is one of the most important phenomena of the present century, which has created many problems and challenges both globally and regionally and nationally. in the second half of the twentieth century, global warming relative to the first half of this century has increased and it is predicted that this increase in temperature will continue in future periods, resulting in changes in the level of climatic conditions in different parts of the world. due to the lack of atmospheric precipitation, due to the increase in temperature, the rate of evaporation has increased significantly and can greatly affect the aggravation of water shortage conditions in surface currents, especially evaporation from the surface of lakes behind dams. percentage by evaporation leads the country to higher values ​​(farajzadeh and ghasemifar, 1398). regarding the changes in iran’s water resources in the horizon of 2100, few studies have been done and most have been case studies (fahmi, 1393). although the results of these studies, based on the climatic models and different scenarios used, sometimes show contradictions, so it is necessary to do more studies in this field.    methodology the present research has been done in three specific sections and the output of each section has been used as the input of the next section. in the first part, climate change in the form of precipitation variables in the study area is detected and subsequently, rainwater runoff in the daryan catchment is simulated. then, while identifying the characteristics of hydrological drought periods in the basin, the probability of occurrence, intensity and duration of hydrological drought periods are calculated based on the fit of different statistical distributions for different return periods in the third section.    results and discussion climate change is one of the most important environmental problems of this century. thus, evaluating the phenomenon of climate change and reducing its effects on both global and regional scales has attracted the attention of many researchers, planners and legislators (yohe et al., 2007). proper assessment of these effects requires the existence of climatic information with appropriate spatial distribution and longterm time series, as well as a thorough understanding of its future trends at the regional and local scale. despite the fact that today the output of public circulation models (gcm) are the main sources of future climate data production. one of the most important consequences of climate change includes changes in the hydrological cycle and river flow regime of watersheds. therefore, the present study aimed to investigate the possible effects of climate change on rainfall and runoff in the daryan catchment area north of lake urmia. in this study, statistical method (sdsm) and data of canesm2 canadian climate model in the form of three scenarios rcp2.6, rcp4.5 and rcp8.5 in order to microscale the precipitation data of five synoptic stations adjacent to the sea basin and changes its future is used. here, the basic period (19612005) and future periods (20492020), (20792050) and (20802100) were selected. in this research, the threshold level method has been used to identify hydrological drought periods and extract its characteristics. the results of the analysis of the last 35 years of hydrological droughts in the daryan basin showed that 44 drought events occurred in this basin, which in total, led to a reduction in surface flow volume of about 140 million cubic meters in this basin. conclusion the simulation results of swat model showed that the annual average runoff of the sea basin in the first period (202049) in all three scenarios increases by 3.7 and 6%, respectively, compared to the base period. while in the rest of the periods of all scenarios, runoff reduction is predicted compared to the base period. accordingly, a decrease in surface runoff compared to the base period is predicted for five months of the year (april to august) and an increase in the remaining months. future changes in precipitation at tabriz station, which is the basis for modeling runoff in the daryan basin, are not very noticeable compared to the base period, and only in the period (20492020) all three scenarios are predicted to increase by 5, 2 and 8%, respectively, compared to the base period. in the other periods, in all three scenarios, a decrease in rainfall is predicted compared to the base period. results of evaluating the effects of climate change on rainfall and surface runoff in the daryan basin with the results of other researchers in the catchment area of ​​lake urmia, including: goodarzi and fatehifar (2010) in the azarshahrchai basin, qaderpour et al. (2016), dariane et al. (2019) ), sobhani et al. (2015), goodarzi et al. (2015) and salehpour and malekian (2019) are consistent.