عنوان مقاله [English]
Introduction The planet's climate has been constantly changing throughout Earth history, but with the onset of the industrial revolution and human intervention on the environment in recent years, special conditions for rising global temperature have been created.
Increase in Earth's temperature has modified the climatic balance and widespread climate changes have been occurred on the Earth's surface, which is referred to as "climate change". To study the effects of climate change on different systems in future, the climate variables should be initially simulated in the future. There are various methods for simulating climatic variables; the most prudent of them is the use of the outputs of atmosphere-ocean general circulation models (AO-. GCMs).
Since these models simulate climatic variables in large spatial and temporal scales, to use these simulated variables in smaller scales, the output of these models should be scaled down by various techniques. The microscopic statistical method has more advantages, especially when it comes to lower costs and quicker assessment of the factors which affect climate change, including the SDSM model.
Method and methods: The purpose of this study was to predict climate change by the SDSM model using the CanESM2 Climate Change Output based on RCP8.5, RCP4.5, RCP2.6 climate change scenarios for the coming periods of 2040-2011, 2070-2041, and 2100- 2071, as well as study the annual trend of these changes using the Man-Kendall test and the age-related slope estimator. For this purpose, daily data of rainfall and temperature parameters during the statistical period (1981-2010) were collected from the Meteorological Organization. Then, using statistical downscaling model (SDSM), these climatic parameters were simulated in a monthly scale and compared with the base period (1981-2010).In the SDSM model, for the microscopic metering, three types of data are used. The stages of working with this model are briefly summarized as follows: 1. Preparing predictive data and large scale predictors 2. Quality control of data and data conversion (for precipitation data) 3. Choosing the best predictor variables 4. Calibrating the model 5. Production of weather forecasting using observational predictors 6. Statistical analysis 7. Graphical output of model 8. Production of climate scenarios using model climate predictors.
Results and discussion: According to the results, it was found that during the 21st century the temperature in the station of Gorgan is increasing and precipitation is decreasing. In three scenarios RCP8.5, RCP4.5, RCP2.6 in the two periods of near future (2040-2011), and the middle (2041-2070) from February to August and in the distant future period (2071-2100) from December to August there is a decrease in rainfall. The highest precipitation decline is in the near future period in June, July and August, with 19.1, 20.9, and 20 mm, and in the middle and the distant future period in each of the three scenarios belongs to May from 28.8 till 47.15 mm.
Generally, in all scenarios, as we move towards the end of the 21st century, the average rainfall will be reduced, and the decrease in the RCP 8.5 scenario is more than the other two scenarios. Regarding temperature variables, the general trend of temperature variables in future periods is consistent with the trend of these variables in the base period, with the difference that the temperature will increase slightly in the winter and spring until mid-summer, but from late summer to late fall it will decrease. In the upcoming period, at first the temperatures will be higher in June and in the upcoming mid and later periods it will be higher in May than in other months. Moreover, the more moving from the near future towards the end of the century, the temperature will increase. The augmentation in the RCP 8.5 scenario is more than two other scenarios. However, Regarding the annual precipitation rate, RCP 4.5 and RCP 8.5 scenarios are meaningful and decreasing, and in the case of maximum, minimum and mean temperature variations, there is a significant increase. Also, the precipitation drop and temperature rise in the end of the century and in the RCP 8.5 scenario are more than RCP 2.6 and RCP 4.5 scenarios. According to the Conclusion: In this research, the simulation of climatic parameters of temperature and precipitation was carried out using several linear models of SDSM and general atmospheric circulation models in Gorgan. The output of the CanESM2 model was simulated under RCP8.5, RCP4.5, RCP2.6 scenarios for subsequent periods in 21 steps. The results showed that temperature data, better correlation with observation data (compared with rainfall data). According to the results, it was found that during the 21st century the temperature was increasing and the precipitation was decreasing. At Gorgan Station, in three scenarios RCP8.5, RCP4.5, RCP2.6, in the two near future (2040-2011) and mid-term (2041-2070) from February to August and in the distant future period (2071-2100) between December and August we see a decline in rainfall. The highest precipitation falls in the period in June, July and August, at 19.1, 20.9, and 20 mm, and in the middle and long distances in each of the three scenarios it is from May 28.8 to 47.15 mm .In general, in all scenarios, as we move towards the end of the 21st century, the average rainfall will be reduced, and this decrease in the RCP scenario of 8.5 is more than the other two scenarios. Regarding temperature variables, the general trend of temperature variables in future periods is consistent with the trend of these variables in the base period, with the difference that the temperature increased slightly in the winter and spring until mid-summer,but from late summer to late The fall will decrease. In the upcoming period, the higher temperatures will be higher in June and in the upcoming mid and later periods in May than in other months. Also, the more coming the near future towards the end of the century, the higher the temperature will increase. This increase in the RCP 8.5 scenario is more than two other scenarios. overall result of this study, the increase in temperature and precipitation in the spring and summer and the rising rainfall and the cooling of the autumn season seems to be in the planning of water resources, and in particular, the planning of the agricultural sector This should be taken into account in order to minimize the potential negative effects of climate change in the targeted area.
Keywords: precipitation, Climate change, Temperature, SDSM