Modeling and projection of climate parameters in northwest of Yazd using General Circulation Models and Representative Concentration Pathway scenarios

In recent years, addressing of climate change effects in the development of adaptation plans with natural hazards mitigation has been on the agenda of many institutions. Hence, effective planning requires the examination of both current and projected climate change scenarios. To investigate past and future climatic parameters, researchers usually use observations and theoretical models. General Circulation Models (GCMs) based on the physical sciences are the most reliable theoretical methods, that available for simulating the climatic parameters. The main purpose of the study is to project temperature, radiation and precipitation parameters in the northwest of Yazd town and evaluate their impact on climate change.

This research took place at Center of Iran, which is situated in the northwest of Yazd town. The minimum and maximum temperature in this region is -3.5 and 36 degrees Celsius with an average annual precipitation of 48.81 mm.In this research, the parameters of precipitation, minimum, maximum and average temperature and radiation, over the northwest of Yazd town in the base period (2001-2020) with three general circulation models (GFDL-CM3, CMCC-CM and MRI-CGCM3) from the CMIP5 series, under two scenarios RCP4.5 and RCP8.5 were simulated and predicted using the LARS-WG6 model for an 80-year period in future (2021-2100). Then, by evaluating statistics such as Coefficient Of Determination (R^2), Root Mean Square Error (RMSE), Normalized Root Mean Square Error (NRMSE) and Mean Square Error (MSE), the best model in the region was determined to project future climate parameters.

Evaluation of the LARS-WG 6.0 performance in modeling and Prediction daily climate parameters for the northwest of Yazd Province was perfect (R^2=0.996). According to the results, the highest increase in temperature in the base period (2001-2020) was related to 2018, which had the minimum, maximum and average annual values of 14.2, 31.1 and 22.6 degrees Celsius, respectively. Also, based on both Representative Concentration Pathway scenarios, the temperature will increase in the future until the year 2100, and the amount of this increase in RCP8.5 is greater than in RCP4.5. The amount of temperature increase in both scenarios in the GFDL-CM3 model is higher than the other two models, and the MRI-CGCM3 model has the lowest increase in annual temperature compared to the other two models. The average temperature changes among 1.1- 4.3 °C (RCP4.5) and 2.6- 6.7 °C (RCP8.5). In project the temperature parameter, the MRI-CGCM3 and CMCC-CM models are respectively introduced as the best models with NRMSE<20%.In the future, radiation will decrease in the winter season but increase in the summer season. The highest amount of radiation both in the base and future period in both radiative forcing scenarios is related to the months of June and July. Radiation amount modeling in the RCP8.5 is lower than the RCP4.5, and in the GFDL-CM3 model is higher than the MRI-CGCM3 model, and this model is also higher than the CMCC-CM model. Average precipitation in the future has a variable trend. The total average precipitation in the future varies from -17.82 (GFDL-CM3) to +17.23 (MRI-CGCM3) and +34.07 (CMCC_CM) mm in RCP4.5 and from -18.04 (GFDL-CM3) to +14.37 (MRI-CGCM3) and +35.94 (CMCC_CM) mm for RCP8.5. In the projection of precipitation and radiation parameters, the GFDL-CM3 model is introduced as the best model with the lowest error indicators.

According to the obtained results, with the increase of temperature and radiation in the summer season and Decrease in Precipitation in future, the climate of northwest of Yazd town will be warmer than the base period in the future. The possible consequences of this situation in the future include an increase in evapotranspiration and water stress, lack of vegetation cover and bareness of the soil surface, a decrease in soil water and groundwater recharge, an increase in wind speed and the creation of dust storms. That these changes with high human effects of cause the amount with increase in drought and the area of deserts in the region. And these conditions will lead to the destruction of ecosystems and settlements. Therefore, the results of this study can be used in planning related to the management of natural resources such as water resources. Also, the obtained results are valuable in climatic and meteorological studies and can help water resources planners and managers.