The Analysis of Downscaling Results of Weather Parameters for Iran Future

Planning and deciding about consuming water in future, and optimized management of water in line with sustainable agriculture development, need the information the climate change. In this study, the effect of climate change on temperature, solar radiation and precipitation, were evaluated. Daily weather parameters of 30 synoptic stations during 1991 to 2010 were used. HADCM3 in downscaling model of LARS-WG under r scenarios A1B, A2 and B1 for three 34-year periods from 2011 to 2045, 2046 to 2079 and 2080 to 2113 were applied to produce future data. The results of evaluation of model in basic period showed that the maximum accuracy of model belongs to the maximum temperature and the minimum accuracy is related to precipitation. In fact, NRMSE and r values of Tmax were 0.005 and 0.999, while they were 0.079 and 0.996 for the precipitation respectively. The prediction of weather parameters in future years indicated that the temperature and the solar radiation values will increase. However, the similar trend was not observed in precipitation. The scenario A2 was considered as the most crisis scenario, so that the increasing 2.13% solar radiation and 24.56 % temperature and decreasing 11.59 % precipitation until 2113 are predicted. In general, with continuing the present condition and prediction of future climate change, the optimized management in agriculture and water resources is necessary.
Extended Abstract
1-Introduction
Planning and deciding about consuming water in future, and optimized management of water in line with sustainable agriculture development, need the information the climate change. During the last few decades, global climate change has been an important research task throughout the world. Therefore, its consequences have been addressed in many research works. The simulation of weather in a place can lead to predict the climatic events significantly. The assessment and prediction of future changes is regarded important to mitigate climate change impacts on water resources mostly due to economic and socio-economic affairs. The purpose of this research is to predict the weather parameters changes under different scenario of LARS- WG downscaling model over the country in future. 
 
2-Materials and Methods
In this study, the effect of climate change on temperature, solar radiation and precipitation, as the most important parameters of country in future years, were evaluated. Daily weather parameters of 30 synoptic stations during 1991 to 2010 were used, including minimum temperature, maximum temperature, precipitation and sunshine in daily scale. HADCM3 in downscaling model of LARS- WG under scenarios A1B, A2 and B1 for three 34-year periods from 2011 to 2045, 2046 to 2079 and 2080 to 2113 were applied to produce future data.
3-Results and Discussion
 The calibration step of model based on the weather parameters during 1991-2010 years in each station was done with high accuracy. The results of model evaluation in basic period showed that the maximum accuracy of model belonged to the maximum temperature, while the minimum accuracy is related to the precipitation. Although the accuracy of solar radiation was more than the minimum temperature, the accuracy of precipitation was less than the minimum temperature.  The same results have been reported by Goodarzi et al. (2015) and Akhavan et al. (2015) what are in line with the present study. The NRMSE and r values of Tmax were 0.005 and 0.999, while they were 0.079 and 0.996 for the precipitation respectively. Although, in studies of Ansari et al. (2014) and Nasiri and Yarahmadi (2017), the accuracy of prediction of minimum temperature by LARS-WG was more than maximum temperature, the results difference can be due to area extent. In this investigation, the average of weather parameters in all station was used while the results as case study can be different. However, the calibration condition of model and time period are other effective factors in the results (Moradi et al., 2015).
The prediction of weather parameters in future over the country under different scenarios by LARS-WG showed that the air temperature of country will increase in future as the maximum values to 4.04 ^o C.  Moreover, the increasing air temperature in cold period will be more tangible than warm period. The evaluation of spatial distribution of air temperature in both of cold and warm periods showed that in all scenarios the minimum temperature and the maximum temperature will happen in half north of country and in half south respectively. Similar to the air temperature, the amount of solar radiation will be more than the present value, although this increase will occur with less speed. According to results of precipitation, the temporal distribution of precipitation will have more changes in next years. Its trend will be increasing and decreasing. Spatial distribution of precipitation over country area in the future indicated that the less precipitation will be received in southeast region, while the most value will belong to the sea coast and southwest area. The scenario A2 was as the most crisis scenario, so that the increasing 2.13% solar radiation and 24.56 % temperature and decreasing 11.59 % precipitation until 2113 are predicted.
4-Conclusion
In general, the changes of air temperature will be slightly higher than other parameters changes in the future. Continuing the present condition and prediction of future climate change, the optimized management in agriculture part and water resources is necessary. Also, due to prediction of solar radiation increasing, it can be used in optimized management of energy and produce the power in future which can be more effective on water resources management.