Simulation of Temperature and Precipitation Changes of Tabriz Synoptic Station Using Statistical Downscaling and Canesm2 Climate Change Model Output

Document Type : مقاله پژوهشی


1 Zanjan University

2 University of Zanjan


1. Introduction
Climate change is one of the most discussed topics in climatology in the last two decades. Human as part of the climate system plays an important role in climate behavior. Especially, in the current era, increasing population and the human need for food and water sources and agricultural lands, loss of forests, desertification and increased use of fossil fuels lead to changes in the climate system. According to the Fourth Assessment Report of the Board of climate change among States Parties on Climate Change (IPCC), the global climate model predictions for the twenty-first century shows that global warming will continue to accelerate even if humans could take to prevent greenhouse gas emissions. It is predicted that by 2100 global average temperature change increases from 1.8 ° to 4 ° C and mean sea levels rises between 0.18 to 0.59 m up. The frequency and extent of events such as floods, droughts and heat waves are extended by increasing global average temperature. The effect of climate change on the planet is not the same. Some parts of the world are more sensitive to climate change than other areas. For example, areas with Mediterranean climate, their climate is highly dependent on temperature and precipitation, and thus these regions are experiencing stress in the face of climate change (IPCC, 2007).
High statistical downscaling methods have been proposed by Meteorological researchers. Two standard methods that are used extensively in downscaling of climate change models and can be used easily by users are LARS-WG model and SDSM. LARS-WG model is generating a stochastic model time series of climate models and SDSM is a combination of random generator weather and regression methods.
According to studies about downscaling, the SDSM has acceptable accuracy in downscaling climate data, however, most studies have been done on the basis of scenarios (AR4). However, this study intends to use the output of canESM2, one of the coupled climate change CMIP5 models based on new scenarios (AR5), to examine and simulate the climate variables, temperature and precipitation during the 21st century.

2. Study Area
Tabriz, East Azarbaijan province with an area of 1,200 square kilometers is located in 46 degrees 17 minutes east longitude and 38 degrees 05 minutes north latitude. Its height from sea level is 1366 meters. Tabriz is bounded on the north by mountains Einali and to the south slope of Mount Sahand and from the West to the plains of Tabriz and Urmia Lake.

3. Matarials and Methods
In this study, the effects of climate change in the study of Tabriz station due to long-term data were used. The basic observation period is 30-year period of 1990-1961. The daily minimum temperature, maximum temperature, rainfall in the corresponding period assessmented and validated by statistical tests and data were processed to produce daily random series. In this research, modeling canESM2 is the fourth generation of climate models by the Centre for Climate Modeling and Analysis of Canada (cccma) developed under the auspices of the country's environment. In this model, all the surface of the grid is 64 × 128 cells (charron, 2014). This study attempted to simulate climate, temperature and rainfall SDSM using multiple linear models and general circulation models of the atmosphere in the city of Tabriz. In this research, modeling scenarios canESM2, RCP8.5, RCP4.5 and RCP2.6 for future periods were studied in the 21st century simulations.

4.Result and Discussion
Study Rainfall Changes
The results show that overall rainfall scenario evaluated in three studied scenarios, for the two periods 2010-2039 and 2070-2099 showed reduced precipitation and precipitation will increase for the period 2040-2069. On the whole the precipitation in the in the three scenarios examined, for two periods 2010-2039 , 2070-2099 will have been decreased and for 2040-2069 will have been increased. Also precipitation will generally increase in winter and the rest of the seasons will decrease.
Study Minimum Temperature Changes
Results show that the mean minimum temperature of Tabriz station in all months except November and December will increase in the coming period. In the period 2010-2039 the increase in temperature is not sensible, but in the period 2040-2069 and 2070-2099, the increase is quite significant and clear. Generally, the minimum temperature increases in three scenarios examined for three periods. The lowest increases in minimum temperature occur in the first period for the scenario rcp2.6 and the maximum temperature at the last period for scenario rcp8.5.
Study Maximum Temperature Changes
Results show that the mean maximum temperature as minimum temperature at Tabriz in the coming period will have a sensible increase and the mean maximum temperature of Tabriz station have increased in all months except October and November in the coming period. According to the results, we see that generally the maximum temperature in the scenario examined for three periods of study, increases the lowest maximum temperature rise in the first period for the scenario rcp4.5, and the highest maximum temperature rise in the last period for rcp8.5 scenario will occur. Generally, the maximum temperature increase can be seen in all seasons except the autumn rise in summer to 11 degrees temperature.

5. Conclusion
The results showed that temperature data have a higher correlation with the observed data; this is because of the less variability of temperature than rainfall and normal distribution parameter. The one of the reasons for the reduction of correlation in the rain is that various factors are effective on rainfall and other hand the precipitation is a discontinuous variable. So, the problem of solidarity in the development of future climate change models should be considered. Climate change can cause changes in climate variables time and space. The effects of these variables can have harmful effects on the ecosystem components. According to the results showed that in the 21st century temperatures are rising and rainfall is declining. Generally, precipitation in Tabriz station for two periods 2010-2039 and 2070-2099 decrease in three studied scenarios and increases for the period 2040-2069. The precipitation generally increases in winter and decreases in the other seasons. The mean minimum temperatures of Tabriz station in all months except November and December have increased in the coming period. The minimum temperature increases in the studied scenario for three periods. The minimum temperature increases in all seasons and in summer reaches to 8 degrees. The average maximum temperature increases in the studied scenario for three periods. Generally, the maximum temperature can be seen increasing in all seasons except the autumn rise in summer to 11 degrees temperature. Also as we approach the end of the 21st century this situation will be more intensified, This indicates that the climate change situation in the region is serious. However, more studies are needed to ensure more climate change in the study area.


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