واکاوی سناریوهای انتشار گازهای گلخانه ای در بخش جلگه ای حوزة آبخیز هراز استان مازندران

Abstract
In order to achieve the objectives of this study and according to the statistics of existing stations, for research about the phenomenon of climate change in the plains of Haraz watershed of Mazandaran province have been used LARS-WG5 model and three scenarios A1B, A2, B1 and each in three series 2011, 2065-2046 and 2099-2080. By determining the 30-year base year from the statistics of the nearest synoptic station to this study area, the average monthly precipitation and temperature were simulated.According to the results of this study, very irregularly increasing changes in rainfall in October, November and January and decreasing changes in August in the period of 2095-2080 are expected in the area. In the case of temperature changes in the watershed of Haraz plains area in the period 2095-2080 for scenarios A1B, A2 and B1, the trend of increasing the average monthly temperature shows even more than the two previously studied periods, so that the average temperature of July and August in the next period 2099-2080 by scenario A1B with 30/44 and 31/03, respectively, that it will reach 30 higher degrees Celsius and the average temperature in January and December will increase to 11.08 and 12.55 with an increase compared to the base period. The increase in temperature in the summer months, which coincides with the decrease in rainfall, has a significant role in the agriculture of this region, which is one of the important rice production areas of the country, and affects the downstream hydrological cycle of Haraz watershed. On the other hand, winter temperature changes can affect the time of snow melting in the basin, which has a significant effect on the peak flood discharge downstream of the watershed.

Introduction
The Intergovernmental Panel on Climate Change released its Sixth Assessment Report on the Physical Science Basis of Climate Change in August 2014. This report brings together the latest advances in climate science, observations, paleoclimatology, and climate simulations to provide the most up-to-date physical science understanding of climate change. Also, the report describes the human impacts on the current state of the climate and how the future climate will affect different regions around the world. The findings of this report provide a better understanding of current and future climate conditions and describe what is practically required to limit the consequences of climate change on Earth. Future emission scenarios of pollutants from 2015 to 2100 with different levels of greenhouse gas emissions, image It provides a clear picture of how climate change will continue in the current century under the influence of human influence. In all five emission scenarios of pollutants released by the IPCC, the global temperature will increase by the middle of the century. Global warming (more than 2°C) in high emission scenarios will continue during the second century. Increasing global warming increases the possibility of changes in hydrological and meteorological factors. With the increase in temperature due to global warming, there is a possibility that the frequency and intensity of heat, heavy rainfall and droughts will increase. Also, warmer weather will intensify the effects of wet and dry weather phenomena in the future, and droughts and floods related to those phenomena will become more intense.

Methodology
GCM models or atmospheric general circulation models are numerical models that process the processes between the atmosphere and the ocean. The cryosphere and the earth's surface are simulated in three dimensions. These models produce climate parameters by considering a three-dimensional network, typically with a horizontal scale (geographic length) of 650 km and a geographic width of 250 km, 10 to 20 vertical layers in the atmosphere of the land part of the earth and more than 30 layers in the oceans. they do So far, various public circulation models have been compiled and designed in various research centers around the world. Due to the large size of the computational cells, the Earth's total atmospheric circulation models simulate climatic fluctuations with turbulence. In order to eliminate these disturbances, instead of direct use of atmospheric circulation model data in climate change calculations, the average period of this data is used. Therefore, to calculate the climate change scenario in each model, the values for the temperature and (ratio) for rainfall for the average long term of each month in the future or simulated baseline by the same model for each cell of the computational grid Calculated. Regional dynamic models have good spatial accuracy for climatic assessments as well as climate and climate downscale processes as far as possible. But the use of these models for the downscaling, the output of the general circulation models of the atmosphere is faced with the time constraints of the model implementation. In statistical models, in addition to the data of a general circulation model of atmosphere, the observed data is also needed to discover the statistical relationship between the data of the general circulation model of the atmosphere in the past and the observational data is required. With stochastic method, one a time can perform a statistical downscaling for a specific station.The statistical Downscaling method has more advantages compared to dynamic methods, especially in cases where lower costs and faster assessment of the factors affecting climate change are needed. Models that are used for a dynamic downscaling include MM 5 ,RegCM3, and PRECIS. A variety of statistical Downscaling models are LARS-WG,CLIMGEN, SDSM, ET & ROLL, GEM, USCLIMATE, etc. It should be noted that in this research, the LARS-WG exponential downscaling model is used.
Conclusion
According to the results of this study, very irregularly increasing changes in rainfall in October, November and January and decreasing changes in August in the period 2095-2080 are expected in the study area. In the case of temperature changes in the watershed of haraz plains area in the period 2095-2080 for scenarios A1B, A2 and B1, the trend of increasing the average monthly temperature shows even more than the two previously studied periods, so that the average temperature of July and August in the next period 2099-2080 by scenario A1B with 30.44 and 31.03, respectively, that It will reach 30 higher degrees Celsius and the average temperature in January and December will increase to 11.08 and 12.55 with an increase compared to the base period. The increase in temperature in the summer months, which coincides with the decrease in rainfall, has a significant role in the agriculture of this region, which is one of the important rice production areas of the country, and affects the downstream hydrological cycle of haraz watershed. On the other hand, winter temperature changes can affect the time of snow melting in the basin, which has a significant effect on the peak flood discharge downstream of the watershed.