بررسي تغييرات اقليمي حوضه كرخه با استفاده از ريزمقياس نمايي ديناميكي

A study on climate change in Karkheh River Basin using dynamic downscaling model

ﻫﺮ ﮔﻮﻧﻪ ﺗﻐﯿﯿﺮ در ﻏﻠﻈﺖ ﮔﺎزﻫﺎي ﮔﻠﺨﺎﻧﻪ اي ﺑﺎﻋﺚ ﺑﺮ ﻫﻢ ﺧﻮردن ﺗﻌﺎدل ﺑﯿﻦ اﺟﺰا ﺳﯿﺴﺘﻢ اﻗﻠﯿﻢ ﻣﯽ ﺷﻮد. اﻣﺎ ﺗﻐﯿﯿﺮ در ﻣﯿﺰان ﻏﻠﻈﺖ اﯾﻦ ﮔﺎزﻫﺎ و ﭼﮕﻮﻧﮕﯽ اﺛﺮات آنﻫﺎ در آﯾﻨﺪه ﻧﺎﻣﻌﻠﻮم ﻣﯽ ﺑﺎﺷﺪ. ﺑﺮاي ﺑﺮرﺳﯽ اﺛﺮات ﺗﻐﯿﯿﺮ اﻗﻠﯿﻢ ﺑﺮ ﺳﺎﻣﺎﻧﻪﻫﺎي ﻣﺨﺘﻠﻒ در آﯾﻨﺪه، اﺑﺘﺪا ﺑﺎﯾﺪ ﻣﺘﻐﯿﺮﻫﺎي اﻗﻠﯿﻤﯽ ﺗﺤﺖ ﺗﻐﯿﯿﺮات ﮔﺎزﻫﺎي ﮔﻠﺨﺎﻧﻪ اي )ﺳﻨﺎرﯾﻮﻫﺎي اﻗﻠﯿﻤﯽ( ﺷﺒﯿﻪﺳﺎزي ﺷﻮﻧﺪ. روشﻫﺎي ﻣﺨﺘﻠﻔﯽ ﺑﺮاي اﯾﻦ ﮐﺎر وﺟﻮد دارد ﮐﻪ ﻣﻌﺘﺒﺮﺗﺮﯾﻦ آنﻫﺎ اﺳﺘﻔﺎده از ﻣﺪلﻫﺎي اﻗﻠﯿﻤﯽ ﻣﯽﺑﺎﺷﺪ. ﻣﺪل ﻫﺎي آب و ﻫﻮاﯾﯽ ﺟﻬﺎﻧﯽ )AOGCM(، ﻗﺎدر ﺑﻪ ﺷﺒﯿﻪ ﺳﺎزي در ﺳﻄﻮح ﺑﺰرگ ﭼﻨﺪ ﺻﺪ ﮐﯿﻠﻮﻣﺘﺮي ﻫﺴﺘﻨﺪ و ﻧﻤﯽ ﺗﻮاﻧﻨﺪ ﻓﺮاﯾﻨﺪﻫﺎي ﻣﻨﻄﻘﻪ اي و ﮐﻮﭼﮏ ﻣﻘﯿﺎس آب و ﻫﻮا را ﺷﺒﯿﻪ ﺳﺎزي ﮐﻨﻨﺪ. از اﯾﻦ رو، ﺑﺮاي ﺷﻨﺎﺧﺖ ﺗﻐﯿﯿﺮات ﺑﻪ ﻃﻮر دﻗﯿﻖ ﺗﺮ و در ﻣﻘﯿﺎس ﻫﺎي ﮐﻮﭼﮏ ﺗﺮ از روش ﻫﺎي رﯾﺰﻣﻘﯿﺎس ﻧﻤﺎﯾﯽ اﺳﺘﻔﺎده ﻣﯽ ﺷﻮد. ﯾﮑﯽ از ﻣﻬﻤﺘﺮﯾﻦ روشﻫﺎي رﯾﺰﻣﻘﯿﺎس ﻧﻤﺎﯾﯽ روش ﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ اﺳﺖ ﮐﻪ ﻣﺒﺘﻨﯽ ﺑﺮ ﺑﺎﻻﺑﺮدن ﻗﺪرت ﺗﻔﮑﯿﮏ و ﺗﺠﺰﯾﻪ ﻫﺮﭼﻪ ﺑﯿﺸﺘﺮ ﻣﺪل ﻫﺎي آب و ﻫﻮاﯾﯽ ﺳﯿﺎره اي ﻫﺴﺘﻨﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ، ﺑﻪ ﺑﺮرﺳﯽ ﺗﻐﯿﯿﺮات آب و ﻫﻮا در ﺣﻮﺿﻪ ﮐﺮﺧﻪ، ﺑﻪ ﻋﻨﻮان ﯾﮑﯽ از ﻣﻬﻤﺘﺮﯾﻦ ﺣﻮﺿﻪ ﻫﺎي ﮐﺸﻮر از ﻟﺤﺎظ آورد آﺑﯽ و ﮐﺸﺎورزي، در دوره 2070 ﺗﺎ 2100 ﭘﺮداﺧﺘﻪ ﺷﺪ. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر، از ﻣﺪل رﯾﺰﻣﻘﯿﺎس ﻧﻤﺎﯾﯽ دﯾﻨﺎﻣﯿﮑﯽ PRECIS، ﺑﺮاي ﺑﺮآورد ﺑﺎرش و دﻣﺎ ﺗﺤﺖ دو ﺳﻨﺎرﯾﻮي A2 و B2 اﺳﺘﻔﺎده ﺷﺪه اﺳﺖ. ﺑﺮرﺳﯽ ﺗﻐﯿﯿﺮات آب و ﻫﻮاﯾﯽ در ﺣﻮﺿﻪ ﮐﺮﺧﻪ ﻧﺸﺎن داد ﮐﻪ ﺗﺤﺖ ﺳﻨﺎرﯾﻮي A2، ﻣﻘﺪار ﺑﺎرش ﺣﺪود 11 درﺻﺪ و ﻣﯿﺎﻧﮕﯿﻦ دﻣﺎي ﮐﻤﯿﻨﻪ و ﺑﯿﺸﯿﻨﻪ، ﺣﺪود ﭘﻨﺞ درﺟﻪ اﻓﺰاﯾﺶ ﺧﻮاﻫﻨﺪ داﺷﺖ. ﺑﺮاي ﺳﻨﺎرﯾﻮي B2، ﻣﻘﺪار ﺑﺎرش ﺣﺪود ﻫﻔﺖ درﺻﺪ و ﻣﻘﺪار ﻣﯿﺎﻧﮕﯿﻦ دﻣﺎي ﮐﻤﯿﻨﻪ و ﺑﯿﺸﯿﻨﻪ، ﺣﺪود ﺳﻪ درﺟﻪ اﻓﺰاﯾﺶ ﺧﻮاﻫﻨﺪ داﺷﺖ؛ اﯾﻦ در ﺣﺎﻟﯽ اﺳﺖ ﮐﻪ ﺗﺤﺖ ﻫﺮ دو ﺳﻨﺎرﯾﻮ، ﺑﺎرش ﻓﺼﻞ ﭘﺎﯾﯿﺰ ﺑﺮﺧﻼف دوره ﭘﺎﯾﻪ، ﺑﯿﺸﺘﺮ از ﺑﺎرش ﻓﺼﻞ زﻣﺴﺘﺎن ﺧﻮاﻫﺪ ﺑﻮد.

Any change in the concentration of greenhouse gases will upset the balance between the components of the climate system. But, the change in the concentration of these gases and how they will affect in the future is unknown. To study the effects of climate change on different systems in the future, climate variables must first be simulated under changes in greenhouse gases (climate scenarios). There are several ways to do this, the most reliable of which is the use of climatic models. AOGCMs can simulate climate parameters globally in large scale, while these may not be suitable for small scales. One of the most important downscaling methods is dynamic methods that are based on increasing the resolution and analysis of planetary climate models. Here, in this research, climate change status in Karkheh River Basin where a major basin for water and agricultural yields is studied. For this purpose, the PRECIS model was used. PRECIS is an exponential dynamics downscaling model used to estimate the temperature and precipitation rates for the period of 2070 to 2100 under A2 and B2 scenarios. According to the results of climate change assessment under scenario A2, precipitation would increase up to 11% and up to five degree centigrade would rise in average maximum and minimum temperature while concerning B2 scenario, an increase in precipitation up to 7% and a rise in temperature rise up to three degree centigrade are estimated. However, under both the scenarios, despite, the fall’s precipitation is higher than the winter’s precipitation.