چکیده:
ﻫﺪف از ﻣﻄﺎﻟﻌﻪی ﺣﺎﺿﺮ ﭘﺎﺳﺦ ﺑﻪ اﯾﻦ ﺳﺆال اﺳﺖ ﮐﻪ در ﺷﺮاﯾﻂ ﺣﺪی دﻣﺎﯾﯽ، ﻣﯿﺰان ﺗﺒﺨﯿﺮ و ﺗﻌﺮق در ﮔﺴﺘﺮهی اﯾﺮان ﭼﻪ ﺗﻐﯿﯿﺮاﺗﯽ ﻣﯽﮐﻨﺪ. ﺑﺮای اﯾﻦ ﻣﻨﻈﻮر، ﻃﯽ ﺑﺎزهی زﻣﺎﻧﯽ 30ﺳﺎﻟﻪ ﻣﺸﺨﺺ ﺷﺪ ﮐﻪ ﻣﺎه ژاﻧﻮﯾﻪی ﺳﺎل 2008 و ﻣﺎه ژوﺋﯿﻪی ﺳﺎل 2010، ﺷﺮاﯾﻂ ﺣﺪی دﻣﺎﯾﯽ ﺳﺮد و ﮔﺮم ﺛﺒﺖ ﺷﺪه اﺳﺖ. ﺳﭙﺲ، ﺑﺮای اﯾﻦ دو ﻣﺎه، از دادهﻫﺎی دﻣﺎی ﻫﻮای 55 اﯾﺴﺘﮕﺎه، رﻃﻮﺑﺖ ﺧﺎک ﺑﺎزﺗﺤﻠﯿﻞﺷﺪهی NCEP/NCAR، دﻣﺎی ﺳﻄﺢ زﻣﯿﻦ، ﭘﻮﺷﺶ ﮔﯿﺎﻫﯽ و ﺗﺒﺨﯿﺮ و ﺗﻌﺮق ﺳﻨﺠﻨﺪهی ﻣﺎدﯾﺲ ﺑﺎ وﺿﻮح ﻓﻀﺎﯾﯽ ﭘﻨﺞ ﮐﯿﻠﻮﻣﺘﺮی ﺑﻬﺮه ﺑﺮده ﺷﺪ. اﺑﺘﺪا رﯾﺴﮏ رﺧﺪاد دﻣﺎﻫﺎی ﺣﺪی اﯾﻦ دو ﻣﺎه ﺑﺎ ﺗﻮزﯾﻊ ﺧﻄﺮ ﺗﺠﻤﻌﯽ و ﮔﺎﻣﺒﻞ ﻣﺸﺨﺺ ﺷﺪ و ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ رﺧﺪاد دﻣﺎﻫﺎی ﺣﺪی ﺑﺎﻻی 50 درﺟﻪ در ﻣﺎه ژوﺋﯿﻪ 0/06 و دﻣﺎﻫﺎی ﺑﺎﻻی 22 درﺟﻪ در ﻣﺎه ژاﻧﻮﯾﻪ 0/008 اﺳﺖ. ﻫﻤﭽﻨﯿﻦ، اﺣﺘﻤﺎل رﺧﺪاد دﻣﺎﻫﺎی ﺑﺎﻻی 5 درﺟﻪ در ﻣﺎه ژاﻧﻮﯾﻪ 0/50 اﺳﺖ. ﻧﺘﺎﯾﺞ ﻫﻤﺒﺴﺘﮕﯽﻫﺎ ﻣﺸﺨﺺ ﮐﺮد ﮐﻪ دو ﻋﺎﻣﻞ اﻧﺮژی( دﻣﺎی ﻫﻮا) و رﻃﻮﺑﺖ ﺧﺎک ﺗﻌﯿﯿﻦﮐﻨﻨﺪهی اﺻﻠﯽ ارﺗﺒﺎط اﯾﻦ ﭘﺎراﻣﺘﺮﻫﺎ ﺑﺎ ﻫﻢ ﻫﺴﺘﻨﺪ؛ ﺑﻪﻃﻮری ﮐﻪ ﻫﻨﮕﺎﻣﯽﮐﻪ دﻣﺎی ﻫﻮا ﺑﺎﻻی 5 درﺟﻪ ﺑﺎﺷﺪ، ارﺗﺒﺎط ﻣﻨﻔﯽ ﻣﻌﻨﺎداری ﻣﺸﺎﻫﺪه ﻣﯽﺷﻮد (0/24- در ﻣﺎه ژاﻧﻮﯾﻪ و 0/64- در ﻣﺎه ژوﺋﯿﻪ) و ﻫﻨﮕﺎﻣﯽﮐﻪ دﻣﺎی ﻫﻮا زﯾﺮ 5 درﺟﻪ ﺑﺎﺷﺪ، ارﺗﺒﺎط ﻣﺜﺒﺖ ﺧﻮاﻫﺪ ﺑﻮد (0/32 در ﻣﺎه ژاﻧﻮﯾﻪ ﺑﻪﻃﻮر ﮐﻠﯽ و ﺑﺪون درﻧﻈﺮ ﮔﺮﻓﺘﻦ آﺳﺘﺎﻧﻪی دﻣﺎﯾﯽ، در ﻫﺮ دو ﻣﺎه ارﺗﺒﺎط ﻣﻨﻔﯽ ﺑﻪدﺳﺖ آﻣﺪ؛ اﻣﺎ در ﻣﺎه ژاﻧﻮﯾﻪ، ﺑﻪدﻟﯿﻞ ﺛﺒﺖ دﻣﺎﻫﺎی ﺑﯿﺶ از 5 درﺟﻪ ﺑﻪ اﺣﺘﻤﺎل رﺧﺪاد 50 درﺻﺪ، ارﺗﺒﺎط ﻣﻨﻔﯽ ﺿﻌﯿﻒ ﻧﺰدﯾﮏ ﺑﻪ ﺻﻔﺮ ﻣﺸﺎﻫﺪه ﺷﺪ. ﻋﺎﻣﻞ رﻃﻮﺑﺖ ﻧﺸﺎن ﻣﯽدﻫﺪ ﮐﻪ ﻫﺮدو ﻣﺎه از آﺳﺘﺎﻧﻪی رﻃﻮﺑﺘﯽ ﻣﺸﺨﺼﯽ ﺑﻪدﻟﯿﻞ ﺳﺮﻣﺎﯾﺶ و ﮔﺮﻣﺎﯾﺶ ﺑﯿﺶازﺣﺪ رﻧﺞ ﺑﺮدهاﻧﺪ و ﻫﺮﮔﺎه ﻣﺤﺪودﯾﺖ رﻃﻮﺑﺖ وﺟﻮد داﺷﺘﻪ ﺑﺎﺷﺪ، اﯾﻦ ارﺗﺒﺎط ﻣﻨﻔﯽ اﺳﺖ و درﻧﺘﯿﺠﻪ، ارﺗﺒﺎط ﮐﻠﯽ ﻣﻨﻔﯽ (ﺑﺪون درﻧﻈﺮ ﮔﺮﻓﺘﻦ آﺳﺘﺎﻧﻪی دﻣﺎی ﻫﻮا) ﻣﺎه ژاﻧﻮﯾﻪ ﻧﯿﺰ ﺗﻮﺟﯿﻪ ﻣﯽﺷﻮد.
Introduction: According to the Intergovernmental Panel on Climate Change (IPCC) in 2012, globally, a large number of climatic events have increased in recent decades such as extreme temperatures, floods and etc. That’s the number of warm days and nights has increased, and climate models predict extreme temperature by the end of the 21st century (IPCC, 2012). Ecosystems, the global economy and public health are highly vulnerable to these extreme events, especially extreme temperatures (Kunkel et al., 1999). Generally, in Iran, the regionalization of extreme temperatures has been studied. For example, Rezaei et al. (2015) examined the extreme temperatures in two months with extreme temperature and identified different areas for Iran. Masoudian and Darand(2008) also studied extreme cold temperature in Iran and regionalized six areas for Iran. Considering the studies that indicates the occurrence of extreme temperatures for different parts of the world, it is interesting to note the role of these extreme temperatures on evapotranspiration difference between extreme cold and warm temperatures. Evapotranspiration is the water loss from the ground to the atmosphere and defined as a key process in the water cycle (Wang and Dikeson, 2012), which is related to plant growth (Alberto et al., 2014), drought (Anderson et al, 2011), greenhouse gas (Balogh et al., 2015) and climate change (Abtew and Melesse, 2012). The purpose of this study is to answer the question of what is the changes in evapotranspiration under extreme temperature conditions in Iran.
Methodology: For answer the research’s question it found clearly that January 2008 and July 2010 had recorded extreme cold and warm temperatures during the period of 30 years. For these two months, 55- air temperature stations data, soil temperature from NCEP / NCAR reanalysis database, land surface temperature (LST), vegetation cover, and evapotranspiration from Moderate Resolution Imaging Spectroradiometer (MODIS) were utilized in five kilometer or 0.05 degree resolution. At first, the risk of occurrence of the extreme temperatures was determined by the distribution of the cumulative risk and the Gumbel distribution during these two months. The land surface temperature data product (LST) namely MOD11C3, which has 0.05 degrees (approximately 5 kilometers or 5600 meters) and with a monthly and global time scale was used. To investigate the changes in evapotranspiration, the MODIS evapotranspiration product namely MOD16 was utilized (Mu et al., 2012). The data is available on an annual, eight-day and monthly basis. In this process, evapotranspiration is provided globally and with a resolution of one kilometer covering 109 million square kilometers of the land’s surface. The algorithm used the Penman-Monteith equation to produce this product (Monteith, 1965). Then for the analysis Pearson’s correlation and coefficient of determination were used.
Results and discussion: The results showed that the occurrence of extreme temperatures above 50 degrees Celsius is 0.06 in July and temperatures higher than 22 degrees Celsius is 0.008 in January. Also, the probability of temperature higher than 5 degrees Celsius is 0.50 in January. Correlations results indicated that the two factors of energy (air temperature) and soil moisture are the main controller of the relationship between these parameters (LST and evapotranspiration), so that when the air temperature was above 5 degrees Celsius, a significant negative correlation was observed (-0.24 in January and -0.64 In July) and when the air temperature is below than 5 degrees, it will be positive (0.23 in January). Generally, regardless of the threshold, a negative correlation was obtained for every two months, but a weakest negative correlation (close to zero) was observed in January, due to the recording of temperatures exceeding 5 ° C with an incidence of 50%. The humidity factor shows that every two months have suffered from a certain moisture threshold due to extreme cold and warm temperatures, and if there is a moisture limit, this relation will be negative, thus it’s a determination factor for the overall negative relationship (regardless of the temperature threshold) in January.
Conclusion: The extreme temperatures showed the highest impact on evapotranspiration so that air temperature was identified as a trigger for the relationship between LST and evapotranspiration.
خلاصه ماشینی:
سپس ، برای این دو ماه ، از داده های دمای هوای ٥٥ایستگاه ، رطوبت خاک بازتحلیل شده ی NCEP/NCAR، دمای سطح زمین ، پوشش گیاهی و تبخیر و تعرق سنجنده ی مادیس با وضوح فضایی پنج کیلومتری بهره برده شد.
به طور کلی، تبخیر و تعرق و ازدست رفتن آب از سطح زمین به جو به عنوان یک فرآیند کلیدی در چرخه ی آب تعریف میشود (٢٠١٢ ,Dikeson &Wang ) که این فرآیند به رشد گیاه (٢٠١٤ ,et-al &Alberto )، خشکسالی (٢٠١١ ,et-al &Anderson )، گازهای گلخآن های (٢٠١٥ ,et-al &Balogh ) و تغییرات اقلیم (٢٠١٢ ,Melesse &Abtew ) مرتبط است .
(به تصویر صفحه رجوع شود) شکل ١: دمای ماه ژانویه و ژوئیه (چپ -بالا و پایین ) و انحراف معیار دمای ژانویه و ژوئیه (راست -بالا و پایین ) Figure1:the land surface temperature of January and July (left-up and down), and mean LST (right-up and down) ٢-٣- داده ها و روش موردمطالعه داده های ماهواره ای: امروزه ، تصاویر با وضوح زمانی و مکانی بالای ماهواره ای به دلیل پوشش مکانی و زمانی مناسب ، برای بسیاری از اهداف کاربردی منابع طبیعی به کار میروند.
در مطالعه ی حاضر، مشخص میشود که در دماهای بالای ٥درجه در ماه ژانویه ، ارتباط مثبت و معناداری به میزان ٠/٧٥بین رطوبت خاک و تبخیر و تعرق وجود دارد؛ اما در دماهای زیر ٥درجه ی سانتیگراد، این ارتباط نزدیک به صفر است .
Relationship between Evapotranspiration and Land Surface Temperature under Energy- and Water- Limited Conditions in Dry and Cold Climates, Volume 2016 (2016), Article ID 1835487, 9 pages,http://dx.