بررسي تغييرات ناگهاني و الگوي تغييرات دوره‌اي تبخير و تعرق مرجع ايران با تحليل موجك و آزمون t متحرك

Investigating Abrupt Changes and Periodically Changes Pattern of Reference Evapotranspiration in Iran withWavelet Analysis and Moving t Test

تحليل تغييرات زماني و مكاني تبخير و تعرق مرجع (eto)، امكان شناخت تغييرات آب و هوايي و تاثير آن روي ﻧﯿﺎزﻫﺎي آﺑﯽ را ﻓﺮاﻫﻢ ﻣﯽﮐﻨﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﺑﻪ ﺗﺤﻠﯿﻞ ETo ﻣﺎﻫﺎﻧﻪ در 19 اﯾﺴﺘﮕﺎه ﻫﻮاﺷﻨﺎﺳﯽ در اﻗﻠﯿﻢﻫﺎي ﻣﺘﻔﺎوت ﺑﺎ دوره آﻣﺎري ﯾﮑﺴﺎن 42 ﺳﺎﻟﻪ، ﻃﯽ ﺳﺎلﻫﺎي 1961 -2003 ﭘﺮداﺧﺘﻪ ﺷﺪ. ﺳﺮيﻫﺎي زﻣﺎﻧﯽ ﺳﺎﻻﻧﻪ ETo ﺑﻪروش اﺳﺘﺎﻧﺪارد ﭘﻨﻤﻦ ﻣﺎﻧﺘﯿﺚ- ﻓﺎﺋﻮ )FAO-56 PM( ﺗﻮﻟﯿﺪ ﺷﺪﻧﺪ و ﺑﺎ اﺳﺘﻔﺎده از روشﻫﺎي آزﻣﻮن t ﻣﺘﺤﺮك و ﻣﻮﺟﮏ ﻣﻮرﻟﺖ ﺑﻪﺗﺮﺗﯿﺐ ﺑﻪ ﺗﺤﻠﯿﻞ ﺗﻐﯿﯿﺮات ﻧﺎﮔﻬﺎﻧﯽ و ﺑﺮرﺳﯽ دوره ﺗﮑﺮارﭘﺬﯾﺮي در ﻣﺠﻤﻮﻋﻪ دادهﻫﺎي ETo ﭘﺮداﺧﺘﻪ ﺷﺪ. ﻧﻘﺸﻪﻫﺎي ﺗﻮزﯾﻊ ﻣﮑﺎﻧﯽ ﻣﺎﻫﺎﻧﻪ و ﺳﺎﻻﻧﻪ ETo در ﮐﻞ ﮐﺸﻮر ﺑﺮ اﺳﺎس روش IDW ﺗﻮﻟﯿﺪ ﮔﺮدﯾﺪﻧﺪ. ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ آزﻣﻮن t ﻣﺘﺤﺮك در ﺳﺮي زﻣﺎﻧﯽ ETo ﻣﯿﺎﻧﮕﯿﻦ ﮐﻞ ﮐﺸﻮري در ﻃﯽ ﺳﺎلﻫﺎي 1981، 1982، 1983 و 1984 ﺗﻐﯿﯿﺮ ﻧﺎﮔﻬﺎﻧﯽ در روﻧﺪ ﺳﺮي زﻣﺎﻧﯽ رخ داده اﺳﺖ و اﯾﻦ ﺳﺎلﻫﺎ ﻣﻄﺎﺑﻖ ﺑﺎ روﻧﺪ ﮐﻠﯽ ETo ﻣﺸﺎﻫﺪه ﺷﺪه اﺳﺖ. ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ آزﻣﻮن t ﻣﺘﺤﺮك در اﯾﺴﺘﮕﺎهﻫﺎي ﻣﻨﻔﺮد ﻧﯿﺰ ﻣﻼﺣﻈﻪ ﺷﺪ در اﻏﻠﺐ اﯾﺴﺘﮕﺎهﻫﺎي واﻗﻊ در اﻗﻠﯿﻢ ﺧﺸﮏ و ﻧﯿﻤﻪﺧﺸﮏ ﺑﯿﺸﯿﻨﻪ ﺗﻐﯿﯿﺮات ﻧﺎﮔﻬﺎﻧﯽ، در ﻣﺤﺪوده ﺳﺎلﻫﺎي ﺑﯿﻦ 1976 -1986 اﺗﻔﺎق اﻓﺘﺎده اﺳﺖ. ﺑﯿﺸﯿﻨﻪ ﺗﻐﯿﯿﺮات ﻧﺎﮔﻬﺎﻧﯽ ﻣﺮﺑﻮط ﺑﻪ اﯾﺴﺘﮕﺎه ﺧﺮمآﺑﺎد واﻗﻊ در اﻗﻠﯿﻢ ﻧﯿﻤﻪﺧﺸﮏ اﺳﺖ ﮐﻪ در آن 21 ﺗﻐﯿﯿﺮ ﻧﺎﮔﻬﺎﻧﯽ اﺗﻔﺎق اﻓﺘﺎده و ﮐﻤﯿﻨﻪ ﺗﻐﯿﯿﺮات ﻣﺮﺑﻮط ﺑﻪ اﯾﺴﺘﮕﺎهﻫﺎي اﺻﻔﻬﺎن، ﺑﯿﺮﺟﻨﺪ و ﺗﻬﺮان واﻗﻊ در اﻗﻠﯿﻢ ﺧﺸﮏ ﺑﺎ ﺳﻪ ﺗﻐﯿﯿﺮ ﻧﺎﮔﻬﺎﻧﯽ اﺳﺖ. روﯾﮑﺮد اراﺋﻪ ﺷﺪه در ﺗﺤﻘﯿﻖ ﺣﺎﺿﺮ ﻗﺎﺑﻠﯿﺖ ﮔﺴﺘﺮش ﺑﻪ ﻣﻄﺎﻟﻌﺎت ﺳﺮيﻫﺎي زﻣﺎﻧﯽ ﻫﯿﺪروﻟﻮژﯾﮑﯽ، ﺧﺸﮑﺴﺎﻟﯽ و ﻣﻨﺎﺑﻊ آﺑﯽ ﺑﺮاي اﺳﺘﻨﺘﺎج روﻧﺪ ﺗﻐﯿﯿﺮات ﻧﺎﮔﻬﺎﻧﯽ و اﻟﮕﻮﻫﺎي دورهاي و ﭘﺎﯾﺶ ﺗﮑﺮارﭘﺬﯾﺮي آﻧﻬﺎ را داراﺳﺖ

Analysis of the temporal variations of reference evapotranspiration (ETo) declares climate changes and their effects on water demands. In this paper, an analysis of the monthly ETo (calculated by the FAO Penman– Monteith method) was done at 19 stations, located in different climatic regions, during 1961– 2003 in Iran. The annual ETo time series were derived, and the moving t test and Morlet wavelet were conducted to analyze the comprehensive time series for characterizing abrupt change and period in the ETo data sets. The annually and monthly spatial distibuations of ETo were produced by the inverse distance weighting (IDW) method. Based on the moving t test over annual ETo time series there were 4 abrupt changes in 1981,1982,1983, and 1984 years which were coiencidnce with ETo trend. Also moving t test detected abrupt changes in 1976- 1986 period in arid and semi-arid climates. KhoramAbad station in semi-arid climate with 21 abrupt changes had the largest changes and Isfahan, Tehran, and Birjand stations with 3 changes had the smallest changes. The presented methodology in this paper can be extended to hydrological time series, water resources and drought studies to infer their abrupt changes and monitoring periodical changes pattern.