تحليل همديد سازوكارهاي گردش جو در شكل گيري ماه هاي خيلي مرطوب در سوريه

Synoptic analysis of atmospheric circulation mechanisms in the formation of very wet months in Syria

ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺑﺎ ﻫﺪف ﺑﺮرﺳﯽ ﺷﺮاﯾﻂ اﻟﮕﻮﻫﺎي ﮔﺮدش ﺟﻮ در ﻣﺎهﻫﺎي ﺧﯿﻠﯽ ﻣﺮﻃﻮب ﮐﺸﻮر ﺳﻮرﯾﻪ اﻧﺠﺎم ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺎ ﻣﺤﺎﺳﺒﻪ ﺷﺎﺧﺺ ﺑﺎرش اﺳﺘﺎﻧﺪارد )Z( و اﺳﺘﻔﺎده از دادهﻫﺎي ﺑﺎرش 16 اﯾﺴﺘﮕﺎه ﻫﻤﺪﯾﺪ ﺳﻮرﯾﻪ در دوره آﻣﺎري )1977- 2016(، ﻣﺎهﻫﺎي ﺧﯿﻠﯽ ﻣﺮﻃﻮب ﻣﺸﺨﺺ ﺷﺪ. ﺳﭙﺲ ﻧﻘﺸﻪﻫﺎي ﺗﺮﮐﯿﺒﯽ از ﻓﺮاﺳﻨﺞﻫﺎي ﻓﺸﺎر ﺗﺮاز درﯾﺎ، ارﺗﻔﺎع ژﺋﻮﭘﺘﺎﻧﺴﯿﻞ و ﻣﻮﻟﻔﻪ ﻫﺎي ﺑﺎد در ﺗﺮازﻫﺎي 500 ،700 ،850 و 250 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل و ﻫﻤﭽﻨﯿﻦ رﻃﻮﺑﺖ وﯾﮋه ﺗﺮاز 850 و اﻣﮕﺎي ﺗﺮاز 700 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل از دادهﻫﺎي ﺷﺒﮑﻪﺑﻨﺪي ﺷﺪه NCEP-NCAR ﺗﻮﻟﯿﺪ و ﺑﺮاي ﺑﺮرﺳﯽ ﻫﻤﺪﯾﺪ اﻟﮕﻮﻫﺎي ﮔﺮدش ﺟﻮي ﻣﺎهﻫﺎي ﺧﯿﻠﯽ ﻣﺮﻃﻮب ﻣﻮرد اﺳﺘﻔﺎده ﻗﺮار ﮔﺮﻓﺖ. ﯾﺎﻓﺘﻪﻫﺎي ﺗﺤﻘﯿﻖ ﺑﯿﺎﻧﮕﺮ آن اﺳﺖ ﮐﻪ ﭼﻬﺎر اﻟﮕﻮي ﻣﺆﺛﺮ در اﯾﺠﺎد ﻣﺎهﻫﺎي ﺧﯿﻠﯽ ﻣﺮﻃﻮب ﺳﻮرﯾﻪ ﻧﻘﺶ دارﻧﺪ: 1( اﻟﮕﻮي ﻧﺎوه ﻋﻤﯿﻖ )ﻣﺎه ﻧﻮاﻣﺒﺮ 1994(، 2( اﻟﮕﻮي ﺟﺮﯾﺎن ﻣﺪاري ﺑﺎ ﻣﻮج ﮐﻮﺗﺎه )ﻣﺎه دﺳﺎﻣﺒﺮ 1968(، 3( اﻟﮕﻮي ﺑﻨﺪاﻟﯽ )ﻣﺎه ژاﻧﻮﯾﻪ 1969( و 4( اﻟﮕﻮي ﮐﻢارﺗﻔﺎع ﺗﺮﮐﯿﻪ – ﻧﺎوه درﯾﺎي ﺳﺮخ )ﻣﺎه آورﯾﻞ 1971( ﻫﺴﺘﻨﺪ. ﻣﯽﺗﻮان ﮔﻔﺖ ﮐﻪ ﺣﺮﮐﺖ ﺑﻪ ﺳﻤﺖ ﻋﺮضﻫﺎي ﭘﺎﯾﯿﻦ ﺗﺎوه ﻗﻄﺒﯽ در ﺗﺮازﻫﺎي 700 و 500 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل ﺑﻪ وﯾﮋه در ﺗﺮازﻫﺎي ﻣﯿﺎﻧﯽ و ﺑﺎﻻﯾﯽ ﮐﻪ ﺳﺒﺐ ﻓﺮارﻓﺖ و رﯾﺰش ﻫﻮاي ﺳﺮد ﺑﺮ روي ﺷﺮق ﻣﺪﯾﺘﺮاﻧﻪ ﻣﯽﮔﺮدد و ﺷﮑﻞﮔﯿﺮي ﻣﻘﺎدﯾﺮ ﻣﻨﻔﯽ اﻣﮕﺎ و ﺟﺮﯾﺎنﻫﺎي ﺻﻌﻮدي ﻫﻮا ﺑﻪ ﻫﻤﺮاه ﺟﺮﯾﺎنﻫﺎي ﺟﻨﻮبﻏﺮﺑﯽ ﺑﺎد در ﺗﺮاز درﯾﺎ و ﺳﺎﯾﺮ ﺗﺮازﻫﺎ ﺑﺮ روي ﺳﻮرﯾﻪ، ﺑﺎﻋﺚ رﯾﺰشﻫﺎي ﺑﺎﻻﺗﺮ از ﻣﯿﺎﻧﮕﯿﻦ ﺷﺪه اﺳﺖ.

The aim of the study was to investigate the conditions of atmospheric circulation patterns in the very wet months of Syria. By calculating the standard precipitation index (SPI) and using the precipitation data of 16 Syrian synoptic stations in the statistical period of 2016-2017, very wet months were identified. Then, combined maps of sea level pressure parameters, geopotential height and wind components at 850, 700, 500 and 250 hpa levels, as well as specific humidity at 850 level and 700 hpa level omega from NCEP-NCAR gridded reanalysis data were produced and were used to study the synoptic atmospheric patterns of very wet months. The findings show that formation of a deep trough is the most important model for creating very humid Syrian months, which is centred almost between eastern Turkey and western Egypt, and Syria is located in front of this trough. This trough, especially in the middle and upper atmospheric levels, causes to falling cold air on the eastern Mediterranean. The moving polar trough pattern at 700 and 500 hpa levels towards lower latitudes had caused the aforementioned advections. Formation of negative values of omega and rising air currents, along with southwest winds at sea level and other levels over Syria, have caused above-average rainfalls.