بررسي شرايط سينوپتيك همزمان با رخداد بارش‌هاي سيل‌آساي غرب و جنوب غرب كشور مورخ 11 و 12 فروردين 1398

Investigation of Synoptic Conditions coincided with the Occurrence of West and Southwest Floods on March 31 and April 1, 2019

زﻣﯿﻨﻪ و ﻫﺪف: ﺑﺎرش ﻫﺎي ﺳﯿﻞ آﺳﺎ ﻫﻤﻪ ﺳﺎﻟﻪ ﺧﺴﺎرات ﻓﺮاواﻧﯽ را ﺑﻪ ﺑﺨﺶ ﻫﺎي ﻣﺨﺘﻠﻒ ﮐﺸﻮر وارد ﻣﯽ ﺳﺎزد. ﻫﺪف از ﭘﮋوﻫﺶ ﺣﺎﺿﺮ، ﺷﻨﺎﺳﺎﯾﯽ و ﺑﺮرﺳﯽ ﺳﺎﻣﺎﻧﻪ ﻫﺎي ﺳﯿﻨﻮﭘﺘﯿﮏ ﻣﻨﺠﺮ ﺑﻪ رﺧﺪاد ﺳﯿﻼب ﻓﺮاﮔﯿﺮ و ﻣﺨﺮب ﻣﻨﻄﻘﻪ ﻏﺮب و ﺟﻨﻮب ﻏﺮب ﮐﺸﻮر در ﻣﻮرخ 11 و 12 ﻓﺮوردﯾﻦ 1398 ﻣﯽ ﺑﺎﺷﺪ. روش ﺑﺮرﺳﯽ: ﺟﻬﺖ ﺑﺮرﺳﯽ ﺷﺮاﯾﻂ ﺳﯿﻨﻮﭘﺘﯿﮏ ﻫﻤﺰﻣﺎن ﺑﺎ رﺧﺪاد ﺑﺎرش ﻫﺎي ﺷﺪﯾﺪ ﻣﻨﺠﺮ ﺑﻪ ﺳﯿﻼب ﻫﺎي ﻣﻮرد ﻧﻈﺮ، ﻋﻼوه ﺑﺮ اﺳﺘﻔﺎده از ﺗﺼﺎوﯾﺮ ﻣﺎﻫﻮاره اي ﻧﻮآ 18، داده ﻫﺎي ﻓﺸﺎر و ﻧﻢ وﯾﮋه ﺗﺮاز درﯾﺎ، ارﺗﻔﺎع ژﺋﻮﭘﺘﺎﻧﺴﯿﻞ و اﻣﮕﺎي ﻓﺸﺎر ﺗﺮاز 700 ،850 و 500 ﻫﮑﺘﻮﭘﺎﺳﮑﻞ؛ ﻧﻢ ﻧﺴﺒﯽ ﻓﺸﺎر ﺗﺮاز 700 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل، ﻣﻮﻟﻔﻪ ﺑﺎد ﻣﺪاري و ﻧﺼﻒ اﻟﻨﻬﺎري از ﻓﺸﺎر ﺗﺮاز 1000 ﺗﺎ ﻓﺸﺎر ﺗﺮاز 200 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل ﺑﺎ ﺗﻔﮑﯿﮏ ﻣﮑﺎﻧﯽ 2/5 درﺟﻪ در 2/5 درﺟﻪ ﻋﺮض ﺟﻐﺮاﻓﯿﺎﯾﯽ از ﻣﺮﮐﺰ ﻣﻠﯽ ﭘﯿﺶ ﺑﯿﻨﯽ ﻣﺤﯿﻄﯽ و ﻣﺮﮐﺰ ﻣﻠﯽ ﭘﮋوﻫﺶ ﻫﺎي ﺟﻮي اﯾﺎﻻت ﻣﺘﺤﺪه)NCEP/NCAR( درﯾﺎﻓﺖ و ﻧﻘﺸﻪ ﻫﺎي ﻣﻮرد ﻧﻈﺮ ﺗﺮﺳﯿﻢ ﮔﺮدﯾﺪ. ﯾﺎﻓﺘﻪ ﻫﺎ: وﺟﻮد ﭼﺮﺧﻨﺪي ﻋﻤﯿﻖ در ﻓﺸﺎر ﺗﺮاز درﯾﺎ ﺗﺎ ﻓﺸﺎر ﺗﺮاز 500 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل از ﺷﺮق درﯾﺎي ﻣﺪﯾﺘﺮاﻧﻪ ﺗﺎ ﻏﺮب اﯾﺮان و ﻫﻤﭽﻨﯿﻦ اﺳﺘﻘﺮار ﺟﺖ ﺟﻨﺐ ﺣﺎره اي ﺑﺎ ﺟﻬﺖ ﻧﺼﻒ اﻟﻨﻬﺎري)ﺟﻨﻮب ﻏﺮﺑﯽ ـ ﺷﻤﺎل ﺷﺮﻗﯽ( در ﻣﻨﻄﻘﻪ ﺟﻨﻮب ﻏﺮب و ﻏﺮب ﮐﺸﻮر و در ﻧﻬﺎﯾﺖ ﭼﯿﻨﺶ ﺷﺪﯾﺪ ﻗﺎﺋﻢ ﺑﺎد اﻓﻘﯽ از ﻓﺸﺎر ﺗﺮاز درﯾﺎ ﺗﺎ ﻓﺸﺎر ﺗﺮاز 200 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل در ﻣﻨﻄﻘﻪ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ، ﺑﻪ ﻋﻨﻮان ﻋﻮاﻣﻞ اﺻﻠﯽ ﻣﻮﺟﺪ ﻧﺎﭘﺎﯾﺪاري در ﻣﻨﻄﻘﻪ ﻏﺮب و ﺟﻨﻮب ﻏﺮب ﮐﺸﻮر ﺷﻨﺎﺧﺘﻪ ﺷﺪه اﺳﺖ. وﺟﻮد ﻧﻢ وﯾﮋه 14 ﺗﺎ 18 ﮔﺮم ﺑﺮ ﮐﯿﻠﻮﮔﺮم در ﻓﺸﺎر ﺗﺮاز درﯾﺎ و رﻃﻮﺑﺖ ﻧﺴﺒﯽ 95 ﺗﺎ 100 درﺻﺪ در ﻓﺸﺎر ﺗﺮاز 700 ﻫﮑﺘﻮﭘﺎﺳﮑﺎل ﻧﯿﺰ، ﺑﻪ ﻋﻨﻮان ﺷﺮاﯾﻂ ﻣﻨﺎﺳﺐ رﻃﻮﺑﺘﯽ در ﻣﻨﻄﻘﻪ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﺷﻨﺎﺳﺎﯾﯽ ﺷﺪه اﺳﺖ. ﺑﺤﺚ و ﻧﺘﯿﺠﻪ ﮔﯿﺮي: ﻧﺘﺎﯾﺞ اﯾﻦ ﭘﮋوﻫﺶ ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻪ در روزﻫﺎي 11 و 12 ﻓﺮوردﯾﻦ 1398 ﺟﻮ ﻣﻨﻄﻘﻪ ﻏﺮب و ﺟﻨﻮب ﻏﺮب ﮐﺸﻮر در ﺗﻤﺎم ﻋﻤﻖ ﻻﯾﻪ ﺗﺮوﭘﻮﺳﻔﺮ، ﻧﺎﭘﺎﯾﺪاري ﺷﺪﯾﺪي را ﺑﻪ ﻋﻠﺖ اﺳﺘﻘﺮار ﺿﻠﻊ ﺷﺮﻗﯽ ﭼﺮﺧﻨﺪي ﻋﻤﯿﻖ، ﺗﺠﺮﺑﻪ ﮐﺮده اﺳﺖ. در ﺑﺎﻻي ﭼﺮﺧﻨﺪ ﯾﺎدﺷﺪه، ﺟﺮﯾﺎﻧﺎت ﻧﺼﻒ اﻟﻨﻬﺎري ﺟﺖ ﺟﻨﺐ ﺣﺎره اي واﻗﻊ ﺷﺪه ﮐﻪ ﺳﺒﺐ ﺗﺸﺪﯾﺪ ﻧﺎﭘﺎﯾﺪاري ﺗﺎ ﻋﻤﻖ ﻻﯾﻪ وردﺳﭙﻬﺮ ﺷﺪه اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﻓﺮارﻓﺖ رﻃﻮﺑﺖ از ﻏﺮب درﯾﺎي ﻋﺮب، درﯾﺎي ﺳﺮخ و ﺧﻠﯿﺞ ﻓﺎرس ﺳﺒﺐ ﺗﺸﮑﯿﻞ ﺳﻠﻮل ﻫﺎﯾﯽ از اﺑﺮﻫﺎي ﻫﻤﺮﻓﺘﯽ ﺿﺨﯿﻢ در ﺗﻤﺎم ﻣﻨﻄﻘﻪ ﻏﺮب و ﺟﻨﻮب ﻏﺮب ﮐﺸﻮر ﺷﺪه اﺳﺖ. ﺑﺎرش ﻫﺎي ﺧﯿﻠﯽ ﺷﺪﯾﺪ ﻣﻨﺘﺞ از ﻫﻤﯿﻦ اﺑﺮﻫﺎي ﻫﻤﺮﻓﺘﯽ ﻣﻮﺟﺐ ﺳﯿﻼب ﻫﺎي ﺷﺪﯾﺪ و ﻓﺮاﮔﯿﺮ در اﯾﻦ ﻣﻨﻄﻘﻪ از ﮐﺸﻮر ﺷﺪه اﺳﺖ.

Background and Objective: The purpose of this study is to identify and investigate the synoptic systems that led to the extensive and destructive flood events in the west and southwest of the country on March 31 and April 1, 2019. Method: In order to study the synoptic conditions in coincided with the event of heavy rainfall leading to the floods, in addition to using NOAA18 satellite images, sea level pressure data, sea level specific humidity, geopotential height and omega at pressure level 850, 700 and 500 hPa, Relative humidity pressure at 700 hPa, U and V component from pressure 1000 to 200 hPa with a resolution of 2.5 ° to 2.5° latitude from the National Center for Environmental Prediction and the National Center for Atmospheric Research (NCEP / NCAR) Received and the maps were plotted. Findings: Existence of a deep cyclone at sea level pressure to 500 hPa pressure from eastern Mediterranean to western of Iran and also the establishment of a subtropical jet stream with meridian direction (southwest - northeast) in the southwest and west of the country and finally the intense vertical shear of horizontal wind from sea level pressure to 200 hPa in the study area, It is known as the main factors of cause of instability in the west and southwest of the country. existence Specific humidity of 14 to 18 g / kg at sea level pressure and relative humidity of 95 to 100% at a pressure of 700 hPa have also been identified as suitable moisture conditions in the study area. Discussion and Conclusion: The results of this study show that on March 31 and April 1, 2019, the atmosphere of the western and southwestern regions of the country in all depths of the troposphere layer experienced severe instability due to the establishment eastern part of a deep cyclone. Above the cyclone mentioned above, located meridional flows of subtropical jet stream which has intensificated the instability to the depth of the tropospheric layer. Also moisture advection from the western Arabian Sea, the Red Sea and the Persian Gulf has caused form cells from thick convective clouds throughout the west and southwest of the country. The heavy rains resulting from these convective clouds have caused severe and extensive floods in this area of the country.