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Statistical analysis of Iran's heavy rains during sudden stratospheric warming
Sorayya Derikvand1 , Behrooz Nasiri * 2, Hooshang Ghaemi3 , Mostafa Karampoor4 , Mohammad Moradi3
1- University of Lorestan, Lorestan province. Khorramabad city. Hekmat town. Thirty-two meter street. end of Boulivard. Eghbalihouse
2- University of Lorestan, Lorestan, Khorram Abad. Ghaziabad Next to Olive Park , nasiri.b@lu.ac.ir
3- Atmospheric Science & Meteorogical Research Center, Atmospheric Science & Meteorogical Research Center
4- University of Lorestan, University of Lorestan . Faculty of Literature and Human Sciences. Department of Geography
Abstract:   (5253 Views)
sudden stratospheric warming has an obvious effect on the Earth's surface climate. In this research, the changes in precipitation during the occurrence of this phenomenon have been investigated. For this purpose, after revealing the warmings that occurred during the studied period (1986-2020), 18 warmings were identified. The 5th decile and 9th decile of precipitation were calculated for the precipitation data of 117 stations. And the size of the difference from the normal rainfall was checked in two ways. First, the precipitation at the time of warming was compared with the long-term average, and then the trend of changes in precipitation at three times before thewarming, at the same time as the warming, and after the warming was finished. Finally, these results were obtained. Warmings according to the month in which they occur; They have a different effect on the amount of precipitation. In the sudden stratospheric warming that occurred in December, January and February, the northwest experiences the most rainfall changes and is above normal, and the probability of rainfall above the 9th decile increases up to 65%. Western and southwestern regions also have higher than average rainfall and the probability of heavy rainfall is high. Precipitation on the shores of the Caspian Sea shows an inverse relationship with sudden stratospheric warming, so in all the investigations of this research, the lack of precipitation at the time of warming in these areas is significant. Southern regions have less than normal rainfall in all sudden stratospheric warming events. The center of Iran has higher than average rainfall in the sudden stratospheric warming months of March. Eastern Iran also has heavy rains compared to normal during the sudden stratospheric warming months of March.

 
Keywords: number of rainy days, precipitation above the 9th decile, stratospheric sudden warming, wind-zonal fluctuations.
     
Type of Study: Research | Subject: climatology
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