Wintertime atmospheric blocking events in Western Siberia in the period 2004-2016 and their connection with anomalies of surface temperature
2 Institute of Solar-Terrestrial Physics, SB RAS
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Atmospheric blockings are one of the main causes of many natural disasters (droughts, floods, fires, frosts) that have become more frequent recently. We study wintertime blocking events in 2004 – 2016 over Western Siberia and their influence on the surface temperature. The period 2004 – 2016 is very interesting for study because there has been an increase in the blocking frequency over Western Siberia beginning with 2004. In the work we used data ECMWF ERA Interim (geopotential, surface temperature) and criterion proposed by Tibaldi and Molteni. We investigated blockings events with a duration of 5 days or more for winter intervals (1 November – 31 March). We have chosen 15 blockings events: December 2004, January-February 2005, December 2005, November 2006, January 2008 (two events), December 2008, December- January 2010-2011, January 2011, February 2011, December 2011, January-February 2012, December 2012, February-March 2015, December 2015- January 2016. For each event we calculate surface temperature anomaly in the grid points for two sectors 60 – 90 E; 50 – 60 N (southern part of West Siberia) and 60 – 90 E; 60 – 70 N (northern part of West Siberia). Anomalies were calculated as deviation of daily surface temperature values from 1979 – 2015 mean. To estimate advective transfer for studied 15 events we analyzed the potential temperature on the dynamical tropopause (PV-θ). We showed that wintertime blocking events over the Western Siberia lead to the surface temperature increase in the northern part of West Siberia and to the surface temperature decrease in the southern part of West Siberia. This feature apparently due to warm air masses advection from south-west on the western periphery of the blocking ridge (reinforcing it) and arctic air masses intrusion to the southern part of the Western Siberia on the eastern periphery of this ridge.
This research was supported by the Russian Foundation for Basic Research grants no. 17-05-00119 and no. 17-05-00374
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