Abstract
We study wintertime blocking events in 2004–2016 over Western Siberia (WS) 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 WS beginning with 2004. We used data ECMWF ERA-Interim and blocking criterion proposed by Tibaldi and Molteni. We investigated blockings events with duration of 5 days or more for winter interval (1 November–31 March). We have chosen 15 blockings events. For each event we calculate surface temperature anomaly in the grid points for two sectors 60–90 E; 50–60 N (southern part of WS) and 60–90 E; 60–70 N (northern part of WS). To estimate advective transfer for studied events we analyzed the potential temperature on the dynamical tropopause. We showed that wintertime blocking events over WS lead to the surface temperature increase in the northern part of West Siberia and to the surface temperature decrease in the southern part of WS. This feature apparently due to warm air masses advection from south-west on the western periphery of the blocking ridge and arctic air masses intrusion to the southern part of the WS on the eastern periphery of this ridge.
Highlights
Atmospheric blocking is one of the most important large-scale phenomena of mid- and high latitude circulation in the middle troposphere [1,2,3,4,5,6,7,8,9]
The period 2004–2016 is very interesting for study because there has been an increase in the blocking frequency in January–February over Western Siberia beginning with 2004
We see that the periods of blocking often correspond to negative anomalies in the southern part of Western Siberia (December–January 2004/2005 (Figure 2a), December 2005 (Figure 2b), November 2006 (Figure 2c), December–January 2010/2011 (Figure 2f)) and positive in the north part (December 2005 (Figure 2b), November 2008 (Figure 2d), January 2008 (Figure 2e), December–January 2015/2016 (Figure 2h))
Summary
Atmospheric blocking is one of the most important large-scale phenomena of mid- and high latitude circulation in the middle troposphere [1,2,3,4,5,6,7,8,9]. Atmospheric blocking has quasi-stationary regime and characterized by the barotropic anticyclone with a large amplitude and interruption of westerlies [3,4]. The mid-latitude westerly jet and the eastward progression of synoptic systems are often interrupted in long periods of atmospheric blocking. We have investigated long-term variability of the atmospheric blockings over Western Siberia for 1948–. Proceedings 2017, 1, 198 term trends in these two areas for different seasons In both cases insignificance of the calculated trends in comparison with the large amplitude of inerannual variations attracts our attention. In this paper 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 in January–February over Western Siberia beginning with 2004. The study of the individual events can help us understand how this happens
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