15th EMS Annual Meeting & 12th ECAM | 07–11 09 2015 | Sofia, Bulgaria Impact of Arctic sea ice and Eurasian snow cover on interannual variations of summer Ural blocking Ruonan Zhang Chinese Academy of Meteorological Sciences Coauthors: Chenghu Sun and Weijing Li

Question? ? ? Ural blocking Southern China Arctic sea ice & Ural blocking (Wu et al. 2009; Liu et al. 2012; Woollings et al. 2014) ――dynamic mechanism (Petoukhov and Semenov 2010; Li and Wang 2012; Liu et al. 2012; Tang et al. 2013; Woollings et al. 2014) ――thermodynamic mechanism Arctic sea ice & SWE ? ? Ural blocking

Schematic Diagram Summer Arctic SIC Eurasian Wave Train Eurasian SWE Autumn Arctic SIC Persistent signals Summer Arctic SIC Dynamic mechanisms (Jet, Baroclinicity) Eurasian Wave Train Eurasian SWE Air-land interaction Ural Blocking Thermodynamic mechanisms (Thickness, Jet) Persistent signals Spring NAT Summer

Summer Ural blocking Ural blocking frequency index (UFI) Tibaldi and Molteni (1990) Ural height index (UI, 40º–70ºE, 45º–65ºN) Li and Gu (2010) Cor (UFI, UI) = 0.72

Arctic SIC pattern Heavy sea ice over the Greenland and northern Barents Seas Sea ice loss over the southern Barents and Laptev Seas

Dynamic mechanisms Previous studies indicated that Arctic SIC anomalies reflect changes in local heat flux transport, exerting an influence on low-level atmospheric baroclinicity

Thermodynamic mechanisms Arctic SIC anomalies may lead to anomalous Eurasian SWE Summer Ural blocking may also be affected by Eurasian SWE, through thermodynamic processes

Numerical simulation design CAM3.1 T42 2.8º× 2.8º 30 ensemble mean 9.1-8.31 Ctrl test SIC and SST fixed SIC+SWE test SIC test SWE test

SIC test a Eurasian wave train persists to summer westerly decreases over mid-latitudes while increases over subpolar

SWE test positive Ural height anomaly is close to the observation

SIC+SWE test Combined effects intensified wave train is replicated

The role of North Atlantic Tripole SSTA Previous studies have noted that SST anomalies over the North Atlantic ocean may affect Ural blocking on an interannual time scale. In winter, the appearance of the Eurasian wave train does not seem to follow that in high UI years In spring and summer, a pronounced Eurasian wave train forms

Summary Variations of summer Ural blocking are closely linked to a Eurasian wave train and preceding Arctic SIC anomalies The dynamic influences of SIC on Eurasian wave train are investigated The thermodynamic influences of SIC are also explored through spring Eurasian snow cover THANKS ! In addition, NAT during spring and summer also play an important role in affecting the Ural blocking The combined influence should be further explored!