1. 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

2. 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

3. 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

4. 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

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

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

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

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

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

10. SWE test
positive Ural height anomaly is close to the observation

11. SIC+SWE test
Combined effects
intensified wave train is replicated

12. 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

13. 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!