The Role of Warm North Atlantic SST in the Formation of Positive Height Anomalies over the Ural Mountains during January 2008 |
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| Authors: | HAN Zhe LI Shuanglin and MU Mu |
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| Institution: | State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,Graduate University of Chinese Academy of Sciences, Beijing 100049,Nansen-Zhu International Research Centre and Key Laboratory of Regional Climate-Environment Research for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, Key Laboratory of Ocean Circulation and Wave, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 |
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| Abstract: | The most severe snowstorm and freezing-rain event in the past 50 years hit
central and southern China in January 2008. One of the main reasons for the
anomalous climate event was the occurrence of atmospheric circulation
anomalies over middle and high latitudes, particularly the persistent
blocking that occurred over the Ural Mountains. Along with atmospheric
anomalies, a strong La Nina event in the Pacific and warm sea surface
temperature anomalies (SSTAs) in the North Atlantic were the most
significant in the lower boundary. Since a brief analysis suggests that La
Ni\~{n}a exerts no significant impact on the Urals, the key point of focus
in this study is on the role of the warmer SSTAs in the North Atlantic.
Based on an observational composite, North Atlantic SSTAs pattern when the
height anomaly over the Urals is strongly positive is found similar to that
in January 2008, but no significant SSTAs occurred elsewhere, such as the
Pacific. Using an atmospheric general circulation model, ECHAM5, the impact
of North Atlantic SSTAs on the extratropical atmosphere circulation in the
event was investigated. The results show that the warm SSTAs strengthened
the blocking high over the Urals, through anomalous transient eddies. The
consistency between the study model and the observational composite
indicates that the warm SSTAs in the North Atlantic were indeed an important
factor in the formation of the snowstorm disaster of January 2008. |
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| Keywords: | blocking severe snow North Atlantic SSTA transient eddy |
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