Diagnostic analysis of the East Asian cold surges: Terrain effect

Cold surges are dominant weather features in East Asian Continent during winter monsoon time. Empirical statistical analysis suggests that three major cold air reservoirs on Arctic Ocean or Northern Atlantic Ocean contribute to the cold surges in East Asian Continent. In addition, 95% of those cold air masses would pass over a specific region (70šE-90šEš,43šN-65šN) in central Siberia. The formation, outburst, and spread of cold anti-cyclones are still under investigation and did not attract much concern in recent years. Composite analysis through ERA40 data propose that, associated with the intensification and movement of upper troposphere jet stream, the Topographic Rossby Waves are presumed to propagate in high level during the propagation of cold surges. The contribution from Arctic cold air advection and radiative cooling are calculated and compared. The formation of the cold surges, the cold air damming, and the terrain blocking effect by Mongolia Plateau and Tibetan Plateau are studied.