Two distinct types of cold surges over East Asia and their predictability

Cold surges over East Asia can be classified into two distinct types based on their dynamical origin. One is cold surges with an amplification of the Siberian High originating from the upper-tropospheric propagation of the wave-train from northwestern Eurasia into East Asia - wave-train type. The other is cold surges with an amplification of Siberian High induced by atmospheric blocking, which is caused by retrograded High anomalies from the North pacific into Siberia - blocking type. In this study, indices for identifying the two types of cold surges using 300 hPa geopotential height were developed and distinct large-scale upper-tropospheric circulation, Siberian High, and temperature anomalies associated with the two types of cold surges were investigated. It is newly suggest that the blocking type cold surges persist 2 to 3 days longer than wave-train type cold surges with stronger negative temperature anomalies. The predictability of the two types of cold surges were investigated from hindcast dataset of NCEP Climate Forecast System (CFS). The blocking-type cold surges are found to be more predictable compared to the wave-train type cold surges. Correlation coefficient between predicted and observed cold surge index become greater than 0.4 about 14 days prior to the occurrence day for the blocking-type cold surges but 12 days for the wave-train type cold surges.