Impact of Ural Blocking on Winter Warm Arctic-Cold Eurasian Anomalies. Part II: The Link to the North Atlantic Oscillation

摘要

In Part I of this study, the Ural blocking (UB)-induced amplification role of winter warm Arctic-cold Eurasian (WACE) anomalies has been examined. It was found that the long-lived UB together with the positive North Atlantic Oscillation (NAO(+)) significantly contributes to the amplification of the WACE pattern. The present study examines how the UB variability affects quasi-biweekly WACE (QB-WACE) anomalies and depends on the NAO(+) and North Atlantic conditions by classifying the UB based on a case study of a cold event that occurred over southern China in January 2008. A composite analysis during 1979-2013 shows that the QB-WACE anomalies associated with the UB that often occur with the NAO(+) are strong and influenced by the North Atlantic jet (NAJ) and zonal wind strengths over Eurasia. For NAO(+)-related UB, the QB-WACE anomaly depends strongly on the location of UB, and the UB anomalies lag the NAO(+) by approximately 4-7 days.