Winter-to-winter recurrence of atmospheric circulation anomalies in the central North Pacific

摘要

Possible causes of the winter-to-winter recurrence (WWR) of atmospheric circulation anomalies in the central North Pacific (CNP) are investigated in the present study. Results show that tropical ENSO could not lead to the atmospheric WWR in the CNP because the persistence of ENSO itself does not show any recurrence regardless of the starting month. The effect of other external forcing, e.g., sea ice, is also not significant. These results suggest that the dominant source of the atmospheric WWR may come from internal atmospheric dynamics in the North Pacific. The Arctic Oscillation, the dominant pattern of sea level pressure variations north of 20N, seems not to be the cause of atmospheric WWR in the CNP region. The effect of the local internal atmospheric dynamics on the atmospheric WWR may be more important in the CNP region. The CNP region was in the location of the storm track in the North Pacific. It was found that seasonal variability of storm track anomalies and associated synoptic transient eddy dynamics may be one of the causes for the atmospheric WWR. During the WWR years, transient eddy forcing on the mean flow is strong during the winter but very weak in the intervening summer, which leads to a quick transition of anomalous mean atmospheric circulation around March and the maintenance of the opposite sign anomalies for two to three seasons. But this characteristic of transient eddy forcing does not exist during the non-WWR years.