The life cycles of persistent anomalies and blocking over the north pacific

Abstract

This chapter discusses the life cycles of persistent anomalies and blocking over the North Pacific. The behavior of anomalies that persisted at a given location beyond the durations associated with synoptic-scale variability without regard to the character of the concurrent large-scale flow patterns are studied. A description of the evolution of the anomaly and flow patterns associated with persistent height anomalies over the central North Pacific is provided. Raw anomalies are defined as the departures of the analyzed values from the corresponding long-term seasonal trend values. For the 500-mbar height anomaly analyses, the seasonal trend time series at a point is determined by a least-squares quadratic fit to the 14-winter mean time series for that point. Composite time evolution fields for cases of a given region and sign are obtained by averaging over all of the cases relative to the time, when the low-pass filtered anomaly crosses the threshold value at the key point. The variations in the zonal flow over eastern Asia and the western Pacific in advance of the developments over the central Pacific are also elaborated. © 1986, Academic Press Inc. All rights reserved.