North Pacific Storm Track Variations in Winter Season and the Coupled Pattern with the Midlatitude Atmosphere‐Ocean System

• Published in: Chinese Journal of Geophysics
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Pacific; aleutian low
• Online Access: http://dx.doi.org/10.1002/cjg2.1014; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fcjg2.1014; https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/cjg2.1014

Abstract The North Pacific storm track variations in winter are investigated by using European ECMWF (ERA40) reanalysis data and Empirical Orthogonal Function (EOF) method. The coupled patterns between the time‐mean flow anomaly and the sea surface temperature (SST) anomaly, related with the storm track variations are studied by regression method. It is shown that there are two major variation modes of the North Pacific storm track in winter. The first mode is characterized by northward (southward) shift of the mid‐east part of the storm track that connotes a northeastward (southeastward) reorientation of the track. Meanwhile, in the mid‐latitude North Pacific, the high (low) pressure anomaly is overlapped over the warm (cold) SST anomaly, displaying a warm‐ridge (cold‐trough) vertical structure, with negative phase of the Pacific‐North American (PNA) pattern in the middle and upper troposphere. The second type denotes entirely intensified (weakened) and slightly northward (southward) storm track. It is associated with warmer (colder) SST in the Kuroshio region, northward (southward) shift both of the low‐level Aleutian low and high‐level westerly jet, and negative (positive) Western Pacific (WP) phase in the mid‐ and high troposphere. The time coefficients of storm track EOF have significant correlation with the Aleutian low index, PNA and WP indices, Nino‐3 index and the Kuroshio SST index, respectively, which re‐demonstrate the existence of the coupled pattern among the three selected fields: SST, storm track and large‐scale time‐mean flow anomalies.