Interannual Relationship between ENSO and Atlantic Storm Track in Spring Modulated by the Atlantic Multidecadal Oscillation

Chenfei Liao,Jiechun Deng,Haiming Xu,Leying Zhang

doi:10.3390/atmos9110419

Abstract

It has been well documented that storm track activity are closely related to the weather and short-term climate variability in the extratropics, which is affected by sea surface temperature anomalies over the tropical eastern Pacific Ocean. Interannual relationship between the El Niño-Southern Oscillation (ENSO) and the Atlantic storm track (AST) in spring modulated by the Atlantic multidecadal oscillation (AMO) was investigated using reanalysis data and model simulations in this study. The meridional displacement of the AST is significantly correlated with ENSO during negative AMO phase, while no significant relationship is found during positive AMO phase. This may be due to the difference of 500-hPa geopotential height anomalies induced by ENSO in different AMO phases. For an El Niño event during the negative AMO phase, an anomalous 500-hPa wave train propagates eastward across the North American continent, with positive height anomalies at the high latitudes, extending from South Canada to Newfoundland. Thus, easterly wind anomalies appear over central North America, upstream of the negative AST anomaly. Accordingly, the local eddy growth rate (EGR) and baroclinic energy conversion (BC) are obviously reduced, which weaken (strengthen) the southern (northern) part of the climatological AST. As a result, the AST is shifted northward significantly. During the positive AMO phase, the ENSO-related anomalous wave train at 500 hPa only propagates northeastward and is largely suppressed over Northwest Canada, with positive height anomalies confined to the northwest of North America. Therefore, no significant changes of the westerly jet, EGR and BC are found in the upstream region of the AST, and the meridional location of the AST generally remains unchanged. Most previous studies investigate AST variabilities in winter, and few focus on AST in spring. This work may be helpful in understanding more about the interannual and interdecadal variations of springtime AST and in further studying the weather and short-term climate changes caused by AST.

Highlights

The storm track is referred to the most active region of the synoptic-scale transient eddies in the mid latitudes
The first and second Empirical Orthogonal Function (EOF) modes account for 22.4% and 13.6% of the total variance, respectively; and both can be well separated from the other eigenvalues based on the criterion of North et al [46]
In the control experiment (CTRL), the spring Atlantic storm track (AST) is located over the North Atlantic Ocean, extending northwestward from the Great

Summary

Introduction

The storm track is referred to the most active region of the synoptic-scale transient eddies in the mid latitudes. Both the intensity and location of the storm track are closely related to the weather and short-term climate variability in the extratropics [1,2,3]. The Atlantic storm track (AST) is one of the most active storm tracks in the Northern Hemisphere (NH) It varies at different timescales, including seasonal [7,8], interannual [9,10] and interdecadal timescales [3,11]. Ebisuzaki and Chelliah [12] pointed out that the AST was much weaker in the

Methods

Results

Conclusion