Impact of the winter North Atlantic Oscillation (NAO) on the Western Pacific (WP) pattern in the following winter through Arctic sea ice and ENSO: part I—observational evidence

Miki Oshika,Yoshihiro Tachibana,Tetsu Nakamura

doi:10.1007/s00382-014-2384-1

Abstract

On the basis of a 51-year statistical analysis of reanalysis data, we propose for the first time that the positive phase of the Western Pacific (WP) pattern in the winter is linked to the negative phase of the North Atlantic Oscillation (NAO) in the previous winter, and vice versa. We show that there are two possible mechanisms responsible for this interannual remote linkage. One is an Arctic mechanism. Extensive Arctic sea ice in the summer after a negative NAO acts as a bridge to the positive phase of the WP in the next winter. The other mechanism involves the tropics. An El Nino occurrence after a negative winter NAO acts as another bridge to the positive phase of the WP in the following winter. The timescale of the Arctic route is nearly decadal, whereas that of the tropical route is about 3–5 years. The tropical mechanism indicates that the NAO remotely excites an El Nino in the second half of the following year. A process perhaps responsible for the El Nino occurrence was investigated statistically. A negative NAO in the winter increases Eurasian snow cover. This anomalous snow cover then intensifies the cold air outbreak from Asia to the western tropical Pacific. This outbreak can intensify the westerly wind burst and excite El Nino in the following year. We suggest that the phase of the NAO in the winter could be a predictor of the WP in the following year.

Highlights

This study tested the hypothesis that Asian weather and climate in a given winter can be predicted 1 year in advance
We have used statistical analyses to show for the first time that a positive phase of the Western Pacific (WP) pattern during the winter, which brings a warm anomaly to East Asia, including Japan, is related to a negative phase of the North Atlantic Oscillation (NAO) in the previous winter
We found that a negative winter NAO induced an El Niño-like sea surface temperature (SST) anomaly in the following winter

Summary

Introduction

This study tested the hypothesis that Asian weather and climate in a given winter can be predicted 1 year in advance. A persistent cold wave and heavy snowfall during the winter in East Asia have social, economic, and psychological impacts on Japan because of the lack of atomic power stations in the post-Fukushima accident era. A cold wave is associated with an anomaly in hemispheric atmospheric circulation. One of the most important components of atmospheric circulation correlated with surface air temperature (SAT) teleconnections over Eastern Asia is the Western Pacific (WP) pattern identified by Wallace and Gutzler (1981). Prediction of the WP pattern in advance is important for Japanese society. Knowledge of the long-term variation of the WP pattern and its prediction is much less advanced than understanding and prediction of other large-scale atmospheric modes

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Conclusion