Synchronous and Asynchronous Relations Between the North Atlantic SSTA and the Northern Hemisphere Large-scale Circulation Features

A. V. Murav’ev, I. A. Kulikova, and Yu. D. Resnyanskii

The spatial and temporal relationships between sea surface temperature anomalies (SSTA) in the North Atlantic and the large-scale mid-troposphere circulation features in the Northern Hemisphere during the summer and the winter seasons are investigated. Results are based on atmospheric circulation indices (CI), introduced by Wallace and Gutzler for physical reasoning the low frequency atmospheric oscillations. Extreme levels and extreme situations in the mid-troposphere were defined and the SSTA composite charts were constructed with backward lags from 0 to 3 months. Analysis shows that several CI extreme phases of different signs are associated with synchronous and asynchronous SSTA composites of statistically separable types, or even antipodes, which may be interpreted as the intraseasonal influence of the ocean on the large-scale mid-troposphere anomaly features. Noteworthy is the role of the North Atlantic tropical zone in formation of ridges and blocking situations both in synchronous and asynchronous aspects. The North Atlantic SSTA relations to the West Atlantic Oscillation are shown to be significantly weaker that the same to the East Atlantic Oscillation.