ABSTRACT

The atmospheric general circulation often enters into regimes that cause weather anomalies (departures from an average state) to persist over areas of the globe. By considering 500-hPa measurements the authors demonstrate the existence of scale invariance in the variability of extratropical atmospheric circulation anomalies over the whole range of timescales resolved by the available data, from a week to a decade. This scale invariance indicates an absence of characteristic timescales and the presence of positive long-range correlations, meaning that if an anomaly of a particular sign exists in the past it will most likely continue to exist in the future. Moreover, this scale invariance indicates that the dynamics of small scales are connected to the dynamics of large scales via a simple power law. A consequence of this finding is that the memory of the system is not confined only to large scales but extends to small scales as well. By investigating the hemispheric structure of 500-hPa fields over the last 34 yr the authors are able to link this scale invariance to anomaly patterns that exhibit strong spatial coherence and a decadal variability. These findings are related to climate processes considered in the recent literature and discuss the implications of such a property of the general circulation for modeling and prediction of the climate system response.