Meridional-energy-transport extremes and the general circulation of Northern Hemisphere mid-latitudes: dominant weather regimes and preferred zonal wavenumbers

Abstract

Abstract. The extratropical meridional energy transport in the atmosphere is fundamentally intermittent in nature, having extremes large enough to affect the net seasonal transport. Here, we investigate how these extreme transports are associated with the dynamics of the atmosphere at multiple spatial scales, from planetary to synoptic. We use the ERA5 reanalysis data to perform a wavenumber decomposition of meridional energy transport in the Northern Hemisphere mid-latitudes during winter and summer. We then relate extreme transport events to atmospheric circulation anomalies and dominant weather regimes, identified by clustering 500 hPa geopotential height fields. In general, planetary-scale waves determine the strength and meridional position of the synoptic-scale baroclinic activity with their phase and amplitude, but important differences emerge between seasons. During winter, large wavenumbers (k = 2–3) are key drivers of the meridional-energy-transport extremes, and planetary- and synoptic-scale transport extremes virtually never co-occur. In summer, extremes are associated with higher wavenumbers (k = 4–6), identified as synoptic-scale motions. We link these waves and the transport extremes to recent results on exceptionally strong and persistent co-occurring summertime heat waves across the Northern Hemisphere mid-latitudes. We show that the weather regime structures associated with these heat wave events are typical for extremely large poleward-energy-transport events.

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“…Earlier in (Sukhanovskii et al, 2023) it was shown that the atmospheric regime, in which the mean flow and baroclinic waves are similar to those in the real atmosphere, i.e. strongly non-stationary waves with main modes m = 2−8 (see mode decomposition analysis in (Lembo et al, 2019(Lembo et al, , 2022)), can be realized only in a short interval of the main parameters. We have chosen this regime to study Arctic warming using laboratory and numerical modeling.…”

The study of the impact of polar warming on global atmospheric circulation and mid-latitude baroclinic waves using a laboratory analog

“…Earlier in it was shown that the atmospheric regime, in which the mean flow and baroclinic waves are similar to those in the real atmosphere, i.e., strongly non-stationary waves with main modes of m = 2 − 8 (see mode decomposition analysis in Lembo et al, 2019Lembo et al, , 2022, can be realized only in a short interval of the main parameters. We have chosen this regime to study Arc-tic warming using laboratory and numerical modeling.…”

The Dynamical Footprint of Year‐Round North American Weather Regimes

“…Recurrent and/or quasi‐stationary large‐scale circulation patterns, typically referred to as weather regimes, have been identified in a number of regions across the globe. These include the Euro‐Atlantic sector (Michelangeli et al., 1995; Vautard, 1990), the Eastern Mediterranean (Alpert et al., 2004; Hochman et al., 2019), East Asia (Yang et al., 2022), Oceania (Kidson, 2000), the Pacific (Fabiano et al., 2021; Michelangeli et al., 1995), the full Northern Hemisphere (Lembo et al., 2022) and North America (Straus et al., 2007; Vigaud et al., 2018).…”