Cyclonic and anticyclonic contributions to atmospheric energetics

Satoru Okajima,Hisashi Nakamura,Yohai Kaspi

doi:10.1038/s41598-021-92548-7

Satoru Okajima, Hisashi Nakamura + Show 1 more

Open Access

https://doi.org/10.1038/s41598-021-92548-7

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Abstract

Migratory cyclones and anticyclones account for most of the day-to-day weather variability in the extratropics. These transient eddies act to maintain the midlatitude jet streams by systematically transporting westerly momentum and heat. Yet, little is known about the separate contributions of cyclones and anticyclones to their interaction with the westerlies. Here, using a novel methodology for identifying cyclonic and anticyclonic vortices based on curvature, we quantify their separate contributions to atmospheric energetics and their feedback on the westerly jet streams as represented in Eulerian statistics. We show that climatological westerly acceleration by cyclonic vortices acts to dominantly reinforce the wintertime eddy-driven near-surface westerlies and associated cyclonic shear. Though less baroclinic and energetic, anticyclones still play an important role in transporting westerly momentum toward midlatitudes from the upper-tropospheric thermally driven jet core and carrying eddy energy downstream. These new findings have uncovered essential characteristics of atmospheric energetics, storm track dynamics and eddy-mean flow interaction.

Highlights

Migratory cyclones and anticyclones account for most of the day-to-day weather variability in the extratropics
Regions of strong eddy activity measured are called “storm tracks”, and many studies have investigated the climatological seasonality of storm tracks and their interannual or decadal variability based on Eulerian statistics[14,15,16]
The Eulerian statistics can elucidate the dynamical distinction of an eddy-driven, subpolar westerly jet stream from a stronger thermally driven subtropical jet stream[22,23]

Summary

Introduction

Migratory cyclones and anticyclones account for most of the day-to-day weather variability in the extratropics. Though less baroclinic and energetic, anticyclones still play an important role in transporting westerly momentum toward midlatitudes from the upper-tropospheric thermally driven jet core and carrying eddy energy downstream These new findings have uncovered essential characteristics of atmospheric energetics, storm track dynamics and eddy-mean flow interaction. Regions of strong eddy activity measured are called “storm tracks”, and many studies have investigated the climatological seasonality of storm tracks and their interannual or decadal variability based on Eulerian statistics[14,15,16] Another advantage of the Eulerian approach is its suitability to quantitative dynamical diagnoses, including the energetics based on the Lorenz energy c ycle[16,17,18] and the Eliassen-Palm (E-P) flux diagnosis for eddy-mean flow interaction[19,20,21]. This study is the first to evaluate and reconstruct separate contributions from both cyclonic and anticyclonic eddies onto Eulerian statistics, based on instantaneous identification of cyclonic and anticyclonic vortices

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