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Midwinter Suppression of Storm Tracks in an Idealized Zonally Symmetric Setting

Novak, Lenka and Schneider, Tapio and Ait-Chaalal, Farid (2020) Midwinter Suppression of Storm Tracks in an Idealized Zonally Symmetric Setting. Journal of the Atmospheric Sciences, 77 (1). pp. 297-313. ISSN 0022-4928.

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The midwinter suppression of eddy activity in the North Pacific storm track is a phenomenon that has resisted reproduction in idealized models that are initialized independently of the observed atmosphere. Attempts at explaining it have often focused on local mechanisms that depend on zonal asymmetries, such as effects of topography on the mean flow and eddies. Here an idealized aquaplanet GCM is used to demonstrate that a midwinter suppression can also occur in the activity of a statistically zonally symmetric storm track. For a midwinter suppression to occur, it is necessary that parameters, such as the thermal inertia of the upper ocean and the strength of tropical ocean energy transport, are chosen suitably to produce a pronounced seasonal cycle of the subtropical jet characteristics. If the subtropical jet is sufficiently strong and located close to the midlatitude storm track during midwinter, it dominates the upper-level flow and guides eddies equatorward, away from the low-level area of eddy generation. This inhibits the baroclinic interaction between upper and lower levels within the storm track and weakens eddy activity. However, as the subtropical jet continues to move poleward during late winter in the idealized GCM (and unlike what is observed), eddy activity picks up again, showing that the properties of the subtropical jet that give rise to the midwinter suppression are subtle. The idealized GCM simulations provide a framework within which possible mechanisms giving rise to a midwinter suppression of storm tracks can be investigated systematically.

Item Type:Article
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Schneider, Tapio0000-0001-5687-2287
Additional Information:© 2019 American Meteorological Society. Manuscript received 8 December 2018, in final form 3 October 2019. Published online: 23 December 2019. This work was supported by NSF (AGS-1760402). We thank Prof. Simona Bordoni, Dr. Tobias Bischoff, and Dr. Yair Cohen for useful discussions when producing the manuscript.
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Subject Keywords:Baroclinic flows; Eddies; Large-scale motions; Kinetic energy; Storm environments; General circulation models
Issue or Number:1
Record Number:CaltechAUTHORS:20200109-083234021
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100575
Deposited By: Tony Diaz
Deposited On:09 Jan 2020 19:47
Last Modified:09 Jan 2020 19:47

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