Deciphering Mean Flow-Eddy Interaction in Pacific-North American Teleconnection Linked to Storm Tracks at Subseasonal Timescale

Chen Liu 1Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
2Centre for Severe Weather and Climate and Hydro-Geological Hazards, Wuhan 430074, China

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Lei Chen 1Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
2Centre for Severe Weather and Climate and Hydro-Geological Hazards, Wuhan 430074, China

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Stefan Liess 1Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
3Department of Soil, Water, and Climate, University of Minnesota

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Abstract

The features of large-scale atmospheric circulations, storm tracks, and the mean flow-eddy interaction during winter Pacific-North American (PNA) events are investigated using National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data at subseasonal timescale from 1979 to 2022. The day-to-day variations of storm-track activity and stream function reveal that storm-track activity varies along the evolution of mean flow. To better understand storm track variability with the mean flow-eddy interaction, further exploration is made by analyzing local energy energetics. The changes in horizontal and vertical baroclinic energy conversions from background flow correspond to the storm track anomalies over the North Pacific, indicating that the anomalies in storm tracks are due to the anomalous mean flow associated with PNA patterns impacting energy conversion through mean flow-eddy interaction. Eddy feedback driven by vorticity and heat fluxes is analyzed. This provides a concrete illustration of how eddy feedback serves as a positive factor for the upper-tropospheric circulation anomalies associated with the PNA pattern.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Lei Chen, Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074. Email: leichen@cug.edu.cn

Abstract

The features of large-scale atmospheric circulations, storm tracks, and the mean flow-eddy interaction during winter Pacific-North American (PNA) events are investigated using National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data at subseasonal timescale from 1979 to 2022. The day-to-day variations of storm-track activity and stream function reveal that storm-track activity varies along the evolution of mean flow. To better understand storm track variability with the mean flow-eddy interaction, further exploration is made by analyzing local energy energetics. The changes in horizontal and vertical baroclinic energy conversions from background flow correspond to the storm track anomalies over the North Pacific, indicating that the anomalies in storm tracks are due to the anomalous mean flow associated with PNA patterns impacting energy conversion through mean flow-eddy interaction. Eddy feedback driven by vorticity and heat fluxes is analyzed. This provides a concrete illustration of how eddy feedback serves as a positive factor for the upper-tropospheric circulation anomalies associated with the PNA pattern.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Lei Chen, Department of Atmospheric Science, School of Environmental Studies, China University of Geosciences, Wuhan 430074. Email: leichen@cug.edu.cn
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