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Anticyclonic suppression of the North Pacific transient eddy activity in midwinter
  • Satoru Okajima,
  • Hisashi Nakamura,
  • Yohai Kaspi
Satoru Okajima
The University of Tokyo

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Hisashi Nakamura
University of Tokyo
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Yohai Kaspi
Weizmann Institute of Science
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Dynamical understandings of midlatitude transient eddy activity, especially its midwinter minimum over the North Pacific, are still limited, partly because Eulerian eddy statistics are incapable of separating cyclonic and anticyclonic contributions. Here we evaluate the two contributions separately based on local curvature of instantaneous flow fields to compare their seasonality between the North Pacific and North Atlantic storm-tracks. The anticyclonic contribution is found crucial for the midwinter minimum of the North Pacific transient eddy activity. Eddy energetics reveals that the net efficiency of the anticyclonic contribution in replenishing total transient eddy energy over the North Pacific exhibits a pronounced midwinter minimum, while that of the cyclonic counterpart does not in harmony with precipitation that peaks around midwinter. This study suggests that more attention should be paid to anticyclones in studying midlatitude storm-track dynamics.
14 Oct 2023Submitted to ESS Open Archive
17 Oct 2023Published in ESS Open Archive