The Role of Transient Eddies in North Pacific Blocking Formation and Its Seasonality
The Role of Transient Eddies in North Pacific Blocking Formation and Its Seasonality
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DOI：
10.1175/jas-d-20-0011.1
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发表时间：
2020-07-01
影响因子：
3.1
通讯作者：
Nakamura, Hisashi
中科院分区：
文献类型：
--
作者：
Hwang, Jaeyoung;Martineau, Patrick;Nakamura, Hisashi
通过对准地转位势趋势方程的再分析收支分析，探讨了北太平洋阻塞的形成机制。证实了北太平洋阻塞异常的放大主要是由涡度通量引起的，热通量的贡献较小。在冬季，由高频涡旋和缓慢变化的背景气流相互作用产生的交叉频率涡度通量主导阻塞的形成。然而，交叉频率的涡度通量，变得明显减弱，并与低频涡度通量在夏季相当。这种季节性表明，由于不同的背景流，NP阻塞的形成机制随季节而变化。进一步发现，NP阻塞形成对形成区域（即，西部对东部NP）也不依赖于波浪破碎的类型（即，气旋与反气旋波破碎）。
The mechanism of North Pacific (NP) blocking formation is investigated by conducting a reanalysis-based budget analysis of the quasigeostrophic geopotential tendency equation. It is confirmed that the amplification of NP blocking anomalies primarily results from vorticity fluxes with a minor contribution of heat fluxes. In winter, the cross-frequency vorticity fluxes, resulting from interactions between high-frequency eddies and the slowly varying background flow, dominate the blocking formation. The cross-frequency vorticity fluxes, however, become substantially weaker and comparable to the low-frequency vorticity fluxes in summer. This seasonality indicates that the mechanism of NP blocking formation varies with seasons due to the different background flow. It is further found that NP blocking formation is not sensitive to the region of formation (i.e., western vs eastern NP) nor to the type of wave breaking (i.e., cyclonic vs anticyclonic wave breaking).