scholarly journals Energetics of transient eddies related to the midwinter minimum of the North Pacific storm-track activity

2021 ◽  
pp. 1-55
Keyword(s):  
Energy Conversion ◽  
North Pacific ◽  
Storm Track ◽  
Generation Rate ◽  
Net Energy ◽  
The North ◽  
Eddy Heat Flux ◽  
Storm Track Activity ◽  
Baroclinic Energy Conversion ◽  
The North Pacific

Abstract Storm-track activity over the North Pacific climatologically exhibits a clear minimum in midwinter, when the westerly jet speed sharply maximizes. This counterintuitive phenomenon, referred to as the “midwinter minimum (MWM)”, has been investigated from various perspectives, but the mechanisms are still to be unrevealed. Toward better understanding of this phenomenon, the present study delineates the detailed seasonal evolution of climatological-mean Eulerian statistics and energetics of migratory eddies along the NP storm-track over 60 years. As a comprehensive investigation of the mechanisms for the MWM, this study has revealed that the net eddy conversion/generation rate normalized by the eddy total energy, which is independent of eddy amplitude, is indeed reduced in midwinter. The reduction from early winter occurs mainly due to the decreased effectiveness of the baroclinic energy conversion through seasonally weakened temperature fluctuations and the resultant poleward eddy heat flux. The reduced net normalized conversion/generation rate in midwinter is also found to arise in part from the seasonally enhanced kinetic energy conversion from eddies into the strongly diffluent Pacific jet around its exit. The seasonality of the net energy influx also contributes especially to the spring recovery of the net normalized conversion/generation rate. The midwinter reduction in the normalized rates of both the net energy conversion/generation and baroclinic energy conversion was more pronounced in the period before the late 1980s, during which the MWM of the storm-track activity was climatologically more prominent.

Interdecadal changes in the storm track activity over the North Pacific and North Atlantic

2011 ◽  
Vol 39 (1-2) ◽  
pp. 313-327 ◽  
Author(s):  
Sun-Seon Lee ◽  
June-Yi Lee ◽  
Bin Wang ◽  
Kyung-Ja Ha ◽  
Ki-Young Heo ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Storm Track ◽  
The North ◽  
Storm Track Activity ◽  
The North Pacific ◽  
Interdecadal Changes

scholarly journals Comments on “The Source of the Midwinter Suppression in Storminess over the North Pacific”

2011 ◽  
Vol 24 (19) ◽  
pp. 5187-5191 ◽  
Author(s):  
Edmund K. M. Chang ◽  
Yanjuan Guo
Keyword(s):  
North Pacific ◽  
Feature Tracking ◽  
Storm Track ◽  
Northern Asia ◽  
The North ◽  
Relative Minimum ◽  
The Pacific ◽  
Storm Track Activity ◽  
The North Pacific ◽  
Midwinter Suppression

In a recent paper, Penny et al. employed feature tracking to investigate why there is a relative minimum in storminess during winter within the Pacific storm track. They concluded that reduced upstream seeding, especially seeding from northern Asia, is the main “source” of the midwinter suppression of the Pacific storm track. Results presented here show that during midwinter months when upstream seeding is as strong as that in spring/fall, the Pacific storm track is not significantly stronger than average and is still much weaker than that in spring/fall, suggesting that the strength of upstream seeding cannot be the primary cause of the midwinter suppression of Pacific storm-track activity.

Influence of Atmospheric Blocking on Storm Track Activity Over the North Pacific During Boreal Winter

2021 ◽  
Vol 48 (17) ◽  
Author(s):  
Minghao Yang ◽  
Dehai Luo ◽  
Chongyin Li ◽  
Yao Yao ◽  
Xin Li ◽  
...  
Keyword(s):  
North Pacific ◽  
Storm Track ◽  
Boreal Winter ◽  
Atmospheric Blocking ◽  
The North ◽  
Storm Track Activity ◽  
The North Pacific

A comparison of climatological subseasonal variations in the wintertime storm track activity between the North Pacific and Atlantic: local energetics and moisture effect

2011 ◽  
Vol 37 (11-12) ◽  
pp. 2455-2469 ◽  
Author(s):  
Sun-Seon Lee ◽  
June-Yi Lee ◽  
Bin Wang ◽  
Fei-Fei Jin ◽  
Woo-Jin Lee ◽  
...  
Keyword(s):  
North Pacific ◽  
Storm Track ◽  
Moisture Effect ◽  
The North ◽  
Storm Track Activity ◽  
The North Pacific

scholarly journals On the Efficiency of Baroclinic Eddy Growth and How It Reduces the North Pacific Storm-Track Intensity in Midwinter

2019 ◽  
Vol 32 (23) ◽  
pp. 8373-8398 ◽  
Author(s):  
Sebastian Schemm ◽  
Gwendal Rivière
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
Storm Track ◽  
The North ◽  
Eddy Heat Flux ◽  
Subtropical Jet ◽  
The Pacific ◽  
The Mean ◽  
The North Pacific ◽  
North Pacific Storm Track

Abstract This study investigates the efficiency of baroclinic eddy growth in an effort to better understand the suppression of the North Pacific storm-track intensity in winter. The efficiency of baroclinic eddy growth depends on the magnitude and orientation of the vertical tilt of the eddy geopotential isolines. The eddy efficiency is maximized if the orientation of the vertical tilt creates an eddy heat flux that aligns with the mean baroclinicity (defined as minus the temperature gradient divided by a stratification parameter) and if the magnitude of the vertical tilt is neither too strong nor too weak. The eddy efficiency is, in contrast to most other eddy measures, independent of the eddy amplitude and thus useful for improving our mechanistic understanding of the effective eddy growth. During the midwinter suppression, the eddy efficiency is reduced north of 40°N over a region upstream of the main storm track, and baroclinic growth is reduced despite a maximum in baroclinicity. Eulerian diagnostics and feature tracking suggest that the reduction in eddy efficiency is due to a stronger poleward tilt with height of eddies entering the Pacific through the northern seeding branch, which results in a more eastward-oriented eddy heat flux and a reduced alignment with the baroclinicity. The stronger poleward tilt with height is constrained by the eddy propagation direction, which is more equatorward when the subtropical jet moves equatorward in winter. In addition, the westward tilt with height is too strong. South of 40°N, the eddy efficiency increases during midwinter but in a region far away from the main storm track.

scholarly journals On the Relationship between Synoptic Wintertime Atmospheric Variability and Path Shifts in the Gulf Stream and the Kuroshio Extension

2009 ◽  
Vol 22 (12) ◽  
pp. 3177-3192 ◽  
Author(s):  
Terrence M. Joyce ◽  
Young-Oh Kwon ◽  
Lisan Yu
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Western Boundary ◽  
Atmospheric Variability ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Coherent, large-scale shifts in the paths of the Gulf Stream (GS) and the Kuroshio Extension (KE) occur on interannual to decadal time scales. Attention has usually been drawn to causes for these shifts in the overlying atmosphere, with some built-in delay of up to a few years resulting from propagation of wind-forced variability within the ocean. However, these shifts in the latitudes of separated western boundary currents can cause substantial changes in SST, which may influence the synoptic atmospheric variability with little or no time delay. Various measures of wintertime atmospheric variability in the synoptic band (2–8 days) are examined using a relatively new dataset for air–sea exchange [Objectively Analyzed Air–Sea Fluxes (OAFlux)] and subsurface temperature indices of the Gulf Stream and Kuroshio path that are insulated from direct air–sea exchange, and therefore are preferable to SST. Significant changes are found in the atmospheric variability following changes in the paths of these currents, sometimes in a local fashion such as meridional shifts in measures of local storm tracks, and sometimes in nonlocal, broad regions coincident with and downstream of the oceanic forcing. Differences between the North Pacific (KE) and North Atlantic (GS) may be partly related to the more zonal orientation of the KE and the stronger SST signals of the GS, but could also be due to differences in mean storm-track characteristics over the North Pacific and North Atlantic.

Sign in / Sign up

Export Citation Format

Share Document