Impacts of the subarctic frontal zone on the North Pacific storm track in the cold season: an observational study

2018 ◽  
Vol 38 (5) ◽  
pp. 2554-2564 ◽  
Author(s):  
Yao Yao ◽  
Zhong Zhong ◽  
Xiu-Qun Yang
Keyword(s):  
Observational Study ◽  
North Pacific ◽  
Frontal Zone ◽  
Storm Track ◽  
Cold Season ◽  
The North ◽  
Subarctic Frontal Zone ◽  
The North Pacific ◽  
North Pacific Storm Track

scholarly journals The asymmetric eddy-background flow interaction in the North Pacific storm track

2020 ◽  
Author(s):  
Yuan-Bing Zhao
Keyword(s):  
Energy Transfer ◽  
North Pacific ◽  
Storm Track ◽  
Middle Level ◽  
Background Flow ◽  
The North ◽  
Flow Interaction ◽  
The North Pacific ◽  
North Pacific Storm Track ◽  
Canonical Transfer

<p>Using a recently developed methodology, namely, the multiscale window transform (MWT), and the MWT-based theory of canonical transfer and localized multiscale energetics analysis, we investigate in an eddy-following way the nonlinear eddy-background flow interaction in the North Pacific storm track, based on the ERA40 reanalysis data from ECWMF. It is found that more than 50% of the storms occur on the northern flank of the jet stream, about 40% are around the jet center, and very few (less than 5%) happen on the southern flank. For storms near or to the north of the jet center, their interaction with the background flow is asymmetric in latitude. In higher latitudes, strong downscale canonical available potential energy transfer happens, especially in the middle troposphere, which reduces the background baroclinicity and decelerates the jet; in lower latitudes, upscale canonical kinetic energy transfer intensifies at the jet center, accelerating the jet and enhancing the middle-level baroclinicity. The resultant effect is that the jet strengthens but narrows, leading to an anomalous dipolar pattern in the fields of background wind and baroclinicity. For the storms on the southern side of the jet, the baroclinic canonical transfer is rather weak. On average, the local interaction begins from about 3 days before a storm arrives at the site of observation, achieves its maximum as the storm arrives, and then weakens.</p>

scholarly journals Seasonal Evolutions of Atmospheric Response to Decadal SST Anomalies in the North Pacific Subarctic Frontal Zone: Observations and a Coupled Model Simulation

2012 ◽  
Vol 25 (1) ◽  
pp. 111-139 ◽  
Author(s):  
Bunmei Taguchi ◽  
Hisashi Nakamura ◽  
Masami Nonaka ◽  
Nobumasa Komori ◽  
Akira Kuwano-Yoshida ◽  
...  
Keyword(s):  
North Pacific ◽  
Frontal Zone ◽  
Ocean Dynamics ◽  
The North ◽  
The Pacific ◽  
Decadal Scale ◽  
Anomaly Pattern ◽  
Subarctic Frontal Zone ◽  
The North Pacific ◽  
Sst Anomalies

Abstract Potential impacts of pronounced decadal-scale variations in the North Pacific sea surface temperature (SST) that tend to be confined to the subarctic frontal zone (SAFZ) upon seasonally varying atmospheric states are investigated, by using 48-yr observational data and a 120-yr simulation with an ocean–atmosphere coupled general circulation model (CGCM). SST fields based on in situ observations and the ocean component of the CGCM have horizontal resolutions of 2.0° and 0.5°, respectively, which can reasonably resolve frontal SST gradient across the SAFZ. Both the observations and CGCM simulation provide a consistent picture between SST anomalies in the SAFZ yielded by its decadal-scale meridional displacement and their association with atmospheric anomalies. Correlated with SST anomalies persistent in the SAFZ from fall to winter, a coherent decadal-scale signal in the wintertime atmospheric circulation over the North Pacific starts emerging in November and develops into an equivalent barotropic anomaly pattern similar to the Pacific–North American (PNA) pattern. The PNA-like signal with the weakened (enhanced) surface Aleutian low correlated with positive (negative) SST anomalies in the SAFZ becomes strongest and most robust in January, under the feedback forcing from synoptic-scale disturbances migrating along the Pacific storm track that shifts northward (southward) in accord with the oceanic SAFZ. This PNA-like signal, however, breaks down in February, which is suggestive of a particular sensitivity of that anomaly pattern to subtle differences in the background climatological-mean state. Despite its collapse in February, the PNA-like signal recurs the next January. This subseasonal evolution of the signal suggests that the PNA-like anomaly pattern may develop as a response to the persistent SST anomalies that are maintained mainly through ocean dynamics.

scholarly journals Decadal Variability of Upper-Ocean Heat Content Associated with Meridional Shifts of Western Boundary Current Extensions in the North Pacific

2017 ◽  
Vol 30 (16) ◽  
pp. 6247-6264 ◽  
Author(s):  
Bunmei Taguchi ◽  
Niklas Schneider ◽  
Masami Nonaka ◽  
Hideharu Sasaki
Keyword(s):  
North Pacific ◽  
Frontal Zone ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Upper Ocean ◽  
Upper Ocean Heat Content ◽  
Temperature Anomalies ◽  
The North ◽  
Subarctic Frontal Zone ◽  
The North Pacific

Generation and propagation processes of upper-ocean heat content (OHC) in the North Pacific are investigated using oceanic subsurface observations and an eddy-resolving ocean general circulation model hindcast simulation. OHC anomalies are decomposed into physically distinct dynamical components (OHC ρ) due to temperature anomalies that are associated with density anomalies and spiciness components (OHC χ) due to temperature anomalies that are density compensating with salinity. Analysis of the observational and model data consistently shows that both dynamical and spiciness components contribute to interannual–decadal OHC variability, with the former (latter) component dominating in the subtropical (subpolar) North Pacific. OHC ρ variability represents heaving of thermocline, propagates westward, and intensifies along the Kuroshio Extension, consistent with jet-trapped Rossby waves, while OHC χ variability propagates eastward along the subarctic frontal zone, suggesting advection by mean eastward currents. OHC χ variability tightly corresponds in space to horizontal mean spiciness gradients. Meanwhile, area-averaged OHC χ anomalies in the western subarctic frontal zone closely correspond in time to meridional shifts of the subarctic frontal zone. Regression coefficient of the OHC χ time series on the frontal displacement anomalies quantitatively agree with the area-averaged mean spiciness gradient in the region, and suggest that OHC χ is generated via frontal variability in the subarctic frontal zone.

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