Intraseasonal Modulation of the North Pacific Storm Track by Tropical Convection in Boreal Winter

2011 ◽  
Vol 24 (4) ◽  
pp. 1122-1137 ◽  
Author(s):  
Yi Deng ◽  
Tianyu Jiang
Keyword(s):  
North Pacific ◽  
Storm Track ◽  
Tropical Convection ◽  
Boreal Winter ◽  
Mean Flow ◽  
Central Pacific ◽  
Synoptic Eddy ◽  
The North ◽  
The North Pacific ◽  
North Pacific Storm Track

Abstract The modulation of the North Pacific storm track by tropical convection on intraseasonal time scales (30–90 days) in boreal winter (December–March) is investigated using the NCEP–NCAR reanalysis and NOAA satellite outgoing longwave radiation (OLR) data. Multivariate empirical orthogonal function (MEOF) analysis and case compositing based upon the principal components (PCs) of the EOFs reveal substantial changes in the structure and intensity of the Pacific storm track quantified by vertically (925–200 mb) averaged synoptic eddy kinetic energy (SEKE) during the course of a typical Madden–Julian oscillation (MJO) event. The storm-track response is characterized by an amplitude-varying dipole propagating northeastward as the center of the anomalous tropical convection moves eastward across the eastern Indian Ocean and the western-central Pacific. A diagnosis of the SEKE budget indicates that the storm-track anomaly is induced primarily by changes in the convergence of energy flux, baroclinic conversion, and energy generation due to the interaction between synoptic eddies and intraseasonal flow anomalies. This demonstrates the important roles played by eddy–mean flow interaction and eddy–eddy interaction in the development of the extratropical response to MJO variability. The feedback of synoptic eddy to intraseasonal flow anomalies is pronounced: when the center of the enhanced tropical convection is located over the Maritime Continent (western Pacific), the anomalous synoptic eddy forcing partly drives an upper-tropospheric anticyclonic (cyclonic) and, to its south, a cyclonic (anticyclonic) circulation anomaly over the North Pacific. Associated with the storm-track anomaly, a three-band (dry–wet–dry) anomaly in both precipitable water and surface precipitation propagates poleward over the eastern North Pacific and induces intraseasonal variations in the winter hydroclimate over western North America.

scholarly journals Change In The Variability In The Western Pacific Pattern During Boreal Winter: Roles of Tropical Pacific Sea Surface Temperature Anomalies And North Pacific Storm Track Activity

2021 ◽  
Author(s):  
Hasi Aru ◽  
Shangfeng Chen ◽  
Wen Chen
Keyword(s):  
Surface Temperature ◽  
North Pacific ◽  
Storm Track ◽  
High Variability ◽  
Sea Surface ◽  
Boreal Winter ◽  
The North ◽  
The Western Pacific ◽  
The North Pacific ◽  
North Pacific Storm Track

Abstract Using multiple reanalysis datasets, this study reveals that the variability in the Western Pacific pattern (WP) in boreal winter has shown notable changes during recent decades. The variability in the winter WP exhibited a marked weakening trend before the early 2000s and increased slightly thereafter. Two epochs with the highest and lowest WP variabilities are selected for a comparative analysis. Winter WP-related meridional dipole atmospheric anomalies over the North Pacific were stronger and had a broader range during the high-variability epoch than during the low-variability epoch. Correspondingly, the winter WP had larger impacts on surface temperature variations over Eurasia and North America during the high-variability epoch than during the low-variability epoch. We find that the shift in the winter WP variability is closely related to changes in the connection between the winter WP and the El Niño-Southern Oscillation (ENSO) and to changes in the amplitude of the North Pacific storm track. Specifically, ENSO had a closer connection with the WP during the high-variability epoch, at which time the amplitude of the North Pacific storm track was also stronger. During the high-variability epoch, the extratropical atmospheric anomalies generated by the tropical ENSO shifted westward and projected more on the WP-related atmospheric anomalies, thus contributing to an increase in WP variability. In addition, the larger amplitude of the North Pacific storm track that occurred during the high-variability epoch led to the stronger feedback of synoptic-scale eddies to the mean flow and contributed to stronger WP variability. Further analysis indicates that the change in the connection of ENSO with the WP may be partly related to the zonal shift of the sea surface temperature anomaly in the tropical Pacific associated with ENSO.

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 Synoptic–Dynamic Climatology of Large-Scale Cyclones in the North Pacific

2006 ◽  
Vol 134 (12) ◽  
pp. 3567-3587 ◽  
Author(s):  
Linda M. Keller ◽  
Michael C. Morgan ◽  
David D. Houghton ◽  
Ross A. Lazear
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
The United States ◽  
Height Anomaly ◽  
Maximum Frequency ◽  
Mean Flow ◽  
Central Pacific ◽  
The North ◽  
The Pacific ◽  
The North Pacific

Abstract A climatology of large-scale, persistent cyclonic flow anomalies over the North Pacific was constructed using the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) global reanalysis data for the cold season (November–March) for 1977–2003. These large-scale cyclone (LSC) events were identified as those periods for which the filtered geopotential height anomaly at a given analysis point was at least 100 m below its average for the date for at least 10 days. This study identifies a region of maximum frequency of LSC events at 45°N, 160°W [key point 1 (KP1)] for the entire period. This point is somewhat to the east of regions of maximum height variability noted in previous studies. A second key point (37.5°N, 162.5°W) was defined as the maximum in LSC frequency for the period after November 1988. The authors show that the difference in location of maximum LSC frequency is linked to a climate regime shift at about that time. LSC events occur with a maximum frequency in the period from November through January. A composite 500-hPa synoptic evolution, constructed relative to the event onset, suggests that the upper-tropospheric precursor for LSC events emerges from a quasi-stationary long-wave trough positioned off the east coast of Asia. In the middle and lower troposphere, the events are accompanied by cold thickness advection from a thermal trough over northeastern Asia. The composite mean sea level evolution reveals a cyclone that deepens while moving from the coast of Asia into the central Pacific. As the cyclone amplifies, it slows down in the central Pacific and becomes nearly stationary within a day of onset. Following onset, at 500 hPa, a stationary wave pattern, resembling the Pacific–North American teleconnection pattern, emerges with a ridge immediately downstream (over western North America) and a trough farther downstream (from the southeast coast of the United States into the western North Atlantic). The implications for the resulting sensible weather and predictability of the flow are discussed. An adjoint-derived sensitivity study was conducted for one of the KP1 cases identified in the climatology. The results provide dynamical confirmation of the LSC precursor identification for the events. The upper-tropospheric precursor is seen to play a key role not only in the onset of the lower-tropospheric height falls and concomitant circulation increases, but also in the eastward extension of the polar jet across the Pacific. The evolution of the forecast sensitivities suggest that LSC events are not a manifestation of a modal instability of the time mean flow, but rather the growth of a favorably configured perturbation on the flow.

scholarly journals Winter Extreme Flux Events in the Kuroshio and Gulf Stream Extension Regions and Relationship with Modes of North Pacific and Atlantic Variability

2015 ◽  
Vol 28 (12) ◽  
pp. 4950-4970 ◽  
Author(s):  
Xiaohui Ma ◽  
Ping Chang ◽  
R. Saravanan ◽  
Dexing Wu ◽  
Xiaopei Lin ◽  
...  
Keyword(s):  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Propagation Path ◽  
Northwestern Pacific ◽  
Boreal Winter ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Boreal winter (November–March) extreme flux events in the Kuroshio Extension region (KER) of the northwestern Pacific and the Gulf Stream region (GSR) of the northwestern Atlantic are analyzed and compared, based on NCEP Climate Forecast System Reanalysis (CFSR), NCEP–NCAR reanalysis, and NOAA Twentieth Century Reanalysis data, as well as the observationally derived OAFlux dataset. These extreme flux events, most of which last less than 3 days, are characterized by cold air outbreaks (CAOs) with an anomalous northerly wind that brings cold and dry air from the Eurasian and North American continents to the KER and GSR, respectively. A close relationship between the extreme flux events over KER (GSR) and the Aleutian low pattern (ALP) [east Atlantic pattern (EAP)] is found with more frequent occurrence of the extreme flux events during a positive ALP (EAP) phase and vice versa. A further lag-composite analysis suggests that the ALP (EAP) is associated with accumulated effects of the synoptic winter storms accompanied by the extreme flux events and shows that the event-day storms tend to have a preferred southeastward propagation path over the North Pacific (Atlantic), potentially contributing to the southward shift of the storm track over the eastern North Pacific (Atlantic) basin during the ALP (EAP) positive phase. Finally, lag-regression analyses indicate a potential positive influence of sea surface temperature (SST) anomalies along the KER (GSR) on the development of the extreme flux events in the North Pacific (Atlantic).

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