Abstract
Extratropical cyclones (ETCs) over the Northwest Pacific are identified and tracked by applying an objective tracking algorithm to the 6-h time interval relative vorticity fields from the European Center for Medium-range Weather Forecasts (ECMWF) reanalysis data. A total of 2145 ETCs in the November–February winters for the period of 1979–2018 were identified. First, by comparing the ETC track densities in the two periods 1979–1998 and 1999–2018, a significant difference in ETC track density was detected over the Japan Sea, Japan, and North Pacific. Next, the influence of five teleconnection patterns, the El Niño-Southern Oscillation (ENSO), Western Pacific (WP), North Atlantic Oscillation (NAO), Pacific/North American (PNA), and Pacific Decadal Oscillation (PDO) on the ETC track density was investigated by using composite analysis and correlation analysis. WP, NAO, and PDO patterns contributed more to the interannual variability of ETC track density, and higher cyclone densities usually occur in the negative phase of these teleconnection patterns. In contrast, the effects of ENSO and PNA were relatively weak. Finally, a Poisson generalized linear regression model for the ETC counts with respect to the five teleconnection indices was also developed for the purpose of linking all the teleconnection patterns with ETC activities over Northwest Pacific; and the Bayesian model averaging (BMA) procedure was used for model selection in the statistical modeling. The influence of the five teleconnection patterns on ETC track density was also verified in the regression model. The predicted winter ETC counts agreed well with the historical records during 1979–2018 over the Northwest Pacific.
Highlights
Extratropical cyclones (ETCs), called wave cyclones or midlatitude cyclones, are baroclinic low pressure vortices over mid and high latitudes of the two hemispheres
Before conducting the composite and correlation analyses, the oceanic and atmospheric background states were examined for the purpose of better understanding the climatology of ETCs background states were examined for the purpose of better understanding the climatology of over the Northwest Pacific
Kuroshio–Oyashio Extension, there was an obvious sea surface temperature (SST) meridional gradient, which is associated in the Kuroshio–Oyashio Extension, there was an obvious SST meridional gradient, which is with an intense westerly jet stream in the upper troposphere through the thermal wind balance associated with an intense westerly jet stream in the upper troposphere through the thermal wind (Figure 1b)
Summary
Extratropical cyclones (ETCs), called wave cyclones or midlatitude cyclones, are baroclinic low pressure vortices over mid and high latitudes of the two hemispheres. The El Niño-Southern Oscillation (ENSO) is one main oceanic teleconnection pattern with two opposite phases named El Niño and La Niña, respectively [14]. For the North Atlantic Oscillation (NAO), it has been reported that there exists a significant influence on storm frequency over the Atlantic as well as cyclonic activity over the North Pacific [16]. PDO, PNA, and WP teleconnection patterns were closely related to the variation of the North Pacific storm track in winter. The BMA method produces a weighted average of all model predictions, rather than choosing a single model [23] In this way, the problem of model uncertainty could be effectively solved.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
