Development of waves under explosive cyclones in the Northwestern Pacific

Abstract This study investigated recent changes in the characteristics of explosively developing extratropical cyclones over the northwestern Pacific region in winter from 1979/80 to 2010/11 by using reanalysis data from the Japanese 25-yr Reanalysis/Japan Meteorological Agency Climate Data Assimilation System (JRA-25/JCDAS). The results showed that the frequency of explosive cyclones increased in the northwestern Pacific region east of Japan. This increase was accompanied by a decrease in the number of slowly developing cyclones, indicating an increase in the cyclone growth rate. Moreover, most of the increased explosive cyclones east of Japan originated southwest of Japan. A comparison of the dynamical features and energy budgets of two composite cyclones in the earlier and later halves of the study period suggested that the increase was due to an enhancement of the low-level baroclinicity to the east of Japan and an increase in humidity associated with sea surface temperature warming and enhanced evaporation along the eastern shore of the Asian continent.

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The quantification of development processes of explosive cyclones over Northwestern Pacific and Atlantic in boreal winter

10.5194/egusphere-egu2020-4307 ◽

2020 ◽

Author(s):

Joonsuk Kang ◽

Seok-Woo Son

Keyword(s):

Potential Vorticity ◽

Geopotential Height ◽

Reanalysis Data ◽

Northwestern Pacific ◽

Boreal Winter ◽

Mean Flow ◽

Explosive Cyclones ◽

Development Processes ◽

Zonal Advection ◽

Negative Factors

<p>A method utilizing a prognostic potential vorticity (PV) inversion is designed and applied to quantify the processes that contribute to the explosive cyclone (EC) development over Northwestern Pacific and Atlantic in boreal winter. The ECs deepening in the two remarked regions are identified and tracked, by using the automated tracking method on ERA-Interim reanalysis data over the period of 1979&#8211;2017. The quantification process first involves time differentiation of linearized potential vorticity (PV), which results in a linear function of geopotential height tendency. It is then equated with the PV tendency equation that consists of mean and transient advection terms to represent dynamical processes that contribute to EC development. The quantification, finally, is performed through the inversion of PV tendency budgets, which yields corresponding geopotential height tendency. The results indicate that EC development is primarily caused by zonal advection of PV anomalies by mean flow (~65%) and diabatic production of PV (~40%), with some negative factors in both regions. The former contributes more for ECs deepening over Northwestern Atlantic (~71%) than Northwestern Pacific (~60%), whereas the latter contributes to a similar extent.</p>

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Predictability of Explosive Cyclogenesis over the Northwestern Pacific Region Using Ensemble Reanalysis

Monthly Weather Review ◽

10.1175/mwr-d-12-00161.1 ◽

2013 ◽

Vol 141 (11) ◽

pp. 3769-3785 ◽

Cited By ~ 13

Author(s):

Akira Kuwano-Yoshida ◽

Takeshi Enomoto

Keyword(s):

Heat Release ◽

Sea Level ◽

Northwestern Pacific ◽

Pacific Region ◽

Latent Heat Release ◽

Sea Level Pressure ◽

Cyclone Center ◽

Explosive Cyclone ◽

Level Pressure ◽

Explosive Cyclones

Abstract The predictability of explosive cyclones over the northwestern Pacific region is investigated using an ensemble reanalysis dataset. Explosive cyclones are categorized into two types according to whether the region of the most rapid development is in the Sea of Okhotsk or Sea of Japan (OJ) or in the northwestern Pacific Ocean (PO). Cyclone-relative composite analyses are performed for analysis increments (the differences between the analysis and the 6-h forecast) and ensemble spreads (the standard deviations of ensemble members of the analysis or first guess) at the time of the maximum deepening rate. The increment composite shows that the OJ explosive cyclone center is forecast too far north compared to the analyzed center, whereas the PO explosive cyclone is forecast shallower than the analyzed center. To understand the cause of these biases, a diagnosis of the increment using the Zwack–Okossi (Z-O) development equation is conducted. The results suggest that the increment characteristics of both the OJ and PO explosive cyclones are associated with the most important cyclone development mechanisms. The OJ explosive cyclone forecast error is related to a deeper upper trough, whereas the PO explosive cyclone error is related to weaker latent heat release in the model. A diagnosis of the spread utilizing the Z-O development equation clarifies the mechanism underlying the uncertainty in the modeled sea level pressure. For OJ explosive cyclones, the spread of adiabatic warming causes substantial sea level pressure spreading southwest of the center of the cyclones. For PO explosive cyclones, the latent heat release causes substantial sea level pressure spreading around the cyclone center.

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