Structures and Environment of Explosively Developing Extratropical Cyclones in the Northwestern Pacific Region

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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Phylogeny and phylogeography of the land hermit crabCoenobita purpureus(Decapoda: Anomura: Coenobitidae) in the Northwestern Pacific Region

Marine Ecology ◽

10.1111/maec.12369 ◽

2017 ◽

Vol 38 (1) ◽

pp. e12369 ◽

Cited By ~ 12

Author(s):

Katsuyuki Hamasaki ◽

Chikako Iizuka ◽

Tetsuya Sanda ◽

Hideyuki Imai ◽

Shuichi Kitada

Keyword(s):

Northwestern Pacific ◽

Pacific Region

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Metamorphic Belts of Northwestern Pacific Region: ABSTRACT

AAPG Bulletin ◽

10.1306/5d25cce1-16c1-11d7-8645000102c1865d ◽

1970 ◽

Vol 54 ◽

Author(s):

N. L. Dobretsov

Keyword(s):

Northwestern Pacific ◽

Pacific Region

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Storm-Track Response to SST Fronts in the Northwestern Pacific Region in an AGCM

Journal of Climate ◽

10.1175/jcli-d-16-0331.1 ◽

2017 ◽

Vol 30 (3) ◽

pp. 1081-1102 ◽

Cited By ~ 46

Author(s):

Akira Kuwano-Yoshida ◽

Shoshiro Minobe

Keyword(s):

General Circulation ◽

Large Scale ◽

Kuroshio Extension ◽

Storm Track ◽

Northwestern Pacific ◽

Jet Stream ◽

Pacific Region ◽

Northeastern Pacific ◽

The Kuroshio ◽

Sst Fronts

Abstract The storm-track response to sea surface temperature (SST) fronts in the northwestern Pacific region is investigated using an atmospheric general circulation model with a 50-km horizontal resolution. The following two experiments are conducted: one with 0.25° daily SST data (CNTL) and the other with smoothed SSTs over an area covering SST fronts associated with the Kuroshio, the Kuroshio Extension, the Oyashio, and the subpolar front (SMTHK). The storm track estimated from the local deepening rate of surface pressure (LDR) exhibits a prominent peak in this region in CNTL in January, whereas the storm-track peak weakens and moves eastward in SMTHK. Storm-track differences between CNTL and SMTHK are only found in explosive deepening events with LDR larger than 1 hPa h−1. A diagnostic equation of LDR suggests that latent heat release associated with large-scale condensation contributes to the storm-track enhancement. The SST fronts also affect the large-scale atmospheric circulation over the northeastern Pacific Ocean. The jet stream in the upper troposphere tends to meander northward, which is associated with positive sea level pressure (SLP) anomalies in CNTL, whereas the jet stream flows zonally in SMTHK. A composite analysis for the northwestern Pacific SLP anomaly suggests that frequent explosive cyclone development in the northwestern Pacific in CNTL causes downstream positive SLP anomalies over the Gulf of Alaska. Cyclones in SMTHK developing over the northeastern Pacific enhance the moisture flux along the west coast of North America, increasing precipitation in that region.

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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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Numerical Study of Explosively Developing Extratropical Cyclones in the Northwestern Pacific Region

Monthly Weather Review ◽

10.1175/2007mwr2111.1 ◽

2008 ◽

Vol 136 (2) ◽

pp. 712-740 ◽

Cited By ~ 43

Author(s):

Akira Kuwano-Yoshida ◽

Yoshio Asuma

Keyword(s):

Pacific Ocean ◽

Heat Release ◽

Latent Heat ◽

Moisture Distribution ◽

Northwestern Pacific ◽

Extratropical Cyclones ◽

Latent Heat Release ◽

Northwestern Pacific Ocean ◽

Asian Continent ◽

Upper Level

Abstract Numerical simulations of six explosively developing extratropical cyclones in the northwestern Pacific Ocean region are conducted using a regional mesoscale numerical model [the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)]. Cyclones are categorized according to the locations where they form and develop: Okhotsk–Japan Sea (OJ) cyclones originate over the eastern Asian continent and develop over the Sea of Japan or the Sea of Okhotsk, Pacific Ocean–land (PO–L) cyclones also form over the Asian continent and develop over the northwestern Pacific Ocean, and Pacific Ocean–ocean (PO–O) cyclones form and develop over the northwestern Pacific Ocean. Two cases (the most extreme and normal deepening rate cases for each cyclone type) are selected and simulated. Simulations show that the extreme cyclone of each type is characterized by a different mesoscale structure and evolutionary path, which strongly reflect the larger-scale environment: an OJ cyclone has the smallest deepening rates, associated with a distinct upper-level shortwave trough, a clear lower-level cold front, and a precipitation area that is far from the cyclone center; a PO–L cyclone has moderate deepening rates with high propagation speeds under zonally stretched upper-level jets; and a PO–O cyclone has the strongest deepening rates associated with large amounts of precipitation near its center. Sensitivity experiments involving the latent heat release associated with water vapor condensation show that PO–O cyclones rarely develop without a release of latent heat and their structures are drastically different from the control runs, while OJ cyclones exhibit almost the same developments and have similar structures to the control runs. These tendencies can be seen in both extreme and normal deepening rate cases. These results reveal that the importance of latent heat release to explosive cyclone development varies among the cyclone types, as is reflected by the cyclone origin, frontal structure, moisture distribution, and jet stream configuration.

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