Meso-&amp;alpha;-scale Low Development over the Northeastern Japan Sea under the Influence of a Parent Large-scale Low and a Cold Vortex Aloft

Self Cite

Development of a meso-scale low family over the northeastern Japan Sea on 3-4 January 1987 is studied. The meso-scale low family formed in the northwestern part of a parent polar low. Local low-level frontogenesis occurred as a result of the horizontal differential thermal advection between polar air streams from the continent to the southwestern side of the parent polar low and warm air streams from the Pacific to the northwestern side of the polar low. A low-level shear line of WNW-ESE orientation formed in the frontogenesis zone.While upper-air observations showed a thermal gradient of-1.5K/100km and a lateral wind shear of N15 (m/sec)/100km across the shear line, dense surface observations indicated a strong lateral shear of 5-10 (m/sec)/10km within the shear zone of 20-30km width.Two meso-scale lows developed along the shear line with an interval of-200km. Each meso-scale low showed the warm core structure and brought strong gusts of-25m/sec with intense precipitation.While the generation of these lows in the strong shear zone suggested the barotropic process, the mesoscale cyclogenesis in association with the local frontogensis indicated the baroclinic generation process. It was examined whether the observed meteorological parameters would satisfy the criterion of barotropic shear or Eady's type baroclinic instability in the shallow layer obtained from linear instability analyses. It was shown that the maximum growth rates of these instabilities appeared around a wavelength of 200km, although the maximum growth rate of the baroclinic instability calculated from sparse aerological data was considerably smaller than that of the barotropic instability calculated from dense surface data.

Section: Introductionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

A Meso-Scale Low Family Formed over the Northeastern Japan Sea in the Northwestern Part of a Parent Polar Low

Ninomiya

1994

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“…PMCs developed usually over areas of large air-sea temperature difference, which caused large heat energy supply from the sea to the atmosphere. These climatological features of PMCs over the Japan Sea are consistent with results of many observational studies (e.g., Ninomiya 1991;Ninomiya et al 1993;Tsuboki and Wakahama 1992;Fu et al 2004), a climatological study (Yanase et al 2016), and numerical simulation studies (e.g., Yanase et al 2004;Yanase and Niino 2007).…”

Section: Introductionsupporting

confidence: 86%

“…development of PMCs Observational studies on PMCs over the Japan Sea (e.g., Ninomiya 1989Ninomiya , 1991Tsuboki and Wakahama 1992;Ninomiya et al 1993;Fu et al 2004) showed that PMC formed and developed in the lower tropospheric moist-neutral layer under the condition of strong baroclinicity. Yanase et al (2004) concluded that, in a sensitivity experiment of a PMC developed under the strong baroclinicity, the condensational heating was an additional cause for the rapid development.…”

Section: Comment On Conditions For Genesis Andmentioning

confidence: 99%

A Polar Mesoscale Cyclone Formed over the East China Sea and Developed into a Secondary Cyclone over the Northwestern Pacific — An Observational Case Study on 19-22 February 1975 —

Ninomiya¹

2017

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Polar mesoscale cyclones (PMCs) frequently develop over the Japan Sea. Genesis of PMCs over the East China Sea is rare, but can occur under certain synoptic-scale conditions. In this observational case study, the feature of a PMC generated over the eastern East China Sea on 20 February 1975 is studied using observation data including those obtained during Air-mass Transformation Experiment, satellite cloud images, and objectivereanalysis data.The PMC with a comma-cloud formed within cyclonic polar-air streams induced by an upper cold trough and a synoptic-scale parent cyclone that developed near Japan. Within 3-hour period after the generation of the PMC, its central pressure deepened from 1016 to 1012 hPa. Strong surface winds occurred in the trailing portion of the comma-cloud. The large-scale conditions for the PMC's genesis were characterized by the southward intruding of the cold core in the upper cold trough beyond 34°N to the East China Sea, positive vorticity advection at 500 hPa, and the moist-neutral layer formed over the warm Tsushima Current in the eastern East China Sea.The PMC, after passing over Kyushu, developed as it moved eastward along the Pacific coast of Japan. The PMC developed further into the secondary cyclone comparable to the parent cyclone, as it moved in the lowlevel baroclinic zone over the northwestern Pacific. The large-scale conditions for the development were characterized by the upper cold trough and the low-level baroclinic zone formed over the zone of maximum sea-surface temperature gradient along north of the Kuroshio extension.

“…These snow bands formed behind a synoptic low and under a strong influence of the low's circulation, where a thermal stratification was unstable in a deep layer and similar to that favorable for the formation of mesoscale polar low (Ninomiya 1991;Ninomiya et al 1993). The snow bands had rather tall cloud tops (4@5 km), and were different from the typical snow bands with shallow cloud tops appearing during polar cold airmass outbreaks.…”

Section: Introductionmentioning

confidence: 99%

The Precipitation Process in Convective Cells Embedded in Deep Snow Bands over the Sea of Japan

Murakami¹,

Yamada²,

Matsuo³

et al. 2003

Convective cells in two deep snow bands were examined over the Sea of Japan with an instrumented aircraft and dual-Doppler radars. A combination of the relatively warm air stream (westerly) at lower levels secluded near the center of the low and the polar air stream (west-southwesterly) at middle and upper levels produced a deep unstable stratification to the southwestern quadrant of a well-developed low, where snow bands A1 and B1 were respectively observed at around 1600 and 1700 JST on 28 Jan. 1993.Radar data showed that both snow bands were in quasi-steady state within a dual Doppler radar observation area. However, the two snow bands showed quite different development; the maximum reflectivities in bands A1 and B1 were 15 dBZ and 30 dBZ, respectively.Aircraft data showed that the accretional growth of snow particles was the primary precipitation formation mechanism in the convective cells embedded in both snow bands.From aircraft and radar data, it appears that vertical wind shear within the cloud layer influenced the precipitation process. In the cell embedded in snow band A1, the updraft at middle and upper levels tilted downshear due to a strong wind shear and precipitation embryos initiated in the updraft were advected downshear from the main supercooled cloud water region. Therefore, these embryos did not grow to large graupel particles. By comparison, in the cell embedded in snow band B1, the updraft tilted upshear at lower levels and stood almost erect at middle and upper levels due to weak wind shear. Therefore, precipitation embryos initiated in the updraft grew into 5 mm graupel particles as they descended through the main supercooled cloud water region. In addition, re-circulation of graupel particles, which had descended in a vicinity of the updraft core, seemed to play an important role to efficiently produce larger graupel particles.