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Author Masataka Murakami |
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Kinematic and Thermodynamical Structures of Longitudinal-Mode Snow Bands over the Sea of Japan during Cold-Air Outbreaks Part I: Snow Bands in Large Vertical Shear Environment in the Band-Transverse Direction
Journal of the Meteorological Society of Japan, Vol. 88. No 4. Yamada Yoshinori; Murakami Masataka; Mizuno Hakaru - Meteorological Society of Japan, 2010The kinematic and thermodynamical structures of two longitudinal-mode (termed “L-mode”) snow bands over the Sea of Japan occurring on February 8, 1991 and January 21, 1993 are analyzed mainly based on dual-Doppler radar data. The L-mode snow bands with multicellular structure in 1991 and 1993 formed, respectively, at the early onset of and toward the end of cold-air outbreaks, where the magnitude of the band-transverse vertical shear was roughly 2 × 10-3 s-1 approximately in the lower-half of the mixed layer. This magnitude was larger than that associated with L-mode snow bands characterized b ...
[article]Kinematic and Thermodynamical Structures of Longitudinal-Mode Snow Bands over the Sea of Japan during Cold-Air Outbreaks Part I: Snow Bands in Large Vertical Shear Environment in the Band-Transverse Direction
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Available online: https://www.jstage.jst.go.jp/browse/jmsj/88/4/_contents
in Journal of the Meteorological Society of Japan > Vol. 88. No 4 (2010) . - 45 p.The kinematic and thermodynamical structures of two longitudinal-mode (termed “L-mode”) snow bands over the Sea of Japan occurring on February 8, 1991 and January 21, 1993 are analyzed mainly based on dual-Doppler radar data. The L-mode snow bands with multicellular structure in 1991 and 1993 formed, respectively, at the early onset of and toward the end of cold-air outbreaks, where the magnitude of the band-transverse vertical shear was roughly 2 × 10-3 s-1 approximately in the lower-half of the mixed layer. This magnitude was larger than that associated with L-mode snow bands characterized by axi-symmetric circulation, which will be described in Part II. Thermodynamical structures and the spatial distributions of water substances in the two snow bands were inferred from variational-based retrieval.
A pronounced feature of the airflow structures in both snow bands was upshear-tilting updrafts in the band-transverse vertical cross-section. At least two factors could account for their formation: the existence of a certain depth of the vertical layer of the environmental band-transverse system-relative wind components directing to the upshear, and the lower terminal fall velocities of snow and graupels. The retrieval results showed that both snow bands had a subsaturated cold pool beneath the band around the surface, whose collision with the unstable ambient air could have been responsible for overall upward motion in the bands. With regard to the energetics of the band circulation, energy production by buoyancy and the band-transverse shear was dominant.
The repeated formation of new cells was observed in the two snow bands in the downshear side, which may have been triggered by the low-level collision of the outflow from active cells or a cold pool with the unstable ambient air. As the new cell developed enough, the older cell significantly decayed. Consequently, the successive formation of cells did not change the overall echo pattern of the L-mode snow bands without producing elongated echoes branching o. into the downshear direction at large angles to the orientation of the L-mode snow bands.Language(s): English; Other Languages: Japanese
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The Structure and Formation Mechanism of Transversal Cloud Bands Associated with the Japan-Sea Polar-Airmass Convergence Zone
Journal of the Meteorological Society of Japan, Vol. 88. No 4. Eito Hisaki; Murakami Masataka; Muroi Chiashi - Meteorological Society of Japan, 2010During a cold-air outbreak, a broad cloud band is occasionally observed over the Japan-Sea Polar-Airmass Convergence Zone (JPCZ) that forms over the Sea of Japan from the base of the Korean Peninsula to the Japanese Islands. On 14 January 2001, a broad cloud band associated with the JPCZ (JPCZ cloud band) extended in a southeastward direction from the base of the Korean Peninsula to Wakasa Bay, and it stagnated for half a day. The JPCZ cloud band consisted of two cloud regions: one was a long cloud band extending along its southwestern edge (a developed convective cloud band), and the other wa ...
[article]The Structure and Formation Mechanism of Transversal Cloud Bands Associated with the Japan-Sea Polar-Airmass Convergence Zone
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Available online: https://www.jstage.jst.go.jp/browse/jmsj/88/4/_contents
in Journal of the Meteorological Society of Japan > Vol. 88. No 4 (2010) . - 23 p.During a cold-air outbreak, a broad cloud band is occasionally observed over the Japan-Sea Polar-Airmass Convergence Zone (JPCZ) that forms over the Sea of Japan from the base of the Korean Peninsula to the Japanese Islands. On 14 January 2001, a broad cloud band associated with the JPCZ (JPCZ cloud band) extended in a southeastward direction from the base of the Korean Peninsula to Wakasa Bay, and it stagnated for half a day. The JPCZ cloud band consisted of two cloud regions: one was a long cloud band extending along its southwestern edge (a developed convective cloud band), and the other was the region consisting of cloud bands normal to a wind direction of winter monsoon (transversal cloud bands). The structure and formation mechanism of the transversal cloud bands were examined on the basis of observations (e.g., satellite images, in situ measurement and cloud-pro.ling radar data from an instrumented aircraft and upper-air soundings from observation vessels) and simulation results of a cloud-resolving model with a horizontal resolution of 1 km.
The transversal cloud bands had the following characteristic structures; they extended along a northeast-southwest direction, which was parallel to the direction pointed by the vertical shear vector of horizontal wind in the mixed layer, they mainly consisted of convective clouds, which slanted with height toward the down-shear side, and they widened and deepened toward southwest, as the depth of the mixed layer increased. An examination of simulation results presented that the transversal cloud bands were accompanied by roll circulations. The axes of rolls were oriented nearly parallel to the direction of the vertical shear vector in the mixed layer. An analysis of the eddy kinetic energy budget indicated that the roll circulations derived most of its energy from the mean vertical shear and the buoyancy.Language(s): English; Other Languages: Japanese
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