Evolution and Fine Structure of a Long-Lived Meso-α-Scale Convective System in Baiu Frontal Zone

Abstract

The evolution process and fine structure of a long-lived M*CS(meso-*-scale convective system) in the subtropical East Asia was studied for 14-15 July 1979 using Geostationary Meteorological Satellite IR observation and radar observation data. This M*CS was generated in the Baiu frontal zone under the influence of a weak shortwave trough and developed into a weak Baiu frontal depression. The M*CS consisted of a few M*CSs (meso-*-scale convective systems). The evolution and propagation of the M*CS were related to both development and displacement of M*CSs. The successive generation of M*CSs over the western coast of Kyushu (western part of Japan) indicated the orographic influence on the formation of convection. The successive development of M*CSs to the west of the preexisting one over Kyushu resulted in the slow moving of the M*CS over Kyushu. The environmental conditions for development of M*CS and the strong response in the upper-level wind field to M*CSs are also discussed.

Diurnal Variation of Cb-Clusters over China and Its Relation to Large-Scale Conditions in the Summer of 1979

“…On the other hand, many deep convective clouds in such a horizontal scale also appear to the north of the Baiu frontal zone in China where the time-averaged cloud amount is rather smaller than in the Baiu frontal zone, according to the statistical studies by Ninomiya (1989), Takeda and Iwasaki (1987) and Iwasaki and Takeda (1993). The meso-a-scale convective clouds show multiscale structures in which meso-, Q or 7-scale clouds are embedded, and are considered as significant weather systems (Akiyama, 1984a, b;Madox, 1980Madox, , 1983McAnelly and Cotton, 1986;Ninomiya et al , 1981Ninomiya et al , , 1988a. In the present study we simply refer to such meso-a-scale deep convective clouds (including larger meso-/13-scale ones) as the Cb-clusters, although stratiform clouds might be sometimes embedded in them.…”

Structure and Behavior of Mesoscale Cloud Clusters Traveling over the Baiu-Frontal Zone

“…The discrepancies in wind speed and direction between Kamigoshima and Fukue was large at 2300 JST and 2400 JST 14 July, suggesting that a horizontal shear line with a convergence zone existed to the south of the echo groups. Mesoscale cloud clusters to the west of their accompanying shear line were pointed out by Ogura et al (1985) and Ninomiya et al (1988b). Cumulonimbus clouds in Cb group B2 and Cb group B3 were formed to the north of the shear line.…”

“…Meso-3 scale areas of TBB lower than -70C would correspond to deep convection. Hereafter, these low-TBB areas are referred to as "cold regions," which correspond to the meso-3 scale convective system according to the definition of Ninomiya et al (1988a). The northern and middle cold regions, which are denoted by N and M, continued to move eastward.…”

“…Not only the replacement of Cb groups but also their slow-moving stage had an influence on the movement of the mesoscale cloud cluster. Successive development of the clusters of Cb groups (meso-3 scale convective systems) on the west side of decaying one had an influence on the movement of a meso-a scale cloud cluster (Akiyama, 1984a;Ninomiya et al, 1988a).…”

The Effect of Surface Friction on the Mesoscale Organization of Cumulus Convection in Tropical Cyclones

“…The lifetime of a few hours (Yamasaki, 1983) has also been observed in mesoscale phenomena; MPFs (Mesoscale Precipitating Features, defined by Leary and Houze, 1979) in GATE (Houze, 1977;Zipser et al, 1981), convective systems in TOGA-COARE (Satoh et al, 1995;Takahashi and Uyeda, 1995), mid-latitude squall-lines (Wilhelmson and Klemp, 1981) or cloud clusters (Iwasaki and Takeda, 1989), and heavy rainstorms associated with a decaying typhoon (Matsumoto and Akiyama, 1969;Matsumoto and Tsuneoka, 1969) and Baiu front (Akiyama, 1984;Ninomiya et al, 1988). In a rainband of a tropical cyclone, a period of 4 hours was also observed (May, 1996).…”