Nocturnal development of cloud clusters during the Meiyu period in eastern China
Zhuxiao Li (1), Masayuki Kawashima (2), Yasushi Fujiyoshi (2)
(1) Graduate school of Environmental Earth Science, Hokkaido University, Sapporo, Japan
(2) Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
Sixty-one long-lived cloud clusters that developed in eastern China during the Meiyu period in 1998 (June, July and August) and 1999 (June and July) were investigated using GMS-IR imagery. Most (more than 2/3) of the cloud clusters had a maximum area of cloud blackbody temperature (TBB) (<-70C) near 02 LST Local Standard Time (LST) and were called Nocturnal type. The others peaked from late afternoon to evening named Evening type, as a second cluster type. The evening-type cloud clusters developed smaller areas of cold TBBs than Nocturnal-type cluster did. Most Nocturnal-type cloud clusters formed immediately south of or in the Meiyu frontal zone.
Analyses of GAME Reanalysis data (Version 1.5) showed that the ageostrophic wind component shifted from easterly to southerly and increased the velocity of southwesterly airflow largely at low-level layer at nighttime over large domain south to the Meiyu front. This southwesterly ageostrophic synoptic-scale LLJ (S-LLJ) transported large amount of water vapor to the Meiyu front, forcing large moisture convergence within and immediately south of the Meiyu frontal zone. The low-level moisture convergence and the S-LLJ itself were proposed to support the nocturnal development of cloud clesters.
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Ms Zhuxiao Li
03-Aug-04-17:32:55
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Institute of Low Temperature Science, Hokkaido University, Japan
Theme 2
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N306 room, Institute of Low Temperature Science, North 19 West 8, North District, Sapporo, 060-0819