XXIII General Assembly of the International Union of Geodesy and Geophysics (IUGG2003)

Characteristics of Environment Determining Lifetime of Convective Cells within Mesoscale Convective System in Humid Subtropical Region

Shingo SHIMIZU, Hiroshi UYEDA, Kazuhisa TSUBOKI, Taro SHINODA, Yoshimasa TAKAYA, Teruyuki KATO, Masanori YOSHIZAKI, Hiroyuki YAMADA and Biao GENG


In order to reveal the maintenance mechanism of severe MesoscaleConvective System (MCS), we need to investigate what mechanismdetermines lifetime of convective cells within MCSin a humid subtropical region. Because MCSs in a humid subtropicalregion have convective cells with different lifetime from that in a dry region as the Great Plains in the U.S.The aim of this study is to clarify characteristics of environment determining features of convective cell within MCS in the humid subtropical region such as East Asia. An isolated MCS, observed over the Kanto Plain on 24May 2000, and three line-shaped MCSs, observed during heavy rainfallexperiment in the downstream region of Yangtze River from June to July2001, were selected as examples of MCS developing in the humid subtropical region. These four MCSs were investigated with dual Doppler radar analysis,Meteorological Research Institute Non-Hydrostatic Model (MRI-NHM),and Japan Meteorological Agency Regional objective ANALysis (RANAL).

Dual Doppler radar analysis revealed that the four MCSs had following features. The isolated MCS was supercell type with a short-lived convective cell.Three line-shaped MCSs were back-building rainband type with long-livedconvective cells (BBL), back-building rainband type with short-lived convectivecells (BBS), and broken rainband type with short-lived convective cells (BRS).

By using MRI-NHM and RANAL, it was revealed thateach four MCSs was formed in environments possessing different buoyancy, vertical wind shear, and vapor distribution.This study compared the differences among environments in which four MCSs were formed. Mid-level humidity mainlydetermined the lifetime of convective cell.In a moist mid-level environment, a convective cell within BBL maintained for 78 minutes. On the contrary, in a dry mid-level environment,convective cells within the supercell, BBS, and BRSmaintained for only 30 minutes. The strength of evaporatively-cooled downdraft corresponded to the lifetime.

This paper explained maintenance mechanism of the supercell with short-lived convective cell, and back-building rainband with long-lived convective cell in the humid subtropical region by focusing mid-level humidity. The quantitative, observational or numerical verification of these qualitative understandings obtained in this study would lead us to acquire comprehensive understandingof maintenance mechanism of MCS.


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