Abstracts for the 6th International GAME Conf.
3-5 December 2004
Kyoto Japan
The maintenance mechanism of convecitve cells within mesoscale convective system in humid subtropical region
Shingo Shimizu (1), Hiroshi Uyeda (1), Kazuhisa Tsuboki (1), Taro Shinoda (1), Hiroyuki Yamada (5), Biao Geng (5), Teruyuki Kato (7)
(1) Hydrospheric Atmospheric Research center, Nagoya university
(5) Frontier Observational Research System for Global Change
(7) Meteorological Research Institute of Japan Meteorological Agency
In order to reveal the maintenance mechanism of severe
Mesoscale Convective System (MCS),
we need to investigate what environmental factor
determines lifetime of convective cells within MCS
in a humid subtropical region such as East Asia.
Because MCSs in a humid subtropical region have
convective cells with different lifetime from those
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 cells
within a MCS in the humid subtropical region such as East Asia.
Three line-shaped MCSs, observed during heavy rainfall
experiment in the downstream region of Yangtze River
from June to July 2001,
were selected as examples of MCS developing
in the humid subtropical region.
These three MCSs were investigated with dual Doppler radar analysis,
Japan meteorological agency regional objective analysis data (RANAL),
regional spectral model (RSM), and cloud resolving storm simulator (CReSS).
Dual Doppler radar analysis revealed that the three MCSs had
following features. Three line-shaped MCSs were
back-building rainband type with long-lived convective cells (BBL),
back-building rainband type with short-lived convective cells (BBS),
and broken rainband type with short-lived convective cells (BRS).
Using RANAL and RSM, it was revealed that each three
MCSs was formed in environments possessing different vapor
distribution at mid-level layer in the troposphere.
In a moist mid-level environment,
a convective cell within BBL maintained for 90 minutes.
On the contrary, in a dry mid-level environment,
BBS and BRS maintained for only 30 minutes.
We showed that mid-level humidity mainly determines
the lifetime of convective cell. In addition,
the strength of evaporatively-cooled downdraft
corresponded to the lifetime. This study proposes that
the lifetime of convective cells depends on efficiency of
evaporative cooling, which is determined by the
mid-level dryness. In a mid-level moist environment,
the evaporative cooling is inactive, and it
causes weak downdraft, as a result, a moist and warm air supply to an
updraft is maintained for long time.
Long-lived convective cells would organize and form MCS
in a moist mid-level environment, such as that of Meiyu period in East Asia.
The quantitative, observational or numerical verification of these
qualitative understandings in East Asia would lead us to
acquire comprehensive understanding of maintenance mechanism of MCS.
Submittal Information
| Name : | Date : |
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| Organization : | Theme : |
Hydrospheric Atmospheric Research Center, Nagoya University, | |
| Address : | Presentation : |
Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601 | |
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| Phone : | Fax : |
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| E-mail : | |
shimizu@rain.hyarc.nagoya-u.ac.jp | |