Abstracts for the 5th International GAME Conf.
3-5 October 2001
Aichi Trade Center
Nagoya Japan
Structure of a deeply developed and long-lived cumulonimbus cloud in the atmospheric situation of weak vertical wind shear
Yukari Shusse (1), Haruya Minda (1), Biao Geng (3), Kazuhisa Tsuboki (1), Takao Takeda (5)
(1) Hydrospheric Atmospheric Research Center, Nagoya University
(3) Frontier Observational Research System for Global Change
(5) Tottori University of Environmental
Only a few cumulonimbus clouds can develop deeply or can be organized among many clouds under a favorable condition for the development of organized cumulonimbus clouds.
It is important to study how the organized structure of
a cumulonimbus cloud can be realized and why only a few cumulonimbus clouds can developed deeply in the similar environment.
On 13 July 1998 in the intensive field observation of GAME/HUBEX
(the GEWEX Asian Monsoon Experiment/Huaihe River Basin Experiment),
in the environment of small vertical wind shear and high CAPE
a deeply developed and long-lived cumulonimbus cloud was observed by Doppler radars installed at Shouxian and Huainan, Anhui Province, China.
Its structure was studied in detail, mainly using the observational data of Doppler radars.
The radar-echo showed that the cumulonimbus cloud moved north-northeastward with a speed of 9 m/s.
It lasted for at least 3 hours.
The echo-top height of the radar-echo
continued to be higher than 14 km level for 1.5 hours.
It maximum height reached 18.5 km.
This radar-echo was composed of several convective cells.
However, it did not show the organized multicellular structure,
that is, regular formation of new convective cells each of which evolved in a similar fashion on a given storm flank.
In its mature stage,
one cellular echo in the cumulonimbus cloud developed very deeply after merging of two cellular echoes.
Intense echo above 30 dBZ extended to 15 km level without change in its horizontal area.
Two significant updrafts U1 and U2 existed in the advection (north and downshear) and rear (southwest and upshear) sides, respectively.
The primary updraft was U2 in terms of its intensity and area.
It maintained during mature stage.
The northeasterly inflow which descended to the surface (the downdraft D3) was dominant in the low and middle levels within the radar-echo
though the environment winds had no easterly component in these levels.
The strong downdraft D1 existed within the downdraft D3.
The merged outflow from these downdrafts was favorable that westerly inflow came into U2 continued to be forced upward.
It is also reasonable to think that the existence of D3 was advantageous for the development of U1 and U2 because it would exclude the consumption of convective energy by dry stable compensating currents.
It is an interesting fact that, under the influence of the northeasterly inflow at low and middle levels, a deeply and long-lived cumulonimbus cloud was formed in the condition of weak vertical wind shear.
In this study three-dimensional kinematic structure of the cumulonimbus cloud was revealed by dual-Doppler radar analysis.
Submittal Information
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Hydrospheric Atmospheric Research Center, Nagoya University | |
| Address : | Presentation : |
Furo-cho, Chikusa-ku, Nagoya, 464-8601 | |
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shusse@ihas.nagoya-u.ac.jp | |