A Rotor Circulation near the Baiu Front Observed by the MU Radar
Akira Watanabe
Faculty of Education, Fukushima University,
Fukushima 960-12, Japan
Shoichiro Fukao, Manabu D. Yamanaka
Radio Atmospheric Science Center, Kyoto University,
Uji, Kyoto 611, Japan
Akimasa Sumi
Center for Climate System Research, University of Tokyo,
Tokyo 153, Japan
and Hiroshi Uyeda
Department of Geophysics, Hokkaido University,
Sapporo 060, Japan
Journal of the Meteorological Society of Japan ,
Vol. 72 , No.1, pp.91-105.
Extended from a paper presented at
the Fifth Workshop on Technical and Scientific Aspects of MST Radar,
Aberystwyth, Wales, UK, 6--9 August 1991.
First draft: August 3, 1991;
Second draft: November 1, 1992;
Third draft: January 16, 1993;
Submitted: March 25, 1993;
Received: March 31, 1993;
Revised: September 20, 1993;
Final manuscript completed: September 27, 1993;
Received: September 29, 1993
Published: February, 1994
ABSTRACT ,
CONTENTS ,
CORRECTIONS ,
FIGURES ,
REFERENCES ,
CITATIONS
Abstract
A rotor circulation was directly observed near the Baiu front
in the lower troposphere by three-dimensional Doppler measurements
with the MU radar at Shigaraki,
Japan (35\degr N,\ 136\degr E).
The temporal and vertical scale of the rotor were $\sim 50$ min and
$\sim 2$ km,
and the stratification observed by radiosondes was statically stable.
The synoptic meteorological analysis suggests that the rotor existed
just below and between Baiu-frontal banded precipitation clouds
which were organized in a meso-$\alpha$ scale cyclone.
Precipitation echoes observed simultaneously by C/Ku-band radars were
quite weak in downdraft in front of the rotor,
and became significant and tall up to $\sim 9$ km altitude
at the back of the rotor circulation.
The rotor was identified with a meso-$\beta$ scale depression
observed by the routine meteorological network,
which had a horizontal scale of $\sim 40$ km in the zonal direction
and 150--200 km in the meridional direction,
and moved from west to east at $\sim 50$ km/h.
Based on brief discussions,
we conclude that the rotor circulation was locally developed
from an orographic disturbance by shear instability
which was occasionally induced in a weak statically-stable layer
maintained by (conditional) symmetric instability.
Contents
- 1. Introduction
- 2. Synoptic-Scale Situation
- 3. Observations at MU Radar Observatory
- 3.1. MU Radar Observations
- 3.2. Radiosonde Observations
- 3.3. C/Ku-band Radar Observations
- 4. Mesoscale Horizontal Structure
- 5. Discussions on Generation Mechanism
- 6. Conclusion
Corrections and Additional Remarks
(Nothing)
List of Figures
(no tables)
- Fig. 1.
(a) Surface synoptic map at 21 JST (12 UT) on July 2,
1990 and (b) GMS IR image at 00 JST on July 3 (15 UT on July 2),
1990 transcribed directly from the routine products of the Japan
Meteorological Agency (JMA).
- Fig. 2.
Quasi-meridional cross-section at 21 JST (12 UT) on July 2, 1990 of
temperature (thicker solid contours, every 10$^{\circ}$C),
zonal wind velocity (thinner solid contours, every 5 m/s),
relative humidity (dotted contours, every 20\% ) and
the tropopause and frontal surface (thick dashed curves),
based on observations at the MU radar observatory
(34.85\degr N,\ 136.10\degr E) and five JMA stations located along
an approximately NNE-SSW line passing through the central Japan
(a map was given in Fukao et al.,\ 1988; Larsen et al.,\ 1991):
of Sapporo (47412), Akita (47582), Wajima (47600),
Shionomisaki (47778) and Minamidaitojima (47945).
Pressure is taken as the vertical coordinate (the ordinate),
and altitude plotted in the right-hand side axis is correct at Shionomisaki.
Total horizontal winds at standard pressure levels over the JMA stations
are also indicated by short (5 m/s) and long (10 m/s) barbs.
- Fig. 3.
(a) Zonal-vertical (eastward and upward positive)
and (b) meridional-vertical (northward and upward positive) air flows
observed by the MU radar from 2357 JST on July 2
to 0136 JST on July 3,\ 1990.
Time resolution is approximately 2.5 minutes.
- Fig. 4.
(a) Zonal-meridional (eastward and northward positive) and
(b) vertical (upward positive) air flows
observed by the MU radar from 2357 JST on July 2
to 0136 JST on July 3,\ 1990.
Time resolution is approximately 2.5 minutes.
- Fig. 5.
Vertical profiles of potential temperature
(----- 21 JST on July 2;
$\cdot \cdot \cdot$ 03 JST on July 3,\ 1990)
and equivalent potential temperature
(-$\cdot$-$\cdot$- 21 JST on July 2;
- - - 03 JST on July 3,\ 1990),
observed with radiosondes launched at the MU radar observatory.
The data of 03 JST on July 3 are displaced by 5 K.
- Fig. 6.
Distribution of the Richardson number (for wet air) calculated based on
horizontal wind obtained from 10-min averaged MU radar data
and equivalent potential temperature interpolated from the observations
by radiosondes launched at $\sim 21$ JST on July 2 and
at $\sim 03$ JST on July 3,\ 1990 (with correcting the time lags of
balloons passing each altitude).
The regions of values less than 1/4 are shaded.
- Fig. 7.
Echo power observed by the Ku-band radar at the MU radar site
(unit is dBZe) from 1915 JST on July 2 to 0115 JST on July 3,\ 1990.
- Fig. 8.
Distribution of echo power observed by a standard meteorological radar
($\odot$) of the Osaka Meteorological Observatory
(OMO) of JMA at (a) 00 JST and (b) 01 JST on July 3,\ 1990.
The black region indicates rainfall between 1 and 4 mm/h,
and the shaded region indicates rainfall less than 1 mm/h.
The MU radar site is shown by a star.
- Fig. 9.
Surface pressure (solid contours, every 0.2 hPa) and temperature
(dashed contours, every 0.2\degr C) changes
(a) from 23 JST on July 2 to 00 JST on July 3
and (b) during 00--01 JST on July 3 1990,
analyzed from the routine meteorological data collected by OMO.
Surface winds are also indicated by barbs (1 m/s) and pennants (5 m/s).
- Fig. 10.
Schematic structure of the rotor circulation
observed in this study.
References
(Updated after publication)
- Akiyama, 1973: {\it Pap.\ Meteor.\ Geophys.}, {\bf 24}, 157.
- Akiyama, 1978: \jmsj{56}{267--283}
- Bretherton, 1969: \qjrms{95}{213--243}
- Browning et al., 1973: \qjrms{99}{215--231}
- F\"{o}rchtg\"{o}tt, 1949: {\it Bull.\ Meteor.\ Czech.}, {\bf 3}, 1--49.
- Fukao et al., 1985a: \rs{20}{622--630}
- Fukao et al., 1985b: \rs{20}{1155--1168}
- Fukao et al., 1985c: \rs{20}{1169--1176}
- Fukao et al., 1988: \mwr{116}{281--292}
- Fukao et al., 1989: \pageoph{130}{463--479}
- Fukao et al., 1991: \mwr{119}{1479--1489}
- Gerbier and Berenger, 1961: \qjrms{87}{13--23}
- Hobbs, 1978: \rgsp{16}{741--755}
- Klaassen and Peltier, 1985: \jas{42}{1321--1339}
- Kotani et al., 1993: \jmsj{71}{in press}
- Larsen et al., 1991: \jaot{8}{766--776}
- Larsson, 1954: {\it Tellus}, {\bf 6}, 124--138.
- Lilly, 1971: \jgr{76}{6585--6588}
- Matsumoto et al., 1971: \jmsj{49}{267--281}
- Matsuo and Sasyo, 1981: \jmsj{59}{10--25}
- May et al., 1992: {\it Beitr.\ Phys.\ Atmos.}, {\bf 65}, 3--11.
- Nakai, 1990: {\it J.\ Japan Soc.\ Fluid Mech.}, {\bf 9}, 262--271.
(in Japanese)
- Ninomiya and Akiyama, 1974: \jmsj{52}{300--313}
- Palmer et al., 1991: \rs{26}{417--427}
- Saitoh and Tanaka, 1987: \jmsj{65}{675--708}
- Saitoh and Tanaka, 1988: \jmsj{66}{39--54}
- Sato, 1990: \jas{47}{2803--2817}
- Sato et al., 1990: \rs{25}{961--973}
- Takayabu, 1992: \jmsj{70}{733--738}
- Takeda and Fujiyoshi, 1978: \jmsj{56}{293--303}
- Takeda and Horiguchi, 1986: \jmsj{64}{109--122}
- Tanaka, 1975: \jmsj{53}{1--31}
- Wakasugi et al., 1986: \jaot{3}{623--629}
- Yokoyama et al., 1984: \jmsj{62}{668--678}
- Yokoyama et al., 1985: \jmsj{63}{100--111}
Citations by Subsequent Papers
(Under construction !!!!!)
List of Original Papers
by M. D. Yamanaka
Bibliography
by any authors
M. D. YAMANAKA homepage (English)
E-mail : yamanaka@kurasc.kyoto-u.ac.jp