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30 results on '"Yamanaka, M. D."'

2. Combined wind profiler-weather radar observations of orographic rainband around Kyushu, Japan in the Baiu season

Author

Umemoto, Y., Teshiba, M., Shibagaki, Y., Hashiguchi, H., Yamanaka, M. D., Fukao, S., and EGU, Publication

Subjects
[SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences
Abstract

A special observation campaign (X-BAIU), using various instruments (wind profilers, C-band weather radars, X-band Doppler radars, rawinsondes, etc.), was carried out in Kyushu (western Japan) during the Baiu season, from 1998 to 2002. In the X-BAIU-99 and -02 observations, a line-shaped orographic rainband extending northeastward from the Koshikijima Islands appeared in the low-level strong wind with warm-moist airs. The weather radar observation indicated that the rainband was maintained for 11h. The maximum length and width of the rainband observed in 1999 was ~200km and ~20km, respectively. The rainband observed in 2002 was not so developed compared with the case in 1999. The Froude number averaged from sea level to the top of the Koshikijima Islands (~600m) was large (>1), and the lifting condensation level was below the tops of the Koshikijima Islands. Thus, it is suggested that the clouds organizing the rainband are formed by the triggering of the mountains on the airflow passing over them. The vertical profile of horizontal wind in/around the rainband was investigated in the wind profiler observations. In the downdraft region 60km from the Koshikijima Islands, strong wind and its clockwise rotation with increasing height was observed below 3km altitude. In addition, a strong wind component perpendicular to the rainband was observed when the rainband was well developed. These wind behaviors were related to the evolution of the rainband.

Published
2004

4. Picture of the global field of quasi-monochromatic gravity waves observed by stratospheric balloons and MST radars

Author

Yamanaka, M. D

Subjects
Geophysics
Abstract

In MAP observations, it was found that: (1) gravity waves in selected or filtered portions of data are fit for monochromatic structures, whereas (2) those in fully continuous and resolved observations take universal continuous spectra. It is possible to explain (2) by dispersion of quasi-monochromatic (or slowly varying) wave packets observed locally as (1), since the medium atmosphere is unsteady and nonuniform. Complete verification of the wave-mean flow interactions by tracking individual wave packets seems hopeless, because the wave induced flow cannot be distinguished from the basic flow independent of the waves. Instead, the primitive picture is looked at before MAP, that is, the atmosphere is just like an entertainment stage illuminated by cocktail lights of quasi-monochromatic gravity waves. The wave parameters are regarded as functions of time and spatial coordinates. The observational evidences (1) and (2) suggest that the wave parameter field is rather homogeneous, which can be explained by interference of quasi-monochromatic wave packets.

Published
1989

5. A perspective of Middle-Atmosphere Dynamics (MAD) studies at the New International Equatorial Observatory (NIEO)

Author

Yamanaka, M. D and Fukao, S

Subjects
Geophysics
Abstract

The equatorial region has attracted many MAD studies mainly based on data of limited locations and resolutions. Established at NIEO are: (1) Climatology of the equatorial middle atmosphere (all of the mean zonal flow, the meridional and/or east-west circulations and the planetary/gravity waves are described based on massive, reliable data statistics); (2) Troposphere-stratosphere coupling at the equator (the candidate location of NIEO is just at the stratospheric fountain area where the tracers and waves are pumped up into the middle atmosphere); and (3) Mesosphere-thermosphere coupling at the equator; thermospheric superrotation, which may be caused either by ion drag or by tidal breaking, is examined in detail by observations covering a wide altitude range from the mesosphere through the thermosphere.

Published
1989

6. Hierarchical structure of stratospheric wind fluctuations

Author

Yamanaka, M. D and Tanaka, H

Subjects
Geophysics
Abstract

In order to verify the gravity-wave-breaking theories, high resolution observations of middle-stratospheric winds were carried out by balloon-borne anemometers. The observed features were summarized, the parameters of waves generating the turbulence were estimated, and the effect on the general circulation and the transport process were discussed.

Published
1985

24. ‘‘Glow-discharge’’ ionic anemometer.

Author

Yamanaka, M. D., Hirosawa, H., Matsuzaka, Y., and Tanaka, H.

Subjects
*ANEMOMETER, *GLOW discharges, *ATMOSPHERIC turbulence
Abstract

We have developed an ionic anemometer utilizing a glow discharge for the purpose of observing stratospheric turbulence. The anemometer has a three-electrode structure; two electrodes made of Ni mesh hold a glow discharge between them and act as the source of ion tracers. The third electrode collects the ions interacting with wind. The minimum detectable wind speed is less than 1 cm/s over a pressure range of 15–35 Torr. The lifetime of this device is more than 50 h. The anemometer has been successfully operated on balloon-borne experiments carried out in 1983 and 1984. [ABSTRACT FROM AUTHOR]

Published
1985
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