Analytical and Numerical Study of the 26 June 1998 Orographic Rainband Observed in Western Kyushu, Japan

Yoshizaki, Masanori; Kato, Teruyuki; Tanaka, Yoshinobu; Takayama, Hajime; Shoji, Yasuhiro; Seko, Hiromu; Arao, Kimio; Manabe, Kunihiko

doi:10.2151/jmsj1965.78.6_835

Cited by 65 publications

(84 citation statements)

References 20 publications

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“…The wind direction changed clockwise below 3 km altitude. Yoshizaki et al (2000) also found a similar clockwise rotation of wind direction with height for the Nagasaki line, on 26 June 1998. On the other hand, wind direction was almost constant from 3 to 5 km.…”

Section: Background Field Generating the Koshikijima Linesupporting

confidence: 55%

“…They showed that a rainband migrated over the East China Sea, stopped its migration when its tip reached the Nagasaki area, and remained there for 5 h. It was suggested that the rainband was trapped orographically. Yoshizaki et al (2000) examined both a wide and a narrow rainband, which appeared stationary and was maintained for a long time over Kyushu, by using a nonhydrostatic spectrum model of MRI/NPD-NHM developed by the Japan Meteorological Agency (JMA). The generating and maintaining mechanisms of the wide rainband were clarified.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2004

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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 11 h. The maximum length and width of the rainband observed in 1999 was ∼200 km and ∼20 km, 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 (∼600 m) 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 60 km from the Koshikijima Islands, strong wind and its clockwise rotation with increasing height was observed below 3 km 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.

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Section: Background Field Generating the Koshikijima Linesupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

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

et al. 2004

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“…The formation of the Nagasaki line is strongly affected by the topography of Nagasaki Peninsula, as concluded by Yoshizaki et al (2000). Meanwhile, this statistical study suggests that the Koshikijima line is not only caused by the Koshikijima Islands, but their formation and maintenance are also affected by the topography of Kyushu Island and other disturbances found around the Koshikijima Islands.…”

Section: Discussionmentioning

confidence: 57%

“…Some previous studies indicated that the formation and maintenance mechanisms of these two lines were related to the topography of Koshikijima Islands and Nagasaki Peninsula (Morita et al 1998;Yoshizaki et al 2000;Tashiro 2004;Umemoto et al 2004). Meanwhile, Kato and Niino (1998) showed from numerical experiments that those mechanisms of the Koshikijima line hardly depended on the topography of Koshikijima Islands.…”

Section: Introductionmentioning

confidence: 94%

Statistical Study of Band-Shaped Rainfall Systems, the Koshikijima and Nagasaki Lines, Observed around Kyushu Island, Japan

Kato¹

2005

Journal of the Meteorological Society of Japan

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The favorable environmental low-level wind condition under which band-shaped rainfall systems form around Kyushu Island, located in the western part of Japan, was statistically examined using upper-air sounding data at Kagoshima and meteorological radar data. The representative rainbands extending northeastward from the Koshikijima Islands (the Koshikijima line), and the Nagasaki Peninsula (the Nagasaki line), are discussed in this study. The favorable conditions for their formation and maintenance are that the southwesterly low-level wind field persists for longer than 12 hours, and that the wind speed at an 850 hPa level is between 5 m s À1 and 25 m s À1 . When the Koshikijima line stagnates for a long time to cause heavy rainfall, other disturbances are usually found around the Koshikijima Islands. Meanwhile, the Nagasaki line forms more frequently than the Koshikijima line, and it often stagnates for a long time without other disturbance.

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“…Now, based on this model, the Japan Meteorological Agency (JMA) is developing a new operational mesoscale model. Some special observations, targeting mesoscale convective systems (MCSs) during the Baiu/winter season around the Japan Islands, have been performed to clarify the mechanisms of MCSs, and to validate the simulation results of the NHM (e.g., TREX observation group 1998; Yoshizaki et al 2000a;Yoshizaki et al 2000b). During the Baiu season, the period from early June through the middle of July, heavy rainfalls bringing disastrous floods are often observed in Japan.…”

Section: Introductionmentioning

confidence: 99%

Reason for the Failure of the Simulation of Heavy Rainfall during X-BAIU-01—Importance of a Vertical Profile of Water Vapor for Numerical Simulations—

Kato¹,

Yoshizaki²,

Bessho³

et al. 2003

Journal of the Meteorological Society of Japan

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A heavy rainfall band was observed over southern Kyushu on 23 June 2001. This heavy rainfall was not predicted by a nonhydrostatic model (NHM) that was operated twice a day to support the field experiment of X-BAIU-01. The reason for this failure was examined in comparison with X-BAIU-01 special observation and satellite data. The maritime wind convergence zone was retrieved over the sea southwest of Kyushu Island from NASA QuickSCAT data, before the heavy rainfall system formed. This wind convergence was also found in the initial field of NHM. The lower atmosphere observed by aerosondes was very humid, while that simulated by NHM was considerably drier. The existence of this low-level humid air was also supported by total precipitable water (TPW) data derived from Tropical Rainfall Measuring Mission Microwave Imager (TMI) and Defense Meteorological Satellite Program Special Sensor Microwave/Imager (SSM/I). These comparisons indicate that the fact that the lower atmosphere was drier than it is in reality, was the reason that the NHM failed to simulate the heavy rainfall.This indication was ascertained by humidifying the lower atmosphere of NHM to correspond to the observation (MOD), and applying the four-dimensional variational data-assimilation technique to TMIderived TPW data (4DV). For MOD, the band-shaped rainfall was reproduced successfully. For 4DV, the simulated precipitation intensity was not strong enough to forecast a heavy rainfall, because 4DV could not retrieve the vertical profile of water vapor by using only the TMI-derived TPW data. Humid air concentrated in the lower atmosphere is necessary to induce heavy rainfall over the Baiu frontal zone.

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Analytical and Numerical Study of the 26 June 1998 Orographic Rainband Observed in Western Kyushu, Japan

Cited by 65 publications

References 20 publications

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

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

Statistical Study of Band-Shaped Rainfall Systems, the Koshikijima and Nagasaki Lines, Observed around Kyushu Island, Japan

Reason for the Failure of the Simulation of Heavy Rainfall during X-BAIU-01—Importance of a Vertical Profile of Water Vapor for Numerical Simulations—

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