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Hirono, M.

Publications and source records attributed to Hirono, M..

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Lidar observations of the El Chichon cloud in the stratosphere over Fukuoka

A volcanic cloud in the stratosphere, originating from the March to April 1982 eruptions of El Chichon, has been observed for about 2.5 years at Fukuoka (33.5 degrees N, 130.4 degrees E) with two wavelengths of Nd-YAG lidar, 1.06 and 0.53 microns. Time and height variabilities of the cloud are described, using the 1.06 microns data, and some results of the two-wavelength measurements are presented. A sudden enormous increase in the total aerosol backscattering from the stratosphere (backscattering coefficient for 1.06 microns integrated over 13.5 to 28.5 km range) was followed by a decrease from late spring to summer with large fluctuations. The cloud initially appeared stratified into two layers: the upper one with fine structure and sharp edges in the easterly wind region and the lower dumpy one in the westerly wind region. Most of the aerosols were contained in the upper layer. The two layers merged into a broad, single-peaked layer as the easterly prevailed in the whole region in fall, when the total aerosol backscattering began to increase. The layer then decreased its peak height as it broadened. The difference in shape of both layers and the increase of total backscattering from fall can be interpreted by the difference in velocity of material transport in the easterly and the westerly wind region.

Fujiwara, M.↗
NASA NTRS1985

Numerical simulation of El Chichon volcanic cloud

The stratospheric volcanic cloud from the eruption of El Chichon, Mexico, on April 4, 1982 was observed routinely by a Nd:YAG lidar system from April 18, 1982 at Kyushu University. There were two phenomena detected by lidar observation of the El Chichon volcanic cloud: (1) The main enhanced layer was formed in the summer easterly wind region over Fukuoka (33.5 deg N, 130.4 deg E). The layer had two high gradient top and bottom boundaries. The layer width slowly broadened until September 1982, when the easterly wind changed to the westerly wind. A similar phenomenon was observed after the eruption of Mt. St. Helens in May 1980. (2) The stratospheric integrated backscattering coefficient (IBC) reached a peak value on May 3, 1982. It then gradually decreased until August, but reincreased significantly from September to December 1982. After January 1983, IBC decreased slowly. This remarkable reincrease had not been seen in past increases which had been observed by lidar at Kyushu University. These phenomena are briefly discussed.

Shibata, T.↗
NASA NTRS1985

Lidar observations of the nighttime sodium layer at 33 deg N

Measurements of the nighttime atmospheric sodium layer have been performed since 1977, using a dye lidar at Fukuoka (33.4 deg N, 130.2 deg E.). The Kyushu lidar uses a flashlamp pumped dye laser tuned to the sodium D sub 2 line (589.0 nm) as a transmitter. The dye laser used in the Kyushu lidar system has been described elsewhere. Sporadic enhancements of the total column abundance of the layer during the Perseids meteor shower were observed on the nights of August 12 and 13, 1978, 1979, 1981, and 1983. Degrading weather conditions prevented observation on the nights during 1980 and 1983. A contour plot of the sodium layer for the period of 8 hours from 21:00 to 5:00 JST on the night of August 12 to 13 1983, is shown. The predominant feature visible is the increase in the height of peak density from 21:00 to 2:00 JST, and the slight decrease in the height of peak density from 2:00 to 5:00 JST. The average abundance had a maximum of about 7 x 10 to the 13th power/sq m on August 13. A plot is presented of the nightly average abundance for available data. The sodium layer abundance increased on the night of August 12 to 13, 1983, during the peak of the Perseids meteor shower, and the following night, August 13 to 14, almost went back to the monthly mean.

Uchiumi, M.↗