A sudden increase in stratospheric aerosols was recorded on 23 January at 1200 GMT by the Nd-YAG lidar, wavelength 1.06 µm, operated by Kyushu University, Fukuoka, Japan (33.65°N, 130.35°E). The scattering ratio at 17 km altitude (about 4) was about 20 times the normal average value. The same equipment detected a strong aerosol layer at 11-17 km on 30 January and a very strong layer at 10-17 km on 2 February. Peak concentrations were about the same as those recorded 1 month after the 18 May 1980 eruption of St. Helens. NOAA's lidar unit on Mauna Loa, Hawaii (19.5°N, 155.6°W) detected a several-kilometer-thick layer centered at 17 km on 28 January, and its next reading, on 4 February, showed 2-3 different layers between 17 and 20 km altitude. No unusual atmospheric debris had been detected during the previous measurement by this instrument on 19 January. Lidar data gathered during clear weather the last week in January from Wallops Island, Virginia (37.9°N, 75.5°W) revealed no notable stratospheric material. However, ground-based ruby lidar at Garmisch-Partenkirchen, West Germany measured strong aerosol layers at 13-16 km on 2 February and 15-17 km the next night.

Motokazu Hirono interpreted the fine structures of the Kyushu University lidar profiles to indicate a volcanic source. However, SEAN has no recent report of a large explosive eruption and the source of the stratospheric aerosols is not yet known.

Reference. Hirono, M., Fujiwara, M., Shibata, T., and Kugimiya, N., 1981, Lidar Observations of Volcanic Clouds in the Stratospheric over Fukuoka caused by Eruptions of St. Helens in May 1980; Geophysical Research Letters, v. 8, no. 9, p. 1019-1022.

Information Contacts: M. Hirono, Kyushu Univ., Japan; B. Mendonça, NOAA/Air Resources Lab, CO; P. McCormick, NASA, VA; R. Reiter, Garmisch-Partenkirchen, W. Germany.