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Report on Atmospheric Effects (1980-1989) — October 1985


Atmospheric Effects (1980-1989)

Scientific Event Alert Network Bulletin, vol. 10, no. 10 (October 1985)
Managing Editor: Lindsay McClelland.

Atmospheric Effects (1980-1989) El Chichón aerosols persist in the lower stratosphere

Please cite this report as:

Global Volcanism Program, 1985. Report on Atmospheric Effects (1980-1989) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:10. Smithsonian Institution.



Atmospheric Effects (1980-1989)

All times are local (unless otherwise noted)


Lidar data from Japan, Hawaii, and Virginia showed the continuing presence of aerosols from the 1982 eruption of El Chichón (figure 11). Although both peak and integrated backscattering values remained very uniform over Hawaii from measurement to measurement, the lidar profiles showed substantial variation. The 1 October profile was relatively smooth; two small peaks were apparent on the 16 October data; a zone of sharply decreased aerosol concentration was detected between 20.5 and 23 km altitude on 23 October; and there was a step increase (in contrast to the usual gradual increase) in backscattering at the base of the stratosphere on the 30 October profile.

Figure with caption Figure 11. Aerosol layers from the eruptions of El Chichón and Ruiz as monitored from four lidar sites, April 1982-mid 1986. El Chichón aerosols arrived first at lower altitude sites, but by early 1983 measurements were very similar at low and mid-latitudes. Values were much smaller for the Ruiz aerosols (to the right of the arrow). Peak backscatter data (x axis; note logarithmic scale) were normalized to ruby values. Courtesy of M.O. McCormick.

From Holt, England, H. H. Lamb has observed weakening of optical phenomena associated with stratospheric aerosols since his report of strong effects in November and December 1984. On 16 February, the clear sky appeared dirty at twilight and a distinct purple patch developed 20 minutes after sunset. Strong optical effects and colors were observed after sunset on 4-6 and 13 March, and 21 April, with measurements indicating an aerosol height of 20-25 km, as in December. Lamb's next detailed sunset observations were on 1 September and 13 October, with a characteristic fiery red layer along the horizon being particularly notable on the latter date. Measurements of the elevation of the top of the illuminated patch in September and October suggested that the aerosol layer was at 15-18 km altitude.

Information Contacts: H. Lamb, Univ. of East Anglia, England; T. DeFoor, MLO; M. Fujiwara, Kyushu Univ. Japan; M. Osborn, NASA.