Balloon data from Laramie, Wyoming in June and July showed little change in the El Chichón stratospheric aerosol cloud. Maximum concentrations of about 5-6 particles (> 0.15 µm) per cm³ were measured at about 20 km altitude. A few small layers were also detected near the tropopause, perhaps from recent eruptions.

The profile of stratospheric aerosols from the March-April 1982 eruption of El Chichón remained almost constant during August over Fukuoka, Japan. Integrated backscatter of the aerosol cloud over Hampton, Virginia declined slightly in August from July values. New layers near the local tropopause, occasionally observed in recent months, were not reported in August.

From Millville, New Jersey, Fred Schaaf continued to observe moderate to strong twilight glows in August and early September. Primary glow shortly after sunset often blended with somewhat later purple light but faded quickly, indicating aerosol layers that reached a maximum altitude of 8-13 km. Two-stage twilights 14, 15, and 24 August were characterized by long intervals between illumination of the lower and higher layers. If late colors were caused by direct illumination of high-altitude layers, aerosol material was present to roughly 32-40 km altitude. Late colors were usually present, but were not observed 5-6 September. Schaaf noted that their occasional absence during evenings when early colors were visible suggests that they are produced by primary illumination of high-altitude layers rather than secondary glow from material at lower latitudes.

Information Contacts: W. Fuller, NASA; M. Hirono, Kyushu Univ., Japan; D. Hofmann, Univ. of Wyoming; F. Schaaf, Millville, NJ.