Lidar measurements from several locations in the northern hemisphere suggest that the bulk of the El Chichón stratospheric cloud remains confined to lower northern latitudes. Measurements at MLO, Hawaii showed that the cloud remained densest at 25-27 km altitude, but seemed more uniform than last month. Lidar at Fukuoka, Japan showed the aerosols in multi-layer structures above 21 km, in the easterly winds, but well-mixed below that altitude, in the westerly winds. Over Hampton, Virginia, multiple layers were detected between 16 and 31 km, but lower backscattering ratios indicated that the aerosols were much less dense than over Hawaii or Japan. Farther N, at L'Aquila, Italy (42.37°N, 13.4°E) large aerosol enhancements were detected 28 July, and 5, 11-21, and 25-30 August. Layers 3-4 km thick with backscattering ratios as large as 10-12 were observed around 25 km altitude, and on 26 August there was a layer at 32 km altitude with a backscattering ratio of 2.

Scientists from the Department of Physics and Astronomy, University of Wyoming studied the cloud during two unmanned, balloon flights from S Texas (27.3 and 27.7°N) and 7 flights from SE Wyoming (41°N). Optical particle counter measurements of the concentration of particles with radii greater than 0.15 µm revealed two stratospheric layers. The lower layer was 2-3 km thick with peak concentrations, at least 40 times background levels, at about 18 km. The upper was about 3 km thick with peak concentrations, at least 200 times background levels, at about 25 km. Ten sublayers were identified in the upper layer over Texas in May, but only some were found over Wyoming before July.

Since early September brilliant colors persisting at least 30 minutes after sunset have been observed from Norwich, England. At that time on 7 September the brightest area was faintly rimmed with a brown band, interpreted as Bishop's Ring. On 8 September, long smooth streaks at an altitude of 20-25 km were illuminated until 30-35 minutes after sunset.

Information Contacts: T. DeFoor, MLO; M. Hirono, Kyushu Univ., Japan; P. McCormick and W. Fuller, NASA; G. Visconti, Univ. L'Aquila, Italy; D. Hofmann, Univ. of Wyoming; H. Lamb, Univ. of East Anglia, England.