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Report on Atmospheric Effects (1980-1989) — March 1983

Scientific Event Alert Network Bulletin, vol. 8, no. 3 (March 1983)
Managing Editor: Lindsay McClelland.

Atmospheric Effects (1980-1989) Continued monitoring of stratospheric cloud from El Chichón

Please cite this report as:

Global Volcanism Program, 1983. Report on Atmospheric Effects (1980-1989). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 8:3. Smithsonian Institution.

Atmospheric Effects (1980-1989)

All times are local (unless otherwise noted)

Lidar data from Fukuoka, Japan showed a significant decrease in peak values during the limited intervals when weather permitted observations. Broad, almost monolayer profiles were obtained. On 22 March, lidar at Hampton, Virginia showed a broader peak than it had on the 3rd, but about the same total amount of aerosol. From Mauna Loa, Hawaii, lidar detected only minor variations in total aerosol through March. In late April and early May, a lidar-equipped NASA aircraft will collect data on the El Chichón aerosols from high northern to high southern latitudes, and will coordinate with balloon launches from Palestine, Texas.

David Hofmann reported that a balloon launch from Laramie, Wyoming early 8 April detected remnants of the extensive cloud of tiny aerosols observed 28 January. About 20 particles per cm3 remained between 25 and 33 km altitude. A new layer of similar particles, probably about 1 week old, was observed at 20 km, an unusually low altitude. Particle concentrations were about 125/cm3, but the layer was only 200 m thick. The arctic airmass over Wyoming on 8 April lowered the tropopause to 9-10 km altitude, so the densest layers of the main El Chichón cloud were lower than usual. Counts of particles larger than 0.15 µm reached 13/cm3 at 12 km and were still 7/cm3 at 20 km. The layer terminated rather abruptly at 23 km.

Edward Brooks reported brilliant dawns and twilights and visible bands of volcanic aerosols over Jeddah, Saudi Arabia during several periods between late February and late March. In addition to colors observed shortly before sunrise and soon after sunset, caused by illumination of aerosols in the lower stratosphere, the presence of higher layers often resulted in unusual colors long before sunrise and after sunset. Early and late colors were both visible near dawn 21 February, but remained feeble. Brightly colored sunsets were observed 21-22 February, and another 2-stage dawn the 23rd. That evening, brown volcanic aerosols formed a layer at about 6° above the horizon. Clouds obscured the sky for the next several days, but many N-S bands of aerosols were visible at 1-3° elevation in the E sky early 28 February. During the first week in March, both early and late dawn colors were usually faint and were sometimes entirely absent. N-S bands of volcanic aerosols were present early 4 March at about 5° elevation. Clouds made observations difficult 10-14 March, but the return of clear weather revealed more bands of aerosols 15-19 and 22 March accompanying long, brilliant dawns and twilights.

Fred Schaaf saw several examples of Bishop's Ring in March from Millville. New Jersey, but frequent cloudiness limited his observations. Before sunset on 13 March, the sun was surrounded by a band about 6° wide that formed a ring with a radius of about 24-30°. On 15 March, the sun's brightness was considerably diminished by a haze that could not be accounted for by weather conditions or local pollution. A milky area bordered by a Bishop's Ring that was again about 24-30° in radius was visible an hour before sunset 20 March. A similar Bishop's Ring was observed before sunset 30 March. Sunset glows through the month were only weak to moderate and there was only one weak example of late glow indicating illumination of higher aerosols. Richard Keen reported that he had observed no unusual twilights from Boulder, Colorado since mid-January.

Information Contacts: M. Hirono, Kyushu Univ., Japan; M. Osborn, NASA; T. DeFoor, MLO; D. Hofmann, Univ. of Wyoming; E. Brooks, Saudi Arabia; F. Schaaf, Millville NJ; R. Keen, Univ. of Colorado.