Lidar in Hawaii, Virginia, and Germany continued to detect remnants of the aerosols from the November 1985 eruption of Ruiz (figure 41). Total backscatter over Hawaii increased in late May, as a higher altitude layer, centered around 28 km, became evident. This material lacked the sharp sublayering that generally characterizes fresh aerosols, and no large explosive eruptions have recently been reported.

Figure 41. Lidar data from various locations, showing altitudes of aerosol layers. Note that some layers have multiple peaks. Backscattering ratios are for the ruby wavelength of 0.69 µm. Integrated values show total backscatter, expressed in steradians-1, integrated over 300-m intervals from 16-33 km at Mauna Loa. Altitudes of maximum backscattering ratios and coefficients are shown for each layer at Mauna Loa.

Smoke from major forest fires in China that started 6 May could be tracked on polar orbiting satellite imagery as it moved over Kamchatka and S of the Aleutian Islands. The maximum altitude reached by the smoke was uncertain.

Information Contacts: Thomas DeFoor, Mauna Loa Observatory, P.O. Box 275, Hilo, HI 96720 USA; Horst Jäger, Fraunhofer-Institut für Atmosphärische Umweltforschung, Kreuzeckbahnstrasse 19, D-8100 Garmisch-Partenkirchen, West Germany; William Fuller, NASA Langley Research Center, Hampton, VA 23665 USA.