Lidar data from Virginia, USA, again revealed the presence of a volcanic aerosol layer centered at about 22 km altitude in April and May 1996 (table 6), somewhat higher than the 18-19 km measured during August-December 1995 (Bulletin v. 20, no. 10, and table 6). Over Germany, the aerosol layer was concentrated around 15-20 km altitude during January-April 1996, consistent with measurements made during late 1995 (Bulletin v. 21, no. 2). Backscattering ratios continued to show a decreasing trend at Hampton, and remained stable at Garmisch-Partenkirchen. Data from Cuba during January-April 1996 were highly variable, but still comparable to late-1995 data (Bulletin v. 21, no. 2). The base of the aerosol layer was consistently around 15-17.5 km (dropping to 12.7-13.3 km in April), but the layer peak ranged from 18.1 up to 27.1 km. Backscattering ratios were also variable, with seven measurements showing the expected slow decrease to the 1.11-1.17 range, but with the other six being anomalously high in the 1.35-1.51 range.

Table 6. Lidar data from Virginia, Cuba, and Germany showing altitudes of aerosol layers; some layers have multiple peaks. Backscattering ratios from Virginia are for the ruby wavelength of 0.69 µm; those from Germany and Cuba are for the Nd-YAG wavelength of 0.53 µm, with equivalent ruby values in parentheses for data from Germany. The integrated value shows total backscatter, expressed in steradians^-1, integrated over 300-m intervals from 16-33 km for Cuba and from the tropopause to 30 km at Hampton and Garmisch-Partenkirchen. Courtesy of Mary Osborn, Horst Jäger, and Rene Estevan.

Information Contacts: Mary Osborn, NASA Langley Research Center (LaRC), Hampton VA 23665, USA; Horst Jäger, Fraunhofer -- Institut für Atmosphärische Umweltforschung, Kreuzeckbahnstrasse 19, D-8100 Garmisch-Partenkirchen, Germany; Rene Estevan and Juan Carlos Antuña, Centro Meteorologico de Camagüey, Apartado 134, Camagüey 70100, Cuba [J.C.A is presently at Univ. Maryland, Dept. of Meteorology, College Park, MD 20742 USA];