Dale M. Simonich and Barclay R. Clemesha

Instituto Nacional de Pesquisas Espaciais (INPE), CP 515, São José dos Campos, 12201-970 SP, Brazil.

Lidar observations of stratospheric aerosols have been made at São José dos Campos, SP (23° S, 46° W) since 1972. The long term variations in the integrated backscatter are dominated by the effects of the 1982 El Chichón and 1991 Mt. Pinatubo injections. A visual analysis of the data from 1975 to 1985 suggests that the annual sum of the volcanic explosivity index is better correlated with significant changes in the integrated backscatter than is the annual sum of the number of volcanoes with significant injection of SO₂ into the stratosphere, although for both indices the level of correlation is small. Since there have not been any significant volcanic injections in recent years at low latitudes or southern mid-latitudes the integrated backscatter has decayed to around what can be considered to be a background level of ~ 8x10^-5.