Abstract

Stratospheric aerosols resulting from the volcanic eruption of Mount Pinatubo have been observed in lidar measurements at Table Mountain, California (34.4° N, -117.7° W). Two separate lidar systems have been used to make measurements at four different wavelengths; 308 nm, 352 nm, 532 nm, and 1064 nm. A record of the evolution of the stratospheric aerosol loading, in terms of the backscatter ratio, as a function of time and altitude will be presented. The first evidence of the volcanic aerosols was on July 4, 1991, when increased backscattering, centered at approximately 17 km altitude, was observed. Until July 29, 1991, there was no indication of aerosols above 20 km altitude but since then there has been substantial variation and the stratosphere is sometimes essentially clear but on other occasions scattering ratios up to 10 (at 532 nm) have been observed. Large variations in the aerosol scattering have been observed, even on short time scales (10 min).

The presence of these aerosols has a profound effect on the ongoing measurements of stratospheric ozone profiles using the DIAL technique. Corrections for aerosol effects, which have generally been ignored for stratospheric measurements, should be included in the DIAL analysis. It would be useful at this point to obtain as much experimental information as possible concerning the differential scattering and extinction properties of this aerosol for the ozone DIAL wavelengths, otherwise the corrections can only be as good as the model used. Examples of recent results will be used to illustrate the effects. However, even though the ozone measurements are affected in the regions of the aerosol layers they appear to be unaffected in clear regions and ozone measurements up to 50 km altitude are still possible.

© 1991 Optical Society of America