The missing Pinatubo aerosols: a global lidar-SAGE II comparison

The June 1991 Mount Pinatubo volcanic eruption produced the largest stratospheric aerosol loading this century. While the cloud was observed by the limb-scanning Stratospheric Aerosol and Gas Experiment II (SAGE II) satellite, during the initial 6 months after the eruption, the SAGE II signal was saturated. Optical depths reported by the Advanced Very High Resolution Radiometers (AVHRR) on NOAA satellites exceeded those from SAGE II, but the discrepancy has not been completely explained. Here we report measurements from a global network of lidars that quantifies the differences. Previous comparisons used midlatitude lidar observations taken after the densest part of the cloud had dissipated. By using low-latitude lidar data, we show that the AVHRR observations are in better agreement with the lidar observations than SAGE II.