BALLOON-BORNE PHOTOMETRIC STUDIES OF THE STRATOSPHERIC AEROSOL LAYER AFTER MT-PINATUBO ERUPTION

Using Sun-tracking photometers on board balloons, the Pinatubo volcani c aerosol layer has been studied over Hyderabad (17.5-degrees-N) durin g October 1991 and April 1992. From the angular distribution of the sc attered radiation intensity measurements the aerosol size parameter is derived. Over a decade of aerosol measurements at Hyderabad, aerosol extinction and number density obtained during October 1991 in the stra tosphere are found to be the highest ever obtained with a distinct aer osol layer between 16 and 30 km. The derived aerosol size parameter sh ows layered structures. Analysis of the size parameter obtained during April 1992 indicates formation of aerosols at higher altitudes by coa gulation with a subsequent reduction in the aerosol number density. Th e obtained results are found to agree well with that of an independent lidar measurement made over Ahmedabad (23-degrees-N) and with the str atospheric aerosol and gas experiment II results.