CHANGES IN STRATOSPHERIC AEROSOL PARAMETERS OVER 105-135-DEGREES-E LONGITUDE DUE TO ERUPTION OF MOUNT-PINATUBO

The eruption of Mt Pinatubo (15.14 degrees N, 120.35 degrees E) in the Philippines on 15 June 1991 produced the largest volcanic effluents i nto the stratosphere as observed by satellite measurements. In this pa per we demonstrate the application of an inversion technique to satell ite observations to infer the stratospheric aerosol size distributions before and after the eruption. The U.S.A. NASA SAGE (Stratospheric Ae rosol and Gas Experiment) II satellite data were used. As a result, th e stratospheric aerosol size distributions were found to be bimodal du e to the addition of larger particles from Mt Pinatubo ejection. In ad dition, aerosol parameters such as extinction coefficient, effective r adius, total surface area, and mass loading were used to track the nor thward and southward dispersion of Pinatubo volcanic plume unmistakabl y. For example, by 18 July 1991, the Pinatubo plume had reached as hig h as 22 km in the stratosphere above Taiwan area. The extinction profi les for September and October 1991 cases were enhanced about two order s in magnitude at the altitude of 20-24 km owing to Pinatubo aerosols. Regarding the transport in the southern hemisphere, for five months a fter eruption, the plume had reached the Antarctic stratosphere, and d ispersed vertically as high as 40 km. In middle Antarctic stratosphere , the aerosol extinctions were increased in general by an order of 10( 3)-10(5) due to the intrusion of Pinatubo plume. The second mode at 0. 5 mu m was found compared with the one at less than 0.1 mu m, generall y found in background stratosphere. (C) 1997 Elsevier Science Ltd.