A MODEL STUDY ON THE DECAY OF VOLCANIC AEROSOL LAYER AND VERIFICATIONWITH PINATUBO AND EL CHICHON DATA

The time evolution of stratospheric aerosol layer formed after a volca nic eruption is studied taking into account the aerosol microphysical processes of growth, coagulation and sedimentation. Using a simple mod el we could explain the observed evolution of the Pinatubo volcanic la yer which decayed in about 3 gears. The experimental data obtained by Nd:YAG backscatter lidar over Ahmedabad further supports this finding. The data obtained after the El Chichon volcanic eruption also showed that the El Chichon aerosol layer decayed in about 3 years time. Thus, though the amount of SO2 injected has been higher, in the case of Pin atubo, about two to three times more than El Chichon, it has resulted in the production of larger aerosol particles due to faster growth and coagulation processes, and subsequently a faster removal rate, to giv e more or less a similar background aerosol amount at the stratosphere in about 3 years time.