Temporal Variation of the Stratospheric Aerosol Layer after the Fuego Eruption observed by Lidar in Fukuoka

Abstract

The eruption of the Fuego in Guatemala injected a large amount of volcanic sub-stances to the lower stratosphere in mid-Oct. '74. About a month later, an extraordinary intense scattering layer was observed by ruby lidar in the lower stratosphere over Fukuoka. The peak value of the non-molecular radar cross section showed a maximum in Dec. '74. It decreased gradually after spring '75 and attained a secondary maximum in early autumn of the year. The height of the layer peak was located a few kilometers below the normal Junge layer and the half width of the layer which was initially a few kilometers increased as the peak value of the non-molecular radar cross section decreased. The gross feature of the temporal variation of the peak value observed by lidar is in contradiction to the results expected from the 2-dimensional transport models proposed up to this time and the contradiction can not be explained if we consider only the case where the observed radar cross section is assumed to be a good conservative quantity. It is sug-gested that some kinds of in situ formation process should occur in the lower stratosphere.