Abstract
Large amounts of aerosols were injected into the lower stratosphere by the volcanic eruptions of El Chichon (17.3°N, 93.2°W) in late March and early April 1982. A ruby lidar at Meteorological Research Institute (MRI), Tsukuba (36.1°N, 140.1°E) in Japan detected the first increase of aerosols around the altitude of 15km on April 25, 1982. A dominant layer with the maximum value of the scattering ratio, Rmax=12.3 was observed at an altitude of 22.5km on May 5. On May 23, it grew to a layer with a value of Rmax=45.2 at 23.5km. After large fluctuations of Rmax occurred in the first 5 months, Rmax began to increase again in September, and Rmax reached 21.3 at 23.5km in October. During October 1982 through September 1983, Rmax-1 decreased gradually with a time constant of about 6 months.
The data of the maximum value of the optical mixing ratio of aerosols, γ694(=Rmax-1) at a wavelength of 694.3nm observed at Tsukuba were compared with γ340 obtained by UV lidar at 340nm at Fukuoka (33.6°N, 130.3°E) during October 1982 through May 1983. The altitudes of Rmax were almost the same at both observatories. The ratio of γ694 to γ340 was estimated to be about 10 from these observations.
The aerosol backscattering coefficient integrated over an altitude range of 16.5-30.5km, B, exibited enhancements in May and December 1982. During December 1982 through Septembr 1983, the value of B decreased with a time constant of about 7 months at Tsukuba. Latitudinal and time variations of B were briefly discussed comparing with recent model simulations of transport processes of air parcels.
