Combined use of lidar and numerical diffusion models to estimate the quantity and dispersion of volcanic eruption clouds in the stratosphere: Vulcán Fuego, 1974, and Augustine, 1976

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Methods are described for estimating the quantity and dispersion on a global scale of the material injected into the stratosphere by a violent volcanic eruption by using a combination of lidar measurements of stratospheric aerosols and a previously described two-dimensional atmospheric dispersion model with the initial volcanic cloud as the ‘source function’ (Cadle et al., 1976). The technique involves comparing the lidar data with model predictions normalized by using data of various kinds obtained after the Gunung Agung eruption in Bali in 1963. In this paper we show that the estimates for the Fuego eruption of 1974 can be made equally well by comparing model and lidar measurements of peak stratospheric concentrations or the total masses within a range of altitudes in a column above the place where the lidar measurements were made. The lidar data previously reported have been extended to several months following the eruption of Augustine volcano in Alaska during January and February 1976. The results indicate that the Augustine eruption must have injected no more than one fiftieth of the amount of material into the stratosphere that was injected by Agung and confirm the previous finding (Cadle et al., 1976) that Fuego injected one fifth of the amount injected by Agung.