Eruption Of Mount Agung Research Articles

ATMOSPHERIC EXTINCTION: CZECH LUNAR PHOTOMETRY OF THE JUNE 25, 1964 ECLIPSE

eclipses for the purpose of determining the excess of atmospheric extinction due to an apparently large amount of volcanic dust spread over the upper atmosphere after the eruption of Mount Agung, Bali, on March 17, 1963. The total eclipse of June 25, 1964 was not observable from Iowa, but Bouska and Mayer (1965) published the results of their photoelectric observations in the visual region which provide useful data for further comparison with the above calculations. Figure 1, which has been redrawn from Figure 3 of Paper I to include their observations, suggests that 25 km is a better assumption for the maximum height of the dust layers. The values of s, the fraction of dust extinction in terms of the usual extinction coefficient, estimated for the three eclipses are 0.20, 0.15, and 0.11 mag. per air mass for the December 1963, June 1964, and December 1964 eclipses, respectively. The corresponding value for the normal atmosphere ranges from about 0.065 at A 5500 ( Allen 1963 ) to 0.045 mag. per air mass ( Moreno, Sanduleak, and Stock 1965 ) . Hence, the excess in the extinction coefficients due to additional dust may be estimated as 0.145, 0.095, and 0.055 mag. per air mass for the three dates. We can then obtain the total extinction for each

Light illuminance and color in the Earth's shadow

The illuminance in the earth's shadow at three wavelengths is computed by performing a double numerical integration over the atmosphere. As sources of light attenuation, ozone absorption and extinction by dust and clouds are taken into account in addition to the usual Rayleigh scattering and the beam divergence due to refraction. Light inserted into the shadow through scattering by molecules and aerosol particles is also included in the calculations. The solar limb darkening is accounted for. Special emphasis is placed on finding an explanation for the unusual eclipse of December 30, 1963, in which an extremely low illuminance and nonreddening were observed. Calculations are carried out for various models of the earth's atmosphere, and it is shown that the dust particles may account for large changes in the illuminance from eclipse to eclipse. The dust and clouds appear to cause the nonreddening by enhancing the importance of the diffused light in the central region of the earth's shadow. The observation of the 1963 eclipse is explained by assuming an abnormally large extinction, presumably caused by dust spread by the eruption of Mount Agung on March 17, 1963. The required additional extinction amounts to about 14% of the incident light per air mass in the visible region, which agrees with direct measurements of the photometric extinction made at various observatories during the year 1963. The theory also provides a conclusive means of distinguishing between extinction due to dust particles and that due to clouds. An approximate value for the amount of ozone in the atmosphere can be determined. The results suggest useful photometric observations of future eclipses.

Infrasonic observations of the May 16, 1963, volcanic explosion on the island of Bali

The volcanic eruption of Mount Agung on the Island of Bali reached explosive proportions on May 16, 1963. Perturbations generated in the atmosphere traveling at sonic velocities were recorded in Boulder, Colorado, 14,700 km distant, both via the short great-circle path and via the long great-circle path through the antipodes and around the world. In Boston, Massachusetts, 16,200 km distant, and in Washington, D.C., 16,300 km distant, sound waves were received via the short great-circle path. The average transit velocity for the short path was 17 m/sec less than for the long path. The effect of wind velocities at mesospheric heights on the transit velocities is discussed.

Photometry at Cerro Tololo, Chile: Effects of Mount Agung Eruption

Extinction effects of the volcanic dust injected into the stratosphere by the violent eruption of Mount Agung, Bali, 17 March 1963, were studied. Visual extinction coefficients were measured photoelectrically for 153 nights during the period from March 1963 to September 1964. The data indicate that the dust is now widely dispersed and that its effects may persist for several more years. A study of the wavelength dependence of the extinction shows that the dust is a neutral scattering agent. The total global amount of airborne volcanic material is crudely estimated at 10(12) grams as of September 1964.