Volcanic Ash over Arizona in the Spring of 1982: Astronomical Observations

Abstract

Astronomical observations in Arizona recorded the passage of one, and possibly more, volcanic dust clouds between January and June 1982. On 15 May the increase in extinction in visible wavelengths at Tucson was more than 40 percent or 0.4 in optical depth. At Flagstaff, 325 kilometers north, the increase in extinction on the same day was 25 percent. A detailed time history of atmospheric extinction plus evidence for nongray absorption from the cloud is presented.