抄録
A method to estimate the amount of H2O and heat released from a volcano into the atmosphere by vaporous volcanic clouds in the noneruptive stage is developed. The method is based on the laws of conservation of mass and energy for a simple situation of volcanic gases mixing with ambient air. The method is applied to the precise observational data using a TV camera and an infrared video camera of Aso volcano from December 1980 to March 1984, in which period the volcanic activity was in the most tranquil state since 1928. H2O and heat discharge rates in noneruptive stage are estimated by taking the contribution of the crater lake into account. The results are as follows : (1) The mean values of H2O emission rate (W) and heat discharge rate (Q) in this period are 28±8 kg/s and 84±20 MW, respectively ; (2) W and Q in the period after midyear 1982 are two-fold bigger than those in the period before midyear 1982. The amplitude of the volcanic tremors observed at Aso volcano increased at the same period and correlates well with the heat discharge rate ; (3) The total amount of H2O discharged from Aso volcano is almost equal to the total amount of precipitation in the crater area ; (4) The seasonal change of the volcanic cloud's volume is explained by the variations of the atmospheric condition ; (5) The liquid water content in a vaporous volcanic cloud is 1 × 10-3 kg/m3.
