2026 Volume 21 Issue 1 Pages 162-173
Around the northern region of Aso volcano, controlled burning (“Noyaki”) is performed on Sundays from late winter to early spring, with weather conditions being important for implementation. Analyses of “Noyaki” records from the fourth Sunday of February and from the first and second Sundays of March in 2007–2024 revealed that (1) “Noyaki” was conducted when no precipitation occurred on the day before and on the event, (2) “Noyaki” was postponed if precipitation occurred on the day before or on the morning of the event, (3) “Noyaki” was conducted when precipitation was forecast for the afternoon of the event. Based on these criteria, we examined “Noyaki” occurrence for Sundays in February/March in 1978–2024 using meteorological data from AMeDAS Aso-Otohime station. Except for the fifth Sunday in February (0%, n=1 year), the probability of “Noyaki” was highest on the first Sunday in February (66%), and lowest on the third Sunday in February and on the first and fourth Sundays in March (40%). The difference between the highest and lowest probabilities was statistically significant (p<0.05). Comparing sea-level pressure on days with the highest and lowest probabilities to the long-term mean for that week revealed significant differences in pressure anomalies on the day before “Noyaki.”
