The discovery of the quasi-biennial oscillation (QBO) and atmospheric equatorial waves in the stratosphere, and related episodes in the ensuing researches are reviewed focusing on observational data available in Japan. Atmospheric equatorial wave theory and the wave-mean-flow interaction theory developed successfully, and spectral analyses were effectively used to describe structure, activity and climatic behavior of equatorial waves. Progress in simulating the QBO by global general circulation models is expected in the near future.
Tropospheric air samples have been collected over Japan (24-44°N, 128-144°E) since 1978, and analyzed for CCl2F2 and CCl3F using GC-ECD. Mean volume mixing ratios in the troposphere were 453 ppt for CCl2F2 and 272 ppt for CCl3F as of January 1990, and increased at almost constant rates, i.e., 16.2±3.5 ppt/year for CCl2F2 and 10.3±2.0 ppt/year for CCl3F between 1978 and 1990. Since 1990, the growth rate of CCl3F mixing ratios has clearly slowed, while that of CCl2F2 mixing ratios seems to have decreased after 1993. These are presumably in response to their reduced emission.
Magnitudes of earthquakes around Unzen volcano, Japan were estimated. We applied Tsuboi's formula using data from a long period seismograph (To=10s) installed at Unzendake Weather Station. For small earthquakes we developed the formula M=logAz+1.73logΔ-0.46, where Az is the vertical amplitude obtained by an A74 short period seismograph (To=1s) at point A of Unzendake Weather Station. Applying the formula to earthquakes beneath the summit of Unzen volcano, we found that earthquakes with a magnitude of 2 occurred in the period of the emergence of the first lava dome in 1991 and earthquakes with a magnitude of about 1 occurred in another period of 1991. The earthquakes in the former period had two peaks (around M0.2 and M1.1) in their magnitude-frequency distribution. The earthquakes with a peak around M1.1 in the magnitude-frequency distribution are considered to be associated with depression of the summit area due to intrusion of lava.