Abstract
Abnormal temperature rises were found in the lower stratosphere over the north subtropical Pacific after the 1982 eruptions of El Chichon. The significant temperature anomalies at 30 mb level moved westward with the El Chichon volcanic clouds.
The positive temperature anomalies from the normal were simultaneously observed with the large backscattering ratios from the lidar measurements in the southern parts of Japan.
The height-time cross section for the standardized temperature (T'=(T-T)/σT) showed warming in the lower stratosphere over the eastern and central parts of the north subtropical Pacific. In the above formula T is a monthly mean temperature, T is the normal and σT is a standard deviation. The magnitudes of the anomalies were in the range between σT and 2σT at most in this area. On the other hand, in the western part of the north subtropical Pacific, a stratospheric warming was spectacular.
In particular, over Chichijima (about 27°N, 140°E) the air layer between 30 mb and 20 mb levels was abnormally warmed, with a peak anomaly of more than 5σT at 50 mb level in July and over 8σT at 20 mb level in September.
In order to investigate northward diffusion of the volcanic clouds, the height-latitude cross sections of temperature anomalies along the 140°E Meridian were made every month from May to December 1982.
Until June a positive temperature anomaly was limited to the south area of 40°N lat. over Japan. But in July it diffused north of the 40°N circle and the time variations of the monthly maxima of the direct solar radiation in USSR showed that the volcanic clouds passed through 50°N latitude in October and 60°N in November.
Lastly it was found that the lower stratospheric temperature anomalies in the past three El Niño events did not show such remarkable warming as in 1982-83. They were all rather negative. Therefore it is not likely that the temperature rises in the lower stratosphere after the 1982 eruption of El Chichon was caused by the 1982-83 El Niño event.
