COMPARISON OF STRATOSPHERIC WARMING FOLLOWING AGUNG, EL CHICHON AND PINATUBO VOLCANIC-ERUPTIONS

Based on a 63-station radiosonde network and using 9-season-average temperatures to minimize the influence of the quasi-biennial oscillation, the low-stratospheric (16-20 km) warming following Agung and El Chichon was greatest in the equatorial zone and least in polar zones. The warming was not symmetric with respect to the equator, however, with greater warming south than north of the equator. The warming following El Chichon was slightly greater than following Agung in all climatic zones except the south polar zone. Results for Pinatubo are preliminary because of the recency of the eruption, but in north extratropics and tropics the warming following this eruption is indicated to be comparable to the warming following Agung and El Chichon. However, in south temperate and polar zones the warming is considerably greater following Pinatubo, perhaps reflecting a contribution from the eruption of Cerro Hudson in Chile. Globally, therefore, the low-stratospheric warming following Pinatubo is greater than following Agung or El Chichon. Based on a 10-station tropical radiosonde network with data to greater heights, the warming following El Chichon exceeded the warming following Agung to a height of at least 31 km, the difference in warming increasing with height. The warming following Pinatubo is similar to that following Agung to a height of 24 km, but thereafter is indicated to become less, an unexpected result to be reexamined as more data become available.