Preliminary estimate of the radiative and climatic effects of the El Chichon eruption

Abstract

A preliminary estímate of the climatic effect the major El Chichón vokanic eniption of April 1982 has been made using a seasonal version of a zonal climate model with a 70 m slab ocean.The volcanic aerosol was introduced into the model stratosphere at a height of 23 - 29 km where the aerosol perturbs both the solar and infrared tluxes. An aerosol composition of 75°io H2SO4 with a zero-order logarithmic size distribution is assumed. The latitudinal and timevarying pattern of opacity developed by Robock (1983) is used, with the peak opacity readün: 0.3 in June 1982. The volcanically perturbed case is nin from April 1, 1982 to January l. 1983 in this calculation. The Northern Hemisphere temperature is projected to gradually ·decrease during this period, being about 0.2 K cooler than normal at the end of 1982. The model also predicts precipitation anomalies, including a reduction of five to more than ten percent in precipitation rate just north of the ITCZ.