SIMULATION OF THE PINATUBO AEROSOL CLOUD IN GENERAL-CIRCULATION MODEL

A high resolution stratospheric version of the NCAR Community Climate Model (CCM2) with an annual cycle was used to simulate the global transport and dispersion of the Pinatubo aerosol cloud. A passive tracer was injected into the model stratosphere over the Philippine Islands on model day June 15, and the transport was simulated for 180 days using an accurate semi-Lagrangian advection scheme. The simulated volcanic aerosol cloud initially drifted westward and expanded in longitude and latitude. The bulk of the aerosol cloud dispersed zonally to form a continuous belt in longitude, and remained confined to the tropics 30-degrees-N - 25-degrees S) centered near the 20 mb level for the entire 180 day model run, although a small amount was transported episodically into the upper troposphere in association with convective disturbances. Aerosol transported to the troposphere was dispersed within a few weeks into the Northern Hemisphere extratropics. In the Southern Hemisphere the aerosol was mixed into the region equatorward of the core of the polar night jet during the first 50 days, but penetration into Southern Polar latitudes was delayed until the final warming in November. These results, which are generally consistent with observed behavior of the El Chichon aerosol, will be compared with observations of the Pinatubo cloud in the course of the next several months.