A Numerical Study of the Possible Perturbation of Stratospheric Dynamics Due to Pinatubo Aerosols: Implications for Tracer Transport

Abstract

A spectral three-dimensional model of the stratosphere is used to investigate the possible dynamical effects in the stratosphere of the aerosol cloud formed after the eruption of Mt. Pinatubo. A non-negligible perturbation of the diabatic circulation is found, with a substantial upwelling in the tropical latitudes generated by the aerosol-induced diabatic heating. This effect has been recently shown to have also occurred in coincidence with the eruption of El Chichón. In this work a substantial anomaly in the planetary wave activity is also found, with some remarkable similarities to what is observed for the easterly phase of the quasi-biennal oscillation. A parameterization of horizontal eddy mixing for use in photochemical two-dimensional models is attempted: the modeled Kyy anomaly forced by the aerosols during the Northern Hemisphere winter is such that the northward ozone transport toward midhigh latitudes is enhanced. It is shown that this effect coupled with the additional subsidence related to the diabatic circulation anomaly produces a total ozone increase of about 5% at the northern midhigh latitudes during the winter months. This purely dynamical perturbation should be taken into account in ozone assessments following the eruption, along with heterogeneous chemical depletion and changes in the photodissociation.