Abstract: Stratospheric circulation and dynamics significantly influence particle transport in the stratosphere. Several studies have observed zonal asymmetry in the Brewer-Dobson circulation, which can cause zonal asymmetry of particle transport in the stratosphere. In this study, we use a Lagrangian trajectory model (i.e., LAGRANTO) to simulate the transport of particles from stratospheric aerosol injection (SAI), driven by the ERA5 wind field. The LAGRANTO model can track each injected particle from the initial injection location to the tropospheric sink locations at the tropopause (i.e., where injected particles exit the stratosphere into the troposphere). By analyzing the simulating results, we:

(1) explore how the background circulation influences the transport of injected particles in the stratosphere. For example, wavelet transform calculation shows that the steady-state number of particles in the stratosphere has a significant period of approximate 2 years, indicating the modulation from QBO.

(2) find particles injected at different longitudes in the lower tropical stratosphere (e.g., 18 km) show different transport pathways due to the zonal asymmetry of meridional wind. This indicates that the injection longitude can be important for the SAI injection strategies.

(3) identify the tropospheric sink locations of injected particles, which can help us better estimate the local air pollution caused by SAI. The sink locations, mainly located in the mid-latitudes, also show zonal asymmetry. These dominant sink locations (e.g., over Asian areas in DJF) are influenced by tropopause folding, which happens beneath the subtropical jet stream and transports air mass from the stratosphere into the troposphere.