To investigate the possibility that significant amounts of tropical tropospheric air may be convectively introduced into the stratosphere, aerosol samplings over Panama were made at various altitudes using a wire impactor collector.

Percentage of particle sizes less than the mean mode decreases with height above the tropopause, suggesting depletion of small particles, possibly due to coagulation. Larger aerosols (greater than 0.3 &mgr;m in diam.) are more abundant farther above the tropopause, indicating growth, mainly by condensation. The total particle concentration decreases with increasing height above the tropopause, and also with increasing temperature.

Aerosols containing smaller-size particles are thus found closer to the tropopause, and larger-size, more-evolved aerosols occur at higher altitudes. These data indicate that convective activity at the ITCZ may be a source mechanism for stratospheric aerosols.